Change from v2:
- Move dynamic memory allocation to efi_pstore_read() before holding
efivars->lock to protect entry->var.Data.
- Access to entry->scanning while holding efivars->lock.
- Move a comment about a returned value from efi_pstore_read_func() to
efi_pstore_read() because "size < 0" case may happen in efi_pstore_read().
Currently, when mounting pstore file system, a read callback of efi_pstore
driver runs mutiple times as below.
- In the first read callback, scan efivar_sysfs_list from head and pass
a kmsg buffer of a entry to an upper pstore layer.
- In the second read callback, rescan efivar_sysfs_list from the entry and pass
another kmsg buffer to it.
- Repeat the scan and pass until the end of efivar_sysfs_list.
In this process, an entry is read across the multiple read function calls.
To avoid race between the read and erasion, the whole process above is
protected by a spinlock, holding in open() and releasing in close().
At the same time, kmemdup() is called to pass the buffer to pstore filesystem
during it.
And then, it causes a following lockdep warning.
To make the dynamic memory allocation runnable without taking spinlock,
holding off a deletion of sysfs entry if it happens while scanning it
via efi_pstore, and deleting it after the scan is completed.
To implement it, this patch introduces two flags, scanning and deleting,
to efivar_entry.
[ 1.143710] ------------[ cut here ]------------
[ 1.144058] WARNING: CPU: 1 PID: 1 at kernel/lockdep.c:2740
lockdep_trace_alloc+0x104/0x110()
[ 1.144058] DEBUG_LOCKS_WARN_ON(irqs_disabled_flags(flags))
[ 1.144058] Modules linked in:
[ 1.144058] CPU: 1 PID: 1 Comm: systemd Not tainted 3.11.0-rc5 #2
[ 1.144058] 0000000000000009 ffff8800797e9ae0 ffffffff816614a5
ffff8800797e9b28
[ 1.144058] ffff8800797e9b18 ffffffff8105510d 0000000000000080
0000000000000046
[ 1.144058] 00000000000000d0 00000000000003af ffffffff81ccd0c0
ffff8800797e9b78
[ 1.144058] Call Trace:
[ 1.144058] [<ffffffff816614a5>] dump_stack+0x54/0x74
[ 1.144058] [<ffffffff8105510d>] warn_slowpath_common+0x7d/0xa0
[ 1.144058] [<ffffffff8105517c>] warn_slowpath_fmt+0x4c/0x50
[ 1.144058] [<ffffffff8131290f>] ? vsscanf+0x57f/0x7b0
[ 1.144058] [<ffffffff810bbd74>] lockdep_trace_alloc+0x104/0x110
[ 1.144058] [<ffffffff81192da0>] __kmalloc_track_caller+0x50/0x280
[ 1.144058] [<ffffffff815147bb>] ?
efi_pstore_read_func.part.1+0x12b/0x170
[ 1.144058] [<ffffffff8115b260>] kmemdup+0x20/0x50
[ 1.144058] [<ffffffff815147bb>] efi_pstore_read_func.part.1+0x12b/0x170
[ 1.144058] [<ffffffff81514800>] ?
efi_pstore_read_func.part.1+0x170/0x170
[ 1.144058] [<ffffffff815148b4>] efi_pstore_read_func+0xb4/0xe0
[ 1.144058] [<ffffffff81512b7b>] __efivar_entry_iter+0xfb/0x120
[ 1.144058] [<ffffffff8151428f>] efi_pstore_read+0x3f/0x50
[ 1.144058] [<ffffffff8128d7ba>] pstore_get_records+0x9a/0x150
[ 1.158207] [<ffffffff812af25c>] ? selinux_d_instantiate+0x1c/0x20
[ 1.158207] [<ffffffff8128ce30>] ? parse_options+0x80/0x80
[ 1.158207] [<ffffffff8128ced5>] pstore_fill_super+0xa5/0xc0
[ 1.158207] [<ffffffff811ae7d2>] mount_single+0xa2/0xd0
[ 1.158207] [<ffffffff8128ccf8>] pstore_mount+0x18/0x20
[ 1.158207] [<ffffffff811ae8b9>] mount_fs+0x39/0x1b0
[ 1.158207] [<ffffffff81160550>] ? __alloc_percpu+0x10/0x20
[ 1.158207] [<ffffffff811c9493>] vfs_kern_mount+0x63/0xf0
[ 1.158207] [<ffffffff811cbb0e>] do_mount+0x23e/0xa20
[ 1.158207] [<ffffffff8115b51b>] ? strndup_user+0x4b/0xf0
[ 1.158207] [<ffffffff811cc373>] SyS_mount+0x83/0xc0
[ 1.158207] [<ffffffff81673cc2>] system_call_fastpath+0x16/0x1b
[ 1.158207] ---[ end trace 61981bc62de9f6f4 ]---
Signed-off-by: Seiji Aguchi <[email protected]>
---
drivers/firmware/efi/efi-pstore.c | 143 +++++++++++++++++++++++++++++++++++---
drivers/firmware/efi/efivars.c | 12 ++--
drivers/firmware/efi/vars.c | 12 +++-
include/linux/efi.h | 2 +
4 files changed, 153 insertions(+), 16 deletions(-)
diff --git a/drivers/firmware/efi/efi-pstore.c b/drivers/firmware/efi/efi-pstore.c
index 5002d50..ebd5dbc 100644
--- a/drivers/firmware/efi/efi-pstore.c
+++ b/drivers/firmware/efi/efi-pstore.c
@@ -18,14 +18,12 @@ module_param_named(pstore_disable, efivars_pstore_disable, bool, 0644);
static int efi_pstore_open(struct pstore_info *psi)
{
- efivar_entry_iter_begin();
psi->data = NULL;
return 0;
}
static int efi_pstore_close(struct pstore_info *psi)
{
- efivar_entry_iter_end();
psi->data = NULL;
return 0;
}
@@ -91,19 +89,125 @@ static int efi_pstore_read_func(struct efivar_entry *entry, void *data)
__efivar_entry_get(entry, &entry->var.Attributes,
&entry->var.DataSize, entry->var.Data);
size = entry->var.DataSize;
+ memcpy(*cb_data->buf, entry->var.Data, (size_t)min_t(unsigned long,
+ 1024, size));
- *cb_data->buf = kmemdup(entry->var.Data, size, GFP_KERNEL);
- if (*cb_data->buf == NULL)
- return -ENOMEM;
return size;
}
+/**
+ * efi_pstore_scan_sysfs_enter
+ * @entry: scanning entry
+ * @next: next entry
+ * @head: list head
+ */
+static void efi_pstore_scan_sysfs_enter(struct efivar_entry *pos,
+ struct efivar_entry *next,
+ struct list_head *head)
+{
+ pos->scanning = true;
+ if (&next->list != head)
+ next->scanning = true;
+}
+
+/**
+ * __efi_pstore_scan_sysfs_exit
+ * @entry: deleting entry
+ * @turn_off_scanning: Check if a scanning flag should be turned off
+ */
+static inline void __efi_pstore_scan_sysfs_exit(struct efivar_entry *entry,
+ bool turn_off_scanning)
+{
+ if (entry->deleting) {
+ list_del(&entry->list);
+ efivar_entry_iter_end();
+ efivar_unregister(entry);
+ efivar_entry_iter_begin();
+ } else if (turn_off_scanning)
+ entry->scanning = false;
+}
+
+/**
+ * efi_pstore_scan_sysfs_exit
+ * @pos: scanning entry
+ * @next: next entry
+ * @head: list head
+ * @stop: a flag checking if scanning will stop
+ */
+static void efi_pstore_scan_sysfs_exit(struct efivar_entry *pos,
+ struct efivar_entry *next,
+ struct list_head *head, bool stop)
+{
+ __efi_pstore_scan_sysfs_exit(pos, true);
+ if (stop)
+ __efi_pstore_scan_sysfs_exit(next, &next->list != head);
+}
+
+/**
+ * efi_pstore_sysfs_entry_iter
+ *
+ * @data: function-specific data to pass to callback
+ * @pos: entry to begin iterating from
+ *
+ * You MUST call efivar_enter_iter_begin() before this function, and
+ * efivar_entry_iter_end() afterwards.
+ *
+ * It is possible to begin iteration from an arbitrary entry within
+ * the list by passing @pos. @pos is updated on return to point to
+ * the next entry of the last one passed to efi_pstore_read_func().
+ * To begin iterating from the beginning of the list @pos must be %NULL.
+ */
+static int efi_pstore_sysfs_entry_iter(void *data, struct efivar_entry **pos)
+{
+ struct efivar_entry *entry, *n;
+ struct list_head *head = &efivar_sysfs_list;
+ int size = 0;
+
+ if (!*pos) {
+ list_for_each_entry_safe(entry, n, head, list) {
+ efi_pstore_scan_sysfs_enter(entry, n, head);
+
+ size = efi_pstore_read_func(entry, data);
+ efi_pstore_scan_sysfs_exit(entry, n, head, size < 0);
+ if (size)
+ break;
+ }
+ *pos = n;
+ return size;
+ }
+
+ list_for_each_entry_safe_from((*pos), n, head, list) {
+ efi_pstore_scan_sysfs_enter((*pos), n, head);
+
+ size = efi_pstore_read_func((*pos), data);
+ efi_pstore_scan_sysfs_exit((*pos), n, head, size < 0);
+ if (size)
+ break;
+ }
+ *pos = n;
+ return size;
+}
+
+/**
+ * efi_pstore_read
+ *
+ * This function returns a size of NVRAM entry logged via efi_pstore_write().
+ * The meaning and behavior of efi_pstore/pstore are as below.
+ *
+ * size > 0: Got data of an entry logged via efi_pstore_write() successfully,
+ * and pstore filesystem will continue reading subsequent entries.
+ * size == 0: Entry was not logged via efi_pstore_write(),
+ * and efi_pstore driver will continue reading subsequent entries.
+ * size < 0: Failed to get data of entry logging via efi_pstore_write(),
+ * and pstore will stop reading entry.
+ */
static ssize_t efi_pstore_read(u64 *id, enum pstore_type_id *type,
int *count, struct timespec *timespec,
char **buf, bool *compressed,
struct pstore_info *psi)
{
struct pstore_read_data data;
+ ssize_t size;
data.id = id;
data.type = type;
@@ -112,8 +216,17 @@ static ssize_t efi_pstore_read(u64 *id, enum pstore_type_id *type,
data.compressed = compressed;
data.buf = buf;
- return __efivar_entry_iter(efi_pstore_read_func, &efivar_sysfs_list, &data,
- (struct efivar_entry **)&psi->data);
+ *data.buf = kzalloc(1024, GFP_KERNEL);
+ if (!*data.buf)
+ return -ENOMEM;
+
+ efivar_entry_iter_begin();
+ size = efi_pstore_sysfs_entry_iter(&data,
+ (struct efivar_entry **)&psi->data);
+ efivar_entry_iter_end();
+ if (size <= 0)
+ kfree(*data.buf);
+ return size;
}
static int efi_pstore_write(enum pstore_type_id type,
@@ -184,9 +297,17 @@ static int efi_pstore_erase_func(struct efivar_entry *entry, void *data)
return 0;
}
+ if (entry->scanning) {
+ /*
+ * Skip deletion because this entry will be deleted
+ * after scanning is completed.
+ */
+ entry->deleting = true;
+ } else
+ list_del(&entry->list);
+
/* found */
__efivar_entry_delete(entry);
- list_del(&entry->list);
return 1;
}
@@ -214,10 +335,12 @@ static int efi_pstore_erase(enum pstore_type_id type, u64 id, int count,
efivar_entry_iter_begin();
found = __efivar_entry_iter(efi_pstore_erase_func, &efivar_sysfs_list, &edata, &entry);
- efivar_entry_iter_end();
- if (found)
+ if (found && !entry->scanning) {
+ efivar_entry_iter_end();
efivar_unregister(entry);
+ } else
+ efivar_entry_iter_end();
return 0;
}
diff --git a/drivers/firmware/efi/efivars.c b/drivers/firmware/efi/efivars.c
index 8a7432a..8c5a61a 100644
--- a/drivers/firmware/efi/efivars.c
+++ b/drivers/firmware/efi/efivars.c
@@ -383,12 +383,16 @@ static ssize_t efivar_delete(struct file *filp, struct kobject *kobj,
else if (__efivar_entry_delete(entry))
err = -EIO;
- efivar_entry_iter_end();
-
- if (err)
+ if (err) {
+ efivar_entry_iter_end();
return err;
+ }
- efivar_unregister(entry);
+ if (!entry->scanning) {
+ efivar_entry_iter_end();
+ efivar_unregister(entry);
+ } else
+ efivar_entry_iter_end();
/* It's dead Jim.... */
return count;
diff --git a/drivers/firmware/efi/vars.c b/drivers/firmware/efi/vars.c
index 391c67b..b22659c 100644
--- a/drivers/firmware/efi/vars.c
+++ b/drivers/firmware/efi/vars.c
@@ -683,8 +683,16 @@ struct efivar_entry *efivar_entry_find(efi_char16_t *name, efi_guid_t guid,
if (!found)
return NULL;
- if (remove)
- list_del(&entry->list);
+ if (remove) {
+ if (entry->scanning) {
+ /*
+ * The entry will be deleted
+ * after scanning is completed.
