[PATCH] md: raid10 read-error handling - resync and read-only

Add in correct read-error handling for resync and read-only situations.

When read-only, we don't over-write, so we need to mark the failed drive in
the r10_bio so we don't re-try it.  During resync, we always read all blocks,
so if there is a read error, we simply over-write it with the good block that
we found (assuming we found one).

Note that the recovery case still isn't handled in an interesting way.  There
is nothing useful to do for the 2-copies case.  If there are 3 or more copies,
then we could try reading from one of the non-missing copies, but this is a
bit complicated and very rarely would be used, so I'm leaving it for now.

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/raid10.c b/drivers/md/raid10.c
index 64bb4ddc6798232f1cda5cfbf87fa6e7c6d3792f..3f8df2ecbae31cdc335c525f8099de4e2bb2e158 100644 (file)
--- a/drivers/md/raid10.c
+++ b/drivers/md/raid10.c
@@ -172,7 +172,7 @@ static void put_all_bios(conf_t *conf, r10bio_t *r10_bio)
 
        for (i = 0; i < conf->copies; i++) {
                struct bio **bio = & r10_bio->devs[i].bio;
-               if (*bio)
+               if (*bio && *bio != IO_BLOCKED)
                        bio_put(*bio);
                *bio = NULL;
        }
@@ -500,6 +500,7 @@ static int read_balance(conf_t *conf, r10bio_t *r10_bio)
                disk = r10_bio->devs[slot].devnum;
 
                while ((rdev = rcu_dereference(conf->mirrors[disk].rdev)) == NULL ||
+                      r10_bio->devs[slot].bio == IO_BLOCKED ||
                       !test_bit(In_sync, &rdev->flags)) {
                        slot++;
                        if (slot == conf->copies) {
@@ -517,6 +518,7 @@ static int read_balance(conf_t *conf, r10bio_t *r10_bio)
        slot = 0;
        disk = r10_bio->devs[slot].devnum;
        while ((rdev=rcu_dereference(conf->mirrors[disk].rdev)) == NULL ||
+              r10_bio->devs[slot].bio == IO_BLOCKED ||
               !test_bit(In_sync, &rdev->flags)) {
                slot ++;
                if (slot == conf->copies) {
@@ -537,6 +539,7 @@ static int read_balance(conf_t *conf, r10bio_t *r10_bio)
 
 
                if ((rdev=rcu_dereference(conf->mirrors[ndisk].rdev)) == NULL ||
+                   r10_bio->devs[nslot].bio == IO_BLOCKED ||
                    !test_bit(In_sync, &rdev->flags))
                        continue;
 
@@ -1104,7 +1107,6 @@ abort:
 
 static int end_sync_read(struct bio *bio, unsigned int bytes_done, int error)
 {
-       int uptodate = test_bit(BIO_UPTODATE, &bio->bi_flags);
        r10bio_t * r10_bio = (r10bio_t *)(bio->bi_private);
        conf_t *conf = mddev_to_conf(r10_bio->mddev);
        int i,d;
@@ -1119,7 +1121,10 @@ static int end_sync_read(struct bio *bio, unsigned int bytes_done, int error)
                BUG();
        update_head_pos(i, r10_bio);
        d = r10_bio->devs[i].devnum;
-       if (!uptodate)
+
+       if (test_bit(BIO_UPTODATE, &bio->bi_flags))
+               set_bit(R10BIO_Uptodate, &r10_bio->state);
+       else if (!test_bit(MD_RECOVERY_SYNC, &conf->mddev->recovery))
                md_error(r10_bio->mddev,
                         conf->mirrors[d].rdev);
 
@@ -1209,25 +1214,30 @@ static void sync_request_write(mddev_t *mddev, r10bio_t *r10_bio)
        fbio = r10_bio->devs[i].bio;
 
