[PATCH] md: tidyup some issues with raid1 resync and prepare for catching read errors

We are dereferencing ->rdev without an rcu lock!

Signed-off-by: Neil Brown <neilb@suse.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 56 insertions, 54 deletions

diff --git a/drivers/md/raid1.c b/drivers/md/raid1.c
index b3856db8d6c2..ea1f1eb93c77 100644
--- a/drivers/md/raid1.c
+++ b/drivers/md/raid1.c
@@ -177,6 +177,13 @@ static inline void free_r1bio(r1bio_t *r1_bio)
 static inline void put_buf(r1bio_t *r1_bio)
 {
         conf_t *conf = mddev_to_conf(r1_bio->mddev);
+        int i;
+
+        for (i=0; i<conf->raid_disks; i++) {
+                struct bio *bio = r1_bio->bios[i];
+                if (bio->bi_end_io)
+                        rdev_dec_pending(conf->mirrors[i].rdev, r1_bio->mddev);
+        }
 
         mempool_free(r1_bio, conf->r1buf_pool);
 
@@ -1085,7 +1092,6 @@ static int end_sync_read(struct bio *bio, unsigned int bytes_done, int error)
                          conf->mirrors[r1_bio->read_disk].rdev);
         } else
                 set_bit(R1BIO_Uptodate, &r1_bio->state);
-        rdev_dec_pending(conf->mirrors[r1_bio->read_disk].rdev, conf->mddev);
         reschedule_retry(r1_bio);
         return 0;
 }
@@ -1116,7 +1122,6 @@ static int end_sync_write(struct bio *bio, unsigned int bytes_done, int error)
                 md_done_sync(mddev, r1_bio->sectors, uptodate);
                 put_buf(r1_bio);
         }
-        rdev_dec_pending(conf->mirrors[mirror].rdev, mddev);
         return 0;
 }
 
@@ -1153,10 +1158,14 @@ static void sync_request_write(mddev_t *mddev, r1bio_t *r1_bio)
         atomic_set(&r1_bio->remaining, 1);
         for (i = 0; i < disks ; i++) {
                 wbio = r1_bio->bios[i];
-                if (wbio->bi_end_io != end_sync_write)
+                if (wbio->bi_end_io == NULL ||
+                    (wbio->bi_end_io == end_sync_read &&
+                     (i == r1_bio->read_disk ||
+                      !test_bit(MD_RECOVERY_SYNC, &mddev->recovery))))
                         continue;
 
-                atomic_inc(&conf->mirrors[i].rdev->nr_pending);
+                wbio->bi_rw = WRITE;
+                wbio->bi_end_io = end_sync_write;
                 atomic_inc(&r1_bio->remaining);
                 md_sync_acct(conf->mirrors[i].rdev->bdev, wbio->bi_size >> 9);
 
@@ -1388,14 +1397,13 @@ static int init_resync(conf_t *conf)
 static sector_t sync_request(mddev_t *mddev, sector_t sector_nr, int *skipped, int go_faster)
 {
         conf_t *conf = mddev_to_conf(mddev);
-        mirror_info_t *mirror;
         r1bio_t *r1_bio;
         struct bio *bio;
         sector_t max_sector, nr_sectors;
-        int disk;
+        int disk = -1;
         int i;
-        int wonly;
-        int write_targets = 0;
+        int wonly = -1;
+        int write_targets = 0, read_targets = 0;
         int sync_blocks;
         int still_degraded = 0;
 
@@ -1447,44 +1455,24 @@ static sector_t sync_request(mddev_t *mddev, sector_t sector_nr, int *skipped, i
 
         conf->next_resync = sector_nr;
 
+        r1_bio = mempool_alloc(conf->r1buf_pool, GFP_NOIO);
+        rcu_read_lock();
         /*
-         * If reconstructing, and >1 working disc,
-         * could dedicate one to rebuild and others to
-         * service read requests ..
+         * If we get a correctably read error during resync or recovery,
+         * we might want to read from a different device.  So we
+         * flag all drives that could conceivably be read from for READ,
+         * and any others (which will be non-In_sync devices) for WRITE.
+         * If a read fails, we try reading from something else for which READ
+         * is OK.
          */
-        disk = conf->last_used;
-        /* make sure disk is operational */
-        wonly = disk;
-        while (conf->mirrors[disk].rdev == NULL ||
-               !test_bit(In_sync, &conf->mirrors[disk].rdev->flags) ||
-               test_bit(WriteMostly, &conf->mirrors[disk].rdev->flags)
-                ) {
-                if (conf->mirrors[disk].rdev  &&
-                    test_bit(In_sync, &conf->mirrors[disk].rdev->flags))
-                        wonly = disk;
-                if (disk <= 0)
-                        disk = conf->raid_disks;
-                disk--;
-                if (disk == conf->last_used) {
-                        disk = wonly;
-                        break;
-                }
-        }
-        conf->last_used = disk;
-        atomic_inc(&conf->mirrors[disk].rdev->nr_pending);
-
-
-        mirror = conf->mirrors + disk;
-
-        r1_bio = mempool_alloc(conf->r1buf_pool, GFP_NOIO);
 
