From: Dan Williams <[EMAIL PROTECTED]>
Prepare the raid5 implementation to use async_tx and a workqueue for
running stripe operations:
* biofill (copy data into request buffers to satisfy a read request)
* compute block (generate a missing block in the cache from the other
blocks)
* prexor (subtract existing data as part of the read-modify-write process)
* biodrain (copy data out of request buffers to satisfy a write request)
* postxor (recalculate parity for new data that has entered the cache)
* check (verify that the parity is correct)
* io (submit i/o to the member disks)
Signed-off-by: Dan Williams <[EMAIL PROTECTED]>
---
drivers/md/raid5.c | 560 ++++++++++++++++++++++++++++++++++++++++++++
include/linux/raid/raid5.h | 67 +++++
2 files changed, 619 insertions(+), 8 deletions(-)
diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c
index 0c8ada5..232f525 100644
--- a/drivers/md/raid5.c
+++ b/drivers/md/raid5.c
@@ -52,6 +52,7 @@ #include <asm/atomic.h>
#include "raid6.h"
#include <linux/raid/bitmap.h>
+#include <linux/async_tx.h>
/*
* Stripe cache
@@ -222,7 +223,8 @@ static void init_stripe(struct stripe_he
BUG_ON(atomic_read(&sh->count) != 0);
BUG_ON(test_bit(STRIPE_HANDLE, &sh->state));
-
+ BUG_ON(sh->ops.pending || sh->ops.ack || sh->ops.complete);
+
CHECK_DEVLOCK();
PRINTK("init_stripe called, stripe %llu\n",
(unsigned long long)sh->sector);
@@ -238,11 +240,11 @@ static void init_stripe(struct stripe_he
for (i = sh->disks; i--; ) {
struct r5dev *dev = &sh->dev[i];
- if (dev->toread || dev->towrite || dev->written ||
+ if (dev->toread || dev->read || dev->towrite || dev->written ||
test_bit(R5_LOCKED, &dev->flags)) {
- printk("sector=%llx i=%d %p %p %p %d\n",
+ printk("sector=%llx i=%d %p %p %p %p %d\n",
(unsigned long long)sh->sector, i, dev->toread,
- dev->towrite, dev->written,
+ dev->read, dev->towrite, dev->written,
test_bit(R5_LOCKED, &dev->flags));
BUG();
}
@@ -322,6 +324,556 @@ static struct stripe_head *get_active_st
return sh;
}
+static int
+raid5_end_read_request(struct bio * bi, unsigned int bytes_done, int error);
+static int
+raid5_end_write_request (struct bio *bi, unsigned int bytes_done, int error);
+
+static void ops_run_io(struct stripe_head *sh)
+{
+ raid5_conf_t *conf = sh->raid_conf;
+ int i;
+
+ might_sleep();
+
+ for (i = sh->disks; i-- ;) {
+ int rw;
+ struct bio *bi;
+ mdk_rdev_t *rdev;
+ if (test_and_clear_bit(R5_Wantwrite, &sh->dev[i].flags))
+ rw = 1;
+ else if (test_and_clear_bit(R5_Wantread, &sh->dev[i].flags))
+ rw = 0;
+ else
+ continue;
+
+ bi = &sh->dev[i].req;
+
+ bi->bi_rw = rw;
+ if (rw)
+ bi->bi_end_io = raid5_end_write_request;
+ else
+ bi->bi_end_io = raid5_end_read_request;
+
+ rcu_read_lock();
+ rdev = rcu_dereference(conf->disks[i].rdev);
+ if (rdev && test_bit(Faulty, &rdev->flags))
+ rdev = NULL;
+ if (rdev)
+ atomic_inc(&rdev->nr_pending);
+ rcu_read_unlock();
