MD: raid5 avoid unnecessary zero page for trim
We want to avoid zero discarded dev page, because it's useless for discard.
But if we don't zero it, another read/write hit such page in the cache and will
get inconsistent data.
To avoid zero the page, we don't set R5_UPTODATE flag after construction is
done. In this way, discard write request is still issued and finished, but read
will not hit the page. If the stripe gets accessed soon, we need reread the
stripe, but since the chance is low, the reread isn't a big deal.
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 74dcf19..758b772 100644
--- a/drivers/md/raid5.c
+++ b/drivers/md/raid5.c
@@ -547,7 +547,7 @@
rw = WRITE_FUA;
else
rw = WRITE;
- if (test_and_clear_bit(R5_Discard, &sh->dev[i].flags))
+ if (test_bit(R5_Discard, &sh->dev[i].flags))
rw |= REQ_DISCARD;
} else if (test_and_clear_bit(R5_Wantread, &sh->dev[i].flags))
rw = READ;
@@ -1172,11 +1172,9 @@
set_bit(R5_WantFUA, &dev->flags);
if (wbi->bi_rw & REQ_SYNC)
set_bit(R5_SyncIO, &dev->flags);
- if (wbi->bi_rw & REQ_DISCARD) {
- memset(page_address(dev->page), 0,
- STRIPE_SECTORS << 9);
+ if (wbi->bi_rw & REQ_DISCARD)
set_bit(R5_Discard, &dev->flags);
- } else
+ else
tx = async_copy_data(1, wbi, dev->page,
dev->sector, tx);
wbi = r5_next_bio(wbi, dev->sector);
@@ -1194,7 +1192,7 @@
int pd_idx = sh->pd_idx;
int qd_idx = sh->qd_idx;
int i;
- bool fua = false, sync = false;
+ bool fua = false, sync = false, discard = false;
pr_debug("%s: stripe %llu\n", __func__,
(unsigned long long)sh->sector);
@@ -1202,13 +1200,15 @@
for (i = disks; i--; ) {
fua |= test_bit(R5_WantFUA, &sh->dev[i].flags);
sync |= test_bit(R5_SyncIO, &sh->dev[i].flags);
+ discard |= test_bit(R5_Discard, &sh->dev[i].flags);
}
for (i = disks; i--; ) {
struct r5dev *dev = &sh->dev[i];
if (dev->written || i == pd_idx || i == qd_idx) {
- set_bit(R5_UPTODATE, &dev->flags);
+ if (!discard)
+ set_bit(R5_UPTODATE, &dev->flags);
if (fua)
set_bit(R5_WantFUA, &dev->flags);
if (sync)
@@ -1252,8 +1252,6 @@
}
if (i >= sh->disks) {
atomic_inc(&sh->count);
- memset(page_address(sh->dev[pd_idx].page), 0,
- STRIPE_SECTORS << 9);
set_bit(R5_Discard, &sh->dev[pd_idx].flags);
ops_complete_reconstruct(sh);
return;
@@ -1314,10 +1312,6 @@
}
if (i >= sh->disks) {
atomic_inc(&sh->count);
- memset(page_address(sh->dev[sh->pd_idx].page), 0,
- STRIPE_SECTORS << 9);
- memset(page_address(sh->dev[sh->qd_idx].page), 0,
- STRIPE_SECTORS << 9);
set_bit(R5_Discard, &sh->dev[sh->pd_idx].flags);
set_bit(R5_Discard, &sh->dev[sh->qd_idx].flags);
ops_complete_reconstruct(sh);
@@ -2775,7 +2769,8 @@
if (sh->dev[i].written) {
dev = &sh->dev[i];
if (!test_bit(R5_LOCKED, &dev->flags) &&
- test_bit(R5_UPTODATE, &dev->flags)) {
+ (test_bit(R5_UPTODATE, &dev->flags) ||
+ test_and_clear_bit(R5_Discard, &dev->flags))) {
/* We can return any write requests */
struct bio *wbi, *wbi2;
pr_debug("Return write for disc %d\n", i);
@@ -3493,10 +3488,12 @@
if (s.written &&
(s.p_failed || ((test_bit(R5_Insync, &pdev->flags)
&& !test_bit(R5_LOCKED, &pdev->flags)
- && test_bit(R5_UPTODATE, &pdev->flags)))) &&
+ && (test_bit(R5_UPTODATE, &pdev->flags) ||
+ test_bit(R5_Discard, &pdev->flags))))) &&
(s.q_failed || ((test_bit(R5_Insync, &qdev->flags)
&& !test_bit(R5_LOCKED, &qdev->flags)
- && test_bit(R5_UPTODATE, &qdev->flags)))))
+ && (test_bit(R5_UPTODATE, &qdev->flags) ||
+ test_bit(R5_Discard, &qdev->flags))))))
handle_stripe_clean_event(conf, sh, disks, &s.return_bi);
/* Now we might consider reading some blocks, either to check/generate
@@ -3523,9 +3520,11 @@
/* All the 'written' buffers and the parity block are ready to
* be written back to disk
*/
- BUG_ON(!test_bit(R5_UPTODATE, &sh->dev[sh->pd_idx].flags));
+ BUG_ON(!test_bit(R5_UPTODATE, &sh->dev[sh->pd_idx].flags) &&
+ !test_bit(R5_Discard, &sh->dev[sh->pd_idx].flags));
BUG_ON(sh->qd_idx >= 0 &&
- !test_bit(R5_UPTODATE, &sh->dev[sh->qd_idx].flags));
+ !test_bit(R5_UPTODATE, &sh->dev[sh->qd_idx].flags) &&
+ !test_bit(R5_Discard, &sh->dev[sh->qd_idx].flags));
for (i = disks; i--; ) {
struct r5dev *dev = &sh->dev[i];
if (test_bit(R5_LOCKED, &dev->flags) &&