         r1_bio->mddev = mddev;
         r1_bio->sector = sector_nr;
         r1_bio->state = 0;
         set_bit(R1BIO_IsSync, &r1_bio->state);
-        r1_bio->read_disk = disk;
 
         for (i=0; i < conf->raid_disks; i++) {
+                mdk_rdev_t *rdev;
                 bio = r1_bio->bios[i];
 
                 /* take from bio_init */
@@ -1499,35 +1487,49 @@ static sector_t sync_request(mddev_t *mddev, sector_t sector_nr, int *skipped, i
                 bio->bi_end_io = NULL;
                 bio->bi_private = NULL;
 
-                if (i == disk) {
-                        bio->bi_rw = READ;
-                        bio->bi_end_io = end_sync_read;
-                } else if (conf->mirrors[i].rdev == NULL ||
-                           test_bit(Faulty, &conf->mirrors[i].rdev->flags)) {
+                rdev = rcu_dereference(conf->mirrors[i].rdev);
+                if (rdev == NULL ||
+                           test_bit(Faulty, &rdev->flags)) {
                         still_degraded = 1;
                         continue;
-                } else if (!test_bit(In_sync, &conf->mirrors[i].rdev->flags) ||
-                           sector_nr + RESYNC_SECTORS > mddev->recovery_cp   ||
-                           test_bit(MD_RECOVERY_REQUESTED, &mddev->recovery)) {
+                } else if (!test_bit(In_sync, &rdev->flags)) {
                         bio->bi_rw = WRITE;
                         bio->bi_end_io = end_sync_write;
                         write_targets ++;
-                } else
-                        /* no need to read or write here */
-                        continue;
-                bio->bi_sector = sector_nr + conf->mirrors[i].rdev->data_offset;
-                bio->bi_bdev = conf->mirrors[i].rdev->bdev;
+                } else {
+                        /* may need to read from here */
+                        bio->bi_rw = READ;
+                        bio->bi_end_io = end_sync_read;
+                        if (test_bit(WriteMostly, &rdev->flags)) {
+                                if (wonly < 0)
+                                        wonly = i;
+                        } else {
+                                if (disk < 0)
+                                        disk = i;
+                        }
+                        read_targets++;
+                }
+                atomic_inc(&rdev->nr_pending);
+                bio->bi_sector = sector_nr + rdev->data_offset;
+                bio->bi_bdev = rdev->bdev;
                 bio->bi_private = r1_bio;
         }
+        rcu_read_unlock();
+        if (disk < 0)
+                disk = wonly;
+        r1_bio->read_disk = disk;
 
-        if (write_targets == 0) {
+        if (test_bit(MD_RECOVERY_SYNC, &mddev->recovery) && read_targets > 0)
+                /* extra read targets are also write targets */
+                write_targets += read_targets-1;
+
+        if (write_targets == 0 || read_targets == 0) {
                 /* There is nowhere to write, so all non-sync
                  * drives must be failed - so we are finished
                  */
                 sector_t rv = max_sector - sector_nr;
                 *skipped = 1;
                 put_buf(r1_bio);
-                rdev_dec_pending(conf->mirrors[disk].rdev, mddev);
                 return rv;
         }
 
@@ -1578,10 +1580,10 @@ static sector_t sync_request(mddev_t *mddev, sector_t sector_nr, int *skipped, i
                 sync_blocks -= (len>>9);
         } while (r1_bio->bios[disk]->bi_vcnt < RESYNC_PAGES);
  bio_full:
-        bio = r1_bio->bios[disk];
+        bio = r1_bio->bios[r1_bio->read_disk];
         r1_bio->sectors = nr_sectors;
 
-        md_sync_acct(mirror->rdev->bdev, nr_sectors);
+        md_sync_acct(conf->mirrors[r1_bio->read_disk].rdev->bdev, nr_sectors);
 
         generic_make_request(bio);