+
+ if (rdev) {
+ if (test_bit(STRIPE_SYNCING, &sh->state) ||
+ test_bit(STRIPE_EXPAND_SOURCE, &sh->state) ||
+ test_bit(STRIPE_EXPAND_READY, &sh->state))
+ md_sync_acct(rdev->bdev, STRIPE_SECTORS);
+
+ bi->bi_bdev = rdev->bdev;
+ PRINTK("%s: stripe %llu schedule op %ld on disc %d\n",
+ __FUNCTION__,
+ (unsigned long long)sh->sector, bi->bi_rw, i);
+ atomic_inc(&sh->count);
+ bi->bi_sector = sh->sector + rdev->data_offset;
+ bi->bi_flags = 1 << BIO_UPTODATE;
+ bi->bi_vcnt = 1;
+ bi->bi_max_vecs = 1;
+ bi->bi_idx = 0;
+ bi->bi_io_vec = &sh->dev[i].vec;
+ bi->bi_io_vec[0].bv_len = STRIPE_SIZE;
+ bi->bi_io_vec[0].bv_offset = 0;
+ bi->bi_size = STRIPE_SIZE;
+ bi->bi_next = NULL;
+ if (rw == WRITE &&
+ test_bit(R5_ReWrite, &sh->dev[i].flags))
+ atomic_add(STRIPE_SECTORS,
&rdev->corrected_errors);
+ generic_make_request(bi);
+ } else {
+ if (rw == 1)
+ set_bit(STRIPE_DEGRADED, &sh->state);
+ PRINTK("skip op %ld on disc %d for sector %llu\n",
+ bi->bi_rw, i, (unsigned long long)sh->sector);
+ clear_bit(R5_LOCKED, &sh->dev[i].flags);
+ set_bit(STRIPE_HANDLE, &sh->state);
+ }
+ }
+}
+
+static struct dma_async_tx_descriptor *
+async_copy_data(int frombio, struct bio *bio, struct page *page, sector_t
sector,
+ struct dma_async_tx_descriptor *tx)
+{
+ struct bio_vec *bvl;
+ struct page *bio_page;
+ int i;
+ int page_offset;
+
+ if (bio->bi_sector >= sector)
+ page_offset = (signed)(bio->bi_sector - sector) * 512;
+ else
+ page_offset = (signed)(sector - bio->bi_sector) * -512;
+ bio_for_each_segment(bvl, bio, i) {
+ int len = bio_iovec_idx(bio,i)->bv_len;
+ int clen;
+ int b_offset = 0;
+
+ if (page_offset < 0) {
+ b_offset = -page_offset;
+ page_offset += b_offset;
+ len -= b_offset;
+ }
+
+ if (len > 0 && page_offset + len > STRIPE_SIZE)
+ clen = STRIPE_SIZE - page_offset;
+ else clen = len;
+
+ if (clen > 0) {
+ b_offset += bio_iovec_idx(bio,i)->bv_offset;
+ bio_page = bio_iovec_idx(bio,i)->bv_page;
+ if (frombio)
+ tx = async_memcpy(page, bio_page, page_offset,
+ b_offset, clen,
+ ASYNC_TX_DEP_ACK | ASYNC_TX_KMAP_SRC,
+ tx, NULL, NULL);
+ else
+ tx = async_memcpy(bio_page, page, b_offset,
+ page_offset, clen,
+ ASYNC_TX_DEP_ACK | ASYNC_TX_KMAP_DST,
+ tx, NULL, NULL);
+ }
+ if (clen < len) /* hit end of page */
+ break;
+ page_offset += len;
+ }
+
+ return tx;
+}
+
+static void ops_complete_biofill(void *stripe_head_ref)
+{
+ struct stripe_head *sh = stripe_head_ref;
+
+ PRINTK("%s: stripe %llu\n", __FUNCTION__,
+ (unsigned long long)sh->sector);
+
+ BUG_ON(test_and_set_bit(STRIPE_OP_BIOFILL, &sh->ops.complete));
+ set_bit(STRIPE_HANDLE, &sh->state);
+ release_stripe(sh);
+}
+
+static void ops_run_biofill(struct stripe_head *sh)
+{
+ struct bio *return_bi = NULL;
+ struct dma_async_tx_descriptor *tx = NULL;
+ raid5_conf_t *conf = sh->raid_conf;
+ int i;
+
+ PRINTK("%s: stripe %llu\n", __FUNCTION__,
