[PATCH] btrfs: unlock i_mutex after attempting to delete subvolume during send

[PATCH] btrfs: unlock i_mutex after attempting to delete subvolume during send

[Omar Sandoval]

Whenever the check for a send in progress introduced in commit
521e0546c970 (btrfs: protect snapshots from deleting during send) is
hit, we return without unlocking inode->i_mutex. This is easy to see
with lockdep enabled:

[  +0.000059] ================================================
[  +0.000028] [ BUG: lock held when returning to user space! ]
[  +0.000029] 4.0.0-rc5-00096-g3c435c1 #93 Not tainted
[  +0.000026] ------------------------------------------------
[  +0.000029] btrfs/211 is leaving the kernel with locks still held!
[  +0.000029] 1 lock held by btrfs/211:
[  +0.000023]  #0:  (&type->i_mutex_dir_key){+.+.+.}, at: [<ffffffff8135b8df>] btrfs_ioctl_snap_destroy+0x2df/0x7a0

Make sure we unlock it in the error path.

Signed-off-by: Omar Sandoval <osandov@osandov.com>
---
 fs/btrfs/ioctl.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
index 74609b9..9fde01f 100644
--- a/fs/btrfs/ioctl.c
+++ b/fs/btrfs/ioctl.c
@@ -2403,7 +2403,7 @@ static noinline int btrfs_ioctl_snap_destroy(struct file *file,
 			"Attempt to delete subvolume %llu during send",
 			dest->root_key.objectid);
 		err = -EPERM;
-		goto out_dput;
+		goto out_unlock_inode;
 	}
 
 	d_invalidate(dentry);
@@ -2498,6 +2498,7 @@ out_up_write:
 				root_flags & ~BTRFS_ROOT_SUBVOL_DEAD);
 		spin_unlock(&dest->root_item_lock);
 	}
+out_unlock_inode:
 	mutex_unlock(&inode->i_mutex);
 	if (!err) {
 		shrink_dcache_sb(root->fs_info->sb);
-- 
2.3.4

Re: [PATCH] btrfs: unlock i_mutex after attempting to delete subvolume during send

[Filipe David Manana]

On Sat, Mar 28, 2015 at 11:02 AM, Omar Sandoval <osandov@osandov.com> wrote:
> Whenever the check for a send in progress introduced in commit
> 521e0546c970 (btrfs: protect snapshots from deleting during send) is
> hit, we return without unlocking inode->i_mutex. This is easy to see
> with lockdep enabled:
>
> [  +0.000059] ================================================
> [  +0.000028] [ BUG: lock held when returning to user space! ]
> [  +0.000029] 4.0.0-rc5-00096-g3c435c1 #93 Not tainted
> [  +0.000026] ------------------------------------------------
> [  +0.000029] btrfs/211 is leaving the kernel with locks still held!
> [  +0.000029] 1 lock held by btrfs/211:
> [  +0.000023]  #0:  (&type->i_mutex_dir_key){+.+.+.}, at: [<ffffffff8135b8df>] btrfs_ioctl_snap_destroy+0x2df/0x7a0
>
> Make sure we unlock it in the error path.
>
> Signed-off-by: Omar Sandoval <osandov@osandov.com>
Reviewed-by: Filipe Manana <fdmanana@suse.com>

Thanks, should go to stable in my opinion.


> ---
>  fs/btrfs/ioctl.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
> index 74609b9..9fde01f 100644
> --- a/fs/btrfs/ioctl.c
> +++ b/fs/btrfs/ioctl.c
> @@ -2403,7 +2403,7 @@ static noinline int btrfs_ioctl_snap_destroy(struct file *file,
>                         "Attempt to delete subvolume %llu during send",
>                         dest->root_key.objectid);
>                 err = -EPERM;
> -               goto out_dput;
> +               goto out_unlock_inode;
>         }
>
>         d_invalidate(dentry);
> @@ -2498,6 +2498,7 @@ out_up_write:
>                                 root_flags & ~BTRFS_ROOT_SUBVOL_DEAD);
>                 spin_unlock(&dest->root_item_lock);
>         }
> +out_unlock_inode:
>         mutex_unlock(&inode->i_mutex);
>         if (!err) {
>                 shrink_dcache_sb(root->fs_info->sb);
> --
> 2.3.4
>
> --
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-- 
Filipe David Manana,

"Reasonable men adapt themselves to the world.
 Unreasonable men adapt the world to themselves.
 That's why all progress depends on unreasonable men."

Re: [PATCH] btrfs: unlock i_mutex after attempting to delete subvolume during send

[David Sterba]

On Sat, Mar 28, 2015 at 11:37:43AM +0000, Filipe David Manana wrote:
> On Sat, Mar 28, 2015 at 11:02 AM, Omar Sandoval <osandov@osandov.com> wrote:
> > Whenever the check for a send in progress introduced in commit
> > 521e0546c970 (btrfs: protect snapshots from deleting during send) is
> > hit, we return without unlocking inode->i_mutex. This is easy to see
> > with lockdep enabled:
> >
> > [  +0.000059] ================================================
> > [  +0.000028] [ BUG: lock held when returning to user space! ]
> > [  +0.000029] 4.0.0-rc5-00096-g3c435c1 #93 Not tainted
> > [  +0.000026] ------------------------------------------------
> > [  +0.000029] btrfs/211 is leaving the kernel with locks still held!
> > [  +0.000029] 1 lock held by btrfs/211:
> > [  +0.000023]  #0:  (&type->i_mutex_dir_key){+.+.+.}, at: [<ffffffff8135b8df>] btrfs_ioctl_snap_destroy+0x2df/0x7a0
> >
> > Make sure we unlock it in the error path.
> >
> > Signed-off-by: Omar Sandoval <osandov@osandov.com>
> Reviewed-by: Filipe Manana <fdmanana@suse.com>
> 
> Thanks, should go to stable in my opinion.

Agreed.

Re: [PATCH] btrfs: unlock i_mutex after attempting to delete subvolume during send

[David Sterba]

On Sat, Mar 28, 2015 at 04:02:06AM -0700, Omar Sandoval wrote:
> Whenever the check for a send in progress introduced in commit
> 521e0546c970 (btrfs: protect snapshots from deleting during send) is
> hit, we return without unlocking inode->i_mutex. This is easy to see
> with lockdep enabled:
> 
> [  +0.000059] ================================================
> [  +0.000028] [ BUG: lock held when returning to user space! ]
> [  +0.000029] 4.0.0-rc5-00096-g3c435c1 #93 Not tainted
> [  +0.000026] ------------------------------------------------
> [  +0.000029] btrfs/211 is leaving the kernel with locks still held!
> [  +0.000029] 1 lock held by btrfs/211:
> [  +0.000023]  #0:  (&type->i_mutex_dir_key){+.+.+.}, at: [<ffffffff8135b8df>] btrfs_ioctl_snap_destroy+0x2df/0x7a0
> 
> Make sure we unlock it in the error path.
> 
> Signed-off-by: Omar Sandoval <osandov@osandov.com>

Reviewed-by: David Sterba <dsterba@suse.cz>