[PATCH v2] xfs: mark slab-allocated xfs_buf backing memory as __GFP_RECLAIMABLE

xfs_bufs have a shrinker and are therefore reclaimable, as is the memory
backing them. Mark slab-allocated backing memory as __GFP_RECLAIMABLE in 
the kmalloc path so that it is accounted properly.

Signed-off-by: Eric Sandeen <[email protected]>
Reviewed-by: Christoph Hellwig <[email protected]>
---
 fs/xfs/xfs_buf.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

The other part of this (non-slab-allocated backing memory) is thornier
but I think this patch is simple, correct, and stands alone, so let's
see if it can move forward.

V2: tidy up title/commit log to clarify this is about the /backing/ memory,
    and add hch's RVB

diff --git a/fs/xfs/xfs_buf.c b/fs/xfs/xfs_buf.c
index 48d7dfd3e15f..2e00a33ebb62 100644
--- a/fs/xfs/xfs_buf.c
+++ b/fs/xfs/xfs_buf.c
@@ -145,7 +145,7 @@ xfs_buf_alloc_kmem(
 	ASSERT(is_power_of_2(size));
 	ASSERT(size < PAGE_SIZE);
 
-	bp->b_addr = kmalloc(size, gfp_mask);
+	bp->b_addr = kmalloc(size, gfp_mask | __GFP_RECLAIMABLE);
 	if (!bp->b_addr)
 		return -ENOMEM;