+ */
+ entry->deleting = true;
+ } else
+ list_del(&entry->list);
+ }
return entry;
}
diff --git a/include/linux/efi.h b/include/linux/efi.h
index 5f8f176..04088fb 100644
--- a/include/linux/efi.h
+++ b/include/linux/efi.h
@@ -782,6 +782,8 @@ struct efivar_entry {
struct efi_variable var;
struct list_head list;
struct kobject kobj;
+ bool scanning;
+ bool deleting;
};
extern struct list_head efivar_sysfs_list;
--
1.8.2.1
Howdy Seiji,
I failed appily this patch to both 3.12-rc2 and 3.12-rc4. Could you
please let me know which is the right tree for this patch?
Thanks,
Madper.
[email protected] writes:
> Change from v2:
> - Move dynamic memory allocation to efi_pstore_read() before holding
> efivars->lock to protect entry->var.Data.
> - Access to entry->scanning while holding efivars->lock.
> - Move a comment about a returned value from efi_pstore_read_func() to
> efi_pstore_read() because "size < 0" case may happen in efi_pstore_read().
>
> Currently, when mounting pstore file system, a read callback of efi_pstore
> driver runs mutiple times as below.
>
> - In the first read callback, scan efivar_sysfs_list from head and pass
> a kmsg buffer of a entry to an upper pstore layer.
> - In the second read callback, rescan efivar_sysfs_list from the entry and pass
> another kmsg buffer to it.
> - Repeat the scan and pass until the end of efivar_sysfs_list.
>
> In this process, an entry is read across the multiple read function calls.
> To avoid race between the read and erasion, the whole process above is
> protected by a spinlock, holding in open() and releasing in close().
>
> At the same time, kmemdup() is called to pass the buffer to pstore filesystem
> during it.
> And then, it causes a following lockdep warning.
>
> To make the dynamic memory allocation runnable without taking spinlock,
> holding off a deletion of sysfs entry if it happens while scanning it
> via efi_pstore, and deleting it after the scan is completed.
>
> To implement it, this patch introduces two flags, scanning and deleting,
> to efivar_entry.
>
> [ 1.143710] ------------[ cut here ]------------
> [ 1.144058] WARNING: CPU: 1 PID: 1 at kernel/lockdep.c:2740
> lockdep_trace_alloc+0x104/0x110()
> [ 1.144058] DEBUG_LOCKS_WARN_ON(irqs_disabled_flags(flags))
> [ 1.144058] Modules linked in:
>
> [ 1.144058] CPU: 1 PID: 1 Comm: systemd Not tainted 3.11.0-rc5 #2
> [ 1.144058] 0000000000000009 ffff8800797e9ae0 ffffffff816614a5
> ffff8800797e9b28
> [ 1.144058] ffff8800797e9b18 ffffffff8105510d 0000000000000080
> 0000000000000046
> [ 1.144058] 00000000000000d0 00000000000003af ffffffff81ccd0c0
> ffff8800797e9b78
> [ 1.144058] Call Trace:
> [ 1.144058] [<ffffffff816614a5>] dump_stack+0x54/0x74
> [ 1.144058] [<ffffffff8105510d>] warn_slowpath_common+0x7d/0xa0
> [ 1.144058] [<ffffffff8105517c>] warn_slowpath_fmt+0x4c/0x50
> [ 1.144058] [<ffffffff8131290f>] ? vsscanf+0x57f/0x7b0
> [ 1.144058] [<ffffffff810bbd74>] lockdep_trace_alloc+0x104/0x110
> [ 1.144058] [<ffffffff81192da0>] __kmalloc_track_caller+0x50/0x280
> [ 1.144058] [<ffffffff815147bb>] ?
> efi_pstore_read_func.part.1+0x12b/0x170
> [ 1.144058] [<ffffffff8115b260>] kmemdup+0x20/0x50
> [ 1.144058] [<ffffffff815147bb>] efi_pstore_read_func.part.1+0x12b/0x170
> [ 1.144058] [<ffffffff81514800>] ?
> efi_pstore_read_func.part.1+0x170/0x170
> [ 1.144058] [<ffffffff815148b4>] efi_pstore_read_func+0xb4/0xe0
> [ 1.144058] [<ffffffff81512b7b>] __efivar_entry_iter+0xfb/0x120
> [ 1.144058] [<ffffffff8151428f>] efi_pstore_read+0x3f/0x50
> [ 1.144058] [<ffffffff8128d7ba>] pstore_get_records+0x9a/0x150
> [ 1.158207] [<ffffffff812af25c>] ? selinux_d_instantiate+0x1c/0x20
> [ 1.158207] [<ffffffff8128ce30>] ? parse_options+0x80/0x80
> [ 1.158207] [<ffffffff8128ced5>] pstore_fill_super+0xa5/0xc0
> [ 1.158207] [<ffffffff811ae7d2>] mount_single+0xa2/0xd0
> [ 1.158207] [<ffffffff8128ccf8>] pstore_mount+0x18/0x20
> [ 1.158207] [<ffffffff811ae8b9>] mount_fs+0x39/0x1b0
> [ 1.158207] [<ffffffff81160550>] ? __alloc_percpu+0x10/0x20
> [ 1.158207] [<ffffffff811c9493>] vfs_kern_mount+0x63/0xf0
> [ 1.158207] [<ffffffff811cbb0e>] do_mount+0x23e/0xa20
> [ 1.158207] [<ffffffff8115b51b>] ? strndup_user+0x4b/0xf0
> [ 1.158207] [<ffffffff811cc373>] SyS_mount+0x83/0xc0
> [ 1.158207] [<ffffffff81673cc2>] system_call_fastpath+0x16/0x1b
> [ 1.158207] ---[ end trace 61981bc62de9f6f4 ]---
>
> Signed-off-by: Seiji Aguchi <[email protected]>
> ---
> drivers/firmware/efi/efi-pstore.c | 143 +++++++++++++++++++++++++++++++++++---
> drivers/firmware/efi/efivars.c | 12 ++--
> drivers/firmware/efi/vars.c | 12 +++-
> include/linux/efi.h | 2 +
> 4 files changed, 153 insertions(+), 16 deletions(-)
>
> diff --git a/drivers/firmware/efi/efi-pstore.c b/drivers/firmware/efi/efi-pstore.c
> index 5002d50..ebd5dbc 100644
> --- a/drivers/firmware/efi/efi-pstore.c
> +++ b/drivers/firmware/efi/efi-pstore.c
> @@ -18,14 +18,12 @@ module_param_named(pstore_disable, efivars_pstore_disable, bool, 0644);
>
> static int efi_pstore_open(struct pstore_info *psi)
> {
> - efivar_entry_iter_begin();
> psi->data = NULL;
> return 0;
> }
>
> static int efi_pstore_close(struct pstore_info *psi)
> {
> - efivar_entry_iter_end();
> psi->data = NULL;
> return 0;
> }
> @@ -91,19 +89,125 @@ static int efi_pstore_read_func(struct efivar_entry *entry, void *data)
> __efivar_entry_get(entry, &entry->var.Attributes,
> &entry->var.DataSize, entry->var.Data);
> size = entry->var.DataSize;
> + memcpy(*cb_data->buf, entry->var.Data, (size_t)min_t(unsigned long,
> + 1024, size));
>
> - *cb_data->buf = kmemdup(entry->var.Data, size, GFP_KERNEL);
> - if (*cb_data->buf == NULL)
> - return -ENOMEM;
> return size;
> }
>
> +/**
> + * efi_pstore_scan_sysfs_enter
> + * @entry: scanning entry
> + * @next: next entry
> + * @head: list head
> + */
> +static void efi_pstore_scan_sysfs_enter(struct efivar_entry *pos,
> + struct efivar_entry *next,
> + struct list_head *head)
> +{
> + pos->scanning = true;
> + if (&next->list != head)
> + next->scanning = true;
> +}
> +
> +/**
> + * __efi_pstore_scan_sysfs_exit
> + * @entry: deleting entry
> + * @turn_off_scanning: Check if a scanning flag should be turned off
> + */
> +static inline void __efi_pstore_scan_sysfs_exit(struct efivar_entry *entry,
> + bool turn_off_scanning)
> +{
> + if (entry->deleting) {
> + list_del(&entry->list);
> + efivar_entry_iter_end();
> + efivar_unregister(entry);
> + efivar_entry_iter_begin();
> + } else if (turn_off_scanning)
> + entry->scanning = false;
> +}
> +
> +/**
> + * efi_pstore_scan_sysfs_exit
> + * @pos: scanning entry
> + * @next: next entry
> + * @head: list head
> + * @stop: a flag checking if scanning will stop
> + */
> +static void efi_pstore_scan_sysfs_exit(struct efivar_entry *pos,
> + struct efivar_entry *next,
> + struct list_head *head, bool stop)
> +{
> + __efi_pstore_scan_sysfs_exit(pos, true);
> + if (stop)
> + __efi_pstore_scan_sysfs_exit(next, &next->list != head);
> +}
> +
> +/**
> + * efi_pstore_sysfs_entry_iter
> + *
> + * @data: function-specific data to pass to callback
> + * @pos: entry to begin iterating from
> + *
> + * You MUST call efivar_enter_iter_begin() before this function, and
> + * efivar_entry_iter_end() afterwards.
> + *
> + * It is possible to begin iteration from an arbitrary entry within
> + * the list by passing @pos. @pos is updated on return to point to
> + * the next entry of the last one passed to efi_pstore_read_func().
> + * To begin iterating from the beginning of the list @pos must be %NULL.
> + */
> +static int efi_pstore_sysfs_entry_iter(void *data, struct efivar_entry **pos)
> +{
> + struct efivar_entry *entry, *n;
> + struct list_head *head = &efivar_sysfs_list;
> + int size = 0;
> +
> + if (!*pos) {
> + list_for_each_entry_safe(entry, n, head, list) {
> + efi_pstore_scan_sysfs_enter(entry, n, head);
> +
> + size = efi_pstore_read_func(entry, data);
> + efi_pstore_scan_sysfs_exit(entry, n, head, size < 0);
> + if (size)
> + break;
> + }
> + *pos = n;
> + return size;
> + }
> +
> + list_for_each_entry_safe_from((*pos), n, head, list) {
> + efi_pstore_scan_sysfs_enter((*pos), n, head);
> +
> + size = efi_pstore_read_func((*pos), data);
> + efi_pstore_scan_sysfs_exit((*pos), n, head, size < 0);
> + if (size)
> + break;
> + }
> + *pos = n;
> + return size;
> +}
> +
> +/**
> + * efi_pstore_read
> + *
> + * This function returns a size of NVRAM entry logged via efi_pstore_write().
> + * The meaning and behavior of efi_pstore/pstore are as below.
> + *
> + * size > 0: Got data of an entry logged via efi_pstore_write() successfully,
> + * and pstore filesystem will continue reading subsequent entries.
> + * size == 0: Entry was not logged via efi_pstore_write(),
> + * and efi_pstore driver will continue reading subsequent entries.
> + * size < 0: Failed to get data of entry logging via efi_pstore_write(),
> + * and pstore will stop reading entry.
> + */
> static ssize_t efi_pstore_read(u64 *id, enum pstore_type_id *type,
> int *count, struct timespec *timespec,
> char **buf, bool *compressed,
> struct pstore_info *psi)
> {
> struct pstore_read_data data;
> + ssize_t size;
>
> data.id = id;
> data.type = type;
> @@ -112,8 +216,17 @@ static ssize_t efi_pstore_read(u64 *id, enum pstore_type_id *type,
> data.compressed = compressed;
> data.buf = buf;
>
> - return __efivar_entry_iter(efi_pstore_read_func, &efivar_sysfs_list, &data,
> - (struct efivar_entry **)&psi->data);
> + *data.buf = kzalloc(1024, GFP_KERNEL);
> + if (!*data.buf)
> + return -ENOMEM;
> +
> + efivar_entry_iter_begin();
> + size = efi_pstore_sysfs_entry_iter(&data,
> + (struct efivar_entry **)&psi->data);
> + efivar_entry_iter_end();
> + if (size <= 0)
> + kfree(*data.buf);
> + return size;
> }
>
> static int efi_pstore_write(enum pstore_type_id type,
> @@ -184,9 +297,17 @@ static int efi_pstore_erase_func(struct efivar_entry *entry, void *data)
> return 0;
> }
>
> + if (entry->scanning) {
> + /*
> + * Skip deletion because this entry will be deleted
> + * after scanning is completed.
