[PATCH] md: fix raid6 resync check/repair code
raid6 currently does not check the P/Q syndromes when doing a resync, it just
calculates the correct value and writes it. Doing the check can reduce writes
(often to 0) for a resync, and it is needed to properly implement the
echo check > sync_action
operation.
This patch implements the appropriate checks and tidies up some related code.
It also allows raid6 user-requested resync to bypass the intent bitmap.
Signed-off-by: Neil Brown <neilb@suse.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
diff --git a/drivers/md/raid6main.c b/drivers/md/raid6main.c
index 304455d..52e8796 100644
--- a/drivers/md/raid6main.c
+++ b/drivers/md/raid6main.c
@@ -805,7 +805,7 @@
}
/* Compute one missing block */
-static void compute_block_1(struct stripe_head *sh, int dd_idx)
+static void compute_block_1(struct stripe_head *sh, int dd_idx, int nozero)
{
raid6_conf_t *conf = sh->raid_conf;
int i, count, disks = conf->raid_disks;
@@ -821,7 +821,7 @@
compute_parity(sh, UPDATE_PARITY);
} else {
ptr[0] = page_address(sh->dev[dd_idx].page);
- memset(ptr[0], 0, STRIPE_SIZE);
+ if (!nozero) memset(ptr[0], 0, STRIPE_SIZE);
count = 1;
for (i = disks ; i--; ) {
if (i == dd_idx || i == qd_idx)
@@ -838,7 +838,8 @@
}
if (count != 1)
xor_block(count, STRIPE_SIZE, ptr);
- set_bit(R5_UPTODATE, &sh->dev[dd_idx].flags);
+ if (!nozero) set_bit(R5_UPTODATE, &sh->dev[dd_idx].flags);
+ else clear_bit(R5_UPTODATE, &sh->dev[dd_idx].flags);
}
}
@@ -871,7 +872,7 @@
return;
} else {
/* We're missing D+Q; recompute D from P */
- compute_block_1(sh, (dd_idx1 == qd_idx) ? dd_idx2 : dd_idx1);
+ compute_block_1(sh, (dd_idx1 == qd_idx) ? dd_idx2 : dd_idx1, 0);
compute_parity(sh, UPDATE_PARITY); /* Is this necessary? */
return;
}
@@ -982,6 +983,12 @@
}
+static int page_is_zero(struct page *p)
+{
+ char *a = page_address(p);
+ return ((*(u32*)a) == 0 &&
+ memcmp(a, a+4, STRIPE_SIZE-4)==0);
+}
/*
* handle_stripe - do things to a stripe.
*
@@ -1000,7 +1007,7 @@
*
*/
-static void handle_stripe(struct stripe_head *sh)
+static void handle_stripe(struct stripe_head *sh, struct page *tmp_page)
{
raid6_conf_t *conf = sh->raid_conf;
int disks = conf->raid_disks;
@@ -1228,7 +1235,7 @@
if (uptodate == disks-1) {
PRINTK("Computing stripe %llu block %d\n",
(unsigned long long)sh->sector, i);
- compute_block_1(sh, i);
+ compute_block_1(sh, i, 0);
uptodate++;
} else if ( uptodate == disks-2 && failed >= 2 ) {
/* Computing 2-failure is *very* expensive; only do it if failed >= 2 */
@@ -1323,7 +1330,7 @@
/* We have failed blocks and need to compute them */
switch ( failed ) {
case 0: BUG();
- case 1: compute_block_1(sh, failed_num[0]); break;
+ case 1: compute_block_1(sh, failed_num[0], 0); break;
case 2: compute_block_2(sh, failed_num[0], failed_num[1]); break;
default: BUG(); /* This request should have been failed? */
}
@@ -1338,12 +1345,10 @@
(unsigned long long)sh->sector, i);
locked++;
set_bit(R5_Wantwrite, &sh->dev[i].flags);
-#if 0 /**** FIX: I don't understand the logic here... ****/
- if (!test_bit(R5_Insync, &sh->dev[i].flags)
- || ((i==pd_idx || i==qd_idx) && failed == 0)) /* FIX? */
- set_bit(STRIPE_INSYNC, &sh->state);
-#endif
}
+ /* after a RECONSTRUCT_WRITE, the stripe MUST be in-sync */
+ set_bit(STRIPE_INSYNC, &sh->state);
+
if (test_and_clear_bit(STRIPE_PREREAD_ACTIVE, &sh->state)) {
atomic_dec(&conf->preread_active_stripes);
if (atomic_read(&conf->preread_active_stripes) < IO_THRESHOLD)
@@ -1356,79 +1361,97 @@
* Any reads will already have been scheduled, so we just see if enough data
* is available
*/
- if (syncing && locked == 0 &&
- !test_bit(STRIPE_INSYNC, &sh->state) && failed <= 2) {
+ if (syncing && locked == 0 && !test_bit(STRIPE_INSYNC, &sh->state)) {
+ int update_p = 0, update_q = 0;
+ struct r5dev *dev;
+
set_bit(STRIPE_HANDLE, &sh->state);
-#if 0 /* RAID-6: Don't support CHECK PARITY yet */
- if (failed == 0) {
- char *pagea;
- if (uptodate != disks)
- BUG();
- compute_parity(sh, CHECK_PARITY);
- uptodate--;
- pagea = page_address(sh->dev[pd_idx].page);
- if ((*(u32*)pagea) == 0 &&
- !memcmp(pagea, pagea+4, STRIPE_SIZE-4)) {
- /* parity is correct (on disc, not in buffer any more) */
- set_bit(STRIPE_INSYNC, &sh->state);
+
+ BUG_ON(failed>2);
+ BUG_ON(uptodate < disks);
+ /* Want to check and possibly repair P and Q.
