When erofs_kill_sb() is called in block dev based mode, s_bdev may not have
been initialised yet, and if CONFIG_EROFS_FS_ONDEMAND is enabled, it will
be mistaken for fscache mode, and then attempt to free an anon_dev that has
never been allocated, triggering the following warning:
============================================
ida_free called for id=0 which is not allocated.
WARNING: CPU: 14 PID: 926 at lib/idr.c:525 ida_free+0x134/0x140
Modules linked in:
CPU: 14 PID: 926 Comm: mount Not tainted 6.9.0-rc3-dirty #630
RIP: 0010:ida_free+0x134/0x140
Call Trace:
<TASK>
erofs_kill_sb+0x81/0x90
deactivate_locked_super+0x35/0x80
get_tree_bdev+0x136/0x1e0
vfs_get_tree+0x2c/0xf0
do_new_mount+0x190/0x2f0
[...]
============================================
Instead of allocating the erofs_sb_info in fill_super() allocate it
during erofs_get_tree() and ensure that erofs can always have the info
available during erofs_kill_sb().
Signed-off-by: Christian Brauner <[email protected]>
Signed-off-by: Baokun Li <[email protected]>
---
Changes since v1:
Allocate and initialise fc->s_fs_info in erofs_fc_get_tree() instead of
modifying fc->sb_flags.
V1: https://lore.kernel.org/r/[email protected]/
fs/erofs/super.c | 51 ++++++++++++++++++++++++++----------------------
1 file changed, 28 insertions(+), 23 deletions(-)
diff --git a/fs/erofs/super.c b/fs/erofs/super.c
index b21bd8f78dc1..4104280be2ea 100644
--- a/fs/erofs/super.c
+++ b/fs/erofs/super.c
@@ -581,8 +581,7 @@ static const struct export_operations erofs_export_ops = {
static int erofs_fc_fill_super(struct super_block *sb, struct fs_context *fc)
{
struct inode *inode;
- struct erofs_sb_info *sbi;
- struct erofs_fs_context *ctx = fc->fs_private;
+ struct erofs_sb_info *sbi = EROFS_SB(sb);
int err;
sb->s_magic = EROFS_SUPER_MAGIC;
@@ -590,19 +589,6 @@ static int erofs_fc_fill_super(struct super_block *sb, struct fs_context *fc)
sb->s_maxbytes = MAX_LFS_FILESIZE;
sb->s_op = &erofs_sops;
- sbi = kzalloc(sizeof(*sbi), GFP_KERNEL);
- if (!sbi)
- return -ENOMEM;
-
- sb->s_fs_info = sbi;
- sbi->opt = ctx->opt;
- sbi->devs = ctx->devs;
- ctx->devs = NULL;
- sbi->fsid = ctx->fsid;
- ctx->fsid = NULL;
- sbi->domain_id = ctx->domain_id;
- ctx->domain_id = NULL;
-
sbi->blkszbits = PAGE_SHIFT;
if (erofs_is_fscache_mode(sb)) {
sb->s_blocksize = PAGE_SIZE;
@@ -704,11 +690,32 @@ static int erofs_fc_fill_super(struct super_block *sb, struct fs_context *fc)
return 0;
}
-static int erofs_fc_get_tree(struct fs_context *fc)
+static void erofs_ctx_to_info(struct fs_context *fc)
{
struct erofs_fs_context *ctx = fc->fs_private;
+ struct erofs_sb_info *sbi = fc->s_fs_info;
+
+ sbi->opt = ctx->opt;
+ sbi->devs = ctx->devs;
+ ctx->devs = NULL;
+ sbi->fsid = ctx->fsid;
+ ctx->fsid = NULL;
+ sbi->domain_id = ctx->domain_id;
+ ctx->domain_id = NULL;
+}
- if (IS_ENABLED(CONFIG_EROFS_FS_ONDEMAND) && ctx->fsid)
+static int erofs_fc_get_tree(struct fs_context *fc)
+{
+ struct erofs_sb_info *sbi;
+
+ sbi = kzalloc(sizeof(*sbi), GFP_KERNEL);
+ if (!sbi)
+ return -ENOMEM;
+
+ fc->s_fs_info = sbi;
+ erofs_ctx_to_info(fc);
+
+ if (IS_ENABLED(CONFIG_EROFS_FS_ONDEMAND) && sbi->fsid)
return get_tree_nodev(fc, erofs_fc_fill_super);
return get_tree_bdev(fc, erofs_fc_fill_super);
@@ -767,6 +774,7 @@ static void erofs_fc_free(struct fs_context *fc)
kfree(ctx->fsid);
kfree(ctx->domain_id);
kfree(ctx);
+ kfree(fc->s_fs_info);
}
static const struct fs_context_operations erofs_context_ops = {
@@ -783,6 +791,7 @@ static int erofs_init_fs_context(struct fs_context *fc)
ctx = kzalloc(sizeof(*ctx), GFP_KERNEL);
if (!ctx)
return -ENOMEM;
+
ctx->devs = kzalloc(sizeof(struct erofs_dev_context), GFP_KERNEL);
if (!ctx->devs) {
kfree(ctx);
@@ -799,17 +808,13 @@ static int erofs_init_fs_context(struct fs_context *fc)
static void erofs_kill_sb(struct super_block *sb)
{
- struct erofs_sb_info *sbi;
+ struct erofs_sb_info *sbi = EROFS_SB(sb);
- if (erofs_is_fscache_mode(sb))
+ if (IS_ENABLED(CONFIG_EROFS_FS_ONDEMAND) && sbi->fsid)
kill_anon_super(sb);
else
kill_block_super(sb);
- sbi = EROFS_SB(sb);
- if (!sbi)
- return;
-
erofs_free_dev_context(sbi->devs);
fs_put_dax(sbi->dax_dev, NULL);
erofs_fscache_unregister_fs(sb);
--
2.31.1
Hi Baokun,
Thanks for catching this and move forward fixing this!