> + */
> + entry->deleting = true;
> + } else
> + list_del(&entry->list);
> +
> /* found */
> __efivar_entry_delete(entry);
> - list_del(&entry->list);
>
> return 1;
> }
> @@ -214,10 +335,12 @@ static int efi_pstore_erase(enum pstore_type_id type, u64 id, int count,
>
> efivar_entry_iter_begin();
> found = __efivar_entry_iter(efi_pstore_erase_func, &efivar_sysfs_list, &edata, &entry);
> - efivar_entry_iter_end();
>
> - if (found)
> + if (found && !entry->scanning) {
> + efivar_entry_iter_end();
> efivar_unregister(entry);
> + } else
> + efivar_entry_iter_end();
>
> return 0;
> }
> diff --git a/drivers/firmware/efi/efivars.c b/drivers/firmware/efi/efivars.c
> index 8a7432a..8c5a61a 100644
> --- a/drivers/firmware/efi/efivars.c
> +++ b/drivers/firmware/efi/efivars.c
> @@ -383,12 +383,16 @@ static ssize_t efivar_delete(struct file *filp, struct kobject *kobj,
> else if (__efivar_entry_delete(entry))
> err = -EIO;
>
> - efivar_entry_iter_end();
> -
> - if (err)
> + if (err) {
> + efivar_entry_iter_end();
> return err;
> + }
>
> - efivar_unregister(entry);
> + if (!entry->scanning) {
> + efivar_entry_iter_end();
> + efivar_unregister(entry);
> + } else
> + efivar_entry_iter_end();
>
> /* It's dead Jim.... */
> return count;
> diff --git a/drivers/firmware/efi/vars.c b/drivers/firmware/efi/vars.c
> index 391c67b..b22659c 100644
> --- a/drivers/firmware/efi/vars.c
> +++ b/drivers/firmware/efi/vars.c
> @@ -683,8 +683,16 @@ struct efivar_entry *efivar_entry_find(efi_char16_t *name, efi_guid_t guid,
> if (!found)
> return NULL;
>
> - if (remove)
> - list_del(&entry->list);
> + if (remove) {
> + if (entry->scanning) {
> + /*
> + * The entry will be deleted
> + * after scanning is completed.
> + */
> + entry->deleting = true;
> + } else
> + list_del(&entry->list);
> + }
>
> return entry;
> }
> diff --git a/include/linux/efi.h b/include/linux/efi.h
> index 5f8f176..04088fb 100644
> --- a/include/linux/efi.h
> +++ b/include/linux/efi.h
> @@ -782,6 +782,8 @@ struct efivar_entry {
> struct efi_variable var;
> struct list_head list;
> struct kobject kobj;
> + bool scanning;
> + bool deleting;
> };
>
> extern struct list_head efivar_sysfs_list;
--
Best,
Madper Xie.
Hi Madper,
I tested this patch on 3.12-rc4.
Could you please send me the log when you failed to apply?
Seiji
> -----Original Message-----
> From: Madper Xie [mailto:[email protected]]
> Sent: Thursday, October 17, 2013 1:54 AM
> To: Seiji Aguchi
> Cc: [email protected]; [email protected]; [email protected]; [email protected]; Tomoki Sekiyama; dle-
> [email protected]
> Subject: Re: [PATCH v3] efivars,efi-pstore: Hold off deletion of sysfs entry until, the scan is completed
>
> Howdy Seiji,
> I failed appily this patch to both 3.12-rc2 and 3.12-rc4. Could you
> please let me know which is the right tree for this patch?
>
> Thanks,
> Madper.
> [email protected] writes:
>
> > Change from v2:
> > - Move dynamic memory allocation to efi_pstore_read() before holding
> > efivars->lock to protect entry->var.Data.
> > - Access to entry->scanning while holding efivars->lock.
> > - Move a comment about a returned value from efi_pstore_read_func() to
> > efi_pstore_read() because "size < 0" case may happen in efi_pstore_read().
> >
> > Currently, when mounting pstore file system, a read callback of efi_pstore
> > driver runs mutiple times as below.
> >
> > - In the first read callback, scan efivar_sysfs_list from head and pass
> > a kmsg buffer of a entry to an upper pstore layer.
> > - In the second read callback, rescan efivar_sysfs_list from the entry and pass
> > another kmsg buffer to it.
> > - Repeat the scan and pass until the end of efivar_sysfs_list.
> >
> > In this process, an entry is read across the multiple read function calls.
> > To avoid race between the read and erasion, the whole process above is
> > protected by a spinlock, holding in open() and releasing in close().
> >
> > At the same time, kmemdup() is called to pass the buffer to pstore filesystem
> > during it.
> > And then, it causes a following lockdep warning.
> >
> > To make the dynamic memory allocation runnable without taking spinlock,
> > holding off a deletion of sysfs entry if it happens while scanning it
> > via efi_pstore, and deleting it after the scan is completed.
> >
> > To implement it, this patch introduces two flags, scanning and deleting,
> > to efivar_entry.
> >
> > [ 1.143710] ------------[ cut here ]------------
> > [ 1.144058] WARNING: CPU: 1 PID: 1 at kernel/lockdep.c:2740
> > lockdep_trace_alloc+0x104/0x110()
> > [ 1.144058] DEBUG_LOCKS_WARN_ON(irqs_disabled_flags(flags))
> > [ 1.144058] Modules linked in:
> >
> > [ 1.144058] CPU: 1 PID: 1 Comm: systemd Not tainted 3.11.0-rc5 #2
> > [ 1.144058] 0000000000000009 ffff8800797e9ae0 ffffffff816614a5
> > ffff8800797e9b28
> > [ 1.144058] ffff8800797e9b18 ffffffff8105510d 0000000000000080
> > 0000000000000046
> > [ 1.144058] 00000000000000d0 00000000000003af ffffffff81ccd0c0
> > ffff8800797e9b78
> > [ 1.144058] Call Trace:
> > [ 1.144058] [<ffffffff816614a5>] dump_stack+0x54/0x74
> > [ 1.144058] [<ffffffff8105510d>] warn_slowpath_common+0x7d/0xa0
> > [ 1.144058] [<ffffffff8105517c>] warn_slowpath_fmt+0x4c/0x50
> > [ 1.144058] [<ffffffff8131290f>] ? vsscanf+0x57f/0x7b0
> > [ 1.144058] [<ffffffff810bbd74>] lockdep_trace_alloc+0x104/0x110
> > [ 1.144058] [<ffffffff81192da0>] __kmalloc_track_caller+0x50/0x280
> > [ 1.144058] [<ffffffff815147bb>] ?
> > efi_pstore_read_func.part.1+0x12b/0x170
> > [ 1.144058] [<ffffffff8115b260>] kmemdup+0x20/0x50
> > [ 1.144058] [<ffffffff815147bb>] efi_pstore_read_func.part.1+0x12b/0x170
> > [ 1.144058] [<ffffffff81514800>] ?
> > efi_pstore_read_func.part.1+0x170/0x170
> > [ 1.144058] [<ffffffff815148b4>] efi_pstore_read_func+0xb4/0xe0
> > [ 1.144058] [<ffffffff81512b7b>] __efivar_entry_iter+0xfb/0x120
> > [ 1.144058] [<ffffffff8151428f>] efi_pstore_read+0x3f/0x50
> > [ 1.144058] [<ffffffff8128d7ba>] pstore_get_records+0x9a/0x150
> > [ 1.158207] [<ffffffff812af25c>] ? selinux_d_instantiate+0x1c/0x20
> > [ 1.158207] [<ffffffff8128ce30>] ? parse_options+0x80/0x80
> > [ 1.158207] [<ffffffff8128ced5>] pstore_fill_super+0xa5/0xc0
> > [ 1.158207] [<ffffffff811ae7d2>] mount_single+0xa2/0xd0
> > [ 1.158207] [<ffffffff8128ccf8>] pstore_mount+0x18/0x20
> > [ 1.158207] [<ffffffff811ae8b9>] mount_fs+0x39/0x1b0
> > [ 1.158207] [<ffffffff81160550>] ? __alloc_percpu+0x10/0x20
> > [ 1.158207] [<ffffffff811c9493>] vfs_kern_mount+0x63/0xf0
> > [ 1.158207] [<ffffffff811cbb0e>] do_mount+0x23e/0xa20
> > [ 1.158207] [<ffffffff8115b51b>] ? strndup_user+0x4b/0xf0
> > [ 1.158207] [<ffffffff811cc373>] SyS_mount+0x83/0xc0
> > [ 1.158207] [<ffffffff81673cc2>] system_call_fastpath+0x16/0x1b
> > [ 1.158207] ---[ end trace 61981bc62de9f6f4 ]---
> >
> > Signed-off-by: Seiji Aguchi <[email protected]>
> > ---
> > drivers/firmware/efi/efi-pstore.c | 143 +++++++++++++++++++++++++++++++++++---
> > drivers/firmware/efi/efivars.c | 12 ++--
> > drivers/firmware/efi/vars.c | 12 +++-
> > include/linux/efi.h | 2 +
> > 4 files changed, 153 insertions(+), 16 deletions(-)
> >
> > diff --git a/drivers/firmware/efi/efi-pstore.c b/drivers/firmware/efi/efi-pstore.c
> > index 5002d50..ebd5dbc 100644
> > --- a/drivers/firmware/efi/efi-pstore.c
> > +++ b/drivers/firmware/efi/efi-pstore.c
> > @@ -18,14 +18,12 @@ module_param_named(pstore_disable, efivars_pstore_disable, bool, 0644);
> >
> > static int efi_pstore_open(struct pstore_info *psi)
> > {
> > - efivar_entry_iter_begin();
> > psi->data = NULL;
> > return 0;
> > }
> >
> > static int efi_pstore_close(struct pstore_info *psi)
> > {
> > - efivar_entry_iter_end();
> > psi->data = NULL;
> > return 0;
> > }
> > @@ -91,19 +89,125 @@ static int efi_pstore_read_func(struct efivar_entry *entry, void *data)
> > __efivar_entry_get(entry, &entry->var.Attributes,
> > &entry->var.DataSize, entry->var.Data);
> > size = entry->var.DataSize;
> > + memcpy(*cb_data->buf, entry->var.Data, (size_t)min_t(unsigned long,
> > + 1024, size));
> >
> > - *cb_data->buf = kmemdup(entry->var.Data, size, GFP_KERNEL);
> > - if (*cb_data->buf == NULL)
> > - return -ENOMEM;
> > return size;
> > }
> >
> > +/**
> > + * efi_pstore_scan_sysfs_enter
> > + * @entry: scanning entry
> > + * @next: next entry
> > + * @head: list head
> > + */
> > +static void efi_pstore_scan_sysfs_enter(struct efivar_entry *pos,
> > + struct efivar_entry *next,
> > + struct list_head *head)
> > +{
> > + pos->scanning = true;
> > + if (&next->list != head)
> > + next->scanning = true;
> > +}
> > +
> > +/**
> > + * __efi_pstore_scan_sysfs_exit
> > + * @entry: deleting entry
> > + * @turn_off_scanning: Check if a scanning flag should be turned off
> > + */
> > +static inline void __efi_pstore_scan_sysfs_exit(struct efivar_entry *entry,
> > + bool turn_off_scanning)
> > +{
> > + if (entry->deleting) {
> > + list_del(&entry->list);
> > + efivar_entry_iter_end();
> > + efivar_unregister(entry);
> > + efivar_entry_iter_begin();
> > + } else if (turn_off_scanning)
> > + entry->scanning = false;
> > +}
> > +
> > +/**
> > + * efi_pstore_scan_sysfs_exit
> > + * @pos: scanning entry
> > + * @next: next entry
> > + * @head: list head
> > + * @stop: a flag checking if scanning will stop
> > + */
> > +static void efi_pstore_scan_sysfs_exit(struct efivar_entry *pos,
> > + struct efivar_entry *next,
> > + struct list_head *head, bool stop)
> > +{
> > + __efi_pstore_scan_sysfs_exit(pos, true);
> > + if (stop)
> > + __efi_pstore_scan_sysfs_exit(next, &next->list != head);
> > +}
> > +
> > +/**
> > + * efi_pstore_sysfs_entry_iter
> > + *
> > + * @data: function-specific data to pass to callback
> > + * @pos: entry to begin iterating from
> > + *
> > + * You MUST call efivar_enter_iter_begin() before this function, and
> > + * efivar_entry_iter_end() afterwards.
> > + *
> > + * It is possible to begin iteration from an arbitrary entry within
> > + * the list by passing @pos. @pos is updated on return to point to
> > + * the next entry of the last one passed to efi_pstore_read_func().
> > + * To begin iterating from the beginning of the list @pos must be %NULL.
> > + */
> > +static int efi_pstore_sysfs_entry_iter(void *data, struct efivar_entry **pos)
> > +{
> > + struct efivar_entry *entry, *n;
> > + struct list_head *head = &efivar_sysfs_list;
> > + int size = 0;
> > +
> > + if (!*pos) {
> > + list_for_each_entry_safe(entry, n, head, list) {
> > + efi_pstore_scan_sysfs_enter(entry, n, head);
> > +
> > + size = efi_pstore_read_func(entry, data);
> > + efi_pstore_scan_sysfs_exit(entry, n, head, size < 0);
> > + if (size)
> > + break;
> > + }
> > + *pos = n;
> > + return size;
> > + }
> > +
> > + list_for_each_entry_safe_from((*pos), n, head, list) {
> > + efi_pstore_scan_sysfs_enter((*pos), n, head);
> > +
> > + size = efi_pstore_read_func((*pos), data);
> > + efi_pstore_scan_sysfs_exit((*pos), n, head, size < 0);
> > + if (size)
> > + break;
> > + }
> > + *pos = n;
> > + return size;
> > +}
> > +
> > +/**
> > + * efi_pstore_read
> > + *
> > + * This function returns a size of NVRAM entry logged via efi_pstore_write().
