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bio: add a helper calculating nr segments to alloc 

Add a helper function calculating the number of bvec segments we need to
allocate to construct a bio. It doesn't change anything functionally,
but will be used to not duplicate special cases in the future.

Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Reviewed-by: Ming Lei <ming.lei@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Pavel Begunkov 2021-01-09 16:03:02 +00:00 committed by Jens Axboe
parent 54c8195b4e
commit 3e1a88ec96
3 changed files with 18 additions and 8 deletions
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7
fs/block_dev.c
View File

@ -416,7 +416,7 @@ __blkdev_direct_IO(struct kiocb *iocb, struct iov_iter *iter, int nr_pages)
dio->size += bio->bi_iter.bi_size; dio->size += bio->bi_iter.bi_size;
pos += bio->bi_iter.bi_size; pos += bio->bi_iter.bi_size;
nr_pages = iov_iter_npages(iter, BIO_MAX_PAGES); nr_pages = bio_iov_vecs_to_alloc(iter, BIO_MAX_PAGES);
if (!nr_pages) { if (!nr_pages) {
bool polled = false; bool polled = false;
@ -481,9 +481,10 @@ blkdev_direct_IO(struct kiocb *iocb, struct iov_iter *iter)
{ {
int nr_pages; int nr_pages;
nr_pages = iov_iter_npages(iter, BIO_MAX_PAGES + 1); if (!iov_iter_count(iter))
if (!nr_pages)
return 0; return 0;
nr_pages = bio_iov_vecs_to_alloc(iter, BIO_MAX_PAGES + 1);
if (is_sync_kiocb(iocb) && nr_pages <= BIO_MAX_PAGES) if (is_sync_kiocb(iocb) && nr_pages <= BIO_MAX_PAGES)
return __blkdev_direct_IO_simple(iocb, iter, nr_pages); return __blkdev_direct_IO_simple(iocb, iter, nr_pages);

9
fs/iomap/direct-io.c
View File

@ -250,11 +250,8 @@ iomap_dio_bio_actor(struct inode *inode, loff_t pos, loff_t length,
orig_count = iov_iter_count(dio->submit.iter); orig_count = iov_iter_count(dio->submit.iter);
iov_iter_truncate(dio->submit.iter, length); iov_iter_truncate(dio->submit.iter, length);
nr_pages = iov_iter_npages(dio->submit.iter, BIO_MAX_PAGES); if (!iov_iter_count(dio->submit.iter))
if (nr_pages <= 0) {
ret = nr_pages;
goto out; goto out;
}
if (need_zeroout) { if (need_zeroout) {
/* zero out from the start of the block to the write offset */ /* zero out from the start of the block to the write offset */
@ -263,6 +260,7 @@ iomap_dio_bio_actor(struct inode *inode, loff_t pos, loff_t length,
iomap_dio_zero(dio, iomap, pos - pad, pad); iomap_dio_zero(dio, iomap, pos - pad, pad);
} }
nr_pages = bio_iov_vecs_to_alloc(dio->submit.iter, BIO_MAX_PAGES);
do { do {
size_t n; size_t n;
if (dio->error) { if (dio->error) {
@ -308,7 +306,8 @@ iomap_dio_bio_actor(struct inode *inode, loff_t pos, loff_t length,
dio->size += n; dio->size += n;
copied += n; copied += n;
nr_pages = iov_iter_npages(dio->submit.iter, BIO_MAX_PAGES); nr_pages = bio_iov_vecs_to_alloc(dio->submit.iter,
BIO_MAX_PAGES);
iomap_dio_submit_bio(dio, iomap, bio, pos); iomap_dio_submit_bio(dio, iomap, bio, pos);
pos += n; pos += n;
} while (nr_pages); } while (nr_pages);

10
include/linux/bio.h
View File

@ -10,6 +10,7 @@
#include <linux/ioprio.h> #include <linux/ioprio.h>
/* struct bio, bio_vec and BIO_* flags are defined in blk_types.h */ /* struct bio, bio_vec and BIO_* flags are defined in blk_types.h */
#include <linux/blk_types.h> #include <linux/blk_types.h>
#include <linux/uio.h>
#define BIO_DEBUG #define BIO_DEBUG
@ -441,6 +442,15 @@ static inline void bio_wouldblock_error(struct bio *bio)
bio_endio(bio); bio_endio(bio);
} }
/*
* Calculate number of bvec segments that should be allocated to fit data
* pointed by @iter.
*/
static inline int bio_iov_vecs_to_alloc(struct iov_iter *iter, int max_segs)
{
return iov_iter_npages(iter, max_segs);
}
struct request_queue; struct request_queue;
extern int submit_bio_wait(struct bio *bio); extern int submit_bio_wait(struct bio *bio);