On 4/17/24 2:55 PM, Baokun Li wrote:
> When erofs_kill_sb() is called in block dev based mode, s_bdev may not have
> been initialised yet, and if CONFIG_EROFS_FS_ONDEMAND is enabled, it will
> be mistaken for fscache mode, and then attempt to free an anon_dev that has
> never been allocated, triggering the following warning:
>
> ============================================
> ida_free called for id=0 which is not allocated.
> WARNING: CPU: 14 PID: 926 at lib/idr.c:525 ida_free+0x134/0x140
> Modules linked in:
> CPU: 14 PID: 926 Comm: mount Not tainted 6.9.0-rc3-dirty #630
> RIP: 0010:ida_free+0x134/0x140
> Call Trace:
> <TASK>
> erofs_kill_sb+0x81/0x90
> deactivate_locked_super+0x35/0x80
> get_tree_bdev+0x136/0x1e0
> vfs_get_tree+0x2c/0xf0
> do_new_mount+0x190/0x2f0
> [...]
> ============================================
>
> Instead of allocating the erofs_sb_info in fill_super() allocate it
> during erofs_get_tree() and ensure that erofs can always have the info
> available during erofs_kill_sb().
I'm not sure if allocating erofs_sb_info in erofs_init_fs_context() will
be better, as I see some filesystems (e.g. autofs) do this way. Maybe
another potential advantage of doing this way is that erofs_fs_context
is not needed anymore and we can use sbi directly.
>
> Signed-off-by: Christian Brauner <[email protected]>
> Signed-off-by: Baokun Li <[email protected]>
> ---
> Changes since v1:
> Allocate and initialise fc->s_fs_info in erofs_fc_get_tree() instead of
> modifying fc->sb_flags.
>
> V1: https://lore.kernel.org/r/[email protected]/
>
> fs/erofs/super.c | 51 ++++++++++++++++++++++++++----------------------
> 1 file changed, 28 insertions(+), 23 deletions(-)
>
> diff --git a/fs/erofs/super.c b/fs/erofs/super.c
> index b21bd8f78dc1..4104280be2ea 100644
> --- a/fs/erofs/super.c
> +++ b/fs/erofs/super.c
> @@ -581,8 +581,7 @@ static const struct export_operations erofs_export_ops = {
> static int erofs_fc_fill_super(struct super_block *sb, struct fs_context *fc)
> {
> struct inode *inode;
> - struct erofs_sb_info *sbi;
> - struct erofs_fs_context *ctx = fc->fs_private;
> + struct erofs_sb_info *sbi = EROFS_SB(sb);
> int err;
>
> sb->s_magic = EROFS_SUPER_MAGIC;
> @@ -590,19 +589,6 @@ static int erofs_fc_fill_super(struct super_block *sb, struct fs_context *fc)
> sb->s_maxbytes = MAX_LFS_FILESIZE;
> sb->s_op = &erofs_sops;
>
> - sbi = kzalloc(sizeof(*sbi), GFP_KERNEL);
> - if (!sbi)
> - return -ENOMEM;
> -
> - sb->s_fs_info = sbi;
> - sbi->opt = ctx->opt;
> - sbi->devs = ctx->devs;
> - ctx->devs = NULL;
> - sbi->fsid = ctx->fsid;
> - ctx->fsid = NULL;
> - sbi->domain_id = ctx->domain_id;
> - ctx->domain_id = NULL;
> -
> sbi->blkszbits = PAGE_SHIFT;
> if (erofs_is_fscache_mode(sb)) {
> sb->s_blocksize = PAGE_SIZE;
> @@ -704,11 +690,32 @@ static int erofs_fc_fill_super(struct super_block *sb, struct fs_context *fc)
> return 0;
> }
>
> -static int erofs_fc_get_tree(struct fs_context *fc)
> +static void erofs_ctx_to_info(struct fs_context *fc)
> {
> struct erofs_fs_context *ctx = fc->fs_private;
> + struct erofs_sb_info *sbi = fc->s_fs_info;
> +
> + sbi->opt = ctx->opt;
> + sbi->devs = ctx->devs;
> + ctx->devs = NULL;
> + sbi->fsid = ctx->fsid;
> + ctx->fsid = NULL;
> + sbi->domain_id = ctx->domain_id;
> + ctx->domain_id = NULL;
> +}
I'm not sure if abstracting this logic into a seperate helper really
helps understanding the code as the logic itself is quite simple and
easy to be understood. Usually it's a hint of over-abstraction when a
simple helper has only one caller.
