md/raid5: replace sh->lock with an 'active' flag.
sh->lock is now mainly used to ensure that two threads aren't running
in the locked part of handle_stripe[56] at the same time.
That can more neatly be achieved with an 'active' flag which we set
while running handle_stripe. If we find the flag is set, we simply
requeue the stripe for later by setting STRIPE_HANDLE.
For safety we take ->device_lock while examining the state of the
stripe and creating a summary in 'stripe_head_state / r6_state'.
This possibly isn't needed but as shared fields like ->toread,
->towrite are checked it is safer for now at least.
We leave the label after the old 'unlock' called "unlock" because it
will disappear in a few patches, so renaming seems pointless.
This leaves the stripe 'locked' for longer as we clear STRIPE_ACTIVE
later, but that is not a problem.
Signed-off-by: NeilBrown <neilb@suse.de>
Reviewed-by: Namhyung Kim <namhyung@gmail.com>
diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c
index 9985138..f8275b5 100644
--- a/drivers/md/raid5.c
+++ b/drivers/md/raid5.c
@@ -1020,14 +1020,12 @@
if (test_and_clear_bit(R5_Wantdrain, &dev->flags)) {
struct bio *wbi;
- spin_lock(&sh->lock);
spin_lock_irq(&sh->raid_conf->device_lock);
chosen = dev->towrite;
dev->towrite = NULL;
BUG_ON(dev->written);
wbi = dev->written = chosen;
spin_unlock_irq(&sh->raid_conf->device_lock);
- spin_unlock(&sh->lock);
while (wbi && wbi->bi_sector <
dev->sector + STRIPE_SECTORS) {
@@ -1322,7 +1320,6 @@
return 0;
sh->raid_conf = conf;
- spin_lock_init(&sh->lock);
#ifdef CONFIG_MULTICORE_RAID456
init_waitqueue_head(&sh->ops.wait_for_ops);
#endif
@@ -1442,7 +1439,6 @@
break;
nsh->raid_conf = conf;
- spin_lock_init(&nsh->lock);
#ifdef CONFIG_MULTICORE_RAID456
init_waitqueue_head(&nsh->ops.wait_for_ops);
#endif
@@ -2148,7 +2144,6 @@
(unsigned long long)sh->sector);
- spin_lock(&sh->lock);
spin_lock_irq(&conf->device_lock);
if (forwrite) {
bip = &sh->dev[dd_idx].towrite;
@@ -2184,7 +2179,6 @@
set_bit(R5_OVERWRITE, &sh->dev[dd_idx].flags);
}
spin_unlock_irq(&conf->device_lock);
- spin_unlock(&sh->lock);
pr_debug("added bi b#%llu to stripe s#%llu, disk %d.\n",
(unsigned long long)(*bip)->bi_sector,
@@ -2201,7 +2195,6 @@
overlap:
set_bit(R5_Overlap, &sh->dev[dd_idx].flags);
spin_unlock_irq(&conf->device_lock);
- spin_unlock(&sh->lock);
return 0;
}
@@ -3023,12 +3016,10 @@
atomic_read(&sh->count), sh->pd_idx, sh->check_state,
sh->reconstruct_state);
- spin_lock(&sh->lock);
if (test_and_clear_bit(STRIPE_SYNC_REQUESTED, &sh->state)) {
set_bit(STRIPE_SYNCING, &sh->state);
clear_bit(STRIPE_INSYNC, &sh->state);
}
- clear_bit(STRIPE_HANDLE, &sh->state);
clear_bit(STRIPE_DELAYED, &sh->state);
s.syncing = test_bit(STRIPE_SYNCING, &sh->state);
@@ -3037,6 +3028,7 @@
/* Now to look around and see what can be done */
rcu_read_lock();
+ spin_lock_irq(&conf->device_lock);
for (i=disks; i--; ) {
mdk_rdev_t *rdev;
@@ -3099,6 +3091,7 @@
s.failed_num = i;
}
}
+ spin_unlock_irq(&conf->device_lock);
rcu_read_unlock();
if (unlikely(blocked_rdev)) {
@@ -3275,7 +3268,6 @@
handle_stripe_expansion(conf, sh, NULL);
unlock:
- spin_unlock(&sh->lock);
/* wait for this device to become unblocked */
if (unlikely(blocked_rdev))
@@ -3318,12 +3310,10 @@
sh->check_state, sh->reconstruct_state);
memset(&s, 0, sizeof(s));
- spin_lock(&sh->lock);
if (test_and_clear_bit(STRIPE_SYNC_REQUESTED, &sh->state)) {
set_bit(STRIPE_SYNCING, &sh->state);
clear_bit(STRIPE_INSYNC, &sh->state);
}
- clear_bit(STRIPE_HANDLE, &sh->state);
clear_bit(STRIPE_DELAYED, &sh->state);
s.syncing = test_bit(STRIPE_SYNCING, &sh->state);
@@ -3332,6 +3322,7 @@
/* Now to look around and see what can be done */
rcu_read_lock();
+ spin_lock_irq(&conf->device_lock);
for (i=disks; i--; ) {
mdk_rdev_t *rdev;
dev = &sh->dev[i];
@@ -3395,6 +3386,7 @@
s.failed++;
}
}
+ spin_unlock_irq(&conf->device_lock);
rcu_read_unlock();
if (unlikely(blocked_rdev)) {
@@ -3580,7 +3572,6 @@
handle_stripe_expansion(conf, sh, &r6s);
unlock:
- spin_unlock(&sh->lock);
/* wait for this device to become unblocked */
if (unlikely(blocked_rdev))
@@ -3608,10 +3599,19 @@
static void handle_stripe(struct stripe_head *sh)
{
+ clear_bit(STRIPE_HANDLE, &sh->state);
+ if (test_and_set_bit(STRIPE_ACTIVE, &sh->state)) {
+ /* already being handled, ensure it gets handled
+ * again when current action finishes */
+ set_bit(STRIPE_HANDLE, &sh->state);
+ return;
+ }
+
if (sh->raid_conf->level == 6)
handle_stripe6(sh);
else
handle_stripe5(sh);
+ clear_bit(STRIPE_ACTIVE, &sh->state);
}
static void raid5_activate_delayed(raid5_conf_t *conf)
diff --git a/drivers/md/raid5.h b/drivers/md/raid5.h
index a330011..bb246d9 100644
--- a/drivers/md/raid5.h
+++ b/drivers/md/raid5.h
@@ -6,11 +6,11 @@
/*
*
- * Each stripe contains one buffer per disc. Each buffer can be in
+ * Each stripe contains one buffer per device. Each buffer can be in
* one of a number of states stored in "flags". Changes between
- * these states happen *almost* exclusively under a per-stripe
- * spinlock. Some very specific changes can happen in bi_end_io, and
- * these are not protected by the spin lock.
