[PATCH v2] block: consider merge of segments when merge bio into rq

When account the nr_phys_segments during merging bios into rq, only consider segments merging in individual bio but not all the bios in a rq. This leads to the bigger nr_phys_segments of rq than the real one when the segments of bios in rq are contiguous and mergeable. The nr_phys_segments of rq

[PATCH v2] block: consider merge of segments when merge bio into rq

When account the nr_phys_segments during merging bios into rq, only consider segments merging in individual bio but not all the bios in a rq. This leads to the bigger nr_phys_segments of rq than the real one when the segments of bios in rq are contiguous and mergeable. The nr_phys_segments of rq