>
> - if (IS_ENABLED(CONFIG_EROFS_FS_ONDEMAND) && ctx->fsid)
> +static int erofs_fc_get_tree(struct fs_context *fc)
> +{
> + struct erofs_sb_info *sbi;
> +
> + sbi = kzalloc(sizeof(*sbi), GFP_KERNEL);
> + if (!sbi)
> + return -ENOMEM;
> +
> + fc->s_fs_info = sbi;
> + erofs_ctx_to_info(fc);
> +
> + if (IS_ENABLED(CONFIG_EROFS_FS_ONDEMAND) && sbi->fsid)
> return get_tree_nodev(fc, erofs_fc_fill_super);
>
> return get_tree_bdev(fc, erofs_fc_fill_super);
> @@ -767,6 +774,7 @@ static void erofs_fc_free(struct fs_context *fc)
> kfree(ctx->fsid);
> kfree(ctx->domain_id);
> kfree(ctx);
> + kfree(fc->s_fs_info);
> }
>
> static const struct fs_context_operations erofs_context_ops = {
> @@ -783,6 +791,7 @@ static int erofs_init_fs_context(struct fs_context *fc)
> ctx = kzalloc(sizeof(*ctx), GFP_KERNEL);
> if (!ctx)
> return -ENOMEM;
> +
> ctx->devs = kzalloc(sizeof(struct erofs_dev_context), GFP_KERNEL);
> if (!ctx->devs) {
> kfree(ctx);
> @@ -799,17 +808,13 @@ static int erofs_init_fs_context(struct fs_context *fc)
>
> static void erofs_kill_sb(struct super_block *sb)
> {
> - struct erofs_sb_info *sbi;
> + struct erofs_sb_info *sbi = EROFS_SB(sb);
>
> - if (erofs_is_fscache_mode(sb))
> + if (IS_ENABLED(CONFIG_EROFS_FS_ONDEMAND) && sbi->fsid)
> kill_anon_super(sb);
> else
> kill_block_super(sb);
>
> - sbi = EROFS_SB(sb);
> - if (!sbi)
> - return;
> -
> erofs_free_dev_context(sbi->devs);
> fs_put_dax(sbi->dax_dev, NULL);
> erofs_fscache_unregister_fs(sb);
--
Thanks,
Jingbo
On 2024/4/18 10:16, Jingbo Xu wrote:
> Hi Baokun,
>
> Thanks for catching this and move forward fixing this!
Hi Jingbo，
Thanks for your review！
>
> On 4/17/24 2:55 PM, Baokun Li wrote:
>> When erofs_kill_sb() is called in block dev based mode, s_bdev may not have
>> been initialised yet, and if CONFIG_EROFS_FS_ONDEMAND is enabled, it will
>> be mistaken for fscache mode, and then attempt to free an anon_dev that has
>> never been allocated, triggering the following warning:
>>
>> ============================================
>> ida_free called for id=0 which is not allocated.
>> WARNING: CPU: 14 PID: 926 at lib/idr.c:525 ida_free+0x134/0x140
>> Modules linked in:
>> CPU: 14 PID: 926 Comm: mount Not tainted 6.9.0-rc3-dirty #630
>> RIP: 0010:ida_free+0x134/0x140
>> Call Trace:
>> <TASK>
>> erofs_kill_sb+0x81/0x90
>> deactivate_locked_super+0x35/0x80
>> get_tree_bdev+0x136/0x1e0
>> vfs_get_tree+0x2c/0xf0
>> do_new_mount+0x190/0x2f0
>> [...]
>> ============================================
>>
>> Instead of allocating the erofs_sb_info in fill_super() allocate it
>> during erofs_get_tree() and ensure that erofs can always have the info
>> available during erofs_kill_sb().
>
> I'm not sure if allocating erofs_sb_info in erofs_init_fs_context() will
> be better, as I see some filesystems (e.g. autofs) do this way. Maybe
> another potential advantage of doing this way is that erofs_fs_context
> is not needed anymore and we can use sbi directly.
Yes, except for some extra memory usage when remounting,
this idea sounds great. Let me send a version of v3 to get rid
of erofs_fs_context.
>
>> Signed-off-by: Christian Brauner <[email protected]>
>> Signed-off-by: Baokun Li <[email protected]>
>> ---
>> Changes since v1:
>> Allocate and initialise fc->s_fs_info in erofs_fc_get_tree() instead of
>> modifying fc->sb_flags.
>>
>> V1: https://lore.kernel.org/r/[email protected]/
>>
>> fs/erofs/super.c | 51 ++++++++++++++++++++++++++----------------------
>> 1 file changed, 28 insertions(+), 23 deletions(-)
>>
>> diff --git a/fs/erofs/super.c b/fs/erofs/super.c
>> index b21bd8f78dc1..4104280be2ea 100644
>> --- a/fs/erofs/super.c
>> +++ b/fs/erofs/super.c
>> @@ -581,8 +581,7 @@ static const struct export_operations erofs_export_ops = {
>> static int erofs_fc_fill_super(struct super_block *sb, struct fs_context *fc)
>> {
>> struct inode *inode;
>> - struct erofs_sb_info *sbi;
>> - struct erofs_fs_context *ctx = fc->fs_private;
>> + struct erofs_sb_info *sbi = EROFS_SB(sb);
>> int err;
>>
>> sb->s_magic = EROFS_SUPER_MAGIC;
>> @@ -590,19 +589,6 @@ static int erofs_fc_fill_super(struct super_block *sb, struct fs_context *fc)
>> sb->s_maxbytes = MAX_LFS_FILESIZE;
>> sb->s_op = &erofs_sops;
>>
>> - sbi = kzalloc(sizeof(*sbi), GFP_KERNEL);
>> - if (!sbi)
>> - return -ENOMEM;
>> -
>> - sb->s_fs_info = sbi;
>> - sbi->opt = ctx->opt;
>> - sbi->devs = ctx->devs;
>> - ctx->devs = NULL;
>> - sbi->fsid = ctx->fsid;
>> - ctx->fsid = NULL;
>> - sbi->domain_id = ctx->domain_id;
>> - ctx->domain_id = NULL;
>> -
>> sbi->blkszbits = PAGE_SHIFT;
>> if (erofs_is_fscache_mode(sb)) {
>> sb->s_blocksize = PAGE_SIZE;
>> @@ -704,11 +690,32 @@ static int erofs_fc_fill_super(struct super_block *sb, struct fs_context *fc)
>> return 0;
>> }
>>
>> -static int erofs_fc_get_tree(struct fs_context *fc)
>> +static void erofs_ctx_to_info(struct fs_context *fc)
>> {
>> struct erofs_fs_context *ctx = fc->fs_private;
>> + struct erofs_sb_info *sbi = fc->s_fs_info;
>> +
>> + sbi->opt = ctx->opt;
>> + sbi->devs = ctx->devs;
>> + ctx->devs = NULL;
>> + sbi->fsid = ctx->fsid;
>> + ctx->fsid = NULL;
>> + sbi->domain_id = ctx->domain_id;
>> + ctx->domain_id = NULL;
>> +}
> I'm not sure if abstracting this logic into a seperate helper really
> helps understanding the code as the logic itself is quite simple and
> easy to be understood. Usually it's a hint of over-abstraction when a
> simple helper has only one caller.
