2020-05-08 04:26:55

by Daeho Jeong

Subject: [PATCH] f2fs: remove race condition in releasing cblocks

From: Daeho Jeong <[email protected]>

Now, if writing pages and releasing compress blocks occur
simultaneously, and releasing cblocks is executed more than one time
to a file, then total block count of filesystem and block count of the
file could be incorrect and damaged.

We have to execute releasing compress blocks only one time for a file
without being interfered by writepages path.

Signed-off-by: Daeho Jeong <[email protected]>
---
fs/f2fs/file.c | 31 ++++++++++++++++++++++++-------
1 file changed, 24 insertions(+), 7 deletions(-)

diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c
index 4aab4b42d8ba..a92bc51b9b28 100644
--- a/fs/f2fs/file.c
+++ b/fs/f2fs/file.c
@@ -3488,6 +3488,7 @@ static int f2fs_release_compress_blocks(struct file *filp, unsigned long arg)
pgoff_t page_idx = 0, last_idx;
unsigned int released_blocks = 0;
int ret;
+ int writecount;

if (!f2fs_sb_has_compression(F2FS_I_SB(inode)))
return -EOPNOTSUPP;
@@ -3509,13 +3510,29 @@ static int f2fs_release_compress_blocks(struct file *filp, unsigned long arg)

inode_lock(inode);

- if (!IS_IMMUTABLE(inode)) {
- F2FS_I(inode)->i_flags |= F2FS_IMMUTABLE_FL;
- f2fs_set_inode_flags(inode);
- inode->i_ctime = current_time(inode);
- f2fs_mark_inode_dirty_sync(inode, true);
+ writecount = atomic_read(&inode->i_writecount);
+ if ((filp->f_mode & FMODE_WRITE && writecount != 1) || writecount) {
+ ret = -EBUSY;
+ goto out;
}

+ if (IS_IMMUTABLE(inode)) {
+ ret = -EINVAL;
+ goto out;
+ }
+
+ ret = filemap_write_and_wait_range(inode->i_mapping, 0, LLONG_MAX);
+ if (ret)
+ goto out;
+
+ if (!F2FS_I(inode)->i_compr_blocks)
+ goto out;
+
+ F2FS_I(inode)->i_flags |= F2FS_IMMUTABLE_FL;
+ f2fs_set_inode_flags(inode);
+ inode->i_ctime = current_time(inode);
+ f2fs_mark_inode_dirty_sync(inode, true);
+
down_write(&F2FS_I(inode)->i_gc_rwsem[WRITE]);
down_write(&F2FS_I(inode)->i_mmap_sem);

@@ -3554,9 +3571,9 @@ static int f2fs_release_compress_blocks(struct file *filp, unsigned long arg)

up_write(&F2FS_I(inode)->i_gc_rwsem[WRITE]);
up_write(&F2FS_I(inode)->i_mmap_sem);
-
- inode_unlock(inode);
out:
+ inode_unlock(inode);
+
mnt_drop_write_file(filp);

if (ret >= 0) {
--
2.26.2.526.g744177e7f7-goog

2020-05-08 06:52:10

by Chao Yu

Subject: Re: [f2fs-dev] [PATCH] f2fs: remove race condition in releasing cblocks

On 2020/5/8 12:25, Daeho Jeong wrote:
> From: Daeho Jeong <[email protected]>
>
> Now, if writing pages and releasing compress blocks occur
> simultaneously, and releasing cblocks is executed more than one time
> to a file, then total block count of filesystem and block count of the
> file could be incorrect and damaged.
>
> We have to execute releasing compress blocks only one time for a file
> without being interfered by writepages path.
>
> Signed-off-by: Daeho Jeong <[email protected]>
> ---
> fs/f2fs/file.c | 31 ++++++++++++++++++++++++-------
> 1 file changed, 24 insertions(+), 7 deletions(-)
>
> diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c
> index 4aab4b42d8ba..a92bc51b9b28 100644
> --- a/fs/f2fs/file.c
> +++ b/fs/f2fs/file.c
> @@ -3488,6 +3488,7 @@ static int f2fs_release_compress_blocks(struct file *filp, unsigned long arg)
> pgoff_t page_idx = 0, last_idx;
> unsigned int released_blocks = 0;
> int ret;
> + int writecount;
>
> if (!f2fs_sb_has_compression(F2FS_I_SB(inode)))
> return -EOPNOTSUPP;

