blk_bio_discard_split

Name:blk_bio_discard_split

Proto:static struct bio *blk_bio_discard_split(struct request_queue *q, struct bio *bio, struct bio_set *bs, unsigned *nsegs)

Type:struct bio

Parameter:

Type	Parameter	Name
struct request_queue *	q
struct bio *	bio
struct bio_set *	bs
unsigned *	nsegs

71

nsegs = 1

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granularity = max - return maximum of two values of the same or compatible types*@x: first value*@y: second value(discard_granularity >> 9, 1U)

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max_discard_sectors = min - return minimum of two values of the same or compatible types*@x: first value*@y: second value(max_discard_sectors, The max size one bio can handle is UINT_MAX becasue bvec_iter.bi_size* is defined as 'unsigned int', meantime it has to aligned to with logical* block size which is the minimum accepted unit by hardware.)

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max_discard_sectors -= max_discard_sectors % granularity

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If Value for the false possibility is greater at compile time(!max_discard_sectors) Then

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Return NULL

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If bio_sectors(bio) <= max_discard_sectors Then Return NULL

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split_sectors = max_discard_sectors

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alignment = (discard_alignment >> 9) % granularity

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tmp = device address in 512 byte sectors + split_sectors - alignment

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tmp = sector_div(tmp, granularity)

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If split_sectors > tmp Then split_sectors -= tmp

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Return _split - split a bio*@bio: bio to split*@sectors: number of sectors to split from the front of @bio*@gfp: gfp mask*@bs: bio set to allocate from* Allocates and returns a new bio which represents @sectors from the start of

**Caller**
Name	Describe
__blk_queue_split	__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

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