On Wed, Apr 13, 2016 at 03:31:22PM +1000, Dave Chinner wrote:
> From: Dave Chinner <dchinner@xxxxxxxxxx>
>
> Joe Lawrence reported a list_add corruption with 4.6-rc1 when
> testing some custom md administration code that made it's own
> block device nodes for the md array. The simple test loop of:
>
> for i in {0..100}; do
> mknod --mode=0600 $tmp/tmp_node b $MAJOR $MINOR
> mdadm --detail --export $tmp/tmp_node > /dev/null
> rm -f $tmp/tmp_node
> done
>
>
> Would produce this warning in bd_acquire() when mdadm opened the
> device node:
>
> list_add double add: new=ffff88043831c7b8, prev=ffff8804380287d8, next=ffff88043831c7b8.
>
> And then produce this from bd_forget from kdevtmpfs evicting a block
> dev inode:
>
> list_del corruption. prev->next should be ffff8800bb83eb10, but was ffff88043831c7b8
>
> This is a regression caused by commit c19b3b05 ("xfs: mode di_mode
> to vfs inode"). The issue is that xfs_inactive() frees the
> unlinked inode, and the above commit meant that this freeing zeroed
> the mode in the struct inode. The problem is that after evict() has
> called ->evict_inode, it expects the i_mode to be intact so that it
> can call bd_forget() or cd_forget() to drop the reference to the
> block device inode attached to the XFS inode.
>
> In reality, the only thing we do in xfs_fs_evict_inode() that is not
> generic is call xfs_inactive(). We can move the xfs_inactive() call
> to xfs_fs_destroy_inode() without any problems at all, and this
> will leave the VFS inode intact until it is completely done with it.
>
> So, remove xfs_fs_evict_inode(), and do the work it used to do in
> ->destroy_inode instead.
>
> Reported-by: Joe Lawrence <joe.lawrence@xxxxxxxxxxx>
> Signed-off-by: Dave Chinner <dchinner@xxxxxxxxxx>
> ---
Reviewed-by: Brian Foster <bfoster@xxxxxxxxxx>
> fs/xfs/xfs_super.c | 28 +++++++---------------------
> 1 file changed, 7 insertions(+), 21 deletions(-)
>
> diff --git a/fs/xfs/xfs_super.c b/fs/xfs/xfs_super.c
> index e2f0f52..416421d 100644
> --- a/fs/xfs/xfs_super.c
> +++ b/fs/xfs/xfs_super.c
> @@ -928,7 +928,7 @@ xfs_fs_alloc_inode(
>
> /*
> * Now that the generic code is guaranteed not to be accessing
> - * the linux inode, we can reclaim the inode.
> + * the linux inode, we can inactivate and reclaim the inode.
> */
> STATIC void
> xfs_fs_destroy_inode(
> @@ -938,9 +938,14 @@ xfs_fs_destroy_inode(
>
> trace_xfs_destroy_inode(ip);
>
> - XFS_STATS_INC(ip->i_mount, vn_reclaim);
> + ASSERT(!rwsem_is_locked(&ip->i_iolock.mr_lock));
> + XFS_STATS_INC(ip->i_mount, vn_rele);
> + XFS_STATS_INC(ip->i_mount, vn_remove);
> +
> + xfs_inactive(ip);
>
> ASSERT(XFS_FORCED_SHUTDOWN(ip->i_mount) || ip->i_delayed_blks == 0);
> + XFS_STATS_INC(ip->i_mount, vn_reclaim);
>
> /*
> * We should never get here with one of the reclaim flags already set.
> @@ -987,24 +992,6 @@ xfs_fs_inode_init_once(
> "xfsino", ip->i_ino);
> }
>
> -STATIC void
> -xfs_fs_evict_inode(
> - struct inode *inode)
> -{
> - xfs_inode_t *ip = XFS_I(inode);
> -
> - ASSERT(!rwsem_is_locked(&ip->i_iolock.mr_lock));
> -
> - trace_xfs_evict_inode(ip);
> -
> - truncate_inode_pages_final(&inode->i_data);
> - clear_inode(inode);
> - XFS_STATS_INC(ip->i_mount, vn_rele);
> - XFS_STATS_INC(ip->i_mount, vn_remove);
> -
> - xfs_inactive(ip);
> -}
> -
> /*
> * We do an unlocked check for XFS_IDONTCACHE here because we are already
> * serialised against cache hits here via the inode->i_lock and igrab() in
> @@ -1673,7 +1660,6 @@ xfs_fs_free_cached_objects(
> static const struct super_operations xfs_super_operations = {
> .alloc_inode = xfs_fs_alloc_inode,
> .destroy_inode = xfs_fs_destroy_inode,
> - .evict_inode = xfs_fs_evict_inode,
> .drop_inode = xfs_fs_drop_inode,
> .put_super = xfs_fs_put_super,
> .sync_fs = xfs_fs_sync_fs,
> --
> 2.7.0
>
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