[f2fs-dev] [PATCH AUTOSEL 4.19 06/25] f2fs: fix to force keeping write barrier for strict fsync mode

[f2fs-dev] [PATCH AUTOSEL 4.19 06/25] f2fs: fix to force keeping write barrier for strict fsync mode

[Sasha Levin]

From: Chao Yu <chao@kernel.org>

[ Upstream commit 2787991516468bfafafb9bf2b45a848e6b202e7c ]

[1] https://www.mail-archive.com/linux-f2fs-devel@lists.sourceforge.net/msg15126.html

As [1] reported, if lower device doesn't support write barrier, in below
case:

- write page #0; persist
- overwrite page #0
- fsync
 - write data page #0 OPU into device's cache
 - write inode page into device's cache
 - issue flush

If SPO is triggered during flush command, inode page can be persisted
before data page #0, so that after recovery, inode page can be recovered
with new physical block address of data page #0, however there may
contains dummy data in new physical block address.

Then what user will see is: after overwrite & fsync + SPO, old data in
file was corrupted, if any user do care about such case, we can suggest
user to use STRICT fsync mode, in this mode, we will force to use atomic
write sematics to keep write order in between data/node and last node,
so that it avoids potential data corruption during fsync().

Signed-off-by: Chao Yu <chao@kernel.org>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 fs/f2fs/file.c | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c
index 95330dfdbb1a..3b36ee3d915b 100644
--- a/fs/f2fs/file.c
+++ b/fs/f2fs/file.c
@@ -253,6 +253,18 @@ static int f2fs_do_sync_file(struct file *file, loff_t start, loff_t end,
 				f2fs_exist_written_data(sbi, ino, UPDATE_INO))
 			goto flush_out;
 		goto out;
+	} else {
+		/*
+		 * for OPU case, during fsync(), node can be persisted before
+		 * data when lower device doesn't support write barrier, result
+		 * in data corruption after SPO.
+		 * So for strict fsync mode, force to use atomic write sematics
+		 * to keep write order in between data/node and last node to
+		 * avoid potential data corruption.
+		 */
+		if (F2FS_OPTION(sbi).fsync_mode ==
+				FSYNC_MODE_STRICT && !atomic)
+			atomic = true;
 	}
 go_write:
 	/*
-- 
2.30.2



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[f2fs-dev] [PATCH AUTOSEL 4.19 07/25] f2fs: fix min_seq_blocks can not make sense in some scenes.

[Sasha Levin]

From: Laibin Qiu <qiulaibin@huawei.com>

[ Upstream commit dc675a97129c4d9d5af55a3d7f23d7e092b8e032 ]

F2FS have dirty page count control for batched sequential
write in writepages, and get the value of min_seq_blocks by
blocks_per_seg * segs_per_sec(segs_per_sec defaults to 1).
But in some scenes we set a lager section size, Min_seq_blocks
will become too large to achieve the expected effect(eg. 4thread
sequential write, the number of merge requests will be reduced).

Signed-off-by: Laibin Qiu <qiulaibin@huawei.com>
Reviewed-by: Chao Yu <chao@kernel.org>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 fs/f2fs/segment.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c
index 0e3e590a250f..0ac907b06cb1 100644
--- a/fs/f2fs/segment.c
+++ b/fs/f2fs/segment.c
@@ -4198,7 +4198,7 @@ int f2fs_build_segment_manager(struct f2fs_sb_info *sbi)
 		sm_info->ipu_policy = 1 << F2FS_IPU_FSYNC;
 	sm_info->min_ipu_util = DEF_MIN_IPU_UTIL;
 	sm_info->min_fsync_blocks = DEF_MIN_FSYNC_BLOCKS;
-	sm_info->min_seq_blocks = sbi->blocks_per_seg * sbi->segs_per_sec;
+	sm_info->min_seq_blocks = sbi->blocks_per_seg;
 	sm_info->min_hot_blocks = DEF_MIN_HOT_BLOCKS;
 	sm_info->min_ssr_sections = reserved_sections(sbi);
 
-- 
2.30.2



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