The following is a revision of the patch with the suggested changes.
-Eliminate the wait_for_block_ops queue
-Simplify the code by tracking the operations at the stripe level not
the block level
-Integrate the work struct into stripe_head (remove the need for memory
allocation)
-Make the work queue multi-threaded. The ordering is maintained by not
advancing the operations state while STRIPE_OP_LOCKED is active.
Applies against 2.6.17-rc4.
---
[PATCH] Move stripe operations outside the spin lock (v2)
Signed-off-by: Dan Williams <[email protected]>
---
drivers/md/raid5.c | 334 +++++++++++++++++++++++++++++++++++++++++---
include/linux/raid/raid5.h | 54 +++++++
2 files changed, 366 insertions(+), 22 deletions(-)
00e3e2bc14baea6fc25e50b9ba34f9259eadcacb
diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c
index 3184360..da70f04 100644
--- a/drivers/md/raid5.c
+++ b/drivers/md/raid5.c
@@ -862,6 +862,116 @@ static void compute_block(struct stripe_
set_bit(R5_UPTODATE, &sh->dev[dd_idx].flags);
}
+static int handle_write_operations(struct stripe_head *sh, int rcw)
+{
+ int i, pd_idx = sh->pd_idx, disks = sh->disks;
+ int ops=0, start=0, rcw_done=0, rmw_done=0;
+
+ PRINTK("%s, stripe %llu, state %lx, op_state %lx\n",
+ __FUNCTION__, (unsigned long long)sh->sector,
+ sh->state, sh->op_state);
+
+ /* If no operation is currently pending use the rcw flag to
+ * select an operation
+ */
+ if (!(test_bit(STRIPE_OP_RCW, &sh->state) ||
+ test_bit(STRIPE_OP_RMW, &sh->state))) {
+ if (rcw==0)
+ set_bit(STRIPE_OP_RCW, &sh->state);
+ else {
+ BUG_ON(!test_bit(R5_UPTODATE, &sh->dev[pd_idx].flags));
+ set_bit(STRIPE_OP_RMW, &sh->state);
+ }
+ start++;
+ } else if (unlikely(test_bit(STRIPE_OP_RCW, &sh->state) &&
+ test_bit(STRIPE_OP_RMW, &sh->state)))
+ BUG();
+
+ if (test_bit(STRIPE_OP_RMW, &sh->state)) {
+ /* enter stage 1 of read modify write operation */
+ if (start) {
+ set_bit(STRIPE_OP_RMW_XorPre, &sh->op_state);
+ for (i=disks ; i-- ;) {
+ struct r5dev *dev = &sh->dev[i];
+ if (i==pd_idx)
+ continue;
+
+ if (dev->towrite &&
+ test_bit(R5_UPTODATE, &dev->flags)) {
+ set_bit(R5_LOCKED, &dev->flags);
+ ops++;
+ }
+ }
+ } else if (test_and_clear_bit(STRIPE_OP_RMW_XorPre, &sh->op_state)) {
+ set_bit(STRIPE_OP_RMW_Drain, &sh->op_state);
+ ops++;
+ } else if (test_and_clear_bit(STRIPE_OP_RMW_Drain, &sh->op_state)) {
+ set_bit(STRIPE_OP_RMW_XorPost, &sh->op_state);
+ ops++;
+ for (i=disks ; i-- ;) {
+ struct r5dev *dev = &sh->dev[i];
+ if (dev->written)
+ set_bit(R5_UPTODATE, &dev->flags);
+ }
+ } else if (test_and_clear_bit(STRIPE_OP_RMW_XorPost, &sh->op_state)) {
+ /* synchronous block_ops routines may be done at this point */
+ if (!test_and_clear_bit(STRIPE_OP_RMW_Done, &sh->op_state)) {
+ set_bit(STRIPE_OP_RMW_End, &sh->op_state);
+ ops++;
+ } else
+ rmw_done++;
+ }
