[PATCH] btrfs: wait between incomplete batch allocations

[Sweet Tea Dorminy]

When allocating memory in a loop, each iteration should call
memalloc_retry_wait() in order to prevent starving memory-freeing
processes (and to mark where allcoation loops are). ext4, f2fs, and xfs
all use this function at present for their allocation loops; btrfs ought
also.

The bulk page allocation is the only place in btrfs with an allocation
retry loop, so add an appropriate call to it.

Suggested-by: David Sterba <dsterba@xxxxxxx>
Signed-off-by: Sweet Tea Dorminy <sweettea-kernel@xxxxxxxxxx>
---
 fs/btrfs/extent_io.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c
index 9f2ada809dea..4bcc182744e4 100644
--- a/fs/btrfs/extent_io.c
+++ b/fs/btrfs/extent_io.c
@@ -6,6 +6,7 @@
 #include <linux/mm.h>
 #include <linux/pagemap.h>
 #include <linux/page-flags.h>
+#include <linux/sched/mm.h>
 #include <linux/spinlock.h>
 #include <linux/blkdev.h>
 #include <linux/swap.h>
@@ -3159,6 +3160,8 @@ int btrfs_alloc_page_array(unsigned int nr_pages, struct page **page_array)
 		 */
 		if (allocated == last)
 			return -ENOMEM;
+
+		memalloc_retry_wait(GFP_NOFS);
 	}
 	return 0;
 }
-- 
2.35.1