| Message ID | bd1ecbdfca4a2873d3825afba00d462a84f7264f.1647436353.git.naohiro.aota@wdc.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | protect relocation with sb_start_write | expand |
On Wed, Mar 16, 2022 at 10:22:37PM +0900, Naohiro Aota wrote: > When btrfs balance is interrupted with umount, the background balance > resumes on the next mount. There is a potential deadlock with FS freezing > here like as described in commit 26559780b953 ("btrfs: zoned: mark > relocation as writing"). > > Mark the process as sb_writing. To preserve the order of sb_start_write() > (or mnt_want_write_file()) and btrfs_exclop_start(), call sb_start_write() > at btrfs_resume_balance_async() before taking fs_info->super_lock. This paragraph is now outdated, it should go away as it applied only to v1. The ordering problem is no longer relevant and we don't do anything at btrfs_resume_balance_async() anymore. > > Cc: stable@vger.kernel.org # 4.9+ > Signed-off-by: Naohiro Aota <naohiro.aota@wdc.com> Other than that, it looks good. Reviewed-by: Filipe Manana <fdmanana@suse.com> Thanks. > --- > fs/btrfs/volumes.c | 2 ++ > 1 file changed, 2 insertions(+) > > diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c > index 3fd17e87815a..3471698fd831 100644 > --- a/fs/btrfs/volumes.c > +++ b/fs/btrfs/volumes.c > @@ -4430,10 +4430,12 @@ static int balance_kthread(void *data) > struct btrfs_fs_info *fs_info = data; > int ret = 0; > > + sb_start_write(fs_info->sb); > mutex_lock(&fs_info->balance_mutex); > if (fs_info->balance_ctl) > ret = btrfs_balance(fs_info, fs_info->balance_ctl, NULL); > mutex_unlock(&fs_info->balance_mutex); > + sb_end_write(fs_info->sb); > > return ret; > } > -- > 2.35.1 >
On Wed, Mar 16, 2022 at 03:57:32PM +0000, Filipe Manana wrote: > On Wed, Mar 16, 2022 at 10:22:37PM +0900, Naohiro Aota wrote: > > When btrfs balance is interrupted with umount, the background balance > > resumes on the next mount. There is a potential deadlock with FS freezing > > here like as described in commit 26559780b953 ("btrfs: zoned: mark > > relocation as writing"). > > > > Mark the process as sb_writing. To preserve the order of sb_start_write() > > (or mnt_want_write_file()) and btrfs_exclop_start(), call sb_start_write() > > at btrfs_resume_balance_async() before taking fs_info->super_lock. > > This paragraph is now outdated, it should go away as it applied only to v1. > The ordering problem is no longer relevant and we don't do anything at > btrfs_resume_balance_async() anymore. Oops. I took the last sentence and unified it with the first paragraph. > > > > Cc: stable@vger.kernel.org # 4.9+ > > Signed-off-by: Naohiro Aota <naohiro.aota@wdc.com> > > Other than that, it looks good. > > Reviewed-by: Filipe Manana <fdmanana@suse.com> Thanks. > Thanks. > > > --- > > fs/btrfs/volumes.c | 2 ++ > > 1 file changed, 2 insertions(+) > > > > diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c > > index 3fd17e87815a..3471698fd831 100644 > > --- a/fs/btrfs/volumes.c > > +++ b/fs/btrfs/volumes.c > > @@ -4430,10 +4430,12 @@ static int balance_kthread(void *data) > > struct btrfs_fs_info *fs_info = data; > > int ret = 0; > > > > + sb_start_write(fs_info->sb); > > mutex_lock(&fs_info->balance_mutex); > > if (fs_info->balance_ctl) > > ret = btrfs_balance(fs_info, fs_info->balance_ctl, NULL); > > mutex_unlock(&fs_info->balance_mutex); > > + sb_end_write(fs_info->sb); > > > > return ret; > > } > > -- > > 2.35.1 > >
diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c index 3fd17e87815a..3471698fd831 100644 --- a/fs/btrfs/volumes.c +++ b/fs/btrfs/volumes.c @@ -4430,10 +4430,12 @@ static int balance_kthread(void *data) struct btrfs_fs_info *fs_info = data; int ret = 0; + sb_start_write(fs_info->sb); mutex_lock(&fs_info->balance_mutex); if (fs_info->balance_ctl) ret = btrfs_balance(fs_info, fs_info->balance_ctl, NULL); mutex_unlock(&fs_info->balance_mutex); + sb_end_write(fs_info->sb); return ret; }
When btrfs balance is interrupted with umount, the background balance resumes on the next mount. There is a potential deadlock with FS freezing here like as described in commit 26559780b953 ("btrfs: zoned: mark relocation as writing"). Mark the process as sb_writing. To preserve the order of sb_start_write() (or mnt_want_write_file()) and btrfs_exclop_start(), call sb_start_write() at btrfs_resume_balance_async() before taking fs_info->super_lock. Cc: stable@vger.kernel.org # 4.9+ Signed-off-by: Naohiro Aota <naohiro.aota@wdc.com> --- fs/btrfs/volumes.c | 2 ++ 1 file changed, 2 insertions(+)