xfs: xfs_mru_cache_insert() should use GFP_NOFS

xfs_mru_cache_insert() can be called from within transaction context
during block allocation like so:

write(2)
....
xfs_get_blocks
xfs_iomap_write_direct
start transaction
xfs_bmapi_write
xfs_bmapi_allocate
xfs_bmap_btalloc
xfs_bmap_btalloc_filestreams
xfs_filestream_new_ag
xfs_filestream_pick_ag
xfs_mru_cache_insert
radix_tree_preload(GFP_KERNEL)

In this case, GFP_KERNEL is incorrect and can potentially lead to
deadlocks in memory reclaim. It should use GFP_NOFS allocations to
avoid lock recursion problems.

[dchinner: rewrote commit message]

Signed-off-by: Byoungyoung Lee <[e-mail]>
Signed-off-by: Sanidhya Kashyap <[e-mail]>
Reviewed-by: Dave Chinner <[e-mail]>
Signed-off-by: Dave Chinner <[e-mail]>

fs/xfs/xfs_mru_cache.c

···
 	if (!mru || !mru->lists)
 		return -EINVAL;
 
-	if (radix_tree_preload(GFP_KERNEL))
+	if (radix_tree_preload(GFP_NOFS))
 		return -ENOMEM;
 
 	INIT_LIST_HEAD(&elem->list_node);