+ } else if (test_bit(STRIPE_OP_RCW, &sh->state)) {
+ if (start) {
+ set_bit(STRIPE_OP_RCW_Drain, &sh->op_state);
+ for (i=disks ; i-- ;) {
+ struct r5dev *dev = &sh->dev[i];
+
+ /* enter stage 1 of reconstruct write operation */
+ if (i!=pd_idx && dev->towrite) {
+ set_bit(R5_LOCKED, &dev->flags);
+ ops++;
+ }
+ }
+ } else if (test_and_clear_bit(STRIPE_OP_RCW_Drain, &sh->op_state)) {
+ set_bit(STRIPE_OP_RCW_Xor, &sh->op_state);
+ ops++;
+ for (i=disks ; i-- ;) {
+ struct r5dev *dev = &sh->dev[i];
+ if (dev->written)
+ set_bit(R5_UPTODATE, &dev->flags);
+ }
+ } else if (test_and_clear_bit(STRIPE_OP_RCW_Xor, &sh->op_state)) {
+ /* synchronous block_ops routines may be done at this point */
+ if (!test_and_clear_bit(STRIPE_OP_RCW_Done, &sh->op_state)) {
+ set_bit(STRIPE_OP_RCW_End, &sh->op_state);
+ ops++;
+ } else
+ rcw_done++;
+ }
+ }
+
+ /* keep the parity disk locked while asynchronous operations
+ * are in flight
+ */
+ if (ops) {
+ set_bit(STRIPE_OP_LOCKED, &sh->state);
+ set_bit(R5_LOCKED, &sh->dev[pd_idx].flags);
+ clear_bit(R5_UPTODATE, &sh->dev[pd_idx].flags);
+ sh->op_count++;
+ atomic_inc(&sh->count);
+ } else {
+ set_bit(R5_UPTODATE, &sh->dev[pd_idx].flags);
+
+ if (rcw_done)
+ clear_bit(STRIPE_OP_RCW, &sh->state);
+ if (rmw_done)
+ clear_bit(STRIPE_OP_RMW, &sh->state);
+ }
+
+ return ops;
+}
+
static void compute_parity(struct stripe_head *sh, int method)
{
raid5_conf_t *conf = sh->raid_conf;
@@ -1044,6 +1154,143 @@ static int stripe_to_pdidx(sector_t stri
}
+static inline void drain_bio(struct bio *wbi, sector_t sector, struct page *page)
+{
+ while (wbi && wbi->bi_sector < sector + STRIPE_SECTORS) {
+ copy_data(1, wbi, page, sector);
+ wbi = r5_next_bio(wbi, sector);
+ }
+}
+
+/*
+ * raid5_do_soft_block_ops - perform block memory operations on stripe data
+ * outside the spin lock.
+ */
+static void raid5_do_soft_block_ops(void *stripe_head_ref)
+{
+ struct stripe_head *sh = stripe_head_ref;
+ int i, pd_idx = sh->pd_idx, disks = sh->disks, count = 1;
+ void *ptr[MAX_XOR_BLOCKS];
+ struct bio *chosen;
+ int overlap=0, rcw_done=0, rmw_done=0;
+
+ /* we only read state bits in this loop and rely on STRIPE_OP_LOCKED
+ * to protect &sh->op_state from modification in handle_stripe
+ */
+ if (test_bit(STRIPE_OP_RMW, &sh->state)) {
+ PRINTK("%s: stripe %llu STRIPE_OP_RMW op_state: %lx\n",
+ __FUNCTION__, (unsigned long long)sh->sector,
+ sh->op_state);
+
+ ptr[0] = page_address(sh->dev[pd_idx].page);
+
+ if (test_bit(STRIPE_OP_RMW_XorPre, &sh->op_state)) {
+ for (i=disks ; i-- ;) {
+ struct r5dev *dev = &sh->dev[i];
+ /* if it is not locked then servicing
+ * has not been requested
+ */
+ if (dev->towrite && test_bit(R5_LOCKED, &dev->flags)) {
+ ptr[count++] = page_address(dev->page);
+ /* ? is the device_lock necessary, compute_parity
+ * does not lock for this operation ?