+ (unsigned long long)sh->sector);
+
+ for (i=sh->disks ; i-- ;) {
+ struct r5dev *dev = &sh->dev[i];
+ if (test_bit(R5_Wantfill, &dev->flags)) {
+ struct bio *rbi, *rbi2;
+ spin_lock_irq(&conf->device_lock);
+ rbi = dev->toread;
+ dev->toread = NULL;
+ spin_unlock_irq(&conf->device_lock);
+ while (rbi && rbi->bi_sector < dev->sector +
STRIPE_SECTORS) {
+ tx = async_copy_data(0, rbi, dev->page,
+ dev->sector, tx);
+ 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;
+ }
+ dev->read = return_bi;
+ }
+ }
+
+ atomic_inc(&sh->count);
+ async_interrupt(ASYNC_TX_DEP_ACK | ASYNC_TX_ACK, tx,
+ ops_complete_biofill, sh);
+}
+
+static void ops_complete_compute5(void *stripe_head_ref)
+{
+ struct stripe_head *sh = stripe_head_ref;
+ int target = sh->ops.target;
+ struct r5dev *tgt = &sh->dev[target];
+
+ PRINTK("%s: stripe %llu\n", __FUNCTION__,
+ (unsigned long long)sh->sector);
+
+ set_bit(R5_UPTODATE, &tgt->flags);
+ BUG_ON(!test_and_clear_bit(R5_Wantcompute, &tgt->flags));
+ BUG_ON(test_and_set_bit(STRIPE_OP_COMPUTE_BLK, &sh->ops.complete));
+ set_bit(STRIPE_HANDLE, &sh->state);
+ release_stripe(sh);
+}
+
+static struct dma_async_tx_descriptor *
+ops_run_compute5(struct stripe_head *sh, unsigned long pending)
+{
+ /* since we are running in a workqueue our stack is not
+ * very deep at this point, but kernel stack size limits the total
+ * number of disks
+ */
+ int disks = sh->disks;
+ struct page *xor_srcs[disks];
+ int target = sh->ops.target;
+ struct r5dev *tgt = &sh->dev[target];
+ struct page *xor_dest = tgt->page;
+ int count = 0;
+ struct dma_async_tx_descriptor *tx;
+ int i;
+
+ PRINTK("%s: stripe %llu block: %d\n",
+ __FUNCTION__, (unsigned long long)sh->sector, target);
+ BUG_ON(!test_bit(R5_Wantcompute, &tgt->flags));
+
+ for (i=disks ; i-- ; )
+ if (i != target)
+ xor_srcs[count++] = sh->dev[i].page;
+
+ atomic_inc(&sh->count);
+
+ tx = async_xor(xor_dest, xor_srcs, 0, count, STRIPE_SIZE,
+ ASYNC_TX_XOR_ZERO_DST | ASYNC_TX_INT_EN, NULL,
+ ops_complete_compute5, sh);
+
+ /* ack now if postxor is not set to be run */
+ if (tx && !test_bit(STRIPE_OP_POSTXOR, &pending))
+ async_tx_ack(tx);
+
+ return tx;
+}
+
+static void ops_complete_prexor(void *stripe_head_ref)
+{
+ struct stripe_head *sh = stripe_head_ref;
+
+ PRINTK("%s: stripe %llu\n", __FUNCTION__,
+ (unsigned long long)sh->sector);
+
+ set_bit(STRIPE_OP_PREXOR, &sh->ops.complete);
+}
+
+static struct dma_async_tx_descriptor *
+ops_run_prexor(struct stripe_head *sh, struct dma_async_tx_descriptor *tx)
+{
+ /* since we are running in a workqueue our stack is not
+ * very deep at this point, but kernel stack size limits the total
+ * number of disks
+ */
+ int disks = sh->disks;
+ struct page *xor_srcs[disks];
+ int count = 0, pd_idx = sh->pd_idx, i;
+
+ /* existing parity data subtracted */
+ struct page *xor_dest = xor_srcs[count++] = sh->dev[pd_idx].page;
+
