vfs: fix spinning prevention in prune_icache_sb

We need to move the inode to the end of the list to actually make the
spinning prevention explained in the comment above it work.  With a
plain list_move it will simply stay in place as we're always reclaiming
from the head of the list.
Signed-off-by: NChristoph Hellwig <hch@lst.de>

fs/inode.c

@@ -634,7 +634,7 @@ void prune_icache_sb(struct super_block *sb, int nr_to_scan)
 		 * inode to the back of the list so we don't spin on it.
 		 */
 		if (!spin_trylock(&inode->i_lock)) {
-			list_move(&inode->i_lru, &sb->s_inode_lru);
+			list_move_tail(&inode->i_lru, &sb->s_inode_lru);
 			continue;
 		}