+ */
+ chosen = dev->towrite;
+ dev->towrite = NULL;
+
+ overlap++;
+
+ BUG_ON(dev->written);
+ dev->written = chosen;
+ check_xor();
+ }
+ }
+ } else if (test_bit(STRIPE_OP_RMW_Drain, &sh->op_state)) {
+ for (i=disks ; i-- ;) {
+ struct r5dev *dev = &sh->dev[i];
+ drain_bio(dev->written, dev->sector, dev->page);
+ }
+ } else if (test_bit(STRIPE_OP_RMW_XorPost, &sh->op_state)) {
+ for (i=disks ; i-- ;) {
+ struct r5dev *dev = &sh->dev[i];
+ if (dev->written) {
+ ptr[count++] = page_address(dev->page);
+ check_xor();
+ }
+ }
+ /* since this routine is synchronous we are done */
+ rmw_done++;
+ } else if (test_bit(STRIPE_OP_RMW_End, &sh->op_state)) {
+ rmw_done++;
+ } else {
+ BUG();
+ }
+ } else if (test_bit(STRIPE_OP_RCW, &sh->state)) {
+ PRINTK("%s: stripe %llu STRIPE_OP_RCW op_state: %lx\n",
+ __FUNCTION__, (unsigned long long)sh->sector,
+ sh->op_state);
+
+ ptr[0] = page_address(sh->dev[pd_idx].page);
+
+ if (test_bit(STRIPE_OP_RCW_Drain, &sh->op_state)) {
+ for (i=disks ; i-- ;) {
+ struct r5dev *dev = &sh->dev[i];
+ if (i!=pd_idx && dev->towrite &&
+ test_bit(R5_LOCKED, &dev->flags)) {
+ chosen = dev->towrite;
+ dev->towrite = NULL;
+
+ BUG_ON(dev->written);
+ dev->written = chosen;
+
+ overlap++;
+
+ drain_bio(dev->written, dev->sector,
+ dev->page);
+ } else if (i==pd_idx)
+ memset(ptr[0], 0, STRIPE_SIZE);
+ }
+ } else if (test_bit(STRIPE_OP_RCW_Xor, &sh->op_state)) {
+ for (i=disks; i--;)
+ if (i != pd_idx) {
+ ptr[count++] = page_address(sh->dev[i].page);
+ check_xor();
+ }
+ /* since this routine is synchronous we are done */
+ rcw_done++;
+ } else if (test_bit(STRIPE_OP_RCW_End, &sh->op_state)) {
+ rcw_done++;
+ } else {
+ BUG();
+ }
+ }
+
+ if (count != 1)
+ xor_block(count, STRIPE_SIZE, ptr);
+
+ spin_lock(&sh->lock);
+ if (overlap)
+ for (i= disks; i-- ;) {
+ struct r5dev *dev = &sh->dev[i];
+ if (test_and_clear_bit(R5_Overlap, &dev->flags))
+ wake_up(&sh->raid_conf->wait_for_overlap);
+ }
+
+ if (! --sh->op_count) {
+ clear_bit(STRIPE_OP_LOCKED, &sh->state);
+ set_bit(STRIPE_HANDLE, &sh->state);
+ }
+
+ if (rcw_done)
+ set_bit(STRIPE_OP_RCW_Done, &sh->op_state);
+ if (rmw_done)
+ set_bit(STRIPE_OP_RMW_Done, &sh->op_state);
+
+ spin_unlock(&sh->lock);
+
+ release_stripe(sh);
+}
+
/*
* handle_stripe - do things to a stripe.
*
@@ -1056,12 +1303,10 @@ static int stripe_to_pdidx(sector_t stri
* schedule a write of some buffers
* return confirmation of parity correctness
*
- * Parity calculations are done inside the stripe lock
* buffers are taken off read_list or write_list, and bh_cache buffers
* get BH_Lock set before the stripe lock is released.