+ * these states happen *almost* exclusively under the protection of the
+ * STRIPE_ACTIVE flag. Some very specific changes can happen in bi_end_io, and
+ * these are not protected by STRIPE_ACTIVE.
*
* The flag bits that are used to represent these states are:
* R5_UPTODATE and R5_LOCKED
@@ -76,12 +76,10 @@
* block and the cached buffer are successfully written, any buffer on
* a written list can be returned with b_end_io.
*
- * The write list and read list both act as fifos. The read list is
- * protected by the device_lock. The write and written lists are
- * protected by the stripe lock. The device_lock, which can be
- * claimed while the stipe lock is held, is only for list
- * manipulations and will only be held for a very short time. It can
- * be claimed from interrupts.
+ * The write list and read list both act as fifos. The read list,
+ * write list and written list are protected by the device_lock.
+ * The device_lock is only for list manipulations and will only be
+ * held for a very short time. It can be claimed from interrupts.
*
*
* Stripes in the stripe cache can be on one of two lists (or on
@@ -96,7 +94,6 @@
*
* The inactive_list, handle_list and hash bucket lists are all protected by the
* device_lock.
- * - stripes on the inactive_list never have their stripe_lock held.
* - stripes have a reference counter. If count==0, they are on a list.
* - If a stripe might need handling, STRIPE_HANDLE is set.
* - When refcount reaches zero, then if STRIPE_HANDLE it is put on
@@ -116,10 +113,10 @@
* attach a request to an active stripe (add_stripe_bh())
* lockdev attach-buffer unlockdev
* handle a stripe (handle_stripe())
- * lockstripe clrSTRIPE_HANDLE ...
+ * setSTRIPE_ACTIVE, clrSTRIPE_HANDLE ...
* (lockdev check-buffers unlockdev) ..
* change-state ..
- * record io/ops needed unlockstripe schedule io/ops
+ * record io/ops needed clearSTRIPE_ACTIVE schedule io/ops
* release an active stripe (release_stripe())
* lockdev if (!--cnt) { if STRIPE_HANDLE, add to handle_list else add to inactive-list } unlockdev
*
@@ -128,8 +125,7 @@
* on a cached buffer, and plus one if the stripe is undergoing stripe
* operations.
*
- * Stripe operations are performed outside the stripe lock,
- * the stripe operations are:
+ * The stripe operations are:
* -copying data between the stripe cache and user application buffers
* -computing blocks to save a disk access, or to recover a missing block
* -updating the parity on a write operation (reconstruct write and
@@ -159,7 +155,8 @@
*/
/*
- * Operations state - intermediate states that are visible outside of sh->lock
+ * Operations state - intermediate states that are visible outside of
+ * STRIPE_ACTIVE.
* In general _idle indicates nothing is running, _run indicates a data
* processing operation is active, and _result means the data processing result
* is stable and can be acted upon. For simple operations like biofill and
@@ -209,7 +206,6 @@
short ddf_layout;/* use DDF ordering to calculate Q */
unsigned long state; /* state flags */
atomic_t count; /* nr of active thread/requests */
- spinlock_t lock;
int bm_seq; /* sequence number for bitmap flushes */
int disks; /* disks in stripe */
enum check_states check_state;
@@ -240,7 +236,7 @@
};
/* stripe_head_state - collects and tracks the dynamic state of a stripe_head
- * for handle_stripe. It is only valid under spin_lock(sh->lock);
+ * for handle_stripe.
*/
struct stripe_head_state {
int syncing, expanding, expanded;
@@ -290,6 +286,7 @@
* Stripe state
*/
enum {
+ STRIPE_ACTIVE,
STRIPE_HANDLE,
STRIPE_SYNC_REQUESTED,
STRIPE_SYNCING,
@@ -339,7 +336,7 @@
* PREREAD_ACTIVE.
* In stripe_handle, if we find pre-reading is necessary, we do it if
* PREREAD_ACTIVE is set, else we set DELAYED which will send it to the delayed queue.
- * HANDLE gets cleared if stripe_handle leave nothing locked.
+ * HANDLE gets cleared if stripe_handle leaves nothing locked.
*/