Commit 88dbcbb3 authored Dec 28, 2018 by Jan Kara Committed by Linus Torvalds Dec 28, 2018

blkdev: avoid migration stalls for blkdev pages

Currently, block device pages don't provide a ->migratepage callback and
thus fallback_migrate_page() is used for them.  This handler cannot deal
with dirty pages in async mode and also with the case a buffer head is in
the LRU buffer head cache (as it has elevated b_count).  Thus such page
can block memory offlining.

Fix the problem by using buffer_migrate_page_norefs() for migrating block
device pages.  That function takes care of dropping bh LRU in case
migration would fail due to elevated buffer refcount to avoid stalls and
can also migrate dirty pages without writing them.

Link: http://lkml.kernel.org/r/20181211172143.7358-6-jack@suse.cz


Signed-off-by: Jan Kara <jack@suse.cz>
Acked-by: Mel Gorman <mgorman@suse.de>
Cc: Michal Hocko <mhocko@suse.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

parent 89cb0888

fs/block_dev.c

+1 −0

Original line number	Diff line number	Diff line
		@@ -1966,6 +1966,7 @@ static const struct address_space_operations def_blk_aops = {
		.writepages = blkdev_writepages,
		.releasepage = blkdev_releasepage,
		.direct_IO = blkdev_direct_IO,
		.migratepage = buffer_migrate_page_norefs,
		.is_dirty_writeback = buffer_check_dirty_writeback,
		};

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