*
*/
-
static void handle_stripe(struct stripe_head *sh)
{
raid5_conf_t *conf = sh->raid_conf;
@@ -1073,6 +1318,7 @@ static void handle_stripe(struct stripe_
int locked=0, uptodate=0, to_read=0, to_write=0, failed=0, written=0;
int non_overwrite = 0;
int failed_num=0;
+ int block_ops=0;
struct r5dev *dev;
PRINTK("handling stripe %llu, cnt=%d, pd_idx=%d\n",
@@ -1122,7 +1368,6 @@ static void handle_stripe(struct stripe_
/* now count some things */
if (test_bit(R5_LOCKED, &dev->flags)) locked++;
if (test_bit(R5_UPTODATE, &dev->flags)) uptodate++;
-
if (dev->toread) to_read++;
if (dev->towrite) {
@@ -1152,6 +1397,18 @@ static void handle_stripe(struct stripe_
* need to be failed
*/
if (failed > 1 && to_read+to_write+written) {
+ if (test_and_clear_bit(STRIPE_OP_RMW, &sh->state)) {
+ clear_bit(STRIPE_OP_RMW_XorPre, &sh->op_state);
+ clear_bit(STRIPE_OP_RMW_Drain, &sh->op_state);
+ clear_bit(STRIPE_OP_RMW_XorPost, &sh->op_state);
+ clear_bit(STRIPE_OP_RMW_Done, &sh->op_state);
+ }
+ if (test_and_clear_bit(STRIPE_OP_RCW, &sh->state)) {
+ clear_bit(STRIPE_OP_RCW_Drain, &sh->op_state);
+ clear_bit(STRIPE_OP_RCW_Xor, &sh->op_state);
+ clear_bit(STRIPE_OP_RCW_Done, &sh->op_state);
+ }
+
for (i=disks; i--; ) {
int bitmap_end = 0;
@@ -1319,7 +1576,9 @@ #endif
}
/* now to consider writing and what else, if anything should be read */
- if (to_write) {
+ if ((to_write || test_bit(STRIPE_OP_RCW, &sh->state) ||
+ test_bit(STRIPE_OP_RMW, &sh->state)) &&
+ !test_bit(STRIPE_OP_LOCKED, &sh->state)) {
int rmw=0, rcw=0;
for (i=disks ; i--;) {
/* would I have to read this buffer for read_modify_write */
@@ -1391,24 +1650,32 @@ #endif
}
}
/* now if nothing is locked, and if we have enough data, we can start a write request */
- if (locked == 0 && (rcw == 0 ||rmw == 0) &&
- !test_bit(STRIPE_BIT_DELAY, &sh->state)) {
- PRINTK("Computing parity...\n");
- compute_parity(sh, rcw==0 ? RECONSTRUCT_WRITE : READ_MODIFY_WRITE);
- /* now every locked buffer is ready to be written */
- for (i=disks; i--;)
- if (test_bit(R5_LOCKED, &sh->dev[i].flags)) {
- PRINTK("Writing block %d\n", i);
- locked++;
- set_bit(R5_Wantwrite, &sh->dev[i].flags);
- if (!test_bit(R5_Insync, &sh->dev[i].flags)
- || (i==sh->pd_idx && failed == 0))
- set_bit(STRIPE_INSYNC, &sh->state);
+ /* ...or, if we have previously started write operations we can now advance the state */
+ if ((locked == 0 && (rcw == 0 ||rmw == 0) &&
+ !test_bit(STRIPE_BIT_DELAY, &sh->state)) ||
+ test_bit(STRIPE_OP_RCW, &sh->state) || test_bit(STRIPE_OP_RMW, &sh->state)) {
+ int block_ops_prev = block_ops;
+ block_ops += handle_write_operations(sh, rcw);
+ if ((block_ops - block_ops_prev) == 0) {
+ /* now every locked buffer is ready to be written */
+ for (i=disks; i--;)
+ if (test_bit(R5_LOCKED, &sh->dev[i].flags)) {
