We've now got 3x2 interfaces for iterating over bios: by page, by bvec, or by folio, and variants that iterate over what bi_iter points to, or the entire bio as created by the filesystem/originator. This adds more detailed kerneldoc comments for each variant. Signed-off-by: Kent Overstreet <kent.overstreet@xxxxxxxxx> Cc: Jens Axboe <axboe@xxxxxxxxx> Cc: Ming Lei <ming.lei@xxxxxxxxxx> Cc: linux-block@xxxxxxxxxxxxxxx --- include/linux/bio.h | 54 ++++++++++++++++++++++++++++++++++++++++----- 1 file changed, 48 insertions(+), 6 deletions(-) diff --git a/include/linux/bio.h b/include/linux/bio.h index eaaf7e5f0d54..21524a953f6e 100644 --- a/include/linux/bio.h +++ b/include/linux/bio.h @@ -103,9 +103,14 @@ static inline void bio_iter_all_advance(const struct bio *bio, ((bvl = bio_iter_all_peek(bio, &iter)), true); \ bio_iter_all_advance((bio), &iter, bvl.bv_len)) -/* - * drivers should _never_ use the all version - the bio may have been split - * before it got to the driver and the driver won't own all of it +/** + * bio_for_each_segment_all - iterate over single pages in a bio + * + * Like other _all versions, this is for the filesystem, or the owner/creator of + * a bio; it iterates over the original contents of a bio. + * + * Drivers that are working with bios that were submitted to them should not use + * the _all version. */ #define bio_for_each_segment_all(bvl, bio, iter) \ for (bvec_iter_all_init(&iter); \ @@ -166,6 +171,13 @@ static inline void bio_advance(struct bio *bio, unsigned int nbytes) ((bvl = bio_iter_iovec((bio), (iter))), 1); \ bio_advance_iter_single((bio), &(iter), (bvl).bv_len)) +/** + * bio_for_each_segment - iterate over single pages in a bio + * + * Like other non-_all versions, this iterates over what bio->bi_iter currently + * points to. This version is for drivers, where the bio may have previously + * been split or cloned. + */ #define bio_for_each_segment(bvl, bio, iter) \ __bio_for_each_segment(bvl, bio, iter, (bio)->bi_iter) @@ -202,6 +214,13 @@ static inline struct folio_vec bio_iter_iovec_folio(struct bio *bio, ((bvl = bio_iter_iovec_folio((bio), (iter))), 1); \ bio_advance_iter_single((bio), &(iter), (bvl).fv_len)) +/** + * bio_for_each_folio - iterate over folios within a bio + * + * Like other non-_all versions, this iterates over what bio->bi_iter currently + * points to. This version is for drivers, where the bio may have previously + * been split or cloned. + */ #define bio_for_each_folio(bvl, bio, iter) \ __bio_for_each_folio(bvl, bio, iter, (bio)->bi_iter) @@ -211,13 +230,30 @@ static inline struct folio_vec bio_iter_iovec_folio(struct bio *bio, ((bvl = mp_bvec_iter_bvec((bio)->bi_io_vec, (iter))), 1); \ bio_advance_iter_single((bio), &(iter), (bvl).bv_len)) -/* iterate over multi-page bvec */ +/** + * bio_for_each_bvec - iterate over bvecs within a bio + * + * This version iterates over entire bio_vecs, which will be a range of + * contiguous pages. + * + * Like other non-_all versions, this iterates over what bio->bi_iter currently + * points to. This version is for drivers, where the bio may have previously + * been split or cloned. + */ #define bio_for_each_bvec(bvl, bio, iter) \ __bio_for_each_bvec(bvl, bio, iter, (bio)->bi_iter) /* - * Iterate over all multi-page bvecs. Drivers shouldn't use this version for the - * same reasons as bio_for_each_segment_all(). + * bio_for_each_bvec_all - iterate over bvecs within a bio + * + * This version iterates over entire bio_vecs, which will be a range of + * contiguous pages. + * + * Like other _all versions, this is for the filesystem, or the owner/creator of + * a bio; it iterates over the original contents of a bio. + * + * Drivers that are working with bios that were submitted to them should not use + * the _all version. */ #define bio_for_each_bvec_all(bvl, bio, i) \ for (i = 0, bvl = bio_first_bvec_all(bio); \ @@ -328,6 +364,12 @@ static inline struct folio_vec bio_folio_iter_all_peek(const struct bio *bio, * bio_for_each_folio_all - Iterate over each folio in a bio. * @fi: struct bio_folio_iter_all which is updated for each folio. * @bio: struct bio to iterate over. + * + * Like other _all versions, this is for the filesystem, or the owner/creator of + * a bio; it iterates over the original contents of a bio. + * + * Drivers that are working with bios that were submitted to them should not use + * the _all version. */ #define bio_for_each_folio_all(fv, bio, iter) \ for (bvec_iter_all_init(&iter); \ -- 2.42.0
