[PATCH v4 5/6] ext4: use kiocb_modified instead of file_modified in DIO/DAX write path

[Baokun Li <libaokun@linux.alibaba.com>]

file_modified() passes flags=0 which drops IOCB_NOWAIT, causing
file_update_time() to sleep in ext4_journal_start() via
ext4_dirty_inode() even in non-blocking contexts.

kiocb_modified(iocb) propagates iocb->ki_flags so that
generic_update_time() correctly returns -EAGAIN when IOCB_NOWAIT
is set and ->dirty_inode could block, matching the behavior
already adopted by XFS, FUSE, and ext2.

Affected paths:
- ext4_dio_write_checks(): DIO NOWAIT write
- ext4_write_checks(): shared by buffered (rejects NOWAIT upfront)
  and DAX write (supports NOWAIT)

ext4_fallocate() in extents.c is not affected as it has no kiocb.

Reviewed-by: Zhang Yi <yi.zhang@huawei.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Signed-off-by: Baokun Li <libaokun@linux.alibaba.com>
---
 fs/ext4/file.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/fs/ext4/file.c b/fs/ext4/file.c
index d12445e3907a..0e9448a110dc 100644
--- a/fs/ext4/file.c
+++ b/fs/ext4/file.c
@@ -307,7 +307,7 @@ static ssize_t ext4_write_checks(struct kiocb *iocb, struct iov_iter *from)
 	if (count <= 0)
 		return count;
 
-	ret = file_modified(iocb->ki_filp);
+	ret = kiocb_modified(iocb);
 	if (ret)
 		return ret;
 
@@ -466,7 +466,7 @@ static const struct iomap_dio_ops ext4_dio_write_ops = {
  *
  * The decision is layered, evaluated in this order:
  *
- * 1. If file_modified() needs to update security info (!IS_NOSEC), upgrade
+ * 1. If kiocb_modified() needs to update security info (!IS_NOSEC), upgrade
  *    to the exclusive lock -- the security update itself requires it,
  *    regardless of whether the write extends the file or is aligned.
  *
@@ -556,7 +556,7 @@ static ssize_t ext4_dio_write_checks(struct kiocb *iocb, struct iov_iter *from,
 		*dio_flags = IOMAP_DIO_FORCE_WAIT;
 	}
 
-	ret = file_modified(file);
+	ret = kiocb_modified(iocb);
 	if (ret < 0)
 		goto out;
 
-- 
2.43.7