+ PRINTK("Writing block %d\n", i);
+ locked++;
+ set_bit(R5_Wantwrite, &sh->dev[i].flags);
+ if (!test_bit(R5_Insync, &sh->dev[i].flags)
+ || (i==sh->pd_idx && failed == 0))
+ set_bit(STRIPE_INSYNC, &sh->state);
+ }
+ if (test_and_clear_bit(STRIPE_PREREAD_ACTIVE, &sh->state)) {
+ atomic_dec(&conf->preread_active_stripes);
+ if (atomic_read(&conf->preread_active_stripes) < IO_THRESHOLD)
+ md_wakeup_thread(conf->mddev->thread);
}
- if (test_and_clear_bit(STRIPE_PREREAD_ACTIVE, &sh->state)) {
- atomic_dec(&conf->preread_active_stripes);
- if (atomic_read(&conf->preread_active_stripes) < IO_THRESHOLD)
- md_wakeup_thread(conf->mddev->thread);
+ } else {
+ set_bit(STRIPE_HANDLE, &sh->state);
+ if (locked == 0)
+ locked += block_ops - block_ops_prev;
}
}
}
@@ -1555,6 +1822,12 @@ #endif
bi->bi_size = 0;
bi->bi_end_io(bi, bytes, 0);
}
+
+ if (block_ops) {
+ INIT_WORK(&sh->work, conf->do_block_ops, sh);
+ queue_work(conf->block_ops_queue, &sh->work);
+ }
+
for (i=disks; i-- ;) {
int rw;
struct bio *bi;
@@ -1613,6 +1886,8 @@ #endif
set_bit(STRIPE_HANDLE, &sh->state);
}
}
+
+ return;
}
static void raid5_activate_delayed(raid5_conf_t *conf)
@@ -2251,6 +2526,20 @@ static int run(mddev_t *mddev)
if ((conf->stripe_hashtbl = kzalloc(PAGE_SIZE, GFP_KERNEL)) == NULL)
goto abort;
+ sprintf(conf->workqueue_name, "%s_raid5_ops",
+ mddev->gendisk->disk_name);
+
+ if ((conf->block_ops_queue = create_workqueue(conf->workqueue_name))
+ == NULL)
+ goto abort;
+
+ /* To Do:
+ * 1/ Offload to asynchronous copy / xor engines
+ * 2/ Automated selection of optimal do_block_ops
+ * routine similar to the xor template selection
+ */
+ conf->do_block_ops = raid5_do_soft_block_ops;
+
spin_lock_init(&conf->device_lock);
init_waitqueue_head(&conf->wait_for_stripe);
init_waitqueue_head(&conf->wait_for_overlap);
@@ -2401,6 +2690,8 @@ abort:
print_raid5_conf(conf);
kfree(conf->disks);
kfree(conf->stripe_hashtbl);
+ if (conf->block_ops_queue)
+ destroy_workqueue(conf->block_ops_queue);
kfree(conf);
}
mddev->private = NULL;
@@ -2421,6 +2712,7 @@ static int stop(mddev_t *mddev)
blk_sync_queue(mddev->queue); /* the unplug fn references 'conf'*/
sysfs_remove_group(&mddev->kobj, &raid5_attrs_group);
kfree(conf->disks);
+ destroy_workqueue(conf->block_ops_queue);
kfree(conf);
mddev->private = NULL;
return 0;
diff --git a/include/linux/raid/raid5.h b/include/linux/raid/raid5.h
index 914af66..aa9e988 100644
--- a/include/linux/raid/raid5.h
+++ b/include/linux/raid/raid5.h
@@ -3,6 +3,7 @@ #define _RAID5_H
#include <linux/raid/md.h>
#include <linux/raid/xor.h>
+#include <linux/workqueue.h>
/*
*
@@ -123,6 +124,17 @@ #include <linux/raid/xor.h>
* The refcount counts each thread that have activated the stripe,
* plus raid5d if it is handling it, plus one for each active request
* on a cached buffer.
