Commit caf336f8 authored by John Garry's avatar John Garry Committed by Jens Axboe
Browse files

block: Add fops atomic write support 



Support atomic writes by submitting a single BIO with the REQ_ATOMIC set.

It must be ensured that the atomic write adheres to its rules, like
naturally aligned offset, so call blkdev_dio_invalid() ->
blkdev_atomic_write_valid() [with renaming blkdev_dio_unaligned() to
blkdev_dio_invalid()] for this purpose. The BIO submission path currently
checks for atomic writes which are too large, so no need to check here.

In blkdev_direct_IO(), if the nr_pages exceeds BIO_MAX_VECS, then we cannot
produce a single BIO, so error in this case.

Finally set FMODE_CAN_ATOMIC_WRITE when the bdev can support atomic writes
and the associated file flag is for O_DIRECT.

Reviewed-by: default avatarMartin K. Petersen <martin.petersen@oracle.com>
Signed-off-by: default avatarJohn Garry <john.g.garry@oracle.com>
Reviewed-by: default avatarKeith Busch <kbusch@kernel.org>
Acked-by: default avatarDarrick J. Wong <djwong@kernel.org>
Reviewed-by: default avatarDarrick J. Wong <djwong@kernel.org>
Link: https://lore.kernel.org/r/20240620125359.2684798-8-john.g.garry@oracle.com


Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
parent 9abcfbd2

block/fops.c

+17 −3
Original line number Diff line number Diff line
@@ -34,9 +34,12 @@ static blk_opf_t dio_bio_write_op(struct kiocb *iocb) 
	return opf;

}



static bool blkdev_dio_unaligned(struct block_device *bdev, loff_t pos,

			      struct iov_iter *iter)

static bool blkdev_dio_invalid(struct block_device *bdev, loff_t pos,

				struct iov_iter *iter, bool is_atomic)

{

	if (is_atomic && !generic_atomic_write_valid(iter, pos))

		return true;



	return pos & (bdev_logical_block_size(bdev) - 1) ||

		!bdev_iter_is_aligned(bdev, iter);

}
@@ -72,6 +75,8 @@ static ssize_t __blkdev_direct_IO_simple(struct kiocb *iocb, 
	bio.bi_iter.bi_sector = pos >> SECTOR_SHIFT;

	bio.bi_write_hint = file_inode(iocb->ki_filp)->i_write_hint;

	bio.bi_ioprio = iocb->ki_ioprio;

	if (iocb->ki_flags & IOCB_ATOMIC)

		bio.bi_opf |= REQ_ATOMIC;



	ret = bio_iov_iter_get_pages(&bio, iter);

	if (unlikely(ret))
@@ -343,6 +348,9 @@ static ssize_t __blkdev_direct_IO_async(struct kiocb *iocb, 
		task_io_account_write(bio->bi_iter.bi_size);

	}



	if (iocb->ki_flags & IOCB_ATOMIC)

		bio->bi_opf |= REQ_ATOMIC;



	if (iocb->ki_flags & IOCB_NOWAIT)

		bio->bi_opf |= REQ_NOWAIT;
@@ -359,12 +367,13 @@ static ssize_t __blkdev_direct_IO_async(struct kiocb *iocb, 
static ssize_t blkdev_direct_IO(struct kiocb *iocb, struct iov_iter *iter)

{

	struct block_device *bdev = I_BDEV(iocb->ki_filp->f_mapping->host);

	bool is_atomic = iocb->ki_flags & IOCB_ATOMIC;

	unsigned int nr_pages;



	if (!iov_iter_count(iter))

		return 0;



	if (blkdev_dio_unaligned(bdev, iocb->ki_pos, iter))

	if (blkdev_dio_invalid(bdev, iocb->ki_pos, iter, is_atomic))

		return -EINVAL;



	nr_pages = bio_iov_vecs_to_alloc(iter, BIO_MAX_VECS + 1);
@@ -373,6 +382,8 @@ static ssize_t blkdev_direct_IO(struct kiocb *iocb, struct iov_iter *iter) 
			return __blkdev_direct_IO_simple(iocb, iter, bdev,

							nr_pages);

		return __blkdev_direct_IO_async(iocb, iter, bdev, nr_pages);

	} else if (is_atomic) {

		return -EINVAL;

	}

	return __blkdev_direct_IO(iocb, iter, bdev, bio_max_segs(nr_pages));

}
@@ -612,6 +623,9 @@ static int blkdev_open(struct inode *inode, struct file *filp) 
	if (!bdev)

		return -ENXIO;



	if (bdev_can_atomic_write(bdev) && filp->f_flags & O_DIRECT)

		filp->f_mode |= FMODE_CAN_ATOMIC_WRITE;



	ret = bdev_open(bdev, mode, filp->private_data, NULL, filp);

	if (ret)

		blkdev_put_no_open(bdev);