fs: fuse: account fuse_inode slab memory as reclaimable

Fuse inodes are currently included in the unreclaimable slab counts -
SUnreclaim in /proc/meminfo, slab_unreclaimable in /proc/vmstat and the
per-cgroup memory.stat.  But they are reclaimable just like other
filesystems' inodes, and /proc/sys/vm/drop_caches frees them easily.

Mark the slab cache reclaimable.

Link: http://lkml.kernel.org/r/20171102202727.12539-1-hannes@cmpxchg.orgSigned-off-by: Johannes Weiner <hannes@cmpxchg.org>
Cc: Miklos Szeredi <mszeredi@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

fs/fuse/inode.c

@@ -1274,7 +1274,7 @@ static int __init fuse_fs_init(void)
 
 	fuse_inode_cachep = kmem_cache_create("fuse_inode",
 			sizeof(struct fuse_inode), 0,
-					      SLAB_HWCACHE_ALIGN|SLAB_ACCOUNT,
+			SLAB_HWCACHE_ALIGN|SLAB_ACCOUNT|SLAB_RECLAIM_ACCOUNT,
 			fuse_inode_init_once);
 	err = -ENOMEM;
 	if (!fuse_inode_cachep)