Before inode_lock(), there is one case we may jump to out label, in
this case, we may unlock inode incorrectly.

if (!F2FS_I(inode)->i_compr_blocks)
goto out;

> -
> - inode_unlock(inode);
> out:
> + inode_unlock(inode);
> +
> mnt_drop_write_file(filp);

Thanks,

2020-05-08 07:00:43

by Daeho Jeong

Subject: Re: [f2fs-dev] [PATCH] f2fs: remove race condition in releasing cblocks

I moved checking i_compr_blocks phrase after calling inode_lock()
already, because we should check this after writing pages.

So, if it fails to check i_compr_blocks, we need to call inode_unlock().

Am I missing something?

2020년 5월 8일 (금) 오후 3:50, Chao Yu <[email protected]>님이 작성:
>
> On 2020/5/8 12:25, Daeho Jeong wrote:
> > From: Daeho Jeong <[email protected]>
> >
> > Now, if writing pages and releasing compress blocks occur
> > simultaneously, and releasing cblocks is executed more than one time
> > to a file, then total block count of filesystem and block count of the
> > file could be incorrect and damaged.
> >
> > We have to execute releasing compress blocks only one time for a file
> > without being interfered by writepages path.
> >
> > Signed-off-by: Daeho Jeong <[email protected]>
> > ---
> > fs/f2fs/file.c | 31 ++++++++++++++++++++++++-------
> > 1 file changed, 24 insertions(+), 7 deletions(-)
> >
> > diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c
> > index 4aab4b42d8ba..a92bc51b9b28 100644
> > --- a/fs/f2fs/file.c
> > +++ b/fs/f2fs/file.c
> > @@ -3488,6 +3488,7 @@ static int f2fs_release_compress_blocks(struct file *filp, unsigned long arg)
> > pgoff_t page_idx = 0, last_idx;
> > unsigned int released_blocks = 0;
> > int ret;
> > + int writecount;
> >
> > if (!f2fs_sb_has_compression(F2FS_I_SB(inode)))
> > return -EOPNOTSUPP;
>
> Before inode_lock(), there is one case we may jump to out label, in
> this case, we may unlock inode incorrectly.
>
> if (!F2FS_I(inode)->i_compr_blocks)
> goto out;
>
> > -
> > - inode_unlock(inode);
> > out:
> > + inode_unlock(inode);
> > +
> > mnt_drop_write_file(filp);
>
> Thanks,

2020-05-08 07:10:58

by Chao Yu

Subject: Re: [f2fs-dev] [PATCH] f2fs: remove race condition in releasing cblocks

On 2020/5/8 14:58, Daeho Jeong wrote:
> I moved checking i_compr_blocks phrase after calling inode_lock()
> already, because we should check this after writing pages.
>
> So, if it fails to check i_compr_blocks, we need to call inode_unlock().
>
> Am I missing something?

After applying this patch, I get this:

ret = mnt_want_write_file(filp);
if (ret)
return ret;

if (!F2FS_I(inode)->i_compr_blocks)
goto out;

f2fs_balance_fs(F2FS_I_SB(inode), true);

inode_lock(inode);

