[PATCH 2/5] f2fs: drain in-flight DIO before buffered writes

[Jiale Yao]

An asynchronous iomap direct write can remain in flight after the inode
lock is released. A buffered write can then dirty page cache before the
direct write completes its post-I/O invalidation, causing the
invalidation to fail and record -EIO in the mapping error sequence.

The pre-write checks can also zero post-EOF page cache while an earlier
direct write is still active.

Wait for in-flight DIO before post-EOF page-cache operations and before
buffered writes. Return -EAGAIN for a NOWAIT write that would need the
blocking post-EOF operation.

Fixes: a1e09b03e6f5 ("f2fs: use iomap for direct I/O")
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Jiale Yao <yaojiale02@xxxxxxx>
---
 fs/f2fs/file.c | 13 +++++++++++--
 1 file changed, 11 insertions(+), 2 deletions(-)

diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c
index 0c759cc99054..d3d0ebf2f6c3 100644
--- a/fs/f2fs/file.c
+++ b/fs/f2fs/file.c
@@ -5328,6 +5328,7 @@ static ssize_t f2fs_write_checks(struct kiocb *iocb, struct iov_iter *from)
 {
 	struct file *file = iocb->ki_filp;
 	struct inode *inode = file_inode(file);
+	loff_t end_pos;
 	ssize_t count;
 	int err;
 
@@ -5345,8 +5346,14 @@ static ssize_t f2fs_write_checks(struct kiocb *iocb, struct iov_iter *from)
 	if (err)
 		return err;
 
-	err = f2fs_zero_post_eof_page(inode,
-		iocb->ki_pos + iov_iter_count(from), true, true);
+	end_pos = iocb->ki_pos + iov_iter_count(from);
+	if (end_pos > i_size_read(inode)) {
+		if (iocb->ki_flags & IOCB_NOWAIT)
+			return -EAGAIN;
+		inode_dio_wait(inode);
+	}
+
+	err = f2fs_zero_post_eof_page(inode, end_pos, true, true);
 	if (err)
 		return err;
 	return count;
@@ -5436,6 +5443,8 @@ static ssize_t f2fs_buffered_write_iter(struct kiocb *iocb,
 	if (iocb->ki_flags & IOCB_NOWAIT)
 		return -EOPNOTSUPP;
 
+	inode_dio_wait(inode);
+
 	ret = generic_perform_write(iocb, from);
 
 	if (ret > 0) {
-- 
2.34.1