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>

diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c
index 6ef1eeb68f7c470f763bf8953276dca20ad4895b..9ad452c6d7e3e074cc0987a86b9197043f7fc9ed 100644 (file)
--- 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);
                        }
                }