block: account for bi_bvec_done in bio_may_need_split() #467
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When checking if a bio fits in a single segment, bio_may_need_split() compares bi_size against the current bvec's bv_len. However, for partially consumed bvecs (bi_bvec_done > 0), such as in cloned or split bios, the remaining bytes in the current bvec is actually (bv_len - bi_bvec_done), not bv_len. This could cause bio_may_need_split() to incorrectly return false, leading to nr_phys_segments being set to 1 when the bio actually spans multiple segments. This triggers the WARN_ON in __blk_rq_map_sg() when the actual mapped segments exceed the expected count. Fix by subtracting bi_bvec_done from bv_len in the comparison. Reported-by: Venkat Rao Bagalkote <venkat88@linux.ibm.com> Close: https://lore.kernel.org/linux-block/9687cf2b-1f32-44e1-b58d-2492dc6e7185@linux.ibm.com/ Repored-and-bisected-by: Christoph Hellwig <hch@infradead.org> Tested-by: Venkat Rao Bagalkote <venkat88@linux.ibm.com> Tested-by: Christoph Hellwig <hch@infradead.org> Fixes: ee623c8 ("block: use bvec iterator helper for bio_may_need_split()") Cc: Nitesh Shetty <nj.shetty@samsung.com> Signed-off-by: Ming Lei <ming.lei@redhat.com>
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Upstream branch: 28fd54b |
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Pull request for series with
subject: block: account for bi_bvec_done in bio_may_need_split()
version: 1
url: https://patchwork.kernel.org/project/linux-block/list/?series=1040728