Commit 75f88659 authored by Christoph Hellwig's avatar Christoph Hellwig Committed by Jens Axboe
Browse files

block: add a bio_add_max_vecs helper 



Add a helper to check how many bio_vecs are needed to add a kernel
virtual address range to a bio, accounting for the always contiguous
direct mapping and vmalloc mappings that usually need a bio_vec
per page sized chunk.

Signed-off-by: default avatarChristoph Hellwig <hch@lst.de>
Reviewed-by: default avatarDamien Le Moal <dlemoal@kernel.org>
Reviewed-by: default avatarJohannes Thumshirn <johannes.thumshirn@wdc.com>
Link: https://lore.kernel.org/r/20250507120451.4000627-4-hch@lst.de


Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
parent 10b1e59c

include/linux/bio.h

+15 −0
Original line number Diff line number Diff line
@@ -418,6 +418,21 @@ void bio_add_folio_nofail(struct bio *bio, struct folio *folio, size_t len, 
			  size_t off);

void bio_add_virt_nofail(struct bio *bio, void *vaddr, unsigned len);



/**

 * bio_add_max_vecs - number of bio_vecs needed to add data to a bio

 * @kaddr: kernel virtual address to add

 * @len: length in bytes to add

 *

 * Calculate how many bio_vecs need to be allocated to add the kernel virtual

 * address range in [@kaddr:@len] in the worse case.

 */

static inline unsigned int bio_add_max_vecs(void *kaddr, unsigned int len)

{

	if (is_vmalloc_addr(kaddr))

		return DIV_ROUND_UP(offset_in_page(kaddr) + len, PAGE_SIZE);

	return 1;

}



int submit_bio_wait(struct bio *bio);

int bdev_rw_virt(struct block_device *bdev, sector_t sector, void *data,

		size_t len, enum req_op op);