From: NeilBrown Date: Sun, 10 Dec 2006 10:20:49 +0000 (-0800) Subject: [PATCH] md: fix innocuous bug in raid6 stripe_to_pdidx X-Git-Url: https://git.stricted.de/?a=commitdiff_plain;h=b875e531fc82db592d6093594593d5cafde0a1cd;p=GitHub%2Fexynos8895%2Fandroid_kernel_samsung_universal8895.git [PATCH] md: fix innocuous bug in raid6 stripe_to_pdidx stripe_to_pdidx finds the index of the parity disk for a given stripe. It assumes raid5 in that it uses "disks-1" to determine the number of data disks. This is incorrect for raid6 but fortunately the two usages cancel each other out. The only way that 'data_disks' affects the calculation of pd_idx in raid5_compute_sector is when it is divided into the sector number. But as that sector number is calculated by multiplying in the wrong value of 'data_disks' the division produces the right value. So it is innocuous but needs to be fixed. Also change the calculation of raid_disks in compute_blocknr to make it more obviously correct (it seems at first to always use disks-1 too). Signed-off-by: Neil Brown Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c index 2e676e33744c..d855f9f59b02 100644 --- a/drivers/md/raid5.c +++ b/drivers/md/raid5.c @@ -823,7 +823,8 @@ static sector_t raid5_compute_sector(sector_t r_sector, unsigned int raid_disks, static sector_t compute_blocknr(struct stripe_head *sh, int i) { raid5_conf_t *conf = sh->raid_conf; - int raid_disks = sh->disks, data_disks = raid_disks - 1; + int raid_disks = sh->disks; + int data_disks = raid_disks - conf->max_degraded; sector_t new_sector = sh->sector, check; int sectors_per_chunk = conf->chunk_size >> 9; sector_t stripe; @@ -859,7 +860,6 @@ static sector_t compute_blocknr(struct stripe_head *sh, int i) } break; case 6: - data_disks = raid_disks - 2; if (i == raid6_next_disk(sh->pd_idx, raid_disks)) return 0; /* It is the Q disk */ switch (conf->algorithm) { @@ -1355,8 +1355,10 @@ static int stripe_to_pdidx(sector_t stripe, raid5_conf_t *conf, int disks) int pd_idx, dd_idx; int chunk_offset = sector_div(stripe, sectors_per_chunk); - raid5_compute_sector(stripe*(disks-1)*sectors_per_chunk - + chunk_offset, disks, disks-1, &dd_idx, &pd_idx, conf); + raid5_compute_sector(stripe * (disks - conf->max_degraded) + *sectors_per_chunk + chunk_offset, + disks, disks - conf->max_degraded, + &dd_idx, &pd_idx, conf); return pd_idx; }