From: zhouxianrong <zhouxianr...@huawei.com>
the reason for why to do this is based on below factors.
1. larg file read/write operations with order 0 can fragmentize
memory rapidly.
2. when a special filesystem does not supply migratepage callback,
kernel would fallback to default function fallback_migrate_page.
but fallback_migrate_page could not migrate diry page nicely;
specially kcompactd with MIGRATE_SYNC_LIGHT could not migrate
diry pages due to this until clear_page_dirty_for_io in some
procedure. i think it is not suitable here in this scenario.
for dirty pages we should migrate it rather than skip or writeout
it in kcomapctd with MIGRATE_SYNC_LIGHT. i think this problem is
for all filesystem without migratepage not only for block device fs.
so for compaction under large file writing supply migratepage for
def_blk_aops.
Signed-off-by: zhouxianrong <zhouxianr...@huawei.com>
---
fs/block_dev.c | 3 +++
1 file changed, 3 insertions(+)
diff --git a/fs/block_dev.c b/fs/block_dev.c
index 1c62845..9343b60 100644
--- a/fs/block_dev.c
+++ b/fs/block_dev.c
@@ -2062,6 +2062,9 @@ static int blkdev_writepages(struct address_space
*mapping,
.releasepage = blkdev_releasepage,
.direct_IO = blkdev_direct_IO,
.is_dirty_writeback = buffer_check_dirty_writeback,
+#ifdef CONFIG_MIGRATION
+ .migratepage = buffer_migrate_page,
+#endif
};
#define BLKDEV_FALLOC_FL_SUPPORTED
\
--
1.7.9.5