+ PRINTK("%s: stripe %llu\n", __FUNCTION__,
+ (unsigned long long)sh->sector);
+
+ for (i=disks ; i-- ;) {
+ struct r5dev *dev = &sh->dev[i];
+ /* Only process blocks that are known to be uptodate */
+ if (dev->towrite && test_bit(R5_Wantprexor, &dev->flags))
+ xor_srcs[count++] = dev->page;
+ }
+
+ tx = async_xor(xor_dest, xor_srcs, 0, count, STRIPE_SIZE,
+ ASYNC_TX_DEP_ACK | ASYNC_TX_XOR_DROP_DST, tx,
+ ops_complete_prexor, sh);
+
+ /* trigger a channel switch if necesary */
+ tx = async_interrupt_cond(DMA_MEMCPY, ASYNC_TX_DEP_ACK, tx,
+ NULL, NULL);
+
+ return tx;
+}
+
+static void ops_complete_biodrain(void *stripe_head_ref)
+{
+ struct stripe_head *sh = stripe_head_ref;
+
+ PRINTK("%s: stripe %llu\n", __FUNCTION__,
+ (unsigned long long)sh->sector);
+
+ BUG_ON(test_and_set_bit(STRIPE_OP_BIODRAIN, &sh->ops.complete));
+}
+
+static struct dma_async_tx_descriptor *
+ops_run_biodrain(struct stripe_head *sh, struct dma_async_tx_descriptor *tx)
+{
+ int disks = sh->disks;
+ int pd_idx = sh->pd_idx, i;
+
+ /* check if prexor is active which means only process blocks
+ * that are part of a read-modify-write (Wantprexor)
+ */
+ int prexor = test_bit(STRIPE_OP_PREXOR, &sh->ops.pending);
+
+ PRINTK("%s: stripe %llu\n", __FUNCTION__,
+ (unsigned long long)sh->sector);
+
+ for (i=disks ; i-- ;) {
+ struct r5dev *dev = &sh->dev[i];
+ struct bio *chosen;
+ int towrite;
+
+ towrite = 0;
+ if (prexor) { /* rmw */
+ if (dev->towrite && test_bit(R5_Wantprexor,
&dev->flags))
+ towrite = 1;
+ } else { /* rcw */
+ if (i!=pd_idx && dev->towrite &&
+ test_bit(R5_LOCKED, &dev->flags))
+ towrite = 1;
+ }
+
+ if (towrite) {
+ struct bio *wbi;
+
+ spin_lock(&sh->lock);
+ chosen = dev->towrite;
+ dev->towrite = NULL;
+ BUG_ON(dev->written);
+ wbi = dev->written = chosen;
+ spin_unlock(&sh->lock);
+
+ while (wbi && wbi->bi_sector < dev->sector +
STRIPE_SECTORS) {
+ tx = async_copy_data(1, wbi, dev->page,
+ dev->sector, tx);
+ wbi = r5_next_bio(wbi, dev->sector);
+ }
+ }
+ }
+
+ tx = async_interrupt_cond(DMA_XOR, ASYNC_TX_DEP_ACK, tx,
+ ops_complete_biodrain, sh);
+
+ return tx;
+}
+
+static void ops_complete_postxor(void *stripe_head_ref)
+{
+ struct stripe_head *sh = stripe_head_ref;
+ int disks = sh->disks, i, pd_idx = sh->pd_idx;
+
+ PRINTK("%s: stripe %llu\n", __FUNCTION__,
+ (unsigned long long)sh->sector);
+
+ for (i=disks ; i-- ;) {
+ struct r5dev *dev = &sh->dev[i];
+ if (dev->written || i == pd_idx)
+ set_bit(R5_UPTODATE, &dev->flags);
+ }
+
+ BUG_ON(test_and_set_bit(STRIPE_OP_POSTXOR, &sh->ops.complete));
+ set_bit(STRIPE_HANDLE, &sh->state);
+ release_stripe(sh);
+}
+
+static void
+ops_run_postxor(struct stripe_head *sh, struct dma_async_tx_descriptor *tx)
+{
+ /* since we are running in a workqueue our stack is not
+ * very deep at this point, but kernel stack size limits the total
+ * number of disks
+ */
+ int disks = sh->disks;