>
Static functions that have only one caller are compiled inline, so we
don't have to worry about how that affects the code.
The reason these codes are encapsulated in a separate function is so
that the code reader understands that these codes are integrated
as a whole, and that we shouldn't have to move one or two of these
lines individually.
But after we get rid of erofs_fs_context, those won't be needed
anymore.
>>
>> - if (IS_ENABLED(CONFIG_EROFS_FS_ONDEMAND) && ctx->fsid)
>> +static int erofs_fc_get_tree(struct fs_context *fc)
>> +{
>> + struct erofs_sb_info *sbi;
>> +
>> + sbi = kzalloc(sizeof(*sbi), GFP_KERNEL);
>> + if (!sbi)
>> + return -ENOMEM;
>> +
>> + fc->s_fs_info = sbi;
>> + erofs_ctx_to_info(fc);
>> +
>> + if (IS_ENABLED(CONFIG_EROFS_FS_ONDEMAND) && sbi->fsid)
>> return get_tree_nodev(fc, erofs_fc_fill_super);
>>
>> return get_tree_bdev(fc, erofs_fc_fill_super);
>> @@ -767,6 +774,7 @@ static void erofs_fc_free(struct fs_context *fc)
>> kfree(ctx->fsid);
>> kfree(ctx->domain_id);
>> kfree(ctx);
>> + kfree(fc->s_fs_info);
>> }
>>
>> static const struct fs_context_operations erofs_context_ops = {
>> @@ -783,6 +791,7 @@ static int erofs_init_fs_context(struct fs_context *fc)
>> ctx = kzalloc(sizeof(*ctx), GFP_KERNEL);
>> if (!ctx)
>> return -ENOMEM;
>> +
>> ctx->devs = kzalloc(sizeof(struct erofs_dev_context), GFP_KERNEL);
>> if (!ctx->devs) {
>> kfree(ctx);
>> @@ -799,17 +808,13 @@ static int erofs_init_fs_context(struct fs_context *fc)
>>
>> static void erofs_kill_sb(struct super_block *sb)
>> {
>> - struct erofs_sb_info *sbi;
>> + struct erofs_sb_info *sbi = EROFS_SB(sb);
>>
>> - if (erofs_is_fscache_mode(sb))
>> + if (IS_ENABLED(CONFIG_EROFS_FS_ONDEMAND) && sbi->fsid)
>> kill_anon_super(sb);
>> else
>> kill_block_super(sb);
>>
>> - sbi = EROFS_SB(sb);
>> - if (!sbi)
>> - return;
>> -
>> erofs_free_dev_context(sbi->devs);
>> fs_put_dax(sbi->dax_dev, NULL);
>> erofs_fscache_unregister_fs(sb);
--
With Best Regards,
Baokun Li
On 4/18/24 11:36 AM, Baokun Li wrote:
> On 2024/4/18 10:16, Jingbo Xu wrote:
>> Hi Baokun,
>>
>> Thanks for catching this and move forward fixing this!
>
> Hi Jingbo，
>
> Thanks for your review！
>
>>
>> On 4/17/24 2:55 PM, Baokun Li wrote:
>>> When erofs_kill_sb() is called in block dev based mode, s_bdev may
>>> not have
>>> been initialised yet, and if CONFIG_EROFS_FS_ONDEMAND is enabled, it
>>> will
>>> be mistaken for fscache mode, and then attempt to free an anon_dev
>>> that has
>>> never been allocated, triggering the following warning:
>>>
>>> ============================================
>>> ida_free called for id=0 which is not allocated.
>>> WARNING: CPU: 14 PID: 926 at lib/idr.c:525 ida_free+0x134/0x140
>>> Modules linked in:
>>> CPU: 14 PID: 926 Comm: mount Not tainted 6.9.0-rc3-dirty #630
>>> RIP: 0010:ida_free+0x134/0x140
>>> Call Trace:
>>> <TASK>
>>> erofs_kill_sb+0x81/0x90
>>> deactivate_locked_super+0x35/0x80
>>> get_tree_bdev+0x136/0x1e0
>>> vfs_get_tree+0x2c/0xf0
>>> do_new_mount+0x190/0x2f0
>>> [...]
