[PATCH] md: teach raid5 the difference between 'check' and 'repair'.

With this, raid5 can be asked to check parity without repairing it.  It also
keeps a count of the number of incorrect parity blocks found (mismatches) and
reports them through sysfs.

Signed-off-by: Neil Brown <neilb@suse.de>
Cc: Greg KH <greg@kroah.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

diff --git a/drivers/md/md.c b/drivers/md/md.c
index 3740087..e58d61d 100644 (file)
--- a/drivers/md/md.c
+++ b/drivers/md/md.c
@@ -1758,16 +1758,29 @@ md_store_scan(mddev_t *mddev, const char *page, size_t len)
        return len;
 }
 
+static ssize_t
+md_show_mismatch(mddev_t *mddev, char *page)
+{
+       return sprintf(page, "%llu\n",
+                      (unsigned long long) mddev->resync_mismatches);
+}
+
 static struct md_sysfs_entry md_scan_mode = {
        .attr = {.name = "scan_mode", .mode = S_IRUGO|S_IWUSR },
        .show = md_show_scan,
        .store = md_store_scan,
 };
 
+static struct md_sysfs_entry md_mismatches = {
+       .attr = {.name = "mismatch_cnt", .mode = S_IRUGO },
+       .show = md_show_mismatch,
+};
+
 static struct attribute *md_default_attrs[] = {
        &md_level.attr,
        &md_raid_disks.attr,
        &md_scan_mode.attr,
+       &md_mismatches.attr,
        NULL,
 };
 
@@ -3888,12 +3901,13 @@ static void md_do_sync(mddev_t *mddev)
                }
        } while (mddev->curr_resync < 2);
 
-       if (test_bit(MD_RECOVERY_SYNC, &mddev->recovery))
+       if (test_bit(MD_RECOVERY_SYNC, &mddev->recovery)) {
                /* resync follows the size requested by the personality,
                 * which defaults to physical size, but can be virtual size
                 */
                max_sectors = mddev->resync_max_sectors;
-       else
+               mddev->resync_mismatches = 0;
+       } else
                /* recovery follows the physical size of devices */
                max_sectors = mddev->size << 1;
 

diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c
index 121fbaa..ce15455 100644 (file)
--- a/drivers/md/raid5.c
+++ b/drivers/md/raid5.c
@@ -1292,6 +1292,11 @@ static void handle_stripe(struct stripe_head *sh)
                            !memcmp(pagea, pagea+4, STRIPE_SIZE-4)) {
                                /* parity is correct (on disc, not in buffer any more) */
                                set_bit(STRIPE_INSYNC, &sh->state);
+                       } else {
+                               conf->mddev->resync_mismatches += STRIPE_SECTORS;
+                               if (test_bit(MD_RECOVERY_CHECK, &conf->mddev->recovery))
+                                       /* don't try to repair!! */
+                                       set_bit(STRIPE_INSYNC, &sh->state);
                        }
                }
                if (!test_bit(STRIPE_INSYNC, &sh->state)) {

diff --git a/include/linux/raid/md_k.h b/include/linux/raid/md_k.h
index efd04dc..cb8b44d 100644 (file)
--- a/include/linux/raid/md_k.h
+++ b/include/linux/raid/md_k.h
@@ -175,6 +175,10 @@ struct mddev_s
        sector_t                        resync_mark_cnt;/* blocks written at resync_mark */
 
        sector_t                        resync_max_sectors; /* may be set by personality */
+
+       sector_t                        resync_mismatches; /* count of sectors where
+                                                           * parity/replica mismatch found
+                                                           */
        /* recovery/resync flags 
         * NEEDED:   we might need to start a resync/recover
         * RUNNING:  a thread is running, or about to be started