> > + * The meaning and behavior of efi_pstore/pstore are as below.
> > + *
> > + * size > 0: Got data of an entry logged via efi_pstore_write() successfully,
> > + * and pstore filesystem will continue reading subsequent entries.
> > + * size == 0: Entry was not logged via efi_pstore_write(),
> > + * and efi_pstore driver will continue reading subsequent entries.
> > + * size < 0: Failed to get data of entry logging via efi_pstore_write(),
> > + * and pstore will stop reading entry.
> > + */
> > static ssize_t efi_pstore_read(u64 *id, enum pstore_type_id *type,
> > int *count, struct timespec *timespec,
> > char **buf, bool *compressed,
> > struct pstore_info *psi)
> > {
> > struct pstore_read_data data;
> > + ssize_t size;
> >
> > data.id = id;
> > data.type = type;
> > @@ -112,8 +216,17 @@ static ssize_t efi_pstore_read(u64 *id, enum pstore_type_id *type,
> > data.compressed = compressed;
> > data.buf = buf;
> >
> > - return __efivar_entry_iter(efi_pstore_read_func, &efivar_sysfs_list, &data,
> > - (struct efivar_entry **)&psi->data);
> > + *data.buf = kzalloc(1024, GFP_KERNEL);
> > + if (!*data.buf)
> > + return -ENOMEM;
> > +
> > + efivar_entry_iter_begin();
> > + size = efi_pstore_sysfs_entry_iter(&data,
> > + (struct efivar_entry **)&psi->data);
> > + efivar_entry_iter_end();
> > + if (size <= 0)
> > + kfree(*data.buf);
> > + return size;
> > }
> >
> > static int efi_pstore_write(enum pstore_type_id type,
> > @@ -184,9 +297,17 @@ static int efi_pstore_erase_func(struct efivar_entry *entry, void *data)
> > return 0;
> > }
> >
> > + if (entry->scanning) {
> > + /*
> > + * Skip deletion because this entry will be deleted
> > + * after scanning is completed.
> > + */
> > + entry->deleting = true;
> > + } else
> > + list_del(&entry->list);
> > +
> > /* found */
> > __efivar_entry_delete(entry);
> > - list_del(&entry->list);
> >
> > return 1;
> > }
> > @@ -214,10 +335,12 @@ static int efi_pstore_erase(enum pstore_type_id type, u64 id, int count,
> >
> > efivar_entry_iter_begin();
> > found = __efivar_entry_iter(efi_pstore_erase_func, &efivar_sysfs_list, &edata, &entry);
> > - efivar_entry_iter_end();
> >
> > - if (found)
> > + if (found && !entry->scanning) {
> > + efivar_entry_iter_end();
> > efivar_unregister(entry);
> > + } else
> > + efivar_entry_iter_end();
> >
> > return 0;
> > }
> > diff --git a/drivers/firmware/efi/efivars.c b/drivers/firmware/efi/efivars.c
> > index 8a7432a..8c5a61a 100644
> > --- a/drivers/firmware/efi/efivars.c
> > +++ b/drivers/firmware/efi/efivars.c
> > @@ -383,12 +383,16 @@ static ssize_t efivar_delete(struct file *filp, struct kobject *kobj,
> > else if (__efivar_entry_delete(entry))
> > err = -EIO;
> >
> > - efivar_entry_iter_end();
> > -
> > - if (err)
> > + if (err) {
> > + efivar_entry_iter_end();
> > return err;
> > + }
> >
> > - efivar_unregister(entry);
> > + if (!entry->scanning) {
> > + efivar_entry_iter_end();
> > + efivar_unregister(entry);
> > + } else
> > + efivar_entry_iter_end();
> >
> > /* It's dead Jim.... */
> > return count;
> > diff --git a/drivers/firmware/efi/vars.c b/drivers/firmware/efi/vars.c
> > index 391c67b..b22659c 100644
> > --- a/drivers/firmware/efi/vars.c
> > +++ b/drivers/firmware/efi/vars.c
> > @@ -683,8 +683,16 @@ struct efivar_entry *efivar_entry_find(efi_char16_t *name, efi_guid_t guid,
> > if (!found)
> > return NULL;
> >
> > - if (remove)
> > - list_del(&entry->list);
> > + if (remove) {
> > + if (entry->scanning) {
> > + /*
> > + * The entry will be deleted
> > + * after scanning is completed.
> > + */
> > + entry->deleting = true;
> > + } else
> > + list_del(&entry->list);
> > + }
> >
> > return entry;
> > }
> > diff --git a/include/linux/efi.h b/include/linux/efi.h
> > index 5f8f176..04088fb 100644
> > --- a/include/linux/efi.h
> > +++ b/include/linux/efi.h
> > @@ -782,6 +782,8 @@ struct efivar_entry {
> > struct efi_variable var;
> > struct list_head list;
> > struct kobject kobj;
> > + bool scanning;
> > + bool deleting;
> > };
> >
> > extern struct list_head efivar_sysfs_list;
>
>
> --
> Best,
> Madper Xie.
On Fri, 11 Oct, at 02:29:07PM, Seiji Aguchi wrote:
> Change from v2:
> - Move dynamic memory allocation to efi_pstore_read() before holding
> efivars->lock to protect entry->var.Data.
> - Access to entry->scanning while holding efivars->lock.
> - Move a comment about a returned value from efi_pstore_read_func() to
> efi_pstore_read() because "size < 0" case may happen in efi_pstore_read().
It seems to me that because you're no longer dropping __efivars->lock
when reading from the EFI variable store, you actually don't need all
the ->scanning and ->deleting logic because anything that sets those
flags runs to completion while holding the lock.
Can't the patch be simplified to just allocating data.buf at the
beginning of efi_pstore_read()? Also, it would be a good idea to
introduce a #define for the 1024 magic number, e.g.
#define EFIVARS_DATA_SIZE_MAX 1024
--
Matt Fleming, Intel Open Source Technology Center
Oops, It seems my mu4e(a email client for emacs)'s auto-indent breaks the
patch... I apologize for this...
[email protected] writes:
> Hi Madper,
>
> I tested this patch on 3.12-rc4.
> Could you please send me the log when you failed to apply?
>
> Seiji
>
>> -----Original Message-----
>> From: Madper Xie [mailto:[email protected]]
>> Sent: Thursday, October 17, 2013 1:54 AM
>> To: Seiji Aguchi
>> Cc: [email protected]; [email protected]; [email protected]; [email protected]; Tomoki Sekiyama; dle-
>> [email protected]
>> Subject: Re: [PATCH v3] efivars,efi-pstore: Hold off deletion of sysfs entry until, the scan is completed
>>
>> Howdy Seiji,
>> I failed appily this patch to both 3.12-rc2 and 3.12-rc4. Could you
>> please let me know which is the right tree for this patch?
>>
>> Thanks,
>> Madper.
>> [email protected] writes:
>>
>> > Change from v2:
>> > - Move dynamic memory allocation to efi_pstore_read() before holding
>> > efivars->lock to protect entry->var.Data.
>> > - Access to entry->scanning while holding efivars->lock.
>> > - Move a comment about a returned value from efi_pstore_read_func() to
>> > efi_pstore_read() because "size < 0" case may happen in efi_pstore_read().
>> >
>> > Currently, when mounting pstore file system, a read callback of efi_pstore
>> > driver runs mutiple times as below.
>> >
>> > - In the first read callback, scan efivar_sysfs_list from head and pass
>> > a kmsg buffer of a entry to an upper pstore layer.
>> > - In the second read callback, rescan efivar_sysfs_list from the entry and pass
>> > another kmsg buffer to it.
>> > - Repeat the scan and pass until the end of efivar_sysfs_list.
>> >
>> > In this process, an entry is read across the multiple read function calls.
>> > To avoid race between the read and erasion, the whole process above is
>> > protected by a spinlock, holding in open() and releasing in close().
>> >
>> > At the same time, kmemdup() is called to pass the buffer to pstore filesystem
>> > during it.
>> > And then, it causes a following lockdep warning.
>> >
>> > To make the dynamic memory allocation runnable without taking spinlock,
>> > holding off a deletion of sysfs entry if it happens while scanning it
>> > via efi_pstore, and deleting it after the scan is completed.
>> >
>> > To implement it, this patch introduces two flags, scanning and deleting,
>> > to efivar_entry.
>> >
>> > [ 1.143710] ------------[ cut here ]------------
>> > [ 1.144058] WARNING: CPU: 1 PID: 1 at kernel/lockdep.c:2740
>> > lockdep_trace_alloc+0x104/0x110()
>> > [ 1.144058] DEBUG_LOCKS_WARN_ON(irqs_disabled_flags(flags))
>> > [ 1.144058] Modules linked in:
>> >
>> > [ 1.144058] CPU: 1 PID: 1 Comm: systemd Not tainted 3.11.0-rc5 #2
>> > [ 1.144058] 0000000000000009 ffff8800797e9ae0 ffffffff816614a5
>> > ffff8800797e9b28
>> > [ 1.144058] ffff8800797e9b18 ffffffff8105510d 0000000000000080
>> > 0000000000000046
>> > [ 1.144058] 00000000000000d0 00000000000003af ffffffff81ccd0c0
>> > ffff8800797e9b78
>> > [ 1.144058] Call Trace:
>> > [ 1.144058] [<ffffffff816614a5>] dump_stack+0x54/0x74
>> > [ 1.144058] [<ffffffff8105510d>] warn_slowpath_common+0x7d/0xa0
>> > [ 1.144058] [<ffffffff8105517c>] warn_slowpath_fmt+0x4c/0x50
>> > [ 1.144058] [<ffffffff8131290f>] ? vsscanf+0x57f/0x7b0
>> > [ 1.144058] [<ffffffff810bbd74>] lockdep_trace_alloc+0x104/0x110
>> > [ 1.144058] [<ffffffff81192da0>] __kmalloc_track_caller+0x50/0x280
>> > [ 1.144058] [<ffffffff815147bb>] ?
>> > efi_pstore_read_func.part.1+0x12b/0x170
>> > [ 1.144058] [<ffffffff8115b260>] kmemdup+0x20/0x50
>> > [ 1.144058] [<ffffffff815147bb>] efi_pstore_read_func.part.1+0x12b/0x170
>> > [ 1.144058] [<ffffffff81514800>] ?