>>> ============================================
>>>
>>> Instead of allocating the erofs_sb_info in fill_super() allocate it
>>> during erofs_get_tree() and ensure that erofs can always have the info
>>> available during erofs_kill_sb().
>>
>> I'm not sure if allocating erofs_sb_info in erofs_init_fs_context() will
>> be better, as I see some filesystems (e.g. autofs) do this way. Maybe
>> another potential advantage of doing this way is that erofs_fs_context
>> is not needed anymore and we can use sbi directly.
> Yes, except for some extra memory usage when remounting,
> this idea sounds great. Let me send a version of v3 to get rid
> of erofs_fs_context.
I'm not sure if Gao Xaing also prefers this. I think it would be better
to wait and listen for his thoughts before we sending v3.
>>
>>> Signed-off-by: Christian Brauner <[email protected]>
>>> Signed-off-by: Baokun Li <[email protected]>
>>> ---
>>> Changes since v1:
>>> Allocate and initialise fc->s_fs_info in erofs_fc_get_tree()
>>> instead of
>>> modifying fc->sb_flags.
>>>
>>> V1:
>>> https://lore.kernel.org/r/[email protected]/
>>>
>>> fs/erofs/super.c | 51 ++++++++++++++++++++++++++----------------------
>>> 1 file changed, 28 insertions(+), 23 deletions(-)
>>>
>>> diff --git a/fs/erofs/super.c b/fs/erofs/super.c
>>> index b21bd8f78dc1..4104280be2ea 100644
>>> --- a/fs/erofs/super.c
>>> +++ b/fs/erofs/super.c
>>> @@ -581,8 +581,7 @@ static const struct export_operations
>>> erofs_export_ops = {
>>> static int erofs_fc_fill_super(struct super_block *sb, struct
>>> fs_context *fc)
>>> {
>>> struct inode *inode;
>>> - struct erofs_sb_info *sbi;
>>> - struct erofs_fs_context *ctx = fc->fs_private;
>>> + struct erofs_sb_info *sbi = EROFS_SB(sb);
>>> int err;
>>> sb->s_magic = EROFS_SUPER_MAGIC;
>>> @@ -590,19 +589,6 @@ static int erofs_fc_fill_super(struct
>>> super_block *sb, struct fs_context *fc)
>>> sb->s_maxbytes = MAX_LFS_FILESIZE;
>>> sb->s_op = &erofs_sops;
>>> - sbi = kzalloc(sizeof(*sbi), GFP_KERNEL);
>>> - if (!sbi)
>>> - return -ENOMEM;
>>> -
>>> - sb->s_fs_info = sbi;
>>> - sbi->opt = ctx->opt;
>>> - sbi->devs = ctx->devs;
>>> - ctx->devs = NULL;
>>> - sbi->fsid = ctx->fsid;
>>> - ctx->fsid = NULL;
>>> - sbi->domain_id = ctx->domain_id;
>>> - ctx->domain_id = NULL;
>>> -
>>> sbi->blkszbits = PAGE_SHIFT;
>>> if (erofs_is_fscache_mode(sb)) {
>>> sb->s_blocksize = PAGE_SIZE;
>>> @@ -704,11 +690,32 @@ static int erofs_fc_fill_super(struct
>>> super_block *sb, struct fs_context *fc)
>>> return 0;
>>> }
>>> -static int erofs_fc_get_tree(struct fs_context *fc)
>>> +static void erofs_ctx_to_info(struct fs_context *fc)
>>> {
>>> struct erofs_fs_context *ctx = fc->fs_private;
>>> + struct erofs_sb_info *sbi = fc->s_fs_info;
>>> +
>>> + sbi->opt = ctx->opt;
>>> + sbi->devs = ctx->devs;
>>> + ctx->devs = NULL;
>>> + sbi->fsid = ctx->fsid;
>>> + ctx->fsid = NULL;
>>> + sbi->domain_id = ctx->domain_id;
>>> + ctx->domain_id = NULL;
>>> +}
>> I'm not sure if abstracting this logic into a seperate helper really
>> helps understanding the code as the logic itself is quite simple and
>> easy to be understood. Usually it's a hint of over-abstraction when a
>> simple helper has only one caller.
>>
> Static functions that have only one caller are compiled inline, so we
> don't have to worry about how that affects the code.
>
> The reason these codes are encapsulated in a separate function is so
> that the code reader understands that these codes are integrated
> as a whole, and that we shouldn't have to move one or two of these
> lines individually.
>
> But after we get rid of erofs_fs_context, those won't be needed
> anymore.
Yeah, I understand. It's only coding style concerns.
--
Thanks,
Jingbo
On 2024/4/18 13:50, Jingbo Xu wrote:
>
> On 4/18/24 11:36 AM, Baokun Li wrote:
>> On 2024/4/18 10:16, Jingbo Xu wrote:
>>> Hi Baokun,
>>>
>>> Thanks for catching this and move forward fixing this!
>> Hi Jingbo，
>>
>> Thanks for your review！
>>
>>> On 4/17/24 2:55 PM, Baokun Li wrote:
>>>> When erofs_kill_sb() is called in block dev based mode, s_bdev may
>>>> not have
>>>> been initialised yet, and if CONFIG_EROFS_FS_ONDEMAND is enabled, it
>>>> will
>>>> be mistaken for fscache mode, and then attempt to free an anon_dev
>>>> that has
>>>> never been allocated, triggering the following warning:
>>>>
>>>> ============================================
>>>> ida_free called for id=0 which is not allocated.
