block: Document the bio splitting functions (dad77584) · Commits · 戴 / test

block/bio.c

+2 −2

Original line number	Diff line number	Diff line
		@@ -1842,8 +1842,8 @@ EXPORT_SYMBOL(bio_endio);
		* @bio, and updates @bio to represent the remaining sectors.
		*
		* Unless this is a discard request the newly allocated bio will point
		* to @bio's bi_io_vec; it is the caller's responsibility to ensure that
		* @bio is not freed before the split.
		* to @bio's bi_io_vec. It is the caller's responsibility to ensure that
		* neither @bio nor @bs are freed before the split bio.
		*/
		struct bio bio_split(struct bio bio, int sectors,
		gfp_t gfp, struct bio_set *bs)

block/blk-merge.c

+43 −0

Original line number	Diff line number	Diff line
		@@ -195,6 +195,25 @@ static bool bvec_split_segs(const struct request_queue *q,
		return !!len;
		}

		/**
		* blk_bio_segment_split - split a bio in two bios
		* @q: [in] request queue pointer
		* @bio: [in] bio to be split
		* @bs: [in] bio set to allocate the clone from
		* @segs: [out] number of segments in the bio with the first half of the sectors
		*
		* Clone @bio, update the bi_iter of the clone to represent the first sectors
		* of @bio and update @bio->bi_iter to represent the remaining sectors. The
		* following is guaranteed for the cloned bio:
		* - That it has at most get_max_io_size(@q, @bio) sectors.
		* - That it has at most queue_max_segments(@q) segments.
		*
		* Except for discard requests the cloned bio will point at the bi_io_vec of
		* the original bio. It is the responsibility of the caller to ensure that the
		* original bio is not freed before the cloned bio. The caller is also
		* responsible for ensuring that @bs is only destroyed after processing of the
		* split bio has finished.
		*/
		static struct bio blk_bio_segment_split(struct request_queue q,
		struct bio *bio,
		struct bio_set *bs,
		@@ -251,6 +270,19 @@ split:
		return bio_split(bio, sectors, GFP_NOIO, bs);
		}

		/**
		* __blk_queue_split - split a bio and submit the second half
		* @q: [in] request queue pointer
		* @bio: [in, out] bio to be split
		* @nr_segs: [out] number of segments in the first bio
		*
		* Split a bio into two bios, chain the two bios, submit the second half and
		* store a pointer to the first half in *@bio. If the second bio is still too
		* big it will be split by a recursive call to this function. Since this
		* function may allocate a new bio from @q->bio_split, it is the responsibility
		* of the caller to ensure that @q is only released after processing of the
		* split bio has finished.
		*/
		void __blk_queue_split(struct request_queue q, struct bio *bio,
		unsigned int *nr_segs)
		{
		@@ -295,6 +327,17 @@ void __blk_queue_split(struct request_queue q, struct bio *bio,
		}
		}

		/**
		* blk_queue_split - split a bio and submit the second half
		* @q: [in] request queue pointer
		* @bio: [in, out] bio to be split
		*
		* Split a bio into two bios, chains the two bios, submit the second half and
		* store a pointer to the first half in *@bio. Since this function may allocate
		* a new bio from @q->bio_split, it is the responsibility of the caller to
		* ensure that @q is only released after processing of the split bio has
		* finished.
		*/
		void blk_queue_split(struct request_queue q, struct bio *bio)
		{
		unsigned int nr_segs;

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