>> > efi_pstore_read_func.part.1+0x170/0x170
>> > [ 1.144058] [<ffffffff815148b4>] efi_pstore_read_func+0xb4/0xe0
>> > [ 1.144058] [<ffffffff81512b7b>] __efivar_entry_iter+0xfb/0x120
>> > [ 1.144058] [<ffffffff8151428f>] efi_pstore_read+0x3f/0x50
>> > [ 1.144058] [<ffffffff8128d7ba>] pstore_get_records+0x9a/0x150
>> > [ 1.158207] [<ffffffff812af25c>] ? selinux_d_instantiate+0x1c/0x20
>> > [ 1.158207] [<ffffffff8128ce30>] ? parse_options+0x80/0x80
>> > [ 1.158207] [<ffffffff8128ced5>] pstore_fill_super+0xa5/0xc0
>> > [ 1.158207] [<ffffffff811ae7d2>] mount_single+0xa2/0xd0
>> > [ 1.158207] [<ffffffff8128ccf8>] pstore_mount+0x18/0x20
>> > [ 1.158207] [<ffffffff811ae8b9>] mount_fs+0x39/0x1b0
>> > [ 1.158207] [<ffffffff81160550>] ? __alloc_percpu+0x10/0x20
>> > [ 1.158207] [<ffffffff811c9493>] vfs_kern_mount+0x63/0xf0
>> > [ 1.158207] [<ffffffff811cbb0e>] do_mount+0x23e/0xa20
>> > [ 1.158207] [<ffffffff8115b51b>] ? strndup_user+0x4b/0xf0
>> > [ 1.158207] [<ffffffff811cc373>] SyS_mount+0x83/0xc0
>> > [ 1.158207] [<ffffffff81673cc2>] system_call_fastpath+0x16/0x1b
>> > [ 1.158207] ---[ end trace 61981bc62de9f6f4 ]---
>> >
>> > Signed-off-by: Seiji Aguchi <[email protected]>
>> > ---
>> > drivers/firmware/efi/efi-pstore.c | 143 +++++++++++++++++++++++++++++++++++---
>> > drivers/firmware/efi/efivars.c | 12 ++--
>> > drivers/firmware/efi/vars.c | 12 +++-
>> > include/linux/efi.h | 2 +
>> > 4 files changed, 153 insertions(+), 16 deletions(-)
>> >
>> > diff --git a/drivers/firmware/efi/efi-pstore.c b/drivers/firmware/efi/efi-pstore.c
>> > index 5002d50..ebd5dbc 100644
>> > --- a/drivers/firmware/efi/efi-pstore.c
>> > +++ b/drivers/firmware/efi/efi-pstore.c
>> > @@ -18,14 +18,12 @@ module_param_named(pstore_disable, efivars_pstore_disable, bool, 0644);
>> >
>> > static int efi_pstore_open(struct pstore_info *psi)
>> > {
>> > - efivar_entry_iter_begin();
>> > psi->data = NULL;
>> > return 0;
>> > }
>> >
>> > static int efi_pstore_close(struct pstore_info *psi)
>> > {
>> > - efivar_entry_iter_end();
>> > psi->data = NULL;
>> > return 0;
>> > }
>> > @@ -91,19 +89,125 @@ static int efi_pstore_read_func(struct efivar_entry *entry, void *data)
>> > __efivar_entry_get(entry, &entry->var.Attributes,
>> > &entry->var.DataSize, entry->var.Data);
>> > size = entry->var.DataSize;
>> > + memcpy(*cb_data->buf, entry->var.Data, (size_t)min_t(unsigned long,
>> > + 1024, size));
>> >
>> > - *cb_data->buf = kmemdup(entry->var.Data, size, GFP_KERNEL);
>> > - if (*cb_data->buf == NULL)
>> > - return -ENOMEM;
>> > return size;
>> > }
>> >
>> > +/**
>> > + * efi_pstore_scan_sysfs_enter
>> > + * @entry: scanning entry
>> > + * @next: next entry
>> > + * @head: list head
>> > + */
>> > +static void efi_pstore_scan_sysfs_enter(struct efivar_entry *pos,
>> > + struct efivar_entry *next,
>> > + struct list_head *head)
>> > +{
>> > + pos->scanning = true;
>> > + if (&next->list != head)
>> > + next->scanning = true;
>> > +}
>> > +
>> > +/**
>> > + * __efi_pstore_scan_sysfs_exit
>> > + * @entry: deleting entry
>> > + * @turn_off_scanning: Check if a scanning flag should be turned off
>> > + */
>> > +static inline void __efi_pstore_scan_sysfs_exit(struct efivar_entry *entry,
>> > + bool turn_off_scanning)
>> > +{
>> > + if (entry->deleting) {
>> > + list_del(&entry->list);
>> > + efivar_entry_iter_end();
>> > + efivar_unregister(entry);
>> > + efivar_entry_iter_begin();
>> > + } else if (turn_off_scanning)
>> > + entry->scanning = false;
>> > +}
>> > +
>> > +/**
>> > + * efi_pstore_scan_sysfs_exit
>> > + * @pos: scanning entry
>> > + * @next: next entry
>> > + * @head: list head
>> > + * @stop: a flag checking if scanning will stop
>> > + */
>> > +static void efi_pstore_scan_sysfs_exit(struct efivar_entry *pos,
>> > + struct efivar_entry *next,
>> > + struct list_head *head, bool stop)
>> > +{
>> > + __efi_pstore_scan_sysfs_exit(pos, true);
>> > + if (stop)
>> > + __efi_pstore_scan_sysfs_exit(next, &next->list != head);
>> > +}
>> > +
>> > +/**
>> > + * efi_pstore_sysfs_entry_iter
>> > + *
>> > + * @data: function-specific data to pass to callback
>> > + * @pos: entry to begin iterating from
>> > + *
>> > + * You MUST call efivar_enter_iter_begin() before this function, and
>> > + * efivar_entry_iter_end() afterwards.
>> > + *
>> > + * It is possible to begin iteration from an arbitrary entry within
>> > + * the list by passing @pos. @pos is updated on return to point to
>> > + * the next entry of the last one passed to efi_pstore_read_func().
>> > + * To begin iterating from the beginning of the list @pos must be %NULL.
>> > + */
>> > +static int efi_pstore_sysfs_entry_iter(void *data, struct efivar_entry **pos)
>> > +{
>> > + struct efivar_entry *entry, *n;
>> > + struct list_head *head = &efivar_sysfs_list;
>> > + int size = 0;
>> > +
>> > + if (!*pos) {
>> > + list_for_each_entry_safe(entry, n, head, list) {
>> > + efi_pstore_scan_sysfs_enter(entry, n, head);
>> > +
>> > + size = efi_pstore_read_func(entry, data);
>> > + efi_pstore_scan_sysfs_exit(entry, n, head, size < 0);
>> > + if (size)
>> > + break;
>> > + }
>> > + *pos = n;
>> > + return size;
>> > + }
>> > +
>> > + list_for_each_entry_safe_from((*pos), n, head, list) {
>> > + efi_pstore_scan_sysfs_enter((*pos), n, head);
>> > +
>> > + size = efi_pstore_read_func((*pos), data);
>> > + efi_pstore_scan_sysfs_exit((*pos), n, head, size < 0);
>> > + if (size)
>> > + break;
>> > + }
>> > + *pos = n;
>> > + return size;
>> > +}
>> > +
>> > +/**
>> > + * efi_pstore_read
>> > + *
>> > + * This function returns a size of NVRAM entry logged via efi_pstore_write().
>> > + * The meaning and behavior of efi_pstore/pstore are as below.
>> > + *
>> > + * size > 0: Got data of an entry logged via efi_pstore_write() successfully,
>> > + * and pstore filesystem will continue reading subsequent entries.
>> > + * size == 0: Entry was not logged via efi_pstore_write(),
>> > + * and efi_pstore driver will continue reading subsequent entries.
>> > + * size < 0: Failed to get data of entry logging via efi_pstore_write(),
>> > + * and pstore will stop reading entry.
>> > + */
>> > static ssize_t efi_pstore_read(u64 *id, enum pstore_type_id *type,
>> > int *count, struct timespec *timespec,
>> > char **buf, bool *compressed,
>> > struct pstore_info *psi)
>> > {
>> > struct pstore_read_data data;
>> > + ssize_t size;
>> >
>> > data.id = id;
>> > data.type = type;
>> > @@ -112,8 +216,17 @@ static ssize_t efi_pstore_read(u64 *id, enum pstore_type_id *type,
>> > data.compressed = compressed;
>> > data.buf = buf;
>> >
>> > - return __efivar_entry_iter(efi_pstore_read_func, &efivar_sysfs_list, &data,
>> > - (struct efivar_entry **)&psi->data);
>> > + *data.buf = kzalloc(1024, GFP_KERNEL);
>> > + if (!*data.buf)
>> > + return -ENOMEM;
>> > +
>> > + efivar_entry_iter_begin();
>> > + size = efi_pstore_sysfs_entry_iter(&data,
>> > + (struct efivar_entry **)&psi->data);
>> > + efivar_entry_iter_end();
>> > + if (size <= 0)
>> > + kfree(*data.buf);
>> > + return size;
>> > }
>> >
>> > static int efi_pstore_write(enum pstore_type_id type,
>> > @@ -184,9 +297,17 @@ static int efi_pstore_erase_func(struct efivar_entry *entry, void *data)
>> > return 0;
>> > }
>> >
>> > + if (entry->scanning) {
>> > + /*
>> > + * Skip deletion because this entry will be deleted
>> > + * after scanning is completed.
>> > + */
>> > + entry->deleting = true;
>> > + } else
>> > + list_del(&entry->list);
>> > +
>> > /* found */
>> > __efivar_entry_delete(entry);
>> > - list_del(&entry->list);
>> >
>> > return 1;
>> > }
>> > @@ -214,10 +335,12 @@ static int efi_pstore_erase(enum pstore_type_id type, u64 id, int count,
>> >
>> > efivar_entry_iter_begin();
>> > found = __efivar_entry_iter(efi_pstore_erase_func, &efivar_sysfs_list, &edata, &entry);
>> > - efivar_entry_iter_end();
>> >
>> > - if (found)
>> > + if (found && !entry->scanning) {
>> > + efivar_entry_iter_end();
>> > efivar_unregister(entry);
>> > + } else
>> > + efivar_entry_iter_end();
>> >
>> > return 0;
>> > }
>> > diff --git a/drivers/firmware/efi/efivars.c b/drivers/firmware/efi/efivars.c
>> > index 8a7432a..8c5a61a 100644
>> > --- a/drivers/firmware/efi/efivars.c
>> > +++ b/drivers/firmware/efi/efivars.c
>> > @@ -383,12 +383,16 @@ static ssize_t efivar_delete(struct file *filp, struct kobject *kobj,
>> > else if (__efivar_entry_delete(entry))
>> > err = -EIO;
>> >
>> > - efivar_entry_iter_end();
>> > -
>> > - if (err)
>> > + if (err) {
>> > + efivar_entry_iter_end();
>> > return err;
>> > + }
>> >
>> > - efivar_unregister(entry);
>> > + if (!entry->scanning) {
>> > + efivar_entry_iter_end();
>> > + efivar_unregister(entry);
>> > + } else
>> > + efivar_entry_iter_end();
>> >
>> > /* It's dead Jim.... */
>> > return count;
>> > diff --git a/drivers/firmware/efi/vars.c b/drivers/firmware/efi/vars.c
>> > index 391c67b..b22659c 100644
>> > --- a/drivers/firmware/efi/vars.c
>> > +++ b/drivers/firmware/efi/vars.c
>> > @@ -683,8 +683,16 @@ struct efivar_entry *efivar_entry_find(efi_char16_t *name, efi_guid_t guid,
>> > if (!found)
>> > return NULL;
>> >
>> > - if (remove)
>> > - list_del(&entry->list);
>> > + if (remove) {
>> > + if (entry->scanning) {
>> > + /*
>> > + * The entry will be deleted
>> > + * after scanning is completed.
>> > + */
>> > + entry->deleting = true;
>> > + } else
>> > + list_del(&entry->list);
>> > + }
>> >
>> > return entry;
>> > }
>> > diff --git a/include/linux/efi.h b/include/linux/efi.h
>> > index 5f8f176..04088fb 100644
>> > --- a/include/linux/efi.h
>> > +++ b/include/linux/efi.h
>> > @@ -782,6 +782,8 @@ struct efivar_entry {
>> > struct efi_variable var;
>> > struct list_head list;
>> > struct kobject kobj;
>> > + bool scanning;
>> > + bool deleting;
>> > };
>> >
>> > extern struct list_head efivar_sysfs_list;
>>
>>
>> --
>> Best,
>> Madper Xie.
--
Best,
Madper Xie.
Hi folks,
I tested it on my DELL XPS desktop. And it won't show any warnings
when I mounting pstore and deleting pstore items after this patch
applied.
Tested-by: Madper Xie
[email protected] writes:
> Oops, It seems my mu4e(a email client for emacs)'s auto-indent breaks the
> patch... I apologize for this...
>
> [email protected] writes:
>
>> Hi Madper,
>>
>> I tested this patch on 3.12-rc4.
>> Could you please send me the log when you failed to apply?
>>
>> Seiji
>>
>>> -----Original Message-----
>>> From: Madper Xie [mailto:[email protected]]
>>> Sent: Thursday, October 17, 2013 1:54 AM
>>> To: Seiji Aguchi
>>> Cc: [email protected]; [email protected]; [email protected]; [email protected]; Tomoki Sekiyama; dle-
>>> [email protected]
>>> Subject: Re: [PATCH v3] efivars,efi-pstore: Hold off deletion of sysfs entry until, the scan is completed
>>>
>>> Howdy Seiji,
>>> I failed appily this patch to both 3.12-rc2 and 3.12-rc4. Could you
>>> please let me know which is the right tree for this patch?
>>>
>>> Thanks,
>>> Madper.
>>> [email protected] writes:
>>>
>>> > Change from v2:
>>> > - Move dynamic memory allocation to efi_pstore_read() before holding
>>> > efivars->lock to protect entry->var.Data.
>>> > - Access to entry->scanning while holding efivars->lock.
>>> > - Move a comment about a returned value from efi_pstore_read_func() to
>>> > efi_pstore_read() because "size < 0" case may happen in efi_pstore_read().
>>> >
>>> > Currently, when mounting pstore file system, a read callback of efi_pstore
>>> > driver runs mutiple times as below.
>>> >
>>> > - In the first read callback, scan efivar_sysfs_list from head and pass
>>> > a kmsg buffer of a entry to an upper pstore layer.
>>> > - In the second read callback, rescan efivar_sysfs_list from the entry and pass
>>> > another kmsg buffer to it.
>>> > - Repeat the scan and pass until the end of efivar_sysfs_list.
>>> >
>>> > In this process, an entry is read across the multiple read function calls.
>>> > To avoid race between the read and erasion, the whole process above is
>>> > protected by a spinlock, holding in open() and releasing in close().
>>> >
>>> > At the same time, kmemdup() is called to pass the buffer to pstore filesystem
>>> > during it.
>>> > And then, it causes a following lockdep warning.
>>> >
>>> > To make the dynamic memory allocation runnable without taking spinlock,
>>> > holding off a deletion of sysfs entry if it happens while scanning it
>>> > via efi_pstore, and deleting it after the scan is completed.
>>> >
>>> > To implement it, this patch introduces two flags, scanning and deleting,
>>> > to efivar_entry.