>>>> WARNING: CPU: 14 PID: 926 at lib/idr.c:525 ida_free+0x134/0x140
>>>> Modules linked in:
>>>> CPU: 14 PID: 926 Comm: mount Not tainted 6.9.0-rc3-dirty #630
>>>> RIP: 0010:ida_free+0x134/0x140
>>>> Call Trace:
>>>> <TASK>
>>>> erofs_kill_sb+0x81/0x90
>>>> deactivate_locked_super+0x35/0x80
>>>> get_tree_bdev+0x136/0x1e0
>>>> vfs_get_tree+0x2c/0xf0
>>>> do_new_mount+0x190/0x2f0
>>>> [...]
>>>> ============================================
>>>>
>>>> Instead of allocating the erofs_sb_info in fill_super() allocate it
>>>> during erofs_get_tree() and ensure that erofs can always have the info
>>>> available during erofs_kill_sb().
>>> I'm not sure if allocating erofs_sb_info in erofs_init_fs_context() will
>>> be better, as I see some filesystems (e.g. autofs) do this way. Maybe
>>> another potential advantage of doing this way is that erofs_fs_context
>>> is not needed anymore and we can use sbi directly.
>> Yes, except for some extra memory usage when remounting,
>> this idea sounds great. Let me send a version of v3 to get rid
>> of erofs_fs_context.
> I'm not sure if Gao Xaing also prefers this. I think it would be better
> to wait and listen for his thoughts before we sending v3.
Okay, there's no rush on this.
>>>> Signed-off-by: Christian Brauner <[email protected]>
>>>> Signed-off-by: Baokun Li <[email protected]>
>>>> ---
>>>> Changes since v1:
>>>> Allocate and initialise fc->s_fs_info in erofs_fc_get_tree()
>>>> instead of
>>>> modifying fc->sb_flags.
>>>>
>>>> V1:
>>>> https://lore.kernel.org/r/[email protected]/
>>>>
>>>> fs/erofs/super.c | 51 ++++++++++++++++++++++++++----------------------
>>>> 1 file changed, 28 insertions(+), 23 deletions(-)
>>>>
>>>> diff --git a/fs/erofs/super.c b/fs/erofs/super.c
>>>> index b21bd8f78dc1..4104280be2ea 100644
>>>> --- a/fs/erofs/super.c
>>>> +++ b/fs/erofs/super.c
>>>> @@ -581,8 +581,7 @@ static const struct export_operations
>>>> erofs_export_ops = {
>>>> static int erofs_fc_fill_super(struct super_block *sb, struct
>>>> fs_context *fc)
>>>> {
>>>> struct inode *inode;
>>>> - struct erofs_sb_info *sbi;
>>>> - struct erofs_fs_context *ctx = fc->fs_private;
>>>> + struct erofs_sb_info *sbi = EROFS_SB(sb);
>>>> int err;
>>>> sb->s_magic = EROFS_SUPER_MAGIC;
>>>> @@ -590,19 +589,6 @@ static int erofs_fc_fill_super(struct
>>>> super_block *sb, struct fs_context *fc)
>>>> sb->s_maxbytes = MAX_LFS_FILESIZE;
>>>> sb->s_op = &erofs_sops;
>>>> - sbi = kzalloc(sizeof(*sbi), GFP_KERNEL);
>>>> - if (!sbi)
>>>> - return -ENOMEM;
>>>> -
>>>> - sb->s_fs_info = sbi;
>>>> - sbi->opt = ctx->opt;
>>>> - sbi->devs = ctx->devs;
>>>> - ctx->devs = NULL;
>>>> - sbi->fsid = ctx->fsid;
>>>> - ctx->fsid = NULL;
>>>> - sbi->domain_id = ctx->domain_id;
>>>> - ctx->domain_id = NULL;
>>>> -
>>>> sbi->blkszbits = PAGE_SHIFT;
>>>> if (erofs_is_fscache_mode(sb)) {
>>>> sb->s_blocksize = PAGE_SIZE;
>>>> @@ -704,11 +690,32 @@ static int erofs_fc_fill_super(struct
>>>> super_block *sb, struct fs_context *fc)
>>>> return 0;
>>>> }
>>>> -static int erofs_fc_get_tree(struct fs_context *fc)
>>>> +static void erofs_ctx_to_info(struct fs_context *fc)
>>>> {
>>>> struct erofs_fs_context *ctx = fc->fs_private;
>>>> + struct erofs_sb_info *sbi = fc->s_fs_info;
>>>> +
>>>> + sbi->opt = ctx->opt;
>>>> + sbi->devs = ctx->devs;
>>>> + ctx->devs = NULL;
>>>> + sbi->fsid = ctx->fsid;
>>>> + ctx->fsid = NULL;
>>>> + sbi->domain_id = ctx->domain_id;
>>>> + ctx->domain_id = NULL;
>>>> +}
>>> I'm not sure if abstracting this logic into a seperate helper really
>>> helps understanding the code as the logic itself is quite simple and
>>> easy to be understood. Usually it's a hint of over-abstraction when a
>>> simple helper has only one caller.
>>>
>> Static functions that have only one caller are compiled inline, so we
>> don't have to worry about how that affects the code.
>>
>> The reason these codes are encapsulated in a separate function is so
>> that the code reader understands that these codes are integrated
>> as a whole, and that we shouldn't have to move one or two of these
>> lines individually.
>>
>> But after we get rid of erofs_fs_context, those won't be needed
>> anymore.
