raid5: remove unnecessary bitmap write optimization

Neil pointed out the bitmap write optimization in handle_stripe_clean_event()
is unnecessary, because the chance one stripe gets written twice in the mean
time is rare. We can always do a bitmap_startwrite when a write request is
added to a stripe and bitmap_endwrite after write request is done.  Delete the
optimization. With it, we can delete some cases of device_lock.

Signed-off-by: Shaohua Li <shli@fusionio.com>
Signed-off-by: NeilBrown <neilb@suse.de>

1 files changed, 9 insertions, 12 deletions

diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c
index 6ef1eeb68f7..9ad452c6d7e 100644
--- a/drivers/md/raid5.c
+++ b/drivers/md/raid5.c
@@ -2357,7 +2357,7 @@ static int add_stripe_bio(struct stripe_head *sh, struct bio *bi, int dd_idx, in
         spin_lock_irq(&conf->device_lock);
         if (forwrite) {
                 bip = &sh->dev[dd_idx].towrite;
-                if (*bip == NULL && sh->dev[dd_idx].written == NULL)
+                if (*bip == NULL)
                         firstwrite = 1;
         } else
                 bip = &sh->dev[dd_idx].toread;
@@ -2458,6 +2458,7 @@ handle_failed_stripe(struct r5conf *conf, struct stripe_head *sh,
                 /* fail all writes first */
                 bi = sh->dev[i].towrite;
                 sh->dev[i].towrite = NULL;
+                spin_unlock_irq(&conf->device_lock);
                 if (bi) {
                         s->to_write--;
                         bitmap_end = 1;
@@ -2477,6 +2478,10 @@ handle_failed_stripe(struct r5conf *conf, struct stripe_head *sh,
                         }
                         bi = nextbi;
                 }
+                if (bitmap_end)
+                        bitmap_endwrite(conf->mddev->bitmap, sh->sector,
+                                STRIPE_SECTORS, 0, 0);
+                bitmap_end = 0;
                 /* and fail all 'written' */
                 bi = sh->dev[i].written;
                 sh->dev[i].written = NULL;
@@ -2516,7 +2521,6 @@ handle_failed_stripe(struct r5conf *conf, struct stripe_head *sh,
                                 bi = nextbi;
                         }
                 }
-                spin_unlock_irq(&conf->device_lock);
                 if (bitmap_end)
                         bitmap_endwrite(conf->mddev->bitmap, sh->sector,
                                         STRIPE_SECTORS, 0, 0);
@@ -2720,9 +2724,7 @@ static void handle_stripe_clean_event(struct r5conf *conf,
                                 test_bit(R5_UPTODATE, &dev->flags)) {
                                 /* We can return any write requests */
                                 struct bio *wbi, *wbi2;
-                                int bitmap_end = 0;
                                 pr_debug("Return write for disc %d\n", i);
-                                spin_lock_irq(&conf->device_lock);
                                 wbi = dev->written;
                                 dev->written = NULL;
                                 while (wbi && wbi->bi_sector <
@@ -2735,15 +2737,10 @@ static void handle_stripe_clean_event(struct r5conf *conf,
                                         }
                                         wbi = wbi2;
                                 }
-                                if (dev->towrite == NULL)
-                                        bitmap_end = 1;
-                                spin_unlock_irq(&conf->device_lock);
-                                if (bitmap_end)
-                                        bitmap_endwrite(conf->mddev->bitmap,
-                                                        sh->sector,
-                                                        STRIPE_SECTORS,
+                                bitmap_endwrite(conf->mddev->bitmap, sh->sector,
+                                                STRIPE_SECTORS,
                                          !test_bit(STRIPE_DEGRADED, &sh->state),
-                                                        0);
+                                                0);
                         }
                 }