        /* now find blocks with errors */
-       for (i=first+1 ; i < conf->copies ; i++) {
-               int vcnt, j, d;
+       for (i=0 ; i < conf->copies ; i++) {
+               int  j, d;
+               int vcnt = r10_bio->sectors >> (PAGE_SHIFT-9);
 
-               if (!test_bit(BIO_UPTODATE, &r10_bio->devs[i].bio->bi_flags))
-                       continue;
-               /* We know that the bi_io_vec layout is the same for
-                * both 'first' and 'i', so we just compare them.
-                * All vec entries are PAGE_SIZE;
-                */
                tbio = r10_bio->devs[i].bio;
-               vcnt = r10_bio->sectors >> (PAGE_SHIFT-9);
-               for (j = 0; j < vcnt; j++)
-                       if (memcmp(page_address(fbio->bi_io_vec[j].bv_page),
-                                  page_address(tbio->bi_io_vec[j].bv_page),
-                                  PAGE_SIZE))
-                               break;
-               if (j == vcnt)
+
+               if (tbio->bi_end_io != end_sync_read)
+                       continue;
+               if (i == first)
                        continue;
-               mddev->resync_mismatches += r10_bio->sectors;
+               if (test_bit(BIO_UPTODATE, &r10_bio->devs[i].bio->bi_flags)) {
+                       /* We know that the bi_io_vec layout is the same for
+                        * both 'first' and 'i', so we just compare them.
+                        * All vec entries are PAGE_SIZE;
+                        */
+                       for (j = 0; j < vcnt; j++)
+                               if (memcmp(page_address(fbio->bi_io_vec[j].bv_page),
+                                          page_address(tbio->bi_io_vec[j].bv_page),
+                                          PAGE_SIZE))
+                                       break;
+                       if (j == vcnt)
+                               continue;
+                       mddev->resync_mismatches += r10_bio->sectors;
+               }
                if (test_bit(MD_RECOVERY_CHECK, &mddev->recovery))
                        /* Don't fix anything. */
                        continue;
@@ -1308,7 +1318,10 @@ static void recovery_request_write(mddev_t *mddev, r10bio_t *r10_bio)
 
        atomic_inc(&conf->mirrors[d].rdev->nr_pending);
        md_sync_acct(conf->mirrors[d].rdev->bdev, wbio->bi_size >> 9);
-       generic_make_request(wbio);
+       if (test_bit(R10BIO_Uptodate, &r10_bio->state))
+               generic_make_request(wbio);
+       else
+               bio_endio(wbio, wbio->bi_size, -EIO);
 }
 
 
@@ -1445,7 +1458,8 @@ static void raid10d(mddev_t *mddev)
                        unfreeze_array(conf);
 
                        bio = r10_bio->devs[r10_bio->read_slot].bio;
-                       r10_bio->devs[r10_bio->read_slot].bio = NULL;
+                       r10_bio->devs[r10_bio->read_slot].bio =
+                               mddev->ro ? IO_BLOCKED : NULL;
                        bio_put(bio);
                        mirror = read_balance(conf, r10_bio);
                        if (mirror == -1) {

diff --git a/include/linux/raid/raid10.h b/include/linux/raid/raid10.h
index dfa528385e3fe9654a47207bf9f661528c9e0ac6..b1103298a8c2cb043cd7c56d4a32b694463379e7 100644 (file)
--- a/include/linux/raid/raid10.h
+++ b/include/linux/raid/raid10.h
@@ -104,6 +104,13 @@ struct r10bio_s {
        } devs[0];
 };
 
+/* when we get a read error on a read-only array, we redirect to another
+ * device without failing the first device, or trying to over-write to
+ * correct the read error.  To keep track of bad blocks on a per-bio
+ * level, we store IO_BLOCKED in the appropriate 'bios' pointer
+ */
+#define IO_BLOCKED ((struct bio*)1)
+
 /* bits for r10bio.state */
 #define        R10BIO_Uptodate 0
 #define        R10BIO_IsSync   1