> Yeah, I understand. It's only coding style concerns.
>
>
>
Okay, thanks！
--
With Best Regards,
Baokun Li
Hi,
On Thu, Apr 18, 2024 at 02:12:39PM +0800, Baokun Li wrote:
> On 2024/4/18 13:50, Jingbo Xu wrote:
> >
> > On 4/18/24 11:36 AM, Baokun Li wrote:
> > > On 2024/4/18 10:16, Jingbo Xu wrote:
> > > > Hi Baokun,
> > > >
> > > > Thanks for catching this and move forward fixing this!
> > > Hi Jingbo，
> > >
> > > Thanks for your review！
> > >
> > > > On 4/17/24 2:55 PM, Baokun Li wrote:
> > > > > When erofs_kill_sb() is called in block dev based mode, s_bdev may
> > > > > not have
> > > > > been initialised yet, and if CONFIG_EROFS_FS_ONDEMAND is enabled, it
> > > > > will
> > > > > be mistaken for fscache mode, and then attempt to free an anon_dev
> > > > > that has
> > > > > never been allocated, triggering the following warning:
> > > > >
> > > > > ============================================
> > > > > ida_free called for id=0 which is not allocated.
> > > > > WARNING: CPU: 14 PID: 926 at lib/idr.c:525 ida_free+0x134/0x140
> > > > > Modules linked in:
> > > > > CPU: 14 PID: 926 Comm: mount Not tainted 6.9.0-rc3-dirty #630
> > > > > RIP: 0010:ida_free+0x134/0x140
> > > > > Call Trace:
> > > > > <TASK>
> > > > > erofs_kill_sb+0x81/0x90
> > > > > deactivate_locked_super+0x35/0x80
> > > > > get_tree_bdev+0x136/0x1e0
> > > > > vfs_get_tree+0x2c/0xf0
> > > > > do_new_mount+0x190/0x2f0
> > > > > [...]
> > > > > ============================================
> > > > >
> > > > > Instead of allocating the erofs_sb_info in fill_super() allocate it
> > > > > during erofs_get_tree() and ensure that erofs can always have the info
> > > > > available during erofs_kill_sb().
> > > > I'm not sure if allocating erofs_sb_info in erofs_init_fs_context() will
> > > > be better, as I see some filesystems (e.g. autofs) do this way. Maybe
> > > > another potential advantage of doing this way is that erofs_fs_context
> > > > is not needed anymore and we can use sbi directly.
> > > Yes, except for some extra memory usage when remounting,
> > > this idea sounds great. Let me send a version of v3 to get rid
> > > of erofs_fs_context.
> > I'm not sure if Gao Xaing also prefers this. I think it would be better
> > to wait and listen for his thoughts before we sending v3.
> Okay, there's no rush on this.
I checked days ago, for example, XFS is also worked in this way.
And .reconfigure() needs to be carefully handled too.
> > > > > Signed-off-by: Christian Brauner <[email protected]>
> > > > > Signed-off-by: Baokun Li <[email protected]>
> > > > > ---
> > > > > Changes since v1:
> > > > > Allocate and initialise fc->s_fs_info in erofs_fc_get_tree()
> > > > > instead of
> > > > > modifying fc->sb_flags.
> > > > >
> > > > > V1:
> > > > > https://lore.kernel.org/r/[email protected]/
> > > > >
> > > > > fs/erofs/super.c | 51 ++++++++++++++++++++++++++----------------------
> > > > > 1 file changed, 28 insertions(+), 23 deletions(-)
> > > > >
> > > > > diff --git a/fs/erofs/super.c b/fs/erofs/super.c
> > > > > index b21bd8f78dc1..4104280be2ea 100644
> > > > > --- a/fs/erofs/super.c
> > > > > +++ b/fs/erofs/super.c
> > > > > @@ -581,8 +581,7 @@ static const struct export_operations
> > > > > erofs_export_ops = {
> > > > > static int erofs_fc_fill_super(struct super_block *sb, struct
> > > > > fs_context *fc)
> > > > > {
> > > > > struct inode *inode;
> > > > > - struct erofs_sb_info *sbi;
> > > > > - struct erofs_fs_context *ctx = fc->fs_private;
> > > > > + struct erofs_sb_info *sbi = EROFS_SB(sb);
> > > > > int err;
> > > > > sb->s_magic = EROFS_SUPER_MAGIC;
> > > > > @@ -590,19 +589,6 @@ static int erofs_fc_fill_super(struct
> > > > > super_block *sb, struct fs_context *fc)
> > > > > sb->s_maxbytes = MAX_LFS_FILESIZE;
> > > > > sb->s_op = &erofs_sops;
> > > > > - sbi = kzalloc(sizeof(*sbi), GFP_KERNEL);
> > > > > - if (!sbi)
> > > > > - return -ENOMEM;
> > > > > -
> > > > > - sb->s_fs_info = sbi;
> > > > > - sbi->opt = ctx->opt;
> > > > > - sbi->devs = ctx->devs;
> > > > > - ctx->devs = NULL;
> > > > > - sbi->fsid = ctx->fsid;
> > > > > - ctx->fsid = NULL;
> > > > > - sbi->domain_id = ctx->domain_id;
> > > > > - ctx->domain_id = NULL;
> > > > > -
> > > > > sbi->blkszbits = PAGE_SHIFT;
> > > > > if (erofs_is_fscache_mode(sb)) {
> > > > > sb->s_blocksize = PAGE_SIZE;
> > > > > @@ -704,11 +690,32 @@ static int erofs_fc_fill_super(struct
> > > > > super_block *sb, struct fs_context *fc)
> > > > > return 0;
> > > > > }
> > > > > -static int erofs_fc_get_tree(struct fs_context *fc)
> > > > > +static void erofs_ctx_to_info(struct fs_context *fc)
> > > > > {
> > > > > struct erofs_fs_context *ctx = fc->fs_private;
> > > > > + struct erofs_sb_info *sbi = fc->s_fs_info;
> > > > > +
> > > > > + sbi->opt = ctx->opt;
> > > > > + sbi->devs = ctx->devs;
> > > > > + ctx->devs = NULL;
> > > > > + sbi->fsid = ctx->fsid;
> > > > > + ctx->fsid = NULL;
> > > > > + sbi->domain_id = ctx->domain_id;
> > > > > + ctx->domain_id = NULL;
> > > > > +}
> > > > I'm not sure if abstracting this logic into a seperate helper really
> > > > helps understanding the code as the logic itself is quite simple and
> > > > easy to be understood. Usually it's a hint of over-abstraction when a
> > > > simple helper has only one caller.