>>> >
>>> > [ 1.143710] ------------[ cut here ]------------
>>> > [ 1.144058] WARNING: CPU: 1 PID: 1 at kernel/lockdep.c:2740
>>> > lockdep_trace_alloc+0x104/0x110()
>>> > [ 1.144058] DEBUG_LOCKS_WARN_ON(irqs_disabled_flags(flags))
>>> > [ 1.144058] Modules linked in:
>>> >
>>> > [ 1.144058] CPU: 1 PID: 1 Comm: systemd Not tainted 3.11.0-rc5 #2
>>> > [ 1.144058] 0000000000000009 ffff8800797e9ae0 ffffffff816614a5
>>> > ffff8800797e9b28
>>> > [ 1.144058] ffff8800797e9b18 ffffffff8105510d 0000000000000080
>>> > 0000000000000046
>>> > [ 1.144058] 00000000000000d0 00000000000003af ffffffff81ccd0c0
>>> > ffff8800797e9b78
>>> > [ 1.144058] Call Trace:
>>> > [ 1.144058] [<ffffffff816614a5>] dump_stack+0x54/0x74
>>> > [ 1.144058] [<ffffffff8105510d>] warn_slowpath_common+0x7d/0xa0
>>> > [ 1.144058] [<ffffffff8105517c>] warn_slowpath_fmt+0x4c/0x50
>>> > [ 1.144058] [<ffffffff8131290f>] ? vsscanf+0x57f/0x7b0
>>> > [ 1.144058] [<ffffffff810bbd74>] lockdep_trace_alloc+0x104/0x110
>>> > [ 1.144058] [<ffffffff81192da0>] __kmalloc_track_caller+0x50/0x280
>>> > [ 1.144058] [<ffffffff815147bb>] ?
>>> > efi_pstore_read_func.part.1+0x12b/0x170
>>> > [ 1.144058] [<ffffffff8115b260>] kmemdup+0x20/0x50
>>> > [ 1.144058] [<ffffffff815147bb>] efi_pstore_read_func.part.1+0x12b/0x170
>>> > [ 1.144058] [<ffffffff81514800>] ?
>>> > efi_pstore_read_func.part.1+0x170/0x170
>>> > [ 1.144058] [<ffffffff815148b4>] efi_pstore_read_func+0xb4/0xe0
>>> > [ 1.144058] [<ffffffff81512b7b>] __efivar_entry_iter+0xfb/0x120
>>> > [ 1.144058] [<ffffffff8151428f>] efi_pstore_read+0x3f/0x50
>>> > [ 1.144058] [<ffffffff8128d7ba>] pstore_get_records+0x9a/0x150
>>> > [ 1.158207] [<ffffffff812af25c>] ? selinux_d_instantiate+0x1c/0x20
>>> > [ 1.158207] [<ffffffff8128ce30>] ? parse_options+0x80/0x80
>>> > [ 1.158207] [<ffffffff8128ced5>] pstore_fill_super+0xa5/0xc0
>>> > [ 1.158207] [<ffffffff811ae7d2>] mount_single+0xa2/0xd0
>>> > [ 1.158207] [<ffffffff8128ccf8>] pstore_mount+0x18/0x20
>>> > [ 1.158207] [<ffffffff811ae8b9>] mount_fs+0x39/0x1b0
>>> > [ 1.158207] [<ffffffff81160550>] ? __alloc_percpu+0x10/0x20
>>> > [ 1.158207] [<ffffffff811c9493>] vfs_kern_mount+0x63/0xf0
>>> > [ 1.158207] [<ffffffff811cbb0e>] do_mount+0x23e/0xa20
>>> > [ 1.158207] [<ffffffff8115b51b>] ? strndup_user+0x4b/0xf0
>>> > [ 1.158207] [<ffffffff811cc373>] SyS_mount+0x83/0xc0
>>> > [ 1.158207] [<ffffffff81673cc2>] system_call_fastpath+0x16/0x1b
>>> > [ 1.158207] ---[ end trace 61981bc62de9f6f4 ]---
>>> >
>>> > Signed-off-by: Seiji Aguchi <[email protected]>
>>> > ---
>>> > drivers/firmware/efi/efi-pstore.c | 143 +++++++++++++++++++++++++++++++++++---
>>> > drivers/firmware/efi/efivars.c | 12 ++--
>>> > drivers/firmware/efi/vars.c | 12 +++-
>>> > include/linux/efi.h | 2 +
>>> > 4 files changed, 153 insertions(+), 16 deletions(-)
>>> >
>>> > diff --git a/drivers/firmware/efi/efi-pstore.c b/drivers/firmware/efi/efi-pstore.c
>>> > index 5002d50..ebd5dbc 100644
>>> > --- a/drivers/firmware/efi/efi-pstore.c
>>> > +++ b/drivers/firmware/efi/efi-pstore.c
>>> > @@ -18,14 +18,12 @@ module_param_named(pstore_disable, efivars_pstore_disable, bool, 0644);
>>> >
>>> > static int efi_pstore_open(struct pstore_info *psi)
>>> > {
>>> > - efivar_entry_iter_begin();
>>> > psi->data = NULL;
>>> > return 0;
>>> > }
>>> >
>>> > static int efi_pstore_close(struct pstore_info *psi)
>>> > {
>>> > - efivar_entry_iter_end();
>>> > psi->data = NULL;
>>> > return 0;
>>> > }
>>> > @@ -91,19 +89,125 @@ static int efi_pstore_read_func(struct efivar_entry *entry, void *data)
>>> > __efivar_entry_get(entry, &entry->var.Attributes,
>>> > &entry->var.DataSize, entry->var.Data);
>>> > size = entry->var.DataSize;
>>> > + memcpy(*cb_data->buf, entry->var.Data, (size_t)min_t(unsigned long,
>>> > + 1024, size));
>>> >
>>> > - *cb_data->buf = kmemdup(entry->var.Data, size, GFP_KERNEL);
>>> > - if (*cb_data->buf == NULL)
>>> > - return -ENOMEM;
>>> > return size;
>>> > }
>>> >
>>> > +/**
>>> > + * efi_pstore_scan_sysfs_enter
>>> > + * @entry: scanning entry
>>> > + * @next: next entry
>>> > + * @head: list head
>>> > + */
>>> > +static void efi_pstore_scan_sysfs_enter(struct efivar_entry *pos,
>>> > + struct efivar_entry *next,
>>> > + struct list_head *head)
>>> > +{
>>> > + pos->scanning = true;
>>> > + if (&next->list != head)
>>> > + next->scanning = true;
>>> > +}
>>> > +
>>> > +/**
>>> > + * __efi_pstore_scan_sysfs_exit
>>> > + * @entry: deleting entry
>>> > + * @turn_off_scanning: Check if a scanning flag should be turned off
>>> > + */
>>> > +static inline void __efi_pstore_scan_sysfs_exit(struct efivar_entry *entry,
>>> > + bool turn_off_scanning)
>>> > +{
>>> > + if (entry->deleting) {
>>> > + list_del(&entry->list);
>>> > + efivar_entry_iter_end();
>>> > + efivar_unregister(entry);
>>> > + efivar_entry_iter_begin();
>>> > + } else if (turn_off_scanning)
>>> > + entry->scanning = false;
>>> > +}
>>> > +
>>> > +/**
>>> > + * efi_pstore_scan_sysfs_exit
>>> > + * @pos: scanning entry
>>> > + * @next: next entry
>>> > + * @head: list head
>>> > + * @stop: a flag checking if scanning will stop
>>> > + */
>>> > +static void efi_pstore_scan_sysfs_exit(struct efivar_entry *pos,
>>> > + struct efivar_entry *next,
>>> > + struct list_head *head, bool stop)
>>> > +{
>>> > + __efi_pstore_scan_sysfs_exit(pos, true);
>>> > + if (stop)
>>> > + __efi_pstore_scan_sysfs_exit(next, &next->list != head);
>>> > +}
>>> > +
>>> > +/**
>>> > + * efi_pstore_sysfs_entry_iter
>>> > + *
>>> > + * @data: function-specific data to pass to callback
>>> > + * @pos: entry to begin iterating from
>>> > + *
>>> > + * You MUST call efivar_enter_iter_begin() before this function, and
>>> > + * efivar_entry_iter_end() afterwards.
>>> > + *
>>> > + * It is possible to begin iteration from an arbitrary entry within
>>> > + * the list by passing @pos. @pos is updated on return to point to
>>> > + * the next entry of the last one passed to efi_pstore_read_func().
>>> > + * To begin iterating from the beginning of the list @pos must be %NULL.
>>> > + */
>>> > +static int efi_pstore_sysfs_entry_iter(void *data, struct efivar_entry **pos)
>>> > +{
>>> > + struct efivar_entry *entry, *n;
>>> > + struct list_head *head = &efivar_sysfs_list;
>>> > + int size = 0;
>>> > +
>>> > + if (!*pos) {
>>> > + list_for_each_entry_safe(entry, n, head, list) {
>>> > + efi_pstore_scan_sysfs_enter(entry, n, head);
>>> > +
>>> > + size = efi_pstore_read_func(entry, data);
>>> > + efi_pstore_scan_sysfs_exit(entry, n, head, size < 0);
>>> > + if (size)
>>> > + break;
>>> > + }
>>> > + *pos = n;
>>> > + return size;
>>> > + }
>>> > +
>>> > + list_for_each_entry_safe_from((*pos), n, head, list) {
>>> > + efi_pstore_scan_sysfs_enter((*pos), n, head);
>>> > +
>>> > + size = efi_pstore_read_func((*pos), data);
>>> > + efi_pstore_scan_sysfs_exit((*pos), n, head, size < 0);
>>> > + if (size)
>>> > + break;
>>> > + }
>>> > + *pos = n;
>>> > + return size;
>>> > +}
>>> > +
>>> > +/**
>>> > + * efi_pstore_read
>>> > + *
>>> > + * This function returns a size of NVRAM entry logged via efi_pstore_write().
>>> > + * The meaning and behavior of efi_pstore/pstore are as below.
>>> > + *
>>> > + * size > 0: Got data of an entry logged via efi_pstore_write() successfully,
>>> > + * and pstore filesystem will continue reading subsequent entries.
>>> > + * size == 0: Entry was not logged via efi_pstore_write(),
>>> > + * and efi_pstore driver will continue reading subsequent entries.
>>> > + * size < 0: Failed to get data of entry logging via efi_pstore_write(),
>>> > + * and pstore will stop reading entry.
>>> > + */
>>> > static ssize_t efi_pstore_read(u64 *id, enum pstore_type_id *type,
>>> > int *count, struct timespec *timespec,
>>> > char **buf, bool *compressed,
>>> > struct pstore_info *psi)
>>> > {
>>> > struct pstore_read_data data;
>>> > + ssize_t size;
>>> >
>>> > data.id = id;
>>> > data.type = type;
>>> > @@ -112,8 +216,17 @@ static ssize_t efi_pstore_read(u64 *id, enum pstore_type_id *type,
>>> > data.compressed = compressed;
>>> > data.buf = buf;
>>> >
>>> > - return __efivar_entry_iter(efi_pstore_read_func, &efivar_sysfs_list, &data,
>>> > - (struct efivar_entry **)&psi->data);
>>> > + *data.buf = kzalloc(1024, GFP_KERNEL);
>>> > + if (!*data.buf)
>>> > + return -ENOMEM;
>>> > +
>>> > + efivar_entry_iter_begin();
>>> > + size = efi_pstore_sysfs_entry_iter(&data,
>>> > + (struct efivar_entry **)&psi->data);
>>> > + efivar_entry_iter_end();
>>> > + if (size <= 0)
>>> > + kfree(*data.buf);
>>> > + return size;
>>> > }
>>> >
>>> > static int efi_pstore_write(enum pstore_type_id type,
>>> > @@ -184,9 +297,17 @@ static int efi_pstore_erase_func(struct efivar_entry *entry, void *data)
>>> > return 0;
>>> > }
>>> >
>>> > + if (entry->scanning) {
>>> > + /*
>>> > + * Skip deletion because this entry will be deleted
>>> > + * after scanning is completed.
>>> > + */
>>> > + entry->deleting = true;
>>> > + } else
>>> > + list_del(&entry->list);
>>> > +
>>> > /* found */
>>> > __efivar_entry_delete(entry);
>>> > - list_del(&entry->list);
>>> >
>>> > return 1;
>>> > }
>>> > @@ -214,10 +335,12 @@ static int efi_pstore_erase(enum pstore_type_id type, u64 id, int count,
>>> >
>>> > efivar_entry_iter_begin();
>>> > found = __efivar_entry_iter(efi_pstore_erase_func, &efivar_sysfs_list, &edata, &entry);
>>> > - efivar_entry_iter_end();
>>> >
>>> > - if (found)
>>> > + if (found && !entry->scanning) {
>>> > + efivar_entry_iter_end();
>>> > efivar_unregister(entry);
>>> > + } else
>>> > + efivar_entry_iter_end();
>>> >
>>> > return 0;
>>> > }
>>> > diff --git a/drivers/firmware/efi/efivars.c b/drivers/firmware/efi/efivars.c
>>> > index 8a7432a..8c5a61a 100644
>>> > --- a/drivers/firmware/efi/efivars.c
>>> > +++ b/drivers/firmware/efi/efivars.c
>>> > @@ -383,12 +383,16 @@ static ssize_t efivar_delete(struct file *filp, struct kobject *kobj,
>>> > else if (__efivar_entry_delete(entry))
>>> > err = -EIO;
>>> >
>>> > - efivar_entry_iter_end();
>>> > -
>>> > - if (err)
>>> > + if (err) {
>>> > + efivar_entry_iter_end();
>>> > return err;
>>> > + }
>>> >
>>> > - efivar_unregister(entry);
>>> > + if (!entry->scanning) {
>>> > + efivar_entry_iter_end();
>>> > + efivar_unregister(entry);
>>> > + } else
>>> > + efivar_entry_iter_end();
>>> >
>>> > /* It's dead Jim.... */
>>> > return count;
>>> > diff --git a/drivers/firmware/efi/vars.c b/drivers/firmware/efi/vars.c
>>> > index 391c67b..b22659c 100644
>>> > --- a/drivers/firmware/efi/vars.c
>>> > +++ b/drivers/firmware/efi/vars.c
>>> > @@ -683,8 +683,16 @@ struct efivar_entry *efivar_entry_find(efi_char16_t *name, efi_guid_t guid,
>>> > if (!found)
>>> > return NULL;
>>> >
>>> > - if (remove)
>>> > - list_del(&entry->list);
>>> > + if (remove) {
>>> > + if (entry->scanning) {
>>> > + /*
>>> > + * The entry will be deleted
>>> > + * after scanning is completed.
