[PATCH 0/2] fs: Fixup bdev_mark_dead callbacks for ext4 and xfs

[PATCH 0/2] fs: Fixup bdev_mark_dead callbacks for ext4 and xfs

[Jan Kara]

Hello,

Jens, I have found out the recently added handlers (sitting in your tree) of
.bdev_mark_dead callbacks in xfs and ext4 were wrongly using bdev->bd_holder
instead of bdev->bd_super and so they could never work. This series fixes them.

								Honza

[PATCH 1/2] ext4: Fix crash in ext4_bdev_mark_dead()

[Jan Kara]

ext4_bdev_mark_dead() passes bdev->bd_holder to ext4_force_shutdown()
instead of bdev->bd_super leading to crashes. Fix it.

Fixes: dd2e31afba9e ("ext4: wire up the ->mark_dead holder operation for log devices")
Signed-off-by: Jan Kara <jack@suse.cz>
---
 fs/ext4/super.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index 6f43a86ecf16..53d74144ee34 100644
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -1098,7 +1098,7 @@ void ext4_update_dynamic_rev(struct super_block *sb)
 
 static void ext4_bdev_mark_dead(struct block_device *bdev)
 {
-	ext4_force_shutdown(bdev->bd_holder, EXT4_GOING_FLAGS_NOLOGFLUSH);
+	ext4_force_shutdown(bdev->bd_super, EXT4_GOING_FLAGS_NOLOGFLUSH);
 }
 
 static const struct blk_holder_ops ext4_holder_ops = {
-- 
2.35.3

Re: [PATCH 1/2] ext4: Fix crash in ext4_bdev_mark_dead()

[Christoph Hellwig]

On Wed, Jun 21, 2023 at 04:47:42PM +0200, Jan Kara wrote:
> ext4_bdev_mark_dead() passes bdev->bd_holder to ext4_force_shutdown()
> instead of bdev->bd_super leading to crashes. Fix it.

How does this crash? ext4_blkdev_get passes the sb as holder, and I
actually tested this code.

This is not to be confused with the blkdev_get_by_path in get_tree_bdev,
but that never ends up in ext4_bdev_mark_dead.

Re: [PATCH 1/2] ext4: Fix crash in ext4_bdev_mark_dead()

[Jan Kara]

On Wed 21-06-23 07:52:27, Christoph Hellwig wrote:
> On Wed, Jun 21, 2023 at 04:47:42PM +0200, Jan Kara wrote:
> > ext4_bdev_mark_dead() passes bdev->bd_holder to ext4_force_shutdown()
> > instead of bdev->bd_super leading to crashes. Fix it.
> 
> How does this crash? ext4_blkdev_get passes the sb as holder, and I
> actually tested this code.
> 
> This is not to be confused with the blkdev_get_by_path in get_tree_bdev,
> but that never ends up in ext4_bdev_mark_dead.

Indeed, I have confused the method called for journal device with the
method called for the main filesystem device. Both my patches are wrong and
I'm sorry for the confusion!

								Honza
-- 
Jan Kara <jack@suse.com>
SUSE Labs, CR

[PATCH 2/2] xfs: Fix crash in ext4_bdev_mark_dead()

[Jan Kara]

xfs_bdev_mark_dead() passes bdev->bd_holder to ext4_force_shutdown()
instead of bdev->bd_super leading to crashes. Fix it.

Fixes: 8067ca1dcdfc ("xfs: wire up the ->mark_dead holder operation for log and RT devices")
Signed-off-by: Jan Kara <jack@suse.cz>
---
 fs/xfs/xfs_super.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/xfs/xfs_super.c b/fs/xfs/xfs_super.c
index d910b141d52e..3ab188a6fba1 100644
--- a/fs/xfs/xfs_super.c
+++ b/fs/xfs/xfs_super.c
@@ -381,7 +381,7 @@ static void
 xfs_bdev_mark_dead(
 	struct block_device	*bdev)
 {
-	xfs_force_shutdown(bdev->bd_holder, SHUTDOWN_DEVICE_REMOVED);
+	xfs_force_shutdown(XFS_M(bdev->bd_super), SHUTDOWN_DEVICE_REMOVED);
 }
 
 static const struct blk_holder_ops xfs_holder_ops = {
-- 
2.35.3

Re: [PATCH 2/2] xfs: Fix crash in ext4_bdev_mark_dead()

[Christoph Hellwig]

On Wed, Jun 21, 2023 at 04:47:43PM +0200, Jan Kara wrote:
> xfs_bdev_mark_dead() passes bdev->bd_holder to ext4_force_shutdown()
> instead of bdev->bd_super leading to crashes. Fix it.

xfs_bdev_mark_dead is only called for the log and RT devices, for which
the mp is passed as holder to blkdev_get_by_path.  bd_super won't be
set for those devices, so this patch will introduce a crash and not fix
one.