The patch titled
Subject: fs/sync.c: make sync_file_range(2) use WB_SYNC_NONE writeback
has been added to the -mm tree. Its filename is
fs-make-sync_file_range2-use-wb_sync_none-writeback.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/fs-make-sync_file_range2-use-wb_sync_none-writeback.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/fs-make-sync_file_range2-use-wb_sync_none-writeback.patch
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From: Jan Kara <jack@xxxxxxxx>
Subject: fs/sync.c: make sync_file_range(2) use WB_SYNC_NONE writeback
sync_file_range(2) is documented to issue writeback only for pages that
are not currently being written. After all the system call has been
created for userspace to be able to issue background writeout and so
waiting for in-flight IO is undesirable there. However commit
ee53a891f474 (mm: do_sync_mapping_range integrity fix) switched
do_sync_mapping_range() and thus sync_file_range() to issue writeback in
WB_SYNC_ALL mode since do_sync_mapping_range() was used by other code
relying on WB_SYNC_ALL semantics.
These days do_sync_mapping_range() went away and we can switch
sync_file_range(2) back to issuing WB_SYNC_NONE writeback. That should
help PostgreSQL avoid large latency spikes when flushing data in the
background.
Signed-off-by: Jan Kara <jack@xxxxxxxx>
Reported-by: Andres Freund <andres@xxxxxxxxxxx>
Cc: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
fs/sync.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
diff -puN fs/sync.c~fs-make-sync_file_range2-use-wb_sync_none-writeback fs/sync.c
--- a/fs/sync.c~fs-make-sync_file_range2-use-wb_sync_none-writeback
+++ a/fs/sync.c
@@ -348,7 +348,8 @@ SYSCALL_DEFINE4(sync_file_range, int, fd
}
if (flags & SYNC_FILE_RANGE_WRITE) {
- ret = filemap_fdatawrite_range(mapping, offset, endbyte);
+ ret = __filemap_fdatawrite_range(mapping, offset, endbyte,
+ WB_SYNC_NONE);
if (ret < 0)
goto out_put;
}
_
Patches currently in -mm which might be from jack@xxxxxxxx are
fs-make-sync_file_range2-use-wb_sync_none-writeback.patch
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