2015-08-20 10:07:57

by Pierre Morel

Subject: [PATCH] fs/block_dev.c: always return error in thaw_bdev()

When triggering thaw-filesystems via magic sysrq, the system enters a
loop in do_thaw_one(), as thaw_bdev() still returns success if
bd_fsfreeze_count == 0. To fix this, let thaw_bdev() always return
error (and simplify the code a bit at the same time).

Reviewed-by: Eric Farman <[email protected]>
Reviewed-by: Cornelia Huck <[email protected]>
Signed-off-by: Pierre Morel <[email protected]>
---
fs/block_dev.c | 7 ++-----
1 file changed, 2 insertions(+), 5 deletions(-)

diff --git a/fs/block_dev.c b/fs/block_dev.c
index c7e4163..7809c92 100644
--- a/fs/block_dev.c
+++ b/fs/block_dev.c
@@ -269,14 +269,11 @@ int thaw_bdev(struct block_device *bdev, struct super_block *sb)
error = sb->s_op->thaw_super(sb);
else
error = thaw_super(sb);
- if (error) {
+ if (error)
bdev->bd_fsfreeze_count++;
- mutex_unlock(&bdev->bd_fsfreeze_mutex);
- return error;
- }
out:
mutex_unlock(&bdev->bd_fsfreeze_mutex);
- return 0;
+ return error;
}
EXPORT_SYMBOL(thaw_bdev);

--
2.3.0

2016-10-03 04:13:59

by Mateusz Guzik

Subject: Re: [PATCH] fs/block_dev.c: always return error in thaw_bdev()

On Thu, Aug 20, 2015 at 12:07:49PM +0200, Pierre Morel wrote:
> When triggering thaw-filesystems via magic sysrq, the system enters a
> loop in do_thaw_one(), as thaw_bdev() still returns success if
> bd_fsfreeze_count == 0. To fix this, let thaw_bdev() always return
> error (and simplify the code a bit at the same time).
>
> Reviewed-by: Eric Farman <[email protected]>
> Reviewed-by: Cornelia Huck <[email protected]>
> Signed-off-by: Pierre Morel <[email protected]>
> ---
> fs/block_dev.c | 7 ++-----
> 1 file changed, 2 insertions(+), 5 deletions(-)
>
> diff --git a/fs/block_dev.c b/fs/block_dev.c
> index c7e4163..7809c92 100644
> --- a/fs/block_dev.c
> +++ b/fs/block_dev.c
> @@ -269,14 +269,11 @@ int thaw_bdev(struct block_device *bdev, struct super_block *sb)
> error = sb->s_op->thaw_super(sb);
> else
> error = thaw_super(sb);
> - if (error) {
> + if (error)
> bdev->bd_fsfreeze_count++;
> - mutex_unlock(&bdev->bd_fsfreeze_mutex);
> - return error;
> - }
> out:
> mutex_unlock(&bdev->bd_fsfreeze_mutex);
> - return 0;
> + return error;
> }
> EXPORT_SYMBOL(thaw_bdev);
>

Apparently this never got in.

The bug is still there, reproducible with mere:
echo j > /proc/sysrq-trigger

--
Mateusz Guzik