Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751362Ab3JQFyf (ORCPT ); Thu, 17 Oct 2013 01:54:35 -0400 Received: from mx1.redhat.com ([209.132.183.28]:10092 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750866Ab3JQFyd (ORCPT ); Thu, 17 Oct 2013 01:54:33 -0400 References: <52584373.3010202@hds.com> User-agent: mu4e 0.9.9.5; emacs 24.3.1 From: Madper Xie To: Seiji Aguchi Cc: linux-kernel@vger.kernel.org, linux-efi@vger.kernel.org, matt.fleming@intel.com, tony.luck@intel.com, tomoki.sekiyama@hds.com, dle-develop@lists.sourceforge.net Subject: Re: [PATCH v3] efivars,efi-pstore: Hold off deletion of sysfs entry until, the scan is completed In-reply-to: <52584373.3010202@hds.com> Date: Thu, 17 Oct 2013 13:54:12 +0800 Message-ID: <878uxssarf.fsf@redhat.com> MIME-Version: 1.0 Content-Type: text/plain Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 12485 Lines: 364 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. seiji.aguchi@hds.com 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] [] dump_stack+0x54/0x74 > [ 1.144058] [] warn_slowpath_common+0x7d/0xa0 > [ 1.144058] [] warn_slowpath_fmt+0x4c/0x50 > [ 1.144058] [] ? vsscanf+0x57f/0x7b0 > [ 1.144058] [] lockdep_trace_alloc+0x104/0x110 > [ 1.144058] [] __kmalloc_track_caller+0x50/0x280 > [ 1.144058] [] ? > efi_pstore_read_func.part.1+0x12b/0x170 > [ 1.144058] [] kmemdup+0x20/0x50 > [ 1.144058] [] efi_pstore_read_func.part.1+0x12b/0x170 > [ 1.144058] [] ? > efi_pstore_read_func.part.1+0x170/0x170 > [ 1.144058] [] efi_pstore_read_func+0xb4/0xe0 > [ 1.144058] [] __efivar_entry_iter+0xfb/0x120 > [ 1.144058] [] efi_pstore_read+0x3f/0x50 > [ 1.144058] [] pstore_get_records+0x9a/0x150 > [ 1.158207] [] ? selinux_d_instantiate+0x1c/0x20 > [ 1.158207] [] ? parse_options+0x80/0x80 > [ 1.158207] [] pstore_fill_super+0xa5/0xc0 > [ 1.158207] [] mount_single+0xa2/0xd0 > [ 1.158207] [] pstore_mount+0x18/0x20 > [ 1.158207] [] mount_fs+0x39/0x1b0 > [ 1.158207] [] ? __alloc_percpu+0x10/0x20 > [ 1.158207] [] vfs_kern_mount+0x63/0xf0 > [ 1.158207] [] do_mount+0x23e/0xa20 > [ 1.158207] [] ? strndup_user+0x4b/0xf0 > [ 1.158207] [] SyS_mount+0x83/0xc0 > [ 1.158207] [] system_call_fastpath+0x16/0x1b > [ 1.158207] ---[ end trace 61981bc62de9f6f4 ]--- > > Signed-off-by: Seiji Aguchi > --- > 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. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/