majianpeng <majianpeng@xxxxxxxxx> writes: > On 2012-07-27 22:21 Jeff Moyer <jmoyer@xxxxxxxxxx> Wrote: >>majianpeng <majianpeng@xxxxxxxxx> 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@xxxxxxxxx> >> >>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@xxxxxxxxxx> >> > 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 -- To unsubscribe from this list: send the line "unsubscribe linux-raid" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