>>> > + */
>>> > + entry->deleting = true;
>>> > + } else
>>> > + list_del(&entry->list);
>>> > + }
>>> >
>>> > return entry;
>>> > }
>>> > diff --git a/include/linux/efi.h b/include/linux/efi.h
>>> > index 5f8f176..04088fb 100644
>>> > --- a/include/linux/efi.h
>>> > +++ b/include/linux/efi.h
>>> > @@ -782,6 +782,8 @@ struct efivar_entry {
>>> > struct efi_variable var;
>>> > struct list_head list;
>>> > struct kobject kobj;
>>> > + bool scanning;
>>> > + bool deleting;
>>> > };
>>> >
>>> > extern struct list_head efivar_sysfs_list;
>>>
>>>
>>> --
>>> Best,
>>> Madper Xie.
--
Best,
Madper Xie.
Hi Madper,
Thank you for assisting me.
But, I need to discuss the implementation with Matt more.
After the discussion, I will post v4 and ask you to test it.
Please wait for a while.
Seiji
> -----Original Message-----
> From: Madper Xie [mailto:[email protected]]
> Sent: Thursday, October 17, 2013 11:07 AM
> To: Madper Xie
> Cc: Seiji Aguchi; [email protected]; [email protected]; [email protected]; [email protected]; Tomoki
> Sekiyama; [email protected]
> Subject: Re: [PATCH v3] efivars,efi-pstore: Hold off deletion of sysfs entry until, the scan is completed
>
> Hi folks,
> I tested it on my DELL XPS desktop. And it won't show any warnings
> when I mounting pstore and deleting pstore items after this patch
> applied.
>
> Tested-by: Madper Xie
> [email protected] writes:
>
> > Oops, It seems my mu4e(a email client for emacs)'s auto-indent breaks the
> > patch... I apologize for this...
> >
> > [email protected] writes:
> >
> >> Hi Madper,
> >>
> >> I tested this patch on 3.12-rc4.
> >> Could you please send me the log when you failed to apply?
> >>
> >> Seiji
> >>
> >>> -----Original Message-----
> >>> From: Madper Xie [mailto:[email protected]]
> >>> Sent: Thursday, October 17, 2013 1:54 AM
> >>> To: Seiji Aguchi
> >>> Cc: [email protected]; [email protected]; [email protected]; [email protected]; Tomoki Sekiyama;
> dle-
> >>> [email protected]
> >>> Subject: Re: [PATCH v3] efivars,efi-pstore: Hold off deletion of sysfs entry until, the scan is completed
> >>>
> >>> Howdy Seiji,
> >>> I failed appily this patch to both 3.12-rc2 and 3.12-rc4. Could you
> >>> please let me know which is the right tree for this patch?
> >>>
> >>> Thanks,
> >>> Madper.
> >>> [email protected] writes:
> >>>
> >>> > Change from v2:
> >>> > - Move dynamic memory allocation to efi_pstore_read() before holding
> >>> > efivars->lock to protect entry->var.Data.
> >>> > - Access to entry->scanning while holding efivars->lock.
> >>> > - Move a comment about a returned value from efi_pstore_read_func() to
> >>> > efi_pstore_read() because "size < 0" case may happen in efi_pstore_read().
> >>> >
> >>> > Currently, when mounting pstore file system, a read callback of efi_pstore
> >>> > driver runs mutiple times as below.
> >>> >
> >>> > - In the first read callback, scan efivar_sysfs_list from head and pass
> >>> > a kmsg buffer of a entry to an upper pstore layer.
> >>> > - In the second read callback, rescan efivar_sysfs_list from the entry and pass
> >>> > another kmsg buffer to it.
> >>> > - Repeat the scan and pass until the end of efivar_sysfs_list.
> >>> >
> >>> > In this process, an entry is read across the multiple read function calls.
> >>> > To avoid race between the read and erasion, the whole process above is
> >>> > protected by a spinlock, holding in open() and releasing in close().
> >>> >
> >>> > At the same time, kmemdup() is called to pass the buffer to pstore filesystem
> >>> > during it.
> >>> > And then, it causes a following lockdep warning.
> >>> >
> >>> > To make the dynamic memory allocation runnable without taking spinlock,
> >>> > holding off a deletion of sysfs entry if it happens while scanning it
> >>> > via efi_pstore, and deleting it after the scan is completed.
> >>> >
> >>> > To implement it, this patch introduces two flags, scanning and deleting,
> >>> > to efivar_entry.
> >>> >
> >>> > [ 1.143710] ------------[ cut here ]------------
> >>> > [ 1.144058] WARNING: CPU: 1 PID: 1 at kernel/lockdep.c:2740
> >>> > lockdep_trace_alloc+0x104/0x110()
> >>> > [ 1.144058] DEBUG_LOCKS_WARN_ON(irqs_disabled_flags(flags))
> >>> > [ 1.144058] Modules linked in:
> >>> >
> >>> > [ 1.144058] CPU: 1 PID: 1 Comm: systemd Not tainted 3.11.0-rc5 #2
> >>> > [ 1.144058] 0000000000000009 ffff8800797e9ae0 ffffffff816614a5
> >>> > ffff8800797e9b28
> >>> > [ 1.144058] ffff8800797e9b18 ffffffff8105510d 0000000000000080
> >>> > 0000000000000046
> >>> > [ 1.144058] 00000000000000d0 00000000000003af ffffffff81ccd0c0
> >>> > ffff8800797e9b78
> >>> > [ 1.144058] Call Trace:
> >>> > [ 1.144058] [<ffffffff816614a5>] dump_stack+0x54/0x74
> >>> > [ 1.144058] [<ffffffff8105510d>] warn_slowpath_common+0x7d/0xa0
> >>> > [ 1.144058] [<ffffffff8105517c>] warn_slowpath_fmt+0x4c/0x50
> >>> > [ 1.144058] [<ffffffff8131290f>] ? vsscanf+0x57f/0x7b0
> >>> > [ 1.144058] [<ffffffff810bbd74>] lockdep_trace_alloc+0x104/0x110
> >>> > [ 1.144058] [<ffffffff81192da0>] __kmalloc_track_caller+0x50/0x280
> >>> > [ 1.144058] [<ffffffff815147bb>] ?
> >>> > efi_pstore_read_func.part.1+0x12b/0x170
> >>> > [ 1.144058] [<ffffffff8115b260>] kmemdup+0x20/0x50
> >>> > [ 1.144058] [<ffffffff815147bb>] efi_pstore_read_func.part.1+0x12b/0x170
> >>> > [ 1.144058] [<ffffffff81514800>] ?
> >>> > efi_pstore_read_func.part.1+0x170/0x170
> >>> > [ 1.144058] [<ffffffff815148b4>] efi_pstore_read_func+0xb4/0xe0
> >>> > [ 1.144058] [<ffffffff81512b7b>] __efivar_entry_iter+0xfb/0x120
> >>> > [ 1.144058] [<ffffffff8151428f>] efi_pstore_read+0x3f/0x50
> >>> > [ 1.144058] [<ffffffff8128d7ba>] pstore_get_records+0x9a/0x150
> >>> > [ 1.158207] [<ffffffff812af25c>] ? selinux_d_instantiate+0x1c/0x20
> >>> > [ 1.158207] [<ffffffff8128ce30>] ? parse_options+0x80/0x80
> >>> > [ 1.158207] [<ffffffff8128ced5>] pstore_fill_super+0xa5/0xc0
> >>> > [ 1.158207] [<ffffffff811ae7d2>] mount_single+0xa2/0xd0
> >>> > [ 1.158207] [<ffffffff8128ccf8>] pstore_mount+0x18/0x20
> >>> > [ 1.158207] [<ffffffff811ae8b9>] mount_fs+0x39/0x1b0
> >>> > [ 1.158207] [<ffffffff81160550>] ? __alloc_percpu+0x10/0x20
> >>> > [ 1.158207] [<ffffffff811c9493>] vfs_kern_mount+0x63/0xf0
> >>> > [ 1.158207] [<ffffffff811cbb0e>] do_mount+0x23e/0xa20
> >>> > [ 1.158207] [<ffffffff8115b51b>] ? strndup_user+0x4b/0xf0
> >>> > [ 1.158207] [<ffffffff811cc373>] SyS_mount+0x83/0xc0
> >>> > [ 1.158207] [<ffffffff81673cc2>] system_call_fastpath+0x16/0x1b
> >>> > [ 1.158207] ---[ end trace 61981bc62de9f6f4 ]---
> >>> >
> >>> > Signed-off-by: Seiji Aguchi <[email protected]>
> >>> > ---
> >>> > drivers/firmware/efi/efi-pstore.c | 143 +++++++++++++++++++++++++++++++++++---
> >>> > drivers/firmware/efi/efivars.c | 12 ++--
> >>> > drivers/firmware/efi/vars.c | 12 +++-
> >>> > include/linux/efi.h | 2 +
> >>> > 4 files changed, 153 insertions(+), 16 deletions(-)
> >>> >
> >>> > diff --git a/drivers/firmware/efi/efi-pstore.c b/drivers/firmware/efi/efi-pstore.c
> >>> > index 5002d50..ebd5dbc 100644
> >>> > --- a/drivers/firmware/efi/efi-pstore.c
> >>> > +++ b/drivers/firmware/efi/efi-pstore.c
> >>> > @@ -18,14 +18,12 @@ module_param_named(pstore_disable, efivars_pstore_disable, bool, 0644);
> >>> >
> >>> > static int efi_pstore_open(struct pstore_info *psi)
> >>> > {
> >>> > - efivar_entry_iter_begin();
> >>> > psi->data = NULL;
> >>> > return 0;
> >>> > }
> >>> >
> >>> > static int efi_pstore_close(struct pstore_info *psi)
> >>> > {
> >>> > - efivar_entry_iter_end();
> >>> > psi->data = NULL;
> >>> > return 0;
> >>> > }
> >>> > @@ -91,19 +89,125 @@ static int efi_pstore_read_func(struct efivar_entry *entry, void *data)
> >>> > __efivar_entry_get(entry, &entry->var.Attributes,
> >>> > &entry->var.DataSize, entry->var.Data);
> >>> > size = entry->var.DataSize;
> >>> > + memcpy(*cb_data->buf, entry->var.Data, (size_t)min_t(unsigned long,
> >>> > + 1024, size));
> >>> >
> >>> > - *cb_data->buf = kmemdup(entry->var.Data, size, GFP_KERNEL);
> >>> > - if (*cb_data->buf == NULL)
> >>> > - return -ENOMEM;
> >>> > return size;
> >>> > }
> >>> >
> >>> > +/**
> >>> > + * efi_pstore_scan_sysfs_enter
> >>> > + * @entry: scanning entry
> >>> > + * @next: next entry
> >>> > + * @head: list head
> >>> > + */
> >>> > +static void efi_pstore_scan_sysfs_enter(struct efivar_entry *pos,
> >>> > + struct efivar_entry *next,
> >>> > + struct list_head *head)
> >>> > +{
> >>> > + pos->scanning = true;
> >>> > + if (&next->list != head)
> >>> > + next->scanning = true;
> >>> > +}
> >>> > +
> >>> > +/**
> >>> > + * __efi_pstore_scan_sysfs_exit
> >>> > + * @entry: deleting entry
> >>> > + * @turn_off_scanning: Check if a scanning flag should be turned off
> >>> > + */
> >>> > +static inline void __efi_pstore_scan_sysfs_exit(struct efivar_entry *entry,
> >>> > + bool turn_off_scanning)
> >>> > +{
> >>> > + if (entry->deleting) {
> >>> > + list_del(&entry->list);
> >>> > + efivar_entry_iter_end();
> >>> > + efivar_unregister(entry);
> >>> > + efivar_entry_iter_begin();
> >>> > + } else if (turn_off_scanning)
> >>> > + entry->scanning = false;
> >>> > +}
> >>> > +
> >>> > +/**
> >>> > + * efi_pstore_scan_sysfs_exit
> >>> > + * @pos: scanning entry
> >>> > + * @next: next entry
> >>> > + * @head: list head
> >>> > + * @stop: a flag checking if scanning will stop
> >>> > + */
> >>> > +static void efi_pstore_scan_sysfs_exit(struct efivar_entry *pos,
> >>> > + struct efivar_entry *next,
> >>> > + struct list_head *head, bool stop)
> >>> > +{
> >>> > + __efi_pstore_scan_sysfs_exit(pos, true);
> >>> > + if (stop)
> >>> > + __efi_pstore_scan_sysfs_exit(next, &next->list != head);
> >>> > +}
> >>> > +
> >>> > +/**
> >>> > + * efi_pstore_sysfs_entry_iter
> >>> > + *
> >>> > + * @data: function-specific data to pass to callback
> >>> > + * @pos: entry to begin iterating from
> >>> > + *
> >>> > + * You MUST call efivar_enter_iter_begin() before this function, and
> >>> > + * efivar_entry_iter_end() afterwards.