> > > >
> > > Static functions that have only one caller are compiled inline, so we
> > > don't have to worry about how that affects the code.
> > >
> > > The reason these codes are encapsulated in a separate function is so
> > > that the code reader understands that these codes are integrated
> > > as a whole, and that we shouldn't have to move one or two of these
> > > lines individually.
> > >
> > > But after we get rid of erofs_fs_context, those won't be needed
> > > anymore.
> > Yeah, I understand. It's only coding style concerns.
> >
> >
> >
> Okay, thanks！
I'm fine to get rid of those (erofs_fs_context) as long as the codebase
is more clearer and simple. BTW, for the current codebase, I also think
it's unneeded to have a separate helper called once without extra actual
meaning...
Thanks,
Gao Xiang
>
> --
> With Best Regards,
> Baokun Li
On 2024/4/18 15:49, Gao Xiang wrote:
> Hi,
>
> On Thu, Apr 18, 2024 at 02:12:39PM +0800, Baokun Li wrote:
>> On 2024/4/18 13:50, Jingbo Xu wrote:
>>> On 4/18/24 11:36 AM, Baokun Li wrote:
>>>> On 2024/4/18 10:16, Jingbo Xu wrote:
>>>>> Hi Baokun,
>>>>>
>>>>> Thanks for catching this and move forward fixing this!
>>>> Hi Jingbo，
>>>>
>>>> Thanks for your review！
>>>>
>>>>> On 4/17/24 2:55 PM, Baokun Li wrote:
SNIP
>>>>>
>>>>> Instead of allocating the erofs_sb_info in fill_super() allocate it
>>>>> during erofs_get_tree() and ensure that erofs can always have the info
>>>>> available during erofs_kill_sb().
>>>>> I'm not sure if allocating erofs_sb_info in erofs_init_fs_context() will
>>>>> be better, as I see some filesystems (e.g. autofs) do this way. Maybe
>>>>> another potential advantage of doing this way is that erofs_fs_context
>>>>> is not needed anymore and we can use sbi directly.
>>>> Yes, except for some extra memory usage when remounting,
>>>> this idea sounds great. Let me send a version of v3 to get rid
>>>> of erofs_fs_context.
>>> I'm not sure if Gao Xaing also prefers this. I think it would be better
>>> to wait and listen for his thoughts before we sending v3.
>> Okay, there's no rush on this.
> I checked days ago, for example, XFS is also worked in this way.
> And .reconfigure() needs to be carefully handled too.
Ok, I'll implement it in the next iteration.
>>>>>> +static void erofs_ctx_to_info(struct fs_context *fc)
>>>>>> {
>>>>>> struct erofs_fs_context *ctx = fc->fs_private;
>>>>>> + struct erofs_sb_info *sbi = fc->s_fs_info;
>>>>>> +
>>>>>> + sbi->opt = ctx->opt;
>>>>>> + sbi->devs = ctx->devs;
>>>>>> + ctx->devs = NULL;
>>>>>> + sbi->fsid = ctx->fsid;
>>>>>> + ctx->fsid = NULL;
>>>>>> + sbi->domain_id = ctx->domain_id;
>>>>>> + ctx->domain_id = NULL;
>>>>>> +}
>>>>> I'm not sure if abstracting this logic into a seperate helper really
>>>>> helps understanding the code as the logic itself is quite simple and
>>>>> easy to be understood. Usually it's a hint of over-abstraction when a
>>>>> simple helper has only one caller.
>>>>>
>>>> Static functions that have only one caller are compiled inline, so we
>>>> don't have to worry about how that affects the code.
>>>>
>>>> The reason these codes are encapsulated in a separate function is so
>>>> that the code reader understands that these codes are integrated
>>>> as a whole, and that we shouldn't have to move one or two of these
>>>> lines individually.
>>>>
>>>> But after we get rid of erofs_fs_context, those won't be needed
>>>> anymore.
>>> Yeah, I understand. It's only coding style concerns.
>>>
>>>
>>>
>> Okay, thanks！
> I'm fine to get rid of those (erofs_fs_context) as long as the codebase
> is more clearer and simple. BTW, for the current codebase, I also think
> it's unneeded to have a separate helper called once without extra actual
> meaning...
>
> Thanks,
> Gao Xiang
>
Ok, this helper function will be gone in the next iteration.
Thanks for the review!
--
With Best Regards,
Baokun Li