+ struct page *xor_srcs[disks];
+
+ int count = 0, pd_idx = sh->pd_idx, i;
+ struct page *xor_dest;
+ int prexor = test_bit(STRIPE_OP_PREXOR, &sh->ops.pending);
+ unsigned long flags;
+
+ PRINTK("%s: stripe %llu\n", __FUNCTION__,
+ (unsigned long long)sh->sector);
+
+ /* check if prexor is active which means only process blocks
+ * that are part of a read-modify-write (written)
+ */
+ if (prexor) {
+ xor_dest = xor_srcs[count++] = sh->dev[pd_idx].page;
+ for (i=disks; i--;) {
+ struct r5dev *dev = &sh->dev[i];
+ if (dev->written)
+ xor_srcs[count++] = dev->page;
+ }
+ } else {
+ xor_dest = sh->dev[pd_idx].page;
+ for (i=disks; i--;) {
+ struct r5dev *dev = &sh->dev[i];
+ if (i!=pd_idx)
+ xor_srcs[count++] = dev->page;
+ }
+ }
+
+ atomic_inc(&sh->count);
+
+ /* 1/ if we prexor'd then the dest is reused as a source
+ * 2/ if we did not prexor then we are redoing the parity
+ * set ASYNC_TX_XOR_DROP_DST and ASYNC_TX_XOR_ZERO_DST
+ * for the synchronous xor case
+ */
+ flags = ASYNC_TX_DEP_ACK | ASYNC_TX_ACK | ASYNC_TX_INT_EN |
+ (prexor ? ASYNC_TX_XOR_DROP_DST : ASYNC_TX_XOR_ZERO_DST);
+
+ tx = async_xor(xor_dest, xor_srcs, 0, count, STRIPE_SIZE,
+ flags, tx, ops_complete_postxor, sh);
+}
+
+static void ops_complete_check(void *stripe_head_ref)
+{
+ struct stripe_head *sh = stripe_head_ref;
+ int pd_idx = sh->pd_idx;
+
+ PRINTK("%s: stripe %llu\n", __FUNCTION__,
+ (unsigned long long)sh->sector);
+
+ if (test_and_clear_bit(STRIPE_OP_MOD_DMA_CHECK, &sh->ops.pending) &&
+ sh->ops.zero_sum_result == 0)
+ set_bit(R5_UPTODATE, &sh->dev[pd_idx].flags);
+
+ BUG_ON(test_and_set_bit(STRIPE_OP_CHECK, &sh->ops.complete));
+ set_bit(STRIPE_HANDLE, &sh->state);
+ release_stripe(sh);
+}
+
+static void ops_run_check(struct stripe_head *sh)
+{
+ /* since we are running in a workqueue our stack is not
+ * very deep at this point, but kernel stack size limits the total
+ * number of disks
+ */
+ int disks = sh->disks;
+ struct page *xor_srcs[disks];
+ struct dma_async_tx_descriptor *tx;
+
+ int count = 0, pd_idx = sh->pd_idx, i;
+ struct page *xor_dest = xor_srcs[count++] = sh->dev[pd_idx].page;
+
+ PRINTK("%s: stripe %llu\n", __FUNCTION__,
+ (unsigned long long)sh->sector);
+
+ for (i=disks; i--;) {
+ struct r5dev *dev = &sh->dev[i];
+ if (i != pd_idx)
+ xor_srcs[count++] = dev->page;
+ }
+
+ tx = async_xor_zero_sum(xor_dest, xor_srcs, 0, count, STRIPE_SIZE,
+ &sh->ops.zero_sum_result, 0, NULL, NULL, NULL);
+
+ if (tx)
+ set_bit(STRIPE_OP_MOD_DMA_CHECK, &sh->ops.pending);
+ else
+ clear_bit(STRIPE_OP_MOD_DMA_CHECK, &sh->ops.pending);
+
+ atomic_inc(&sh->count);
+ tx = async_interrupt(ASYNC_TX_DEP_ACK | ASYNC_TX_ACK, tx,
+ ops_complete_check, sh);
+}
+
+/* raid5_run_ops can be called multiple times before handle_stripe
+ * has a chance to clear completed operations. check_op() ensures
+ * that we only dequeue an operation once.