+ *
+ * Block operations (copy, xor, block fill, and block compare) are executed
+ * outside the spin lock. A stripe can have at maximum one pending request
+ * in the workqueue at a time (* some operations may be able to run concurrently,
+ * but this is a work in progress). The STRIPE_OP_LOCK bit prevents threads from
+ * advancing the operations state machine before the work queue has had a chance
+ * to dequeue the request. Note that this lock is only held for the enqueue/dequeue
+ * duration. The conf->do_block_ops routine is free to submit the operation to an
+ * asynchronous engine and release the lock, as long as it maintains the completion
+ * order of events. The operations state machine sends a completion request when it
+ * is time to submit the result down to disk, or up to the filesystem.
*/
struct stripe_head {
@@ -133,9 +145,12 @@ struct stripe_head {
int pd_idx; /* parity disk index */
unsigned long state; /* state flags */
atomic_t count; /* nr of active thread/requests */
+ int op_count; /* nr of queued block operations */
+ unsigned long op_state; /* state of block operations */
spinlock_t lock;
int bm_seq; /* sequence number for bitmap flushes */
int disks; /* disks in stripe */
+ struct work_struct work; /* work queue descriptor */
struct r5dev {
struct bio req;
struct bio_vec vec;
@@ -145,6 +160,7 @@ struct stripe_head {
unsigned long flags;
} dev[1]; /* allocated with extra space depending of RAID geometry */
};
+
/* Flags */
#define R5_UPTODATE 0 /* page contains current data */
#define R5_LOCKED 1 /* IO has been submitted on "req" */
@@ -156,8 +172,9 @@ #define R5_Wantwrite 5
#define R5_Overlap 7 /* There is a pending overlapping request on this block */
#define R5_ReadError 8 /* seen a read error here recently */
#define R5_ReWrite 9 /* have tried to over-write the readerror */
-
#define R5_Expanded 10 /* This block now has post-expand data */
+#define R5_Consistent 11 /* Block is HW DMA-able */
+
/*
* Write method
*/
@@ -179,6 +196,36 @@ #define STRIPE_BIT_DELAY 8
#define STRIPE_EXPANDING 9
#define STRIPE_EXPAND_SOURCE 10
#define STRIPE_EXPAND_READY 11
+#define STRIPE_OP_RCW 12
+#define STRIPE_OP_RMW 13
+#define STRIPE_OP_CHECK 14
+#define STRIPE_OP_COMPUTE 15
+#define STRIPE_OP_BIOFILL 16
+#define STRIPE_OP_LOCKED 17
+
+/*
+ * Stripe operations state
+ * - these flags enumerate the stages
+ * of the operations state machine
+ */
+#define STRIPE_OP_RCW_Drain 0
+#define STRIPE_OP_RCW_Xor 1
+#define STRIPE_OP_RCW_End 2
+#define STRIPE_OP_RCW_Done 3
+#define STRIPE_OP_RMW_XorPre 4
+#define STRIPE_OP_RMW_Drain 5
+#define STRIPE_OP_RMW_XorPost 6
+#define STRIPE_OP_RMW_End 7
+#define STRIPE_OP_RMW_Done 8
+#define STRIPE_OP_CHECK_Gen 9
+#define STRIPE_OP_CHECK_Verify 10
+#define STRIPE_OP_CHECK_End 11
+#define STRIPE_OP_CHECK_Done 12
+#define STRIPE_OP_COMPUTE_Prep 13
+#define STRIPE_OP_COMPUTE_Xor 14
+#define STRIPE_OP_COMPUTE_End 15
+#define STRIPE_OP_COMPUTE_Done 16
+
/*
* Plugging:
*
@@ -228,11 +275,16 @@ struct raid5_private_data {
atomic_t preread_active_stripes; /* stripes with scheduled io */
atomic_t reshape_stripes; /* stripes with pending writes for reshape */
+
+ struct workqueue_struct *block_ops_queue;
+ void (*do_block_ops)(void *);
+
/* unfortunately we need two cache names as we temporarily have
* two caches.
*/
int active_name;
char cache_name[2][20];
+ char workqueue_name[20];
kmem_cache_t *slab_cache; /* for allocating stripes */
int seq_flush, seq_write;
--
1.3.0
-
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