> >>> > + *
> >>> > + * It is possible to begin iteration from an arbitrary entry within
> >>> > + * the list by passing @pos. @pos is updated on return to point to
> >>> > + * the next entry of the last one passed to efi_pstore_read_func().
> >>> > + * To begin iterating from the beginning of the list @pos must be %NULL.
> >>> > + */
> >>> > +static int efi_pstore_sysfs_entry_iter(void *data, struct efivar_entry **pos)
> >>> > +{
> >>> > + struct efivar_entry *entry, *n;
> >>> > + struct list_head *head = &efivar_sysfs_list;
> >>> > + int size = 0;
> >>> > +
> >>> > + if (!*pos) {
> >>> > + list_for_each_entry_safe(entry, n, head, list) {
> >>> > + efi_pstore_scan_sysfs_enter(entry, n, head);
> >>> > +
> >>> > + size = efi_pstore_read_func(entry, data);
> >>> > + efi_pstore_scan_sysfs_exit(entry, n, head, size < 0);
> >>> > + if (size)
> >>> > + break;
> >>> > + }
> >>> > + *pos = n;
> >>> > + return size;
> >>> > + }
> >>> > +
> >>> > + list_for_each_entry_safe_from((*pos), n, head, list) {
> >>> > + efi_pstore_scan_sysfs_enter((*pos), n, head);
> >>> > +
> >>> > + size = efi_pstore_read_func((*pos), data);
> >>> > + efi_pstore_scan_sysfs_exit((*pos), n, head, size < 0);
> >>> > + if (size)
> >>> > + break;
> >>> > + }
> >>> > + *pos = n;
> >>> > + return size;
> >>> > +}
> >>> > +
> >>> > +/**
> >>> > + * efi_pstore_read
> >>> > + *
> >>> > + * This function returns a size of NVRAM entry logged via efi_pstore_write().
> >>> > + * The meaning and behavior of efi_pstore/pstore are as below.
> >>> > + *
> >>> > + * size > 0: Got data of an entry logged via efi_pstore_write() successfully,
> >>> > + * and pstore filesystem will continue reading subsequent entries.
> >>> > + * size == 0: Entry was not logged via efi_pstore_write(),
> >>> > + * and efi_pstore driver will continue reading subsequent entries.
> >>> > + * size < 0: Failed to get data of entry logging via efi_pstore_write(),
> >>> > + * and pstore will stop reading entry.
> >>> > + */
> >>> > static ssize_t efi_pstore_read(u64 *id, enum pstore_type_id *type,
> >>> > int *count, struct timespec *timespec,
> >>> > char **buf, bool *compressed,
> >>> > struct pstore_info *psi)
> >>> > {
> >>> > struct pstore_read_data data;
> >>> > + ssize_t size;
> >>> >
> >>> > data.id = id;
> >>> > data.type = type;
> >>> > @@ -112,8 +216,17 @@ static ssize_t efi_pstore_read(u64 *id, enum pstore_type_id *type,
> >>> > data.compressed = compressed;
> >>> > data.buf = buf;
> >>> >
> >>> > - return __efivar_entry_iter(efi_pstore_read_func, &efivar_sysfs_list, &data,
> >>> > - (struct efivar_entry **)&psi->data);
> >>> > + *data.buf = kzalloc(1024, GFP_KERNEL);
> >>> > + if (!*data.buf)
> >>> > + return -ENOMEM;
> >>> > +
> >>> > + efivar_entry_iter_begin();
> >>> > + size = efi_pstore_sysfs_entry_iter(&data,
> >>> > + (struct efivar_entry **)&psi->data);
> >>> > + efivar_entry_iter_end();
> >>> > + if (size <= 0)
> >>> > + kfree(*data.buf);
> >>> > + return size;
> >>> > }
> >>> >
> >>> > static int efi_pstore_write(enum pstore_type_id type,
> >>> > @@ -184,9 +297,17 @@ static int efi_pstore_erase_func(struct efivar_entry *entry, void *data)
> >>> > return 0;
> >>> > }
> >>> >
> >>> > + if (entry->scanning) {
> >>> > + /*
> >>> > + * Skip deletion because this entry will be deleted
> >>> > + * after scanning is completed.
> >>> > + */
> >>> > + entry->deleting = true;
> >>> > + } else
> >>> > + list_del(&entry->list);
> >>> > +
> >>> > /* found */
> >>> > __efivar_entry_delete(entry);
> >>> > - list_del(&entry->list);
> >>> >
> >>> > return 1;
> >>> > }
> >>> > @@ -214,10 +335,12 @@ static int efi_pstore_erase(enum pstore_type_id type, u64 id, int count,
> >>> >
> >>> > efivar_entry_iter_begin();
> >>> > found = __efivar_entry_iter(efi_pstore_erase_func, &efivar_sysfs_list, &edata, &entry);
> >>> > - efivar_entry_iter_end();
> >>> >
> >>> > - if (found)
> >>> > + if (found && !entry->scanning) {
> >>> > + efivar_entry_iter_end();
> >>> > efivar_unregister(entry);
> >>> > + } else
> >>> > + efivar_entry_iter_end();
> >>> >
> >>> > return 0;
> >>> > }
> >>> > diff --git a/drivers/firmware/efi/efivars.c b/drivers/firmware/efi/efivars.c
> >>> > index 8a7432a..8c5a61a 100644
> >>> > --- a/drivers/firmware/efi/efivars.c
> >>> > +++ b/drivers/firmware/efi/efivars.c
> >>> > @@ -383,12 +383,16 @@ static ssize_t efivar_delete(struct file *filp, struct kobject *kobj,
> >>> > else if (__efivar_entry_delete(entry))
> >>> > err = -EIO;
> >>> >
> >>> > - efivar_entry_iter_end();
> >>> > -
> >>> > - if (err)
> >>> > + if (err) {
> >>> > + efivar_entry_iter_end();
> >>> > return err;
> >>> > + }
> >>> >
> >>> > - efivar_unregister(entry);
> >>> > + if (!entry->scanning) {
> >>> > + efivar_entry_iter_end();
> >>> > + efivar_unregister(entry);
> >>> > + } else
> >>> > + efivar_entry_iter_end();
> >>> >
> >>> > /* It's dead Jim.... */
> >>> > return count;
> >>> > diff --git a/drivers/firmware/efi/vars.c b/drivers/firmware/efi/vars.c
> >>> > index 391c67b..b22659c 100644
> >>> > --- a/drivers/firmware/efi/vars.c
> >>> > +++ b/drivers/firmware/efi/vars.c
> >>> > @@ -683,8 +683,16 @@ struct efivar_entry *efivar_entry_find(efi_char16_t *name, efi_guid_t guid,
> >>> > if (!found)
> >>> > return NULL;
> >>> >
> >>> > - if (remove)
> >>> > - list_del(&entry->list);
> >>> > + if (remove) {
> >>> > + if (entry->scanning) {
> >>> > + /*
> >>> > + * The entry will be deleted
> >>> > + * after scanning is completed.
> >>> > + */
> >>> > + entry->deleting = true;
> >>> > + } else
> >>> > + list_del(&entry->list);
> >>> > + }
> >>> >
> >>> > return entry;
> >>> > }
> >>> > diff --git a/include/linux/efi.h b/include/linux/efi.h
> >>> > index 5f8f176..04088fb 100644
> >>> > --- a/include/linux/efi.h
> >>> > +++ b/include/linux/efi.h
> >>> > @@ -782,6 +782,8 @@ struct efivar_entry {
> >>> > struct efi_variable var;
> >>> > struct list_head list;
> >>> > struct kobject kobj;
> >>> > + bool scanning;
> >>> > + bool deleting;
> >>> > };
> >>> >
> >>> > extern struct list_head efivar_sysfs_list;
> >>>
> >>>
> >>> --
> >>> Best,
> >>> Madper Xie.
>
>
> --
> Best,
> Madper Xie.
Matt,
> It seems to me that because you're no longer dropping __efivars->lock
> when reading from the EFI variable store, you actually don't need all
> the ->scanning and ->deleting logic because anything that sets those
> flags runs to completion while holding the lock.
The scanning and deleting logic is still needed.
In case an entry(A) is found, the pointer is saved to psi->data.
And efi_pstore_read() passes the entry(A) to a pstore filesystem by releasing __efivars->lock.
And then, the pstore filesystem calls efi_pstore_read() again and the same entry(A), which is saved to
psi->data, is used for re-scanning a sysfs-list.
(That is why list_for_each_entry_safe_from () is used in efi_pstore_sysfs_entry_iter().)
So, to protect the entry(A), the logic is needed because, in pstore filesystem, __efivars->lock
Is released.
> Can't the patch be simplified to just allocating data.buf at the
> beginning of efi_pstore_read()?
I think data.buf is simply allocated at the beginning of efi_pstore_read() with this patch v3.
If you are not satisfied with it, could you please show me your pseudo code?
>Also, it would be a good idea to
> introduce a #define for the 1024 magic number, e.g.
>
> #define EFIVARS_DATA_SIZE_MAX 1024
It is good idea. I can fix it.
Seiji
<snip>
+/**
+ * efi_pstore_read
+ *
+ * This function returns a size of NVRAM entry logged via efi_pstore_write().
+ * The meaning and behavior of efi_pstore/pstore are as below.
+ *
+ * size > 0: Got data of an entry logged via efi_pstore_write() successfully,
+ * and pstore filesystem will continue reading subsequent entries.
+ * size == 0: Entry was not logged via efi_pstore_write(),
+ * and efi_pstore driver will continue reading subsequent entries.
+ * size < 0: Failed to get data of entry logging via efi_pstore_write(),
+ * and pstore will stop reading entry.
+ */
static ssize_t efi_pstore_read(u64 *id, enum pstore_type_id *type,
int *count, struct timespec *timespec,
char **buf, bool *compressed,
struct pstore_info *psi)
{
struct pstore_read_data data;
+ ssize_t size;
data.id = id;
data.type = type;
@@ -112,8 +216,17 @@ static ssize_t efi_pstore_read(u64 *id, enum pstore_type_id *type,
data.compressed = compressed;
data.buf = buf;
- return __efivar_entry_iter(efi_pstore_read_func, &efivar_sysfs_list, &data,
- (struct efivar_entry **)&psi->data);
+ *data.buf = kzalloc(1024, GFP_KERNEL);
+ if (!*data.buf)
+ return -ENOMEM;
+
+ efivar_entry_iter_begin();
+ size = efi_pstore_sysfs_entry_iter(&data,
+ (struct efivar_entry **)&psi->data);
+ efivar_entry_iter_end();
+ if (size <= 0)
+ kfree(*data.buf);
+ return size;
}
<snip>
On Fri, 18 Oct, at 10:30:58PM, Seiji Aguchi wrote:
> The scanning and deleting logic is still needed. In case an entry(A)
> is found, the pointer is saved to psi->data. And efi_pstore_read()
> passes the entry(A) to a pstore filesystem by releasing
> __efivars->lock.
>
> And then, the pstore filesystem calls efi_pstore_read() again and the
> same entry(A), which is saved to psi->data, is used for re-scanning a
> sysfs-list. (That is why list_for_each_entry_safe_from () is used in
> efi_pstore_sysfs_entry_iter().)
>
> So, to protect the entry(A), the logic is needed because, in pstore
> filesystem, __efivars->lock Is released.
Very good point.
--
Matt Fleming, Intel Open Source Technology Center
> On Fri, 18 Oct, at 10:30:58PM, Seiji Aguchi wrote:
> > The scanning and deleting logic is still needed. In case an entry(A)
> > is found, the pointer is saved to psi->data. And efi_pstore_read()
> > passes the entry(A) to a pstore filesystem by releasing
> > __efivars->lock.
> >
> > And then, the pstore filesystem calls efi_pstore_read() again and the
> > same entry(A), which is saved to psi->data, is used for re-scanning a
> > sysfs-list. (That is why list_for_each_entry_safe_from () is used in
> > efi_pstore_sysfs_entry_iter().)
> >
> > So, to protect the entry(A), the logic is needed because, in pstore
> > filesystem, __efivars->lock Is released.
>
> Very good point.
Thanks,
I will add the description in the next patch.
Seiji