Messages in this thread | | | From | Jeff Moyer <> | Subject | Re: [RFC PATCH] fs/direct-io.c: Set bi_rw when alloc bio. | Date | Mon, 30 Jul 2012 09:31:37 -0400 |
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majianpeng <majianpeng@gmail.com> writes:
> On 2012-07-27 22:21 Jeff Moyer <jmoyer@redhat.com> Wrote: >>majianpeng <majianpeng@gmail.com> writes: >> >>> When exec bio_alloc, the bi_rw is zero.But after calling bio_add_page, >>> it will use bi_rw. >>> Fox example, in functiion __bio_add_page,it will call merge_bvec_fn(). >>> The merge_bvec_fn of raid456 will use the bi_rw to judge the merge. >>>>> if ((bvm->bi_rw & 1) == WRITE) >>>>> return biovec->bv_len; /* always allow writes to be mergeable */ >>> >>> Signed-off-by: Jianpeng Ma <majianpeng@gmail.com> >> >>Good catch. How did you find this? Did you experience data corruption >>as a result of this oversight, reduced performance due to missed merge >>opportunities, or did you just notice it in reviewing the code? >> >>Reviewed-by: Jeff Moyer <jmoyer@redhat.com> >> > Sorry for late to reply. When i analysed the performance of raid5, i found this bug.
OK, thanks. In the future, it would be good to include that information in the patch description.
Cheers, Jeff
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