+ */
+#define check_op(op) do {\
+ if (test_bit(op, &sh->ops.pending) &&\
+ !test_bit(op, &sh->ops.complete)) {\
+ if (test_and_set_bit(op, &sh->ops.ack))\
+ clear_bit(op, &pending);\
+ else\
+ ack++;\
+ } else\
+ clear_bit(op, &pending);\
+} while(0)
+
+static void raid5_run_ops(void *stripe_head_ref)
+{
+ unsigned long pending;
+ struct stripe_head *sh = stripe_head_ref;
+ raid5_conf_t *conf = sh->raid_conf;
+ int overlap=0, ack=0, i, disks = sh->disks;
+ struct dma_async_tx_descriptor *tx = NULL;
+
+ /* find new work to run, do not resubmit work that is already
+ * in flight
+ */
+ spin_lock(&sh->lock);
+
+ pending = sh->ops.pending;
+ check_op(STRIPE_OP_BIOFILL);
+ check_op(STRIPE_OP_COMPUTE_BLK);
+ check_op(STRIPE_OP_PREXOR);
+ check_op(STRIPE_OP_BIODRAIN);
+ check_op(STRIPE_OP_POSTXOR);
+ check_op(STRIPE_OP_CHECK);
+ if (test_and_clear_bit(STRIPE_OP_IO, &sh->ops.pending))
+ ack++;
+ spin_unlock(&sh->lock);
+
+ /* issue operations */
+
+ if (test_bit(STRIPE_OP_BIOFILL, &pending)) {
+ ops_run_biofill(sh);
+ overlap++;
+ }
+
+ if (test_bit(STRIPE_OP_COMPUTE_BLK, &pending))
+ tx = ops_run_compute5(sh, pending);
+
+ if (test_bit(STRIPE_OP_PREXOR, &pending))
+ tx = ops_run_prexor(sh, tx);
+
+ if (test_bit(STRIPE_OP_BIODRAIN, &pending)) {
+ tx = ops_run_biodrain(sh, tx);
+ overlap++;
+ }
+
+ if (test_bit(STRIPE_OP_POSTXOR, &pending))
+ ops_run_postxor(sh, tx);
+
+ if (test_bit(STRIPE_OP_CHECK, &pending))
+ ops_run_check(sh);
+
+ if (test_bit(STRIPE_OP_IO, &pending))
+ ops_run_io(sh);
+
+ spin_lock(&sh->lock);
+
+ sh->ops.count -= ack;
+ clear_bit(STRIPE_OPSQUEUE_ACTIVE, &sh->state);
+
+ 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);
+ }
+
+ /* check to see if new ops arrived while we were working */
+ if (sh->ops.count > 0) {
+ set_bit(STRIPE_OPSQUEUE_ACTIVE, &sh->state);
+ issue_raid_ops(sh);
+ } else if (sh->ops.count < 0)
+ BUG();
+
+ spin_unlock(&sh->lock);
+
+ set_bit(STRIPE_HANDLE, &sh->state);
+ release_stripe(sh);
+}
+
static int grow_one_stripe(raid5_conf_t *conf)
{
struct stripe_head *sh;
diff --git a/include/linux/raid/raid5.h b/include/linux/raid/raid5.h
index f13299a..a1c3f85 100644
--- a/include/linux/raid/raid5.h
+++ b/include/linux/raid/raid5.h
@@ -116,13 +116,43 @@ #include <linux/raid/xor.h>
* attach a request to an active stripe (add_stripe_bh())
* lockdev attach-buffer unlockdev
* handle a stripe (handle_stripe())
- * lockstripe clrSTRIPE_HANDLE ... (lockdev check-buffers unlockdev) ..
change-state .. record io needed unlockstripe schedule io
+ * lockstripe clrSTRIPE_HANDLE ... (lockdev check-buffers unlockdev) ..
change-state .. record io/ops needed unlockstripe 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
*
* 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.
