[PATCH] md: yet another attempt to get bitmap-based resync to do the right thing in all cases...

Firstly, R1BIO_Degraded was being set in a number of places in the resync
code, but is never used there, so get rid of those settings.

Then: When doing a resync, we want to clear the bit in the bitmap iff the
array will be non-degraded when the sync has completed.  However the current
code would clear the bitmap if the array was non-degraded when the resync
*started*, which obviously isn't right (it is for 'resync' but not for
'recovery' - i.e.  rebuilding a failed drive).

This patch calculated 'still_degraded' and uses the to tell bitmap_start_sync
whether this sync should clear the corresponding bit.

Signed-off-by: Neil Brown <neilb@cse.unsw.edu.au>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 15 insertions, 14 deletions

diff --git a/drivers/md/raid1.c b/drivers/md/raid1.c
index d3a64a04a6d8..51d9645ed09c 100644
--- a/drivers/md/raid1.c
+++ b/drivers/md/raid1.c
@@ -893,7 +893,6 @@ static int end_sync_read(struct bio *bio, unsigned int bytes_done, int error)
         if (!uptodate) {
                 md_error(r1_bio->mddev,
                          conf->mirrors[r1_bio->read_disk].rdev);
-                set_bit(R1BIO_Degraded, &r1_bio->state);
         } else
                 set_bit(R1BIO_Uptodate, &r1_bio->state);
         rdev_dec_pending(conf->mirrors[r1_bio->read_disk].rdev, conf->mddev);
@@ -918,10 +917,9 @@ static int end_sync_write(struct bio *bio, unsigned int bytes_done, int error)
                         mirror = i;
                         break;
                 }
-        if (!uptodate) {
+        if (!uptodate)
                 md_error(mddev, conf->mirrors[mirror].rdev);
-                set_bit(R1BIO_Degraded, &r1_bio->state);
-        }
+
         update_head_pos(mirror, r1_bio);
 
         if (atomic_dec_and_test(&r1_bio->remaining)) {
@@ -1109,6 +1107,7 @@ static sector_t sync_request(mddev_t *mddev, sector_t sector_nr, int *skipped, i
         int i;
         int write_targets = 0;
         int sync_blocks;
+        int still_degraded = 0;
 
         if (!conf->r1buf_pool)
         {
@@ -1137,7 +1136,10 @@ static sector_t sync_request(mddev_t *mddev, sector_t sector_nr, int *skipped, i
                 return 0;
         }
 
-        if (!bitmap_start_sync(mddev->bitmap, sector_nr, &sync_blocks, mddev->degraded) &&
+        /* before building a request, check if we can skip these blocks..
+         * This call the bitmap_start_sync doesn't actually record anything
+         */
+        if (!bitmap_start_sync(mddev->bitmap, sector_nr, &sync_blocks, 1) &&
             !conf->fullsync) {
                 /* We can skip this block, and probably several more */
                 *skipped = 1;
@@ -1203,24 +1205,23 @@ static sector_t sync_request(mddev_t *mddev, sector_t sector_nr, int *skipped, i
                 if (i == disk) {
                         bio->bi_rw = READ;
                         bio->bi_end_io = end_sync_read;
-                } else if (conf->mirrors[i].rdev &&
-                           !conf->mirrors[i].rdev->faulty &&
-                           (!conf->mirrors[i].rdev->in_sync ||
-                            sector_nr + RESYNC_SECTORS > mddev->recovery_cp)) {
+                } else if (conf->mirrors[i].rdev == NULL ||
+                           conf->mirrors[i].rdev->faulty) {
+                        still_degraded = 1;
+                        continue;
+                } else if (!conf->mirrors[i].rdev->in_sync ||
+                           sector_nr + RESYNC_SECTORS > mddev->recovery_cp) {
                         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;
                 bio->bi_private = r1_bio;
         }
 
-        if (write_targets + 1 < conf->raid_disks)
-                /* array degraded, can't clear bitmap */
-                set_bit(R1BIO_Degraded, &r1_bio->state);
-
         if (write_targets == 0) {
                 /* There is nowhere to write, so all non-sync
                  * drives must be failed - so we are finished
@@ -1243,7 +1244,7 @@ static sector_t sync_request(mddev_t *mddev, sector_t sector_nr, int *skipped, i
                         break;
                 if (sync_blocks == 0) {
                         if (!bitmap_start_sync(mddev->bitmap, sector_nr,
-                                        &sync_blocks, mddev->degraded) &&
+                                        &sync_blocks, still_degraded) &&
                                         !conf->fullsync)
                                 break;
                         if (sync_blocks < (PAGE_SIZE>>9))