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authorNeilBrown <neilb@suse.de>2006-12-10 11:20:49 +0100
committerLinus Torvalds <torvalds@woody.osdl.org>2006-12-10 18:57:21 +0100
commitb875e531fc82db592d6093594593d5cafde0a1cd (patch)
tree4bf23fcee1a1d1675339ea7e5d671dde6dd8641f /drivers/md
parent[PATCH] md: enable bypassing cache for reads (diff)
downloadlinux-b875e531fc82db592d6093594593d5cafde0a1cd.tar.xz
linux-b875e531fc82db592d6093594593d5cafde0a1cd.zip
[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 <neilb@suse.de> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Diffstat (limited to 'drivers/md')
-rw-r--r--drivers/md/raid5.c10
1 files changed, 6 insertions, 4 deletions
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;
}