Btrfs: fix cleaner thread not working with inode cache option

Right now inode cache inode is treated as the same as space cache
inode, ie. keep inode in memory till putting super.

But this leads to an awkward situation.

If we're going to delete a snapshot/subvolume, btrfs will not
actually delete it and return free space, but will add it to dead
roots list until the last inode on this snap/subvol being destroyed.
Then we'll fetch deleted roots and cleanup them via cleaner thread.

So here is the problem, if we enable inode cache option, each
snap/subvol has a cached inode which is used to store inode allcation
information.  And this cache inode will be kept in memory, as the above
said.  So with inode cache, snap/subvol can only be added into
dead roots list during freeing roots stage in umount, so that we can
ONLY get space back after another remount(we cleanup dead roots on mount).

But the real thing is we'll no more use the snap/subvol if we mark it
deleted, so we can safely iput its cache inode when we delete snap/subvol.

Another thing is that we need to change the rules of droping inode, we
don't keep snap/subvol's cache inode in memory till end so that we can
add snap/subvol into dead roots list in time.

Reported-by: Mitch Harder <mitch.harder@sabayonlinux.org>
Signed-off-by: Liu Bo <bo.li.liu@oracle.com>
Signed-off-by: Josef Bacik <jbacik@fusionio.com>

diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index fce61991213c9284191244b75427f1465c38fbc4..b009fb52bd8a86e633d3d2dab54638ca2ff17a90 100644 (file)
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -7315,8 +7315,9 @@ int btrfs_drop_inode(struct inode *inode)
 {
        struct btrfs_root *root = BTRFS_I(inode)->root;
 
+       /* the snap/subvol tree is on deleting */
        if (btrfs_root_refs(&root->root_item) == 0 &&
-           !btrfs_is_free_space_inode(inode))
+           root != root->fs_info->tree_root)
                return 1;
        else
                return generic_drop_inode(inode);

diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
index e0893036da08ca1bc56f8113ab6ce25c75f55bbf..2bbbed506f5ba64788beb8714dcf7962d8114814 100644 (file)
--- a/fs/btrfs/ioctl.c
+++ b/fs/btrfs/ioctl.c
@@ -2174,6 +2174,12 @@ out_unlock:
                shrink_dcache_sb(root->fs_info->sb);
                btrfs_invalidate_inodes(dest);
                d_delete(dentry);
+
+               /* the last ref */
+               if (dest->cache_inode) {
+                       iput(dest->cache_inode);
+                       dest->cache_inode = NULL;
+               }
        }
 out_dput:
        dput(dentry);