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 stripe_lock.
Signed-off-by: Shaohua Li <shli@xxxxxxxxxxxx>
---
drivers/md/raid5.c | 28 ++++++++--------------------
1 file changed, 8 insertions(+), 20 deletions(-)
Index: linux/drivers/md/raid5.c
===================================================================
--- linux.orig/drivers/md/raid5.c 2012-07-03 14:58:51.241382361 +0800
+++ linux/drivers/md/raid5.c 2012-07-03 15:04:48.568889733 +0800
@@ -2350,7 +2350,7 @@ static int add_stripe_bio(struct stripe_
spin_lock_irq(&sh->stripe_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;
@@ -2427,7 +2427,6 @@ handle_failed_stripe(struct r5conf *conf
int i;
for (i = disks; i--; ) {
struct bio *bi;
- int bitmap_end = 0;
if (test_bit(R5_ReadError, &sh->dev[i].flags)) {
struct md_rdev *rdev;
@@ -2451,10 +2450,9 @@ handle_failed_stripe(struct r5conf *conf
/* fail all writes first */
bi = sh->dev[i].towrite;
sh->dev[i].towrite = NULL;
- if (bi) {
+ if (bi)
s->to_write--;
- bitmap_end = 1;
- }
+ spin_unlock_irq(&sh->stripe_lock);
if (test_and_clear_bit(R5_Overlap, &sh->dev[i].flags))
wake_up(&conf->wait_for_overlap);
@@ -2473,7 +2471,6 @@ handle_failed_stripe(struct r5conf *conf
/* and fail all 'written' */
bi = sh->dev[i].written;
sh->dev[i].written = NULL;
- if (bi) bitmap_end = 1;
while (bi && bi->bi_sector <
sh->dev[i].sector + STRIPE_SECTORS) {
struct bio *bi2 = r5_next_bio(bi, sh->dev[i].sector);
@@ -2509,10 +2506,8 @@ handle_failed_stripe(struct r5conf *conf
bi = nextbi;
}
}
- spin_unlock_irq(&sh->stripe_lock);
- if (bitmap_end)
- bitmap_endwrite(conf->mddev->bitmap, sh->sector,
- STRIPE_SECTORS, 0, 0);
+ bitmap_endwrite(conf->mddev->bitmap, sh->sector,
+ STRIPE_SECTORS, 0, 0);
/* If we were in the middle of a write the parity block might
* still be locked - so just clear all R5_LOCKED flags
*/
@@ -2713,9 +2708,7 @@ static void handle_stripe_clean_event(st
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(&sh->stripe_lock);
wbi = dev->written;
dev->written = NULL;
while (wbi && wbi->bi_sector <
@@ -2728,15 +2721,10 @@ static void handle_stripe_clean_event(st
}
wbi = wbi2;
}
- if (dev->towrite == NULL)
- bitmap_end = 1;
- spin_unlock_irq(&sh->stripe_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);
}
}
--
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