Messages in this thread | | | Subject | Re: [Patch v3] block: return the correct bvec when checking for gaps | From | Jens Axboe <> | Date | Tue, 8 Jun 2021 15:07:15 -0600 |
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On 6/7/21 1:34 PM, longli@linuxonhyperv.com wrote: > From: Long Li <longli@microsoft.com> > > After commit 07173c3ec276 ("block: enable multipage bvecs"), a bvec can > have multiple pages. But bio_will_gap() still assumes one page bvec while > checking for merging. If the pages in the bvec go across the > seg_boundary_mask, this check for merging can potentially succeed if only > the 1st page is tested, and can fail if all the pages are tested. > > Later, when SCSI builds the SG list the same check for merging is done in > __blk_segment_map_sg_merge() with all the pages in the bvec tested. This > time the check may fail if the pages in bvec go across the > seg_boundary_mask (but tested okay in bio_will_gap() earlier, so those > BIOs were merged). If this check fails, we end up with a broken SG list > for drivers assuming the SG list not having offsets in intermediate pages. > This results in incorrect pages written to the disk. > > Fix this by returning the multi-page bvec when testing gaps for merging.
Applied, thanks.
-- Jens Axboe
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