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authorJens Axboe <axboe@kernel.dk>2019-07-16 13:56:42 -0600
committerJens Axboe <axboe@kernel.dk>2019-07-21 21:46:29 -0600
commit6a43074e2f461c2c49a607f9f6f5218d53f97d1e (patch)
treee1781f5c8c89749b67b76157dcc8f57c75a581f1
parent893a1c97205a3ece0cbb3f571a3b972080f3b4c7 (diff)
block: properly handle IOCB_NOWAIT for async O_DIRECT IO
A caller is supposed to pass in REQ_NOWAIT if we can't block for any given operation, but O_DIRECT for block devices just ignore this. Hence we'll block for various resource shortages on the block layer side, like having to wait for requests. Use the new REQ_NOWAIT_INLINE to ask for this error to be returned inline, so we can handle it appropriately and return -EAGAIN to the caller. Signed-off-by: Jens Axboe <axboe@kernel.dk>
-rw-r--r--fs/block_dev.c58
1 files changed, 50 insertions, 8 deletions
diff --git a/fs/block_dev.c b/fs/block_dev.c
index f00b569a9f89..5dc613eec4d2 100644
--- a/fs/block_dev.c
+++ b/fs/block_dev.c
@@ -344,15 +344,24 @@ __blkdev_direct_IO(struct kiocb *iocb, struct iov_iter *iter, int nr_pages)
struct bio *bio;
bool is_poll = (iocb->ki_flags & IOCB_HIPRI) != 0;
bool is_read = (iov_iter_rw(iter) == READ), is_sync;
+ bool nowait = (iocb->ki_flags & IOCB_NOWAIT) != 0;
loff_t pos = iocb->ki_pos;
blk_qc_t qc = BLK_QC_T_NONE;
- int ret = 0;
+ gfp_t gfp;
+ ssize_t ret;
if ((pos | iov_iter_alignment(iter)) &
(bdev_logical_block_size(bdev) - 1))
return -EINVAL;
- bio = bio_alloc_bioset(GFP_KERNEL, nr_pages, &blkdev_dio_pool);
+ if (nowait)
+ gfp = GFP_NOWAIT;
+ else
+ gfp = GFP_KERNEL;
+
+ bio = bio_alloc_bioset(gfp, nr_pages, &blkdev_dio_pool);
+ if (!bio)
+ return -EAGAIN;
dio = container_of(bio, struct blkdev_dio, bio);
dio->is_sync = is_sync = is_sync_kiocb(iocb);
@@ -374,7 +383,10 @@ __blkdev_direct_IO(struct kiocb *iocb, struct iov_iter *iter, int nr_pages)
if (!is_poll)
blk_start_plug(&plug);
+ ret = 0;
for (;;) {
+ int err;
+
bio_set_dev(bio, bdev);
bio->bi_iter.bi_sector = pos >> 9;
bio->bi_write_hint = iocb->ki_hint;
@@ -382,8 +394,10 @@ __blkdev_direct_IO(struct kiocb *iocb, struct iov_iter *iter, int nr_pages)
bio->bi_end_io = blkdev_bio_end_io;
bio->bi_ioprio = iocb->ki_ioprio;
- ret = bio_iov_iter_get_pages(bio, iter);
- if (unlikely(ret)) {
+ err = bio_iov_iter_get_pages(bio, iter);
+ if (unlikely(err)) {
+ if (!ret)
+ ret = err;
bio->bi_status = BLK_STS_IOERR;
bio_endio(bio);
break;
@@ -398,6 +412,14 @@ __blkdev_direct_IO(struct kiocb *iocb, struct iov_iter *iter, int nr_pages)
task_io_account_write(bio->bi_iter.bi_size);
}
+ /*
+ * Tell underlying layer to not block for resource shortage.
+ * And if we would have blocked, return error inline instead
+ * of through the bio->bi_end_io() callback.
+ */
+ if (nowait)
+ bio->bi_opf |= (REQ_NOWAIT | REQ_NOWAIT_INLINE);
+
dio->size += bio->bi_iter.bi_size;
pos += bio->bi_iter.bi_size;
@@ -411,6 +433,11 @@ __blkdev_direct_IO(struct kiocb *iocb, struct iov_iter *iter, int nr_pages)
}
qc = submit_bio(bio);
+ if (qc == BLK_QC_T_EAGAIN) {
+ if (!ret)
+ ret = -EAGAIN;
+ goto error;
+ }
if (polled)
WRITE_ONCE(iocb->ki_cookie, qc);
@@ -431,8 +458,20 @@ __blkdev_direct_IO(struct kiocb *iocb, struct iov_iter *iter, int nr_pages)
atomic_inc(&dio->ref);
}
- submit_bio(bio);
- bio = bio_alloc(GFP_KERNEL, nr_pages);
+ qc = submit_bio(bio);
+ if (qc == BLK_QC_T_EAGAIN) {
+ if (!ret)
+ ret = -EAGAIN;
+ goto error;
+ }
+ ret += bio->bi_iter.bi_size;
+
+ bio = bio_alloc(gfp, nr_pages);
+ if (!bio) {
+ if (!ret)
+ ret = -EAGAIN;
+ goto error;
+ }
}
if (!is_poll)
@@ -452,13 +491,16 @@ __blkdev_direct_IO(struct kiocb *iocb, struct iov_iter *iter, int nr_pages)
}
__set_current_state(TASK_RUNNING);
+out:
if (!ret)
ret = blk_status_to_errno(dio->bio.bi_status);
- if (likely(!ret))
- ret = dio->size;
bio_put(&dio->bio);
return ret;
+error:
+ if (!is_poll)
+ blk_finish_plug(&plug);
+ goto out;
}
static ssize_t