[PATCH 1/2] mm: add cond_resched to generic_swapfile_activate

[Mikulas Patocka]

The function generic_swapfile_activate can take quite long time, it iterates
over all blocks of a file, so add cond_resched to it. I observed about 1 second
stalls when activating a swapfile that was almost unfragmented - this patch
fixes it.

Signed-off-by: Mikulas Patocka <mpatocka@xxxxxxxxxx>

---
 mm/page_io.c |    2 ++
 1 file changed, 2 insertions(+)

Index: linux-4.7-rc7/mm/page_io.c
===================================================================
--- linux-4.7-rc7.orig/mm/page_io.c	2016-05-30 17:34:37.000000000 +0200
+++ linux-4.7-rc7/mm/page_io.c	2016-07-11 17:23:33.000000000 +0200
@@ -166,6 +166,8 @@ int generic_swapfile_activate(struct swa
 		unsigned block_in_page;
 		sector_t first_block;
 
+		cond_resched();
+
 		first_block = bmap(inode, probe_block);
 		if (first_block == 0)
 			goto bad_bmap;