f2fs: shrink node_write lock coverage

- to avoid race between checkpoint and quota file writeback, it
just needs to hold read lock of node_write in writeback path.
- node_write lock has covered all LFS data write paths, it's not
necessary, we only need to hold node_write lock at write path of
quota file.

This refactors commit ca7f76e68074 ("f2fs: fix wrong discard space").

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

1 files changed, 12 insertions, 0 deletions

diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c
index c78ce08f6400..cbdf062d3562 100644
--- a/fs/f2fs/data.c
+++ b/fs/f2fs/data.c
@@ -2719,8 +2719,20 @@ write:
 
 	/* Dentry/quota blocks are controlled by checkpoint */
 	if (S_ISDIR(inode->i_mode) || IS_NOQUOTA(inode)) {
+		/*
+		 * We need to wait for node_write to avoid block allocation during
+		 * checkpoint. This can only happen to quota writes which can cause
+		 * the below discard race condition.
+		 */
+		if (IS_NOQUOTA(inode))
+			down_read(&sbi->node_write);
+
 		fio.need_lock = LOCK_DONE;
 		err = f2fs_do_write_data_page(&fio);
+
+		if (IS_NOQUOTA(inode))
+			up_read(&sbi->node_write);
+
 		goto done;
 	}