raid5: fix 2 bugs in ops_complete_biofill (e4d84909) · Commits · 戴 / test

1/ ops_complete_biofill tried to avoid calling handle_stripe since all the state necessary to return read completions is available. However the process of determining whether more read requests are pending requires locking the stripe (to block add_stripe_bio from updating dev->toead). ops_complete_biofill can run in tasklet context, so rather than upgrading all the stripe locks from spin_lock to spin_lock_bh this patch just unconditionally reschedules handle_stripe after completing the read request. 2/ ops_complete_biofill needlessly qualified processing R5_Wantfill with dev->toread. The result being that the 'biofill' pending bit is cleared before handling the pending read-completions on dev->read. R5_Wantfill can be unconditionally handled because the 'biofill' pending bit prevents new R5_Wantfill requests from being seen by ops_run_biofill and ops_complete_biofill. Found-by:

Yuri Tikhonov <yur@emcraft.com> [neilb@suse.de: simpler fix for bug 1 than moving code] Signed-off-by:

NeilBrown <neilb@suse.de> Signed-off-by:

Dan Williams <dan.j.williams@intel.com>

drivers/md/raid5.c

+7 −10

Original line number	Diff line number	Diff line
		@@ -514,7 +514,7 @@ static void ops_complete_biofill(void *stripe_head_ref)
		struct stripe_head *sh = stripe_head_ref;
		struct bio *return_bi = NULL;
		raid5_conf_t *conf = sh->raid_conf;
		int i, more_to_read = 0;
		int i;

		pr_debug("%s: stripe %llu\n", __FUNCTION__,
		(unsigned long long)sh->sector);
		@@ -522,16 +522,14 @@ static void ops_complete_biofill(void *stripe_head_ref)
		/* clear completed biofills */
		for (i = sh->disks; i--; ) {
		struct r5dev *dev = &sh->dev[i];
		/* check if this stripe has new incoming reads */
		if (dev->toread)
		more_to_read++;

		/* acknowledge completion of a biofill operation */
		/* and check if we need to reply to a read request
		/* and check if we need to reply to a read request,
		* new R5_Wantfill requests are held off until
		* !test_bit(STRIPE_OP_BIOFILL, &sh->ops.pending)
		*/
		if (test_bit(R5_Wantfill, &dev->flags) && !dev->toread) {
		if (test_and_clear_bit(R5_Wantfill, &dev->flags)) {
		struct bio rbi, rbi2;
		clear_bit(R5_Wantfill, &dev->flags);

		/* The access to dev->read is outside of the
		* spin_lock_irq(&conf->device_lock), but is protected
		@@ -558,7 +556,6 @@ static void ops_complete_biofill(void *stripe_head_ref)

		return_io(return_bi);

		if (more_to_read)
		set_bit(STRIPE_HANDLE, &sh->state);
		release_stripe(sh);
		}

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