[PATCH] md: improve the interface to sync_request

1/ change the return value (which is number-of-sectors synced)
 from 'int' to 'sector_t'.
 The number of sectors is usually easily small enough to fit
 in an int, but if resync needs to abort, it may want to return
 the total number of remaining sectors, which could be large.
 Also errors cannot be returned as negative numbers now, so use
 0 instead
2/ Add a 'skipped' return parameter to allow the array to report
 that it skipped the sectors.  This allows md to take this into account
 in the speed calculations.
 Currently there is no important skipping, but the bitmap-based-resync
 that is coming will use this.

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, 23 insertions, 12 deletions

diff --git a/drivers/md/md.c b/drivers/md/md.c
index 177d2a7d7cea..fa608a1a5c20 100644
--- a/drivers/md/md.c
+++ b/drivers/md/md.c
@@ -3241,12 +3241,13 @@ static void md_do_sync(mddev_t *mddev)
         mddev_t *mddev2;
         unsigned int currspeed = 0,
                  window;
-        sector_t max_sectors,j;
+        sector_t max_sectors,j, io_sectors;
         unsigned long mark[SYNC_MARKS];
         sector_t mark_cnt[SYNC_MARKS];
         int last_mark,m;
         struct list_head *tmp;
         sector_t last_check;
+        int skipped = 0;
 
         /* just incase thread restarts... */
         if (test_bit(MD_RECOVERY_DONE, &mddev->recovery))
@@ -3312,7 +3313,7 @@ static void md_do_sync(mddev_t *mddev)
 
         if (test_bit(MD_RECOVERY_SYNC, &mddev->recovery))
                 /* resync follows the size requested by the personality,
-                 * which default to physical size, but can be virtual size
+                 * which defaults to physical size, but can be virtual size
                  */
                 max_sectors = mddev->resync_max_sectors;
         else
@@ -3331,9 +3332,10 @@ static void md_do_sync(mddev_t *mddev)
                 j = mddev->recovery_cp;
         else
                 j = 0;
+        io_sectors = 0;
         for (m = 0; m < SYNC_MARKS; m++) {
                 mark[m] = jiffies;
-                mark_cnt[m] = j;
+                mark_cnt[m] = io_sectors;
         }
         last_mark = 0;
         mddev->resync_mark = mark[last_mark];
@@ -3358,21 +3360,29 @@ static void md_do_sync(mddev_t *mddev)
         }
 
         while (j < max_sectors) {
-                int sectors;
+                sector_t sectors;
 
-                sectors = mddev->pers->sync_request(mddev, j, currspeed < sysctl_speed_limit_min);
-                if (sectors < 0) {
+                skipped = 0;
+                sectors = mddev->pers->sync_request(mddev, j, &skipped,
+                                            currspeed < sysctl_speed_limit_min);
+                if (sectors == 0) {
                         set_bit(MD_RECOVERY_ERR, &mddev->recovery);
                         goto out;
                 }
-                atomic_add(sectors, &mddev->recovery_active);
+
+                if (!skipped) { /* actual IO requested */
+                        io_sectors += sectors;
+                        atomic_add(sectors, &mddev->recovery_active);
+                }
+
                 j += sectors;
                 if (j>1) mddev->curr_resync = j;
 
-                if (last_check + window > j || j == max_sectors)
+
+                if (last_check + window > io_sectors || j == max_sectors)
                         continue;
 
-                last_check = j;
+                last_check = io_sectors;
 
                 if (test_bit(MD_RECOVERY_INTR, &mddev->recovery) ||
                     test_bit(MD_RECOVERY_ERR, &mddev->recovery))
@@ -3386,7 +3396,7 @@ static void md_do_sync(mddev_t *mddev)
                         mddev->resync_mark = mark[next];
                         mddev->resync_mark_cnt = mark_cnt[next];
                         mark[next] = jiffies;
-                        mark_cnt[next] = j - atomic_read(&mddev->recovery_active);
+                        mark_cnt[next] = io_sectors - atomic_read(&mddev->recovery_active);
                         last_mark = next;
                 }
 
@@ -3413,7 +3423,8 @@ static void md_do_sync(mddev_t *mddev)
                 mddev->queue->unplug_fn(mddev->queue);
                 cond_resched();
 
-                currspeed = ((unsigned long)(j-mddev->resync_mark_cnt))/2/((jiffies-mddev->resync_mark)/HZ +1) +1;
+                currspeed = ((unsigned long)(io_sectors-mddev->resync_mark_cnt))/2
+                        /((jiffies-mddev->resync_mark)/HZ +1) +1;
 
                 if (currspeed > sysctl_speed_limit_min) {
                         if ((currspeed > sysctl_speed_limit_max) ||
@@ -3433,7 +3444,7 @@ static void md_do_sync(mddev_t *mddev)
         wait_event(mddev->recovery_wait, !atomic_read(&mddev->recovery_active));
 
         /* tell personality that we are finished */
-        mddev->pers->sync_request(mddev, max_sectors, 1);
+        mddev->pers->sync_request(mddev, max_sectors, &skipped, 1);
 
         if (!test_bit(MD_RECOVERY_ERR, &mddev->recovery) &&
             mddev->curr_resync > 2 &&