[PATCH 1/8] iomap: cleanup up iomap_dio_bio_end_io()

Jens Axboe
2023-07-24T22:55:20Z

Make the logic a bit easier to follow:

1) Add a release_bio out path, as everybody needs to touch that, and
have our bio ref check jump there if it's non-zero.
2) Add a kiocb local variable.
3) Add comments for each of the three conditions (sync, inline, or
async workqueue punt).

No functional changes in this patch.

Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
---
fs/iomap/direct-io.c | 46 +++++++++++++++++++++++++++++---------------
1 file changed, 31 insertions(+), 15 deletions(-)

diff --git a/fs/iomap/direct-io.c b/fs/iomap/direct-io.c
index ea3b868c8355..0ce60e80c901 100644
--- a/fs/iomap/direct-io.c
+++ b/fs/iomap/direct-io.c
@@ -152,27 +152,43 @@ void iomap_dio_bio_end_io(struct bio *bio)
{
struct iomap_dio *dio = bio->bi_private;
bool should_dirty = (dio->flags & IOMAP_DIO_DIRTY);
+ struct kiocb *iocb = dio->iocb;

if (bio->bi_status)
iomap_dio_set_error(dio, blk_status_to_errno(bio->bi_status));
+ if (!atomic_dec_and_test(&dio->ref))
+ goto release_bio;

- if (atomic_dec_and_test(&dio->ref)) {
- if (dio->wait_for_completion) {
- struct task_struct *waiter = dio->submit.waiter;
- WRITE_ONCE(dio->submit.waiter, NULL);
- blk_wake_io_task(waiter);
- } else if (dio->flags & IOMAP_DIO_WRITE) {
- struct inode *inode = file_inode(dio->iocb->ki_filp);
-
- WRITE_ONCE(dio->iocb->private, NULL);
- INIT_WORK(&dio->aio.work, iomap_dio_complete_work);
- queue_work(inode->i_sb->s_dio_done_wq, &dio->aio.work);
- } else {
- WRITE_ONCE(dio->iocb->private, NULL);
- iomap_dio_complete_work(&dio->aio.work);
- }
+ /*
+ * Synchronous dio, task itself will handle any completion work
+ * that needs after IO. All we need to do is wake the task.
+ */
+ if (dio->wait_for_completion) {
+ struct task_struct *waiter = dio->submit.waiter;
+
+ WRITE_ONCE(dio->submit.waiter, NULL);
+ blk_wake_io_task(waiter);
+ goto release_bio;
+ }
+
+ /* Read completion can always complete inline. */
+ if (!(dio->flags & IOMAP_DIO_WRITE)) {
+ WRITE_ONCE(iocb->private, NULL);
+ iomap_dio_complete_work(&dio->aio.work);
+ goto release_bio;
}

+ /*
+ * Async DIO completion that requires filesystem level completion work
+ * gets punted to a work queue to complete as the operation may require
+ * more IO to be issued to finalise filesystem metadata changes or
+ * guarantee data integrity.
+ */
+ WRITE_ONCE(iocb->private, NULL);
+ INIT_WORK(&dio->aio.work, iomap_dio_complete_work);
+ queue_work(file_inode(iocb->ki_filp)->i_sb->s_dio_done_wq,
+ &dio->aio.work);
+release_bio:
if (should_dirty) {
bio_check_pages_dirty(bio);
} else {
--
2.40.1