block: new direct I/O implementation
Similar to the simple fast path, but we now need a dio structure to
track multiple-bio completions. It's basically a cut-down version
of the new iomap-based direct I/O code for filesystems, but without
all the logic to call into the filesystem for extent lookup or
allocation, and without the complex I/O completion workqueue handler
for AIO - instead we just use the FUA bit on the bios to ensure
data is flushed to stable storage.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@fb.com>
diff --git a/fs/block_dev.c b/fs/block_dev.c
index a1b9abe..35cc494 100644
--- a/fs/block_dev.c
+++ b/fs/block_dev.c
@@ -270,11 +270,161 @@
return ret;
}
+struct blkdev_dio {
+ union {
+ struct kiocb *iocb;
+ struct task_struct *waiter;
+ };
+ size_t size;
+ atomic_t ref;
+ bool multi_bio : 1;
+ bool should_dirty : 1;
+ bool is_sync : 1;
+ struct bio bio;
+};
+
+static struct bio_set *blkdev_dio_pool __read_mostly;
+
+static void blkdev_bio_end_io(struct bio *bio)
+{
+ struct blkdev_dio *dio = bio->bi_private;
+ bool should_dirty = dio->should_dirty;
+
+ if (dio->multi_bio && !atomic_dec_and_test(&dio->ref)) {
+ if (bio->bi_error && !dio->bio.bi_error)
+ dio->bio.bi_error = bio->bi_error;
+ } else {
+ if (!dio->is_sync) {
+ struct kiocb *iocb = dio->iocb;
+ ssize_t ret = dio->bio.bi_error;
+
+ if (likely(!ret)) {
+ ret = dio->size;
+ iocb->ki_pos += ret;
+ }
+
+ dio->iocb->ki_complete(iocb, ret, 0);
+ bio_put(&dio->bio);
+ } else {
+ struct task_struct *waiter = dio->waiter;
+
+ WRITE_ONCE(dio->waiter, NULL);
+ wake_up_process(waiter);
+ }
+ }
+
+ if (should_dirty) {
+ bio_check_pages_dirty(bio);
+ } else {
+ struct bio_vec *bvec;
+ int i;
+
+ bio_for_each_segment_all(bvec, bio, i)
+ put_page(bvec->bv_page);
+ bio_put(bio);
+ }
+}
+
static ssize_t
-blkdev_direct_IO(struct kiocb *iocb, struct iov_iter *iter)
+__blkdev_direct_IO(struct kiocb *iocb, struct iov_iter *iter, int nr_pages)
{
struct file *file = iocb->ki_filp;
struct inode *inode = bdev_file_inode(file);
+ struct block_device *bdev = I_BDEV(inode);
+ unsigned blkbits = blksize_bits(bdev_logical_block_size(bdev));
+ struct blkdev_dio *dio;
+ struct bio *bio;
+ bool is_read = (iov_iter_rw(iter) == READ);
+ loff_t pos = iocb->ki_pos;
+ blk_qc_t qc = BLK_QC_T_NONE;
+ int ret;
+
+ if ((pos | iov_iter_alignment(iter)) & ((1 << blkbits) - 1))
+ return -EINVAL;
+
+ bio = bio_alloc_bioset(GFP_KERNEL, nr_pages, blkdev_dio_pool);
+ bio_get(bio); /* extra ref for the completion handler */
+
+ dio = container_of(bio, struct blkdev_dio, bio);
+ dio->is_sync = is_sync_kiocb(iocb);
+ if (dio->is_sync)
+ dio->waiter = current;
+ else
+ dio->iocb = iocb;
+
+ dio->size = 0;
+ dio->multi_bio = false;
+ dio->should_dirty = is_read && (iter->type == ITER_IOVEC);
+
+ for (;;) {
+ bio->bi_bdev = bdev;
+ bio->bi_iter.bi_sector = pos >> blkbits;
+ bio->bi_private = dio;
+ bio->bi_end_io = blkdev_bio_end_io;
+
+ ret = bio_iov_iter_get_pages(bio, iter);
+ if (unlikely(ret)) {
+ bio->bi_error = ret;
+ bio_endio(bio);
+ break;
+ }
+
+ if (is_read) {
+ bio->bi_opf = REQ_OP_READ;
+ if (dio->should_dirty)
+ bio_set_pages_dirty(bio);
+ } else {
+ bio->bi_opf = dio_bio_write_op(iocb);
+ task_io_account_write(bio->bi_iter.bi_size);
+ }
+
+ dio->size += bio->bi_iter.bi_size;
+ pos += bio->bi_iter.bi_size;
+
+ nr_pages = iov_iter_npages(iter, BIO_MAX_PAGES);
+ if (!nr_pages) {
+ qc = submit_bio(bio);
+ break;
+ }
+
+ if (!dio->multi_bio) {
+ dio->multi_bio = true;
+ atomic_set(&dio->ref, 2);
+ } else {
+ atomic_inc(&dio->ref);
+ }
+
+ submit_bio(bio);
+ bio = bio_alloc(GFP_KERNEL, nr_pages);
+ }
+
+ if (!dio->is_sync)
+ return -EIOCBQUEUED;
+
+ for (;;) {
+ set_current_state(TASK_UNINTERRUPTIBLE);
+ if (!READ_ONCE(dio->waiter))
+ break;
+
+ if (!(iocb->ki_flags & IOCB_HIPRI) ||
+ !blk_mq_poll(bdev_get_queue(bdev), qc))
+ io_schedule();
+ }
+ __set_current_state(TASK_RUNNING);
+
+ ret = dio->bio.bi_error;
+ if (likely(!ret)) {
+ ret = dio->size;
+ iocb->ki_pos += ret;
+ }
+
+ bio_put(&dio->bio);
+ return ret;
+}
+
+static ssize_t
+blkdev_direct_IO(struct kiocb *iocb, struct iov_iter *iter)
+{
int nr_pages;
nr_pages = iov_iter_npages(iter, BIO_MAX_PAGES + 1);
@@ -282,11 +432,19 @@
return 0;
if (is_sync_kiocb(iocb) && nr_pages <= BIO_MAX_PAGES)
return __blkdev_direct_IO_simple(iocb, iter, nr_pages);
- return __blockdev_direct_IO(iocb, inode, I_BDEV(inode), iter,
- blkdev_get_block, NULL, NULL,
- DIO_SKIP_DIO_COUNT);
+
+ return __blkdev_direct_IO(iocb, iter, min(nr_pages, BIO_MAX_PAGES));
}
+static __init int blkdev_init(void)
+{
+ blkdev_dio_pool = bioset_create(4, offsetof(struct blkdev_dio, bio));
+ if (!blkdev_dio_pool)
+ return -ENOMEM;
+ return 0;
+}
+module_init(blkdev_init);
+
int __sync_blockdev(struct block_device *bdev, int wait)
{
if (!bdev)