block: kill DIO_MULTI_BIO

Now __blkdev_direct_IO() serves only multi-bio I/O, thus remove
not used anymore single bio refcounting optimisations.

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/88eb488aae9ed4852a30f3a7132f296f56e43b80.1635337135.git.asml.silence@gmail.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/block/fops.c b/block/fops.c
index 983e993..8594852 100644 (file)
--- a/block/fops.c
+++ b/block/fops.c
@@ -124,9 +124,8 @@ out:
 }
 
 enum {
-       DIO_MULTI_BIO           = 1,
-       DIO_SHOULD_DIRTY        = 2,
-       DIO_IS_SYNC             = 4,
+       DIO_SHOULD_DIRTY        = 1,
+       DIO_IS_SYNC             = 2,
 };
 
 struct blkdev_dio {
@@ -150,7 +149,7 @@ static void blkdev_bio_end_io(struct bio *bio)
        if (bio->bi_status && !dio->bio.bi_status)
                dio->bio.bi_status = bio->bi_status;
 
-       if (!(dio->flags & DIO_MULTI_BIO) || atomic_dec_and_test(&dio->ref)) {
+       if (atomic_dec_and_test(&dio->ref)) {
                if (!(dio->flags & DIO_IS_SYNC)) {
                        struct kiocb *iocb = dio->iocb;
                        ssize_t ret;
@@ -165,8 +164,7 @@ static void blkdev_bio_end_io(struct bio *bio)
                        }
 
                        dio->iocb->ki_complete(iocb, ret, 0);
-                       if (dio->flags & DIO_MULTI_BIO)
-                               bio_put(&dio->bio);
+                       bio_put(&dio->bio);
                } else {
                        struct task_struct *waiter = dio->waiter;
 
@@ -201,11 +199,17 @@ static ssize_t __blkdev_direct_IO(struct kiocb *iocb, struct iov_iter *iter,
        bio = bio_alloc_kiocb(iocb, nr_pages, &blkdev_dio_pool);
 
        dio = container_of(bio, struct blkdev_dio, bio);
+       atomic_set(&dio->ref, 1);
+       /*
+        * Grab an extra reference to ensure the dio structure which is embedded
+        * into the first bio stays around.
+        */
+       bio_get(bio);
+
        is_sync = is_sync_kiocb(iocb);
        if (is_sync) {
                dio->flags = DIO_IS_SYNC;
                dio->waiter = current;
-               bio_get(bio);
        } else {
                dio->flags = 0;
                dio->iocb = iocb;
@@ -251,20 +255,7 @@ static ssize_t __blkdev_direct_IO(struct kiocb *iocb, struct iov_iter *iter,
                        submit_bio(bio);
                        break;
                }
-               if (!(dio->flags & DIO_MULTI_BIO)) {
-                       /*
-                        * AIO needs an extra reference to ensure the dio
-                        * structure which is embedded into the first bio
-                        * stays around.
-                        */
-                       if (!is_sync)
-                               bio_get(bio);
-                       dio->flags |= DIO_MULTI_BIO;
-                       atomic_set(&dio->ref, 2);
-               } else {
-                       atomic_inc(&dio->ref);
-               }
-
+               atomic_inc(&dio->ref);
                submit_bio(bio);
                bio = bio_alloc(GFP_KERNEL, nr_pages);
        }