The patch titled
Subject: blkdev: avoid migration stalls for blkdev pages
has been added to the -mm tree. Its filename is
blkdev-avoid-migration-stalls-for-blkdev-pages.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/blkdev-avoid-migration-stalls-for-blkdev-pages.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/blkdev-avoid-migration-stalls-for-blkdev-pages.patch
Before you just go and hit "reply", please:
a) Consider who else should be cc'ed
b) Prefer to cc a suitable mailing list as well
c) Ideally: find the original patch on the mailing list and do a
reply-to-all to that, adding suitable additional cc's
*** Remember to use Documentation/process/submit-checklist.rst when testing your code ***
The -mm tree is included into linux-next and is updated
there every 3-4 working days
------------------------------------------------------
From: Jan Kara <jack@xxxxxxx>
Subject: 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@xxxxxxx
Signed-off-by: Jan Kara <jack@xxxxxxx>
Acked-by: Mel Gorman <mgorman@xxxxxxx>
Cc: Michal Hocko <mhocko@xxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
--- a/fs/block_dev.c~blkdev-avoid-migration-stalls-for-blkdev-pages
+++ a/fs/block_dev.c
@@ -1966,6 +1966,7 @@ static const struct address_space_operat
.writepages = blkdev_writepages,
.releasepage = blkdev_releasepage,
.direct_IO = blkdev_direct_IO,
+ .migratepage = buffer_migrate_page_norefs,
.is_dirty_writeback = buffer_check_dirty_writeback,
};
_
Patches currently in -mm which might be from jack@xxxxxxx are
mm-migration-factor-out-code-to-compute-expected-number-of-page-references.patch
mm-migrate-lock-buffers-before-migrate_page_move_mapping.patch
mm-migrate-move-migrate_page_lock_buffers.patch
mm-migrate-provide-buffer_migrate_page_norefs.patch
blkdev-avoid-migration-stalls-for-blkdev-pages.patch
mm-migrate-drop-unused-argument-of-migrate_page_move_mapping.patch
