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block: new direct I/O implementation

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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>
This commit is contained in:
Christoph Hellwig 2016-11-16 23:14:22 -07:00 committed by Jens Axboe
parent 78250c02d9
commit 542ff7bf18
1 changed files with 162 additions and 4 deletions
repo.diff.show_diff_stats Download patch file Download diff file Expand all files Collapse all files

166
fs/block_dev.c
View file

@ -270,11 +270,161 @@ __blkdev_direct_IO_simple(struct kiocb *iocb, struct iov_iter *iter,
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 @@ blkdev_direct_IO(struct kiocb *iocb, struct iov_iter *iter)
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)