>
> 2020년 5월 8일 (금) 오후 3:50, Chao Yu <[email protected]>님이 작성:
>>
>> On 2020/5/8 12:25, Daeho Jeong wrote:
>>> From: Daeho Jeong <[email protected]>
>>>
>>> Now, if writing pages and releasing compress blocks occur
>>> simultaneously, and releasing cblocks is executed more than one time
>>> to a file, then total block count of filesystem and block count of the
>>> file could be incorrect and damaged.
>>>
>>> We have to execute releasing compress blocks only one time for a file
>>> without being interfered by writepages path.
>>>
>>> Signed-off-by: Daeho Jeong <[email protected]>
>>> ---
>>> fs/f2fs/file.c | 31 ++++++++++++++++++++++++-------
>>> 1 file changed, 24 insertions(+), 7 deletions(-)
>>>
>>> diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c
>>> index 4aab4b42d8ba..a92bc51b9b28 100644
>>> --- a/fs/f2fs/file.c
>>> +++ b/fs/f2fs/file.c
>>> @@ -3488,6 +3488,7 @@ static int f2fs_release_compress_blocks(struct file *filp, unsigned long arg)
>>> pgoff_t page_idx = 0, last_idx;
>>> unsigned int released_blocks = 0;
>>> int ret;
>>> + int writecount;
>>>
>>> if (!f2fs_sb_has_compression(F2FS_I_SB(inode)))
>>> return -EOPNOTSUPP;
>>
>> Before inode_lock(), there is one case we may jump to out label, in
>> this case, we may unlock inode incorrectly.
>>
>> if (!F2FS_I(inode)->i_compr_blocks)
>> goto out;
>>
>>> -
>>> - inode_unlock(inode);
>>> out:
>>> + inode_unlock(inode);
>>> +
>>> mnt_drop_write_file(filp);
>>
>> Thanks,
> .
>

2020-05-08 07:12:38

by Daeho Jeong

Subject: Re: [f2fs-dev] [PATCH] f2fs: remove race condition in releasing cblocks

Oops,

I will re-check it.

Thanks,

2020년 5월 8일 (금) 오후 4:09, Chao Yu <[email protected]>님이 작성:
>
> On 2020/5/8 14:58, Daeho Jeong wrote:
> > I moved checking i_compr_blocks phrase after calling inode_lock()
> > already, because we should check this after writing pages.
> >
> > So, if it fails to check i_compr_blocks, we need to call inode_unlock().
> >
> > Am I missing something?
>
> After applying this patch, I get this:
>
> ret = mnt_want_write_file(filp);
> if (ret)
> return ret;
>
> if (!F2FS_I(inode)->i_compr_blocks)
> goto out;
>
> f2fs_balance_fs(F2FS_I_SB(inode), true);
>
> inode_lock(inode);
>
> >
> > 2020년 5월 8일 (금) 오후 3:50, Chao Yu <[email protected]>님이 작성:
> >>
> >> On 2020/5/8 12:25, Daeho Jeong wrote:
> >>> From: Daeho Jeong <[email protected]>
> >>>
> >>> Now, if writing pages and releasing compress blocks occur
> >>> simultaneously, and releasing cblocks is executed more than one time
> >>> to a file, then total block count of filesystem and block count of the
> >>> file could be incorrect and damaged.
> >>>
> >>> We have to execute releasing compress blocks only one time for a file
> >>> without being interfered by writepages path.
> >>>
> >>> Signed-off-by: Daeho Jeong <[email protected]>
> >>> ---
> >>> fs/f2fs/file.c | 31 ++++++++++++++++++++++++-------
> >>> 1 file changed, 24 insertions(+), 7 deletions(-)
> >>>
> >>> diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c
> >>> index 4aab4b42d8ba..a92bc51b9b28 100644
> >>> --- a/fs/f2fs/file.c
> >>> +++ b/fs/f2fs/file.c
> >>> @@ -3488,6 +3488,7 @@ static int f2fs_release_compress_blocks(struct file *filp, unsigned long arg)
> >>> pgoff_t page_idx = 0, last_idx;
> >>> unsigned int released_blocks = 0;
> >>> int ret;
> >>> + int writecount;
> >>>
> >>> if (!f2fs_sb_has_compression(F2FS_I_SB(inode)))
> >>> return -EOPNOTSUPP;
> >>
> >> Before inode_lock(), there is one case we may jump to out label, in
> >> this case, we may unlock inode incorrectly.
> >>
> >> if (!F2FS_I(inode)->i_compr_blocks)
> >> goto out;
> >>
> >>> -
> >>> - inode_unlock(inode);
> >>> out:
> >>> + inode_unlock(inode);
> >>> +
> >>> mnt_drop_write_file(filp);
> >>
> >> Thanks,
> > .
> >