+ * 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:
+ * -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
read-modify-write)
+ * -checking parity correctness
+ * -running i/o to disk
+ * These operations are carried out by raid5_run_ops which uses the async_tx
+ * api to (optionally) offload operations to dedicated hardware engines.
+ * When requesting an operation handle_stripe sets the pending bit for the
+ * operation and increments the count. The workqueue is then run whenever
+ * the count is non-zero and is not already active (determined by the
+ * STRIPE_OPSQUEUE_ACTIVE flag).
+ * There are some critical dependencies between the operations that prevent
some
+ * from being requested while another is in flight.
+ * 1/ Parity check operations destroy the in cache version of the parity block,
+ * so we prevent parity dependent operations like writes and compute_blocks
+ * from starting while a check is in progress. Some dma engines can perform
+ * the check without damaging the parity block, in these cases the parity
block
+ * is re-marked up to date (assuming the check was successful) and is not
+ * re-read from disk.
+ * 2/ When a write operation is requested we immediately lock the affected
blocks,
+ * and mark them as not up to date. This causes new read requests to be
held
+ * off, as well as parity checks and compute block operations.
+ * 3/ Once a compute block operation has been requested handle_stripe treats
that
+ * block as if it is up to date. raid5_run_ops
+ * guaruntees that any operation that is dependent on the
+ * compute block result is initiated after the compute block completes.
*/
struct stripe_head {
@@ -136,11 +166,19 @@ struct stripe_head {
spinlock_t lock;
int bm_seq; /* sequence number for bitmap flushes */
int disks; /* disks in stripe */
+ struct stripe_operations {
+ unsigned long pending; /* pending operations (set for
request->issue->complete) */
+ unsigned long ack; /* submitted operations (set for
issue->complete */
+ unsigned long complete; /* completed operations flags (set
for complete) */
+ int target; /* STRIPE_OP_COMPUTE_BLK target */
+ int count; /* workqueue runs when this is
non-zero */
+ u32 zero_sum_result;
+ } ops;
struct r5dev {
struct bio req;
struct bio_vec vec;
struct page *page;
- struct bio *toread, *towrite, *written;
+ struct bio *toread, *read, *towrite, *written;
sector_t sector; /* sector of this page
*/
unsigned long flags;
} dev[1]; /* allocated with extra space depending of RAID geometry */
@@ -156,8 +194,12 @@ #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 without a cache
flush */
+#define R5_Wantcompute 12 /* compute_block in progress treat as
uptodate */
+#define R5_Wantfill 13 /* dev->toread contains a bio that
needs filling */
+#define R5_Wantprexor 14 /* distinguish blocks ready for rmw
from other "towrites" */
+
/*
* Write method
*/
@@ -179,6 +221,23 @@ #define STRIPE_BIT_DELAY 8
#define STRIPE_EXPANDING 9
#define STRIPE_EXPAND_SOURCE 10
#define STRIPE_EXPAND_READY 11
+#define STRIPE_OPSQUEUE_ACTIVE 12
+
+/*
+ * Operations flags (in issue order)
+ */
+#define STRIPE_OP_BIOFILL 0
+#define STRIPE_OP_COMPUTE_BLK 1
+#define STRIPE_OP_PREXOR 2
+#define STRIPE_OP_BIODRAIN 3
+#define STRIPE_OP_POSTXOR 4
+#define STRIPE_OP_CHECK 5
+#define STRIPE_OP_IO 6
+
+/* modifiers to the base operations */
+#define STRIPE_OP_MOD_REPAIR_PD 7 /* compute the parity block and write
it back */
+#define STRIPE_OP_MOD_DMA_CHECK 8 /* parity is not corrupted by the
check */
+
/*
* Plugging:
*
-
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