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Subject[PATCH v2] f2fs: wait IO writeback in commit_inmem_pages()
Date
From: Chao Yu <yuchao0@huawei.com>

Thread A Thread B
- f2fs_ioc_commit_atomic_write
- commit_inmem_pages
- f2fs_submit_merged_write_cond
: write data
- write_checkpoint
- do_checkpoint
: commit all node within CP
-> SPO
- f2fs_do_sync_file
- file_write_and_wait_range
: wait data writeback

In above race condition, data/node can be flushed in reversed order when
coming a checkpoint before f2fs_do_sync_file, after SPOR, it results in
atomic written data being corrupted.

This patch adds filemap_fdatawait() in commit_inmem_pages() to keep data
and node of atomic file being flushed orderly.

Signed-off-by: Chao Yu <yuchao0@huawei.com>
---
v2:
- clean up codes suggested by Jaegeuk.
fs/f2fs/file.c | 4 ++++
fs/f2fs/segment.c | 2 ++
2 files changed, 6 insertions(+)

diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c
index bac059474342..0cfa65c21d3f 100644
--- a/fs/f2fs/file.c
+++ b/fs/f2fs/file.c
@@ -217,6 +217,9 @@ static int f2fs_do_sync_file(struct file *file, loff_t start, loff_t end,

trace_f2fs_sync_file_enter(inode);

+ if (atomic)
+ goto write_done;
+
/* if fdatasync is triggered, let's do in-place-update */
if (datasync || get_dirty_pages(inode) <= SM_I(sbi)->min_fsync_blocks)
set_inode_flag(inode, FI_NEED_IPU);
@@ -228,6 +231,7 @@ static int f2fs_do_sync_file(struct file *file, loff_t start, loff_t end,
return ret;
}

+write_done:
/* if the inode is dirty, let's recover all the time */
if (!f2fs_skip_inode_update(inode, datasync)) {
f2fs_write_inode(inode, NULL);
diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c
index 710d817c4350..31336fc54d8e 100644
--- a/fs/f2fs/segment.c
+++ b/fs/f2fs/segment.c
@@ -419,6 +419,8 @@ static int __commit_inmem_pages(struct inode *inode)
__revoke_inmem_pages(inode, &fi->inmem_pages, true, false);
} else {
__revoke_inmem_pages(inode, &revoke_list, false, false);
+
+ err = filemap_fdatawait(inode->i_mapping);
}

return err;
--
2.16.2.17.g38e79b1fd
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