diff options
| author | Keith Busch <kbusch@kernel.org> | 2022-06-10 12:58:29 -0700 |
|---|---|---|
| committer | Jens Axboe <axboe@kernel.dk> | 2022-06-27 06:29:11 -0600 |
| commit | b1a000d3b8ec582da64bb644be633e5a0beffcbf (patch) | |
| tree | 960fc00a20dbe8733f847f441205dae3be20b189 | |
| parent | 5debd9691c3ac64c3acd6867c264ad38bbe48cdc (diff) | |
| download | lwn-b1a000d3b8ec582da64bb644be633e5a0beffcbf.tar.gz lwn-b1a000d3b8ec582da64bb644be633e5a0beffcbf.zip | |
block: relax direct io memory alignment
Use the address alignment requirements from the block_device for direct
io instead of requiring addresses be aligned to the block size. User
space can discover the alignment requirements from the dma_alignment
queue attribute.
User space can specify any hardware compatible DMA offset for each
segment, but every segment length is still required to be a multiple of
the block size.
Signed-off-by: Keith Busch <kbusch@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20220610195830.3574005-11-kbusch@fb.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
| -rw-r--r-- | block/bio.c | 9 | ||||
| -rw-r--r-- | block/fops.c | 4 | ||||
| -rw-r--r-- | include/linux/blkdev.h | 5 |
3 files changed, 16 insertions, 2 deletions
diff --git a/block/bio.c b/block/bio.c index ee5fe1bb015e..933ea3210954 100644 --- a/block/bio.c +++ b/block/bio.c @@ -1220,7 +1220,16 @@ static int __bio_iov_iter_get_pages(struct bio *bio, struct iov_iter *iter) BUILD_BUG_ON(PAGE_PTRS_PER_BVEC < 2); pages += entries_left * (PAGE_PTRS_PER_BVEC - 1); + /* + * Each segment in the iov is required to be a block size multiple. + * However, we may not be able to get the entire segment if it spans + * more pages than bi_max_vecs allows, so we have to ALIGN_DOWN the + * result to ensure the bio's total size is correct. The remainder of + * the iov data will be picked up in the next bio iteration. + */ size = iov_iter_get_pages(iter, pages, LONG_MAX, nr_pages, &offset); + if (size > 0) + size = ALIGN_DOWN(size, bdev_logical_block_size(bio->bi_bdev)); if (unlikely(size <= 0)) return size ? size : -EFAULT; diff --git a/block/fops.c b/block/fops.c index 9d32df6fc315..86d3cab9bf93 100644 --- a/block/fops.c +++ b/block/fops.c @@ -45,8 +45,8 @@ static unsigned int dio_bio_write_op(struct kiocb *iocb) static bool blkdev_dio_unaligned(struct block_device *bdev, loff_t pos, struct iov_iter *iter) { - return ((pos | iov_iter_alignment(iter)) & - (bdev_logical_block_size(bdev) - 1)); + return pos & (bdev_logical_block_size(bdev) - 1) || + !bdev_iter_is_aligned(bdev, iter); } #define DIO_INLINE_BIO_VECS 4 diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h index 0b8bc1fe0b2c..886c44e97434 100644 --- a/include/linux/blkdev.h +++ b/include/linux/blkdev.h @@ -424,6 +424,11 @@ struct request_queue { unsigned long nr_requests; /* Max # of requests */ unsigned int dma_pad_mask; + /* + * Drivers that set dma_alignment to less than 511 must be prepared to + * handle individual bvec's that are not a multiple of a SECTOR_SIZE + * due to possible offsets. + */ unsigned int dma_alignment; #ifdef CONFIG_BLK_INLINE_ENCRYPTION |