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Subject[PATCH 2.6.23-rc7 3/3] raid5: fix ops_complete_biofill
Date
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 moves
read completion handling back into handle_stripe.

Found-by: Yuri Tikhonov <yur@emcraft.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
---
drivers/md/raid5.c | 90 +++++++++++++++++++++++++++-------------------------
1 files changed, 46 insertions(+), 44 deletions(-)
diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c
index 4d63773..38c8893 100644
--- a/drivers/md/raid5.c
+++ b/drivers/md/raid5.c
@@ -512,54 +512,12 @@ async_copy_data(int frombio, struct bio *bio, struct page *page,
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;

pr_debug("%s: stripe %llu\n", __FUNCTION__,
(unsigned long long)sh->sector);

- /* 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) {
- 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
- * by the STRIPE_OP_BIOFILL pending bit
- */
- BUG_ON(!dev->read);
- rbi = dev->read;
- dev->read = NULL;
- while (rbi && rbi->bi_sector <
- dev->sector + STRIPE_SECTORS) {
- rbi2 = r5_next_bio(rbi, dev->sector);
- spin_lock_irq(&conf->device_lock);
- if (--rbi->bi_phys_segments == 0) {
- rbi->bi_next = return_bi;
- return_bi = rbi;
- }
- spin_unlock_irq(&conf->device_lock);
- rbi = rbi2;
- }
- }
- }
- clear_bit(STRIPE_OP_BIOFILL, &sh->ops.ack);
- clear_bit(STRIPE_OP_BIOFILL, &sh->ops.pending);
-
- return_io(return_bi);
-
- if (more_to_read)
- set_bit(STRIPE_HANDLE, &sh->state);
+ set_bit(STRIPE_OP_BIOFILL, &sh->ops.complete);
+ set_bit(STRIPE_HANDLE, &sh->state);
release_stripe(sh);
}

@@ -2112,6 +2070,42 @@ static void handle_issuing_new_read_requests6(struct stripe_head *sh,
}


+/* handle_completed_read_requests - return completion for reads and allow
+ * new read operations to be submitted to the stripe.
+ */
+static void handle_completed_read_requests(raid5_conf_t *conf,
+ struct stripe_head *sh,
+ struct bio **return_bi)
+{
+ int i;
+
+ pr_debug("%s: stripe %llu\n", __FUNCTION__,
+ (unsigned long long)sh->sector);
+
+ /* check if we need to reply to a read request */
+ for (i = sh->disks; i--; ) {
+ struct r5dev *dev = &sh->dev[i];
+
+ if (test_and_clear_bit(R5_Wantfill, &dev->flags)) {
+ struct bio *rbi, *rbi2;
+
+ rbi = dev->read;
+ dev->read = NULL;
+ while (rbi && rbi->bi_sector <
+ dev->sector + STRIPE_SECTORS) {
+ rbi2 = r5_next_bio(rbi, dev->sector);
+ spin_lock_irq(&conf->device_lock);
+ if (--rbi->bi_phys_segments == 0) {
+ rbi->bi_next = *return_bi;
+ *return_bi = rbi;
+ }
+ spin_unlock_irq(&conf->device_lock);
+ rbi = rbi2;
+ }
+ }
+ }
+}
+
/* handle_completed_write_requests
* any written block on an uptodate or failed drive can be returned.
* Note that if we 'wrote' to a failed drive, it will be UPTODATE, but
@@ -2633,6 +2627,14 @@ static void handle_stripe5(struct stripe_head *sh)
s.expanded = test_bit(STRIPE_EXPAND_READY, &sh->state);
/* Now to look around and see what can be done */

+ if (test_bit(STRIPE_OP_BIOFILL, &sh->ops.complete)) {
+ clear_bit(STRIPE_OP_BIOFILL, &sh->ops.ack);
+ clear_bit(STRIPE_OP_BIOFILL, &sh->ops.pending);
+ clear_bit(STRIPE_OP_BIOFILL, &sh->ops.complete);
+
+ handle_completed_read_requests(conf, sh, &return_bi);
+ }
+
rcu_read_lock();
for (i=disks; i--; ) {
mdk_rdev_t *rdev;
-
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