+ * However there could be one 'failed' device, in which
+ * case we can only check one of them, possibly using the
+ * other to generate missing data
+ */
+
+ /* If !tmp_page, we cannot do the calculations,
+ * but as we have set STRIPE_HANDLE, we will soon be called
+ * by stripe_handle with a tmp_page - just wait until then.
+ */
+ if (tmp_page) {
+ if (failed == q_failed) {
+ /* The only possible failed device holds 'Q', so it makes
+ * sense to check P (If anything else were failed, we would
+ * have used P to recreate it).
+ */
+ compute_block_1(sh, pd_idx, 1);
+ if (!page_is_zero(sh->dev[pd_idx].page)) {
+ compute_block_1(sh,pd_idx,0);
+ update_p = 1;
+ }
}
- }
-#endif
- if (!test_bit(STRIPE_INSYNC, &sh->state)) {
- int failed_needupdate[2];
- struct r5dev *adev, *bdev;
-
- if ( failed < 1 )
- failed_num[0] = pd_idx;
- if ( failed < 2 )
- failed_num[1] = (failed_num[0] == qd_idx) ? pd_idx : qd_idx;
-
- failed_needupdate[0] = !test_bit(R5_UPTODATE, &sh->dev[failed_num[0]].flags);
- failed_needupdate[1] = !test_bit(R5_UPTODATE, &sh->dev[failed_num[1]].flags);
-
- PRINTK("sync: failed=%d num=%d,%d fnu=%u%u\n",
- failed, failed_num[0], failed_num[1], failed_needupdate[0], failed_needupdate[1]);
-
-#if 0 /* RAID-6: This code seems to require that CHECK_PARITY destroys the uptodateness of the parity */
- /* should be able to compute the missing block(s) and write to spare */
- if ( failed_needupdate[0] ^ failed_needupdate[1] ) {
- if (uptodate+1 != disks)
- BUG();
- compute_block_1(sh, failed_needupdate[0] ? failed_num[0] : failed_num[1]);
- uptodate++;
- } else if ( failed_needupdate[0] & failed_needupdate[1] ) {
- if (uptodate+2 != disks)
- BUG();
- compute_block_2(sh, failed_num[0], failed_num[1]);
- uptodate += 2;
+ if (!q_failed && failed < 2) {
+ /* q is not failed, and we didn't use it to generate
+ * anything, so it makes sense to check it
+ */
+ memcpy(page_address(tmp_page),
+ page_address(sh->dev[qd_idx].page),
+ STRIPE_SIZE);
+ compute_parity(sh, UPDATE_PARITY);
+ if (memcmp(page_address(tmp_page),
+ page_address(sh->dev[qd_idx].page),
+ STRIPE_SIZE)!= 0) {
+ clear_bit(STRIPE_INSYNC, &sh->state);
+ update_q = 1;
+ }
}
-#else
- compute_block_2(sh, failed_num[0], failed_num[1]);
- uptodate += failed_needupdate[0] + failed_needupdate[1];
-#endif
+ if (update_p || update_q) {
+ conf->mddev->resync_mismatches += STRIPE_SECTORS;
+ if (test_bit(MD_RECOVERY_CHECK, &conf->mddev->recovery))
+ /* don't try to repair!! */
+ update_p = update_q = 0;
+ }
- if (uptodate != disks)
- BUG();
+ /* now write out any block on a failed drive,
+ * or P or Q if they need it
+ */
- PRINTK("Marking for sync stripe %llu blocks %d,%d\n",
- (unsigned long long)sh->sector, failed_num[0], failed_num[1]);
+ if (failed == 2) {
+ dev = &sh->dev[failed_num[1]];
+ locked++;
+ set_bit(R5_LOCKED, &dev->flags);
+ set_bit(R5_Wantwrite, &dev->flags);
+ set_bit(R5_Syncio, &dev->flags);
+ }
