Commit 1dc0f899 authored Feb 27, 2018 by Chao Yu Committed by Jaegeuk Kim Mar 13, 2018

f2fs: fix to avoid race in between atomic write and background GC



Sqlite user			Background GC
				- move_data_block
				  : move page #1
				 - f2fs_is_atomic_file
- f2fs_ioc_start_atomic_write
- f2fs_ioc_commit_atomic_write
 - commit_inmem_pages
   : commit page #1 & set node #2 dirty
				 - f2fs_submit_page_write
				  - f2fs_update_data_blkaddr
				   - set_page_dirty
				     : set node #2 dirty
 - f2fs_do_sync_file
  - fsync_node_pages
   : commit node #1 & node #2, then sudden power-cut

In a race case, we may check FI_ATOMIC_FILE flag before starting atomic
write flow, then we will commit meta data before data with reversed
order, after a sudden pow-cut, database transaction will be inconsistent.

So we'd better to exclude gc/atomic_write to each other by using lock
instead of flag checking.

Signed-off-by: Chao Yu <yuchao0@huawei.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>

parent b27bc809

fs/f2fs/file.c

+3 −0

Original line number	Diff line number	Diff line
		@@ -1715,6 +1715,8 @@ static int f2fs_ioc_commit_atomic_write(struct file *filp)

		inode_lock(inode);

		down_write(&F2FS_I(inode)->dio_rwsem[WRITE]);

		if (f2fs_is_volatile_file(inode))
		goto err_out;

		@@ -1733,6 +1735,7 @@ static int f2fs_ioc_commit_atomic_write(struct file *filp)
		ret = f2fs_do_sync_file(filp, 0, LLONG_MAX, 1, false);
		}
		err_out:
		up_write(&F2FS_I(inode)->dio_rwsem[WRITE]);
		inode_unlock(inode);
		mnt_drop_write_file(filp);
		return ret;

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