From e4d84909dd48b5e5806a5d18b881e1ca1610ba9b Mon Sep 17 00:00:00 2001 From: Dan Williams Date: Mon, 24 Sep 2007 10:06:13 -0700 Subject: [PATCH] raid5: fix 2 bugs in ops_complete_biofill 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 [neilb@suse.de: simpler fix for bug 1 than moving code] Signed-off-by: NeilBrown Signed-off-by: Dan Williams --- drivers/md/raid5.c | 17 +++++++---------- 1 file changed, 7 insertions(+), 10 deletions(-) diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c index 4d63773..f96dea9 100644 --- a/drivers/md/raid5.c +++ b/drivers/md/raid5.c @@ -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 - */ - if (test_bit(R5_Wantfill, &dev->flags) && !dev->toread) { + /* 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_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 @@ -558,8 +556,7 @@ static void ops_complete_biofill(void *stripe_head_ref) return_io(return_bi); - if (more_to_read) - set_bit(STRIPE_HANDLE, &sh->state); + set_bit(STRIPE_HANDLE, &sh->state); release_stripe(sh); } -- 2.7.4