+ if (failed >= 1) {
+ dev = &sh->dev[failed_num[0]];
+ locked++;
+ set_bit(R5_LOCKED, &dev->flags);
+ set_bit(R5_Wantwrite, &dev->flags);
+ set_bit(R5_Syncio, &dev->flags);
+ }
- /**** FIX: Should we really do both of these unconditionally? ****/
- adev = &sh->dev[failed_num[0]];
- locked += !test_bit(R5_LOCKED, &adev->flags);
- set_bit(R5_LOCKED, &adev->flags);
- set_bit(R5_Wantwrite, &adev->flags);
- bdev = &sh->dev[failed_num[1]];
- locked += !test_bit(R5_LOCKED, &bdev->flags);
- set_bit(R5_LOCKED, &bdev->flags);
+ if (update_p) {
+ dev = &sh->dev[pd_idx];
+ locked ++;
+ set_bit(R5_LOCKED, &dev->flags);
+ set_bit(R5_Wantwrite, &dev->flags);
+ set_bit(R5_Syncio, &dev->flags);
+ }
+ if (update_q) {
+ dev = &sh->dev[qd_idx];
+ locked++;
+ set_bit(R5_LOCKED, &dev->flags);
+ set_bit(R5_Wantwrite, &dev->flags);
+ set_bit(R5_Syncio, &dev->flags);
+ }
clear_bit(STRIPE_DEGRADED, &sh->state);
- set_bit(R5_Wantwrite, &bdev->flags);
set_bit(STRIPE_INSYNC, &sh->state);
- set_bit(R5_Syncio, &adev->flags);
- set_bit(R5_Syncio, &bdev->flags);
}
}
+
if (syncing && locked == 0 && test_bit(STRIPE_INSYNC, &sh->state)) {
md_done_sync(conf->mddev, STRIPE_SECTORS,1);
clear_bit(STRIPE_SYNCING, &sh->state);
@@ -1664,7 +1687,7 @@
}
finish_wait(&conf->wait_for_overlap, &w);
raid6_plug_device(conf);
- handle_stripe(sh);
+ handle_stripe(sh, NULL);
release_stripe(sh);
} else {
/* cannot get stripe for read-ahead, just give-up */
@@ -1728,6 +1751,7 @@
return rv;
}
if (!bitmap_start_sync(mddev->bitmap, sector_nr, &sync_blocks, 1) &&
+ !test_bit(MD_RECOVERY_REQUESTED, &mddev->recovery) &&
!conf->fullsync && sync_blocks >= STRIPE_SECTORS) {
/* we can skip this block, and probably more */
sync_blocks /= STRIPE_SECTORS;
@@ -1765,7 +1789,7 @@
clear_bit(STRIPE_INSYNC, &sh->state);
spin_unlock(&sh->lock);
- handle_stripe(sh);
+ handle_stripe(sh, NULL);
release_stripe(sh);
return STRIPE_SECTORS;
@@ -1821,7 +1845,7 @@
spin_unlock_irq(&conf->device_lock);
handled++;
- handle_stripe(sh);
+ handle_stripe(sh, conf->spare_page);
release_stripe(sh);
spin_lock_irq(&conf->device_lock);
@@ -1860,6 +1884,10 @@
goto abort;
memset(conf->stripe_hashtbl, 0, HASH_PAGES * PAGE_SIZE);
+ conf->spare_page = alloc_page(GFP_KERNEL);
+ if (!conf->spare_page)
+ goto abort;
+
spin_lock_init(&conf->device_lock);
init_waitqueue_head(&conf->wait_for_stripe);
init_waitqueue_head(&conf->wait_for_overlap);
@@ -1996,6 +2024,8 @@
abort:
if (conf) {
print_raid6_conf(conf);
+ if (conf->spare_page)
+ page_cache_release(conf->spare_page);
if (conf->stripe_hashtbl)
free_pages((unsigned long) conf->stripe_hashtbl,
HASH_PAGES_ORDER);
diff --git a/include/linux/raid/raid5.h b/include/linux/raid/raid5.h
index f025ba6..e9c1c0d 100644
--- a/include/linux/raid/raid5.h
+++ b/include/linux/raid/raid5.h
@@ -228,6 +228,8 @@
* Cleared when a sync completes.
*/
+ struct page *spare_page; /* Used when checking P/Q in raid6 */
+
/*
* Free stripes pool
*/