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Message-Id: <20061130201035.21313.17329.stgit@dwillia2-linux.ch.intel.com>
Date: Thu, 30 Nov 2006 13:10:35 -0700
From: Dan Williams <dan.j.williams@...el.com>
To: neilb@...e.de, jeff@...zik.org, christopher.leech@...el.com,
akpm@...l.org
Cc: linux-kernel@...r.kernel.org, linux-raid@...r.kernel.org,
olof@...om.net
Subject: [PATCH 07/12] md: move raid5 compute block operations to raid5_run_ops
From: Dan Williams <dan.j.williams@...el.com>
handle_stripe sets STRIPE_OP_COMPUTE_BLK to request servicing from
raid5_run_ops. It also sets a flag for the block being computed to let
other parts of handle_stripe submit dependent operations. raid5_run_ops
guarantees that the compute operation completes before any dependent
operation starts.
Signed-off-by: Dan Williams <dan.j.williams@...el.com>
---
drivers/md/raid5.c | 139 +++++++++++++++++++++++++++++++++++++---------------
1 files changed, 100 insertions(+), 39 deletions(-)
diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c
index 74516ef..8510183 100644
--- a/drivers/md/raid5.c
+++ b/drivers/md/raid5.c
@@ -2020,7 +2020,7 @@ static void handle_stripe5(struct stripe
int i;
int syncing, expanding, expanded;
int locked=0, uptodate=0, to_read=0, to_write=0, failed=0, written=0;
- int non_overwrite = 0;
+ int compute=0, req_compute=0, non_overwrite=0;
int failed_num=0;
struct r5dev *dev;
@@ -2071,8 +2071,8 @@ static void handle_stripe5(struct stripe
/* now count some things */
if (test_bit(R5_LOCKED, &dev->flags)) locked++;
if (test_bit(R5_UPTODATE, &dev->flags)) uptodate++;
+ if (test_bit(R5_Wantcompute, &dev->flags)) BUG_ON(++compute > 1);
-
if (dev->toread) to_read++;
if (dev->towrite) {
to_write++;
@@ -2227,40 +2227,91 @@ static void handle_stripe5(struct stripe
* parity, or to satisfy requests
* or to load a block that is being partially written.
*/
- if (to_read || non_overwrite || (syncing && (uptodate < disks)) || expanding) {
- for (i=disks; i--;) {
- dev = &sh->dev[i];
- if (!test_bit(R5_LOCKED, &dev->flags) && !test_bit(R5_UPTODATE, &dev->flags) &&
- (dev->toread ||
- (dev->towrite && !test_bit(R5_OVERWRITE, &dev->flags)) ||
- syncing ||
- expanding ||
- (failed && (sh->dev[failed_num].toread ||
- (sh->dev[failed_num].towrite && !test_bit(R5_OVERWRITE, &sh->dev[failed_num].flags))))
- )
- ) {
- /* we would like to get this block, possibly
- * by computing it, but we might not be able to
+ if (to_read || non_overwrite || (syncing && (uptodate + compute < disks)) || expanding ||
+ test_bit(STRIPE_OP_COMPUTE_BLK, &sh->ops.pending)) {
+
+ /* Clear completed compute operations. Parity recovery
+ * (STRIPE_OP_MOD_REPAIR_PD) implies a write-back which is handled
+ * later on in this routine
+ */
+ if (test_bit(STRIPE_OP_COMPUTE_BLK, &sh->ops.complete) &&
+ !test_bit(STRIPE_OP_MOD_REPAIR_PD, &sh->ops.pending)) {
+ clear_bit(STRIPE_OP_COMPUTE_BLK, &sh->ops.complete);
+ clear_bit(STRIPE_OP_COMPUTE_BLK, &sh->ops.ack);
+ clear_bit(STRIPE_OP_COMPUTE_BLK, &sh->ops.pending);
+ }
+
+ /* look for blocks to read/compute, skip this if a compute
+ * is already in flight, or if the stripe contents are in the
+ * midst of changing due to a write
+ */
+ if (!test_bit(STRIPE_OP_COMPUTE_BLK, &sh->ops.pending) &&
+ !test_bit(STRIPE_OP_PREXOR, &sh->ops.pending) &&
+ !test_bit(STRIPE_OP_POSTXOR, &sh->ops.pending)) {
+ for (i=disks; i--;) {
+ dev = &sh->dev[i];
+
+ /* don't schedule compute operations or reads on
+ * the parity block while a check is in flight
*/
- if (uptodate == disks-1) {
- PRINTK("Computing block %d\n", i);
- compute_block(sh, i);
- uptodate++;
- } else if (test_bit(R5_Insync, &dev->flags)) {
- set_bit(R5_LOCKED, &dev->flags);
- set_bit(R5_Wantread, &dev->flags);
+ if ((i == sh->pd_idx) && test_bit(STRIPE_OP_CHECK, &sh->ops.pending))
+ continue;
+
+ if (!test_bit(R5_LOCKED, &dev->flags) && !test_bit(R5_UPTODATE, &dev->flags) &&
+ (dev->toread ||
+ (dev->towrite && !test_bit(R5_OVERWRITE, &dev->flags)) ||
+ syncing ||
+ expanding ||
+ (failed && (sh->dev[failed_num].toread ||
+ (sh->dev[failed_num].towrite &&
+ !test_bit(R5_OVERWRITE, &sh->dev[failed_num].flags))))
+ )
+ ) {
+ /* 1/ We would like to get this block, possibly
+ * by computing it, but we might not be able to.
+ *
+ * 2/ Since parity check operations potentially
+ * make the parity block !uptodate it will need
+ * to be refreshed before any compute operations
+ * on data disks are scheduled.
+ *
+ * 3/ We hold off parity block re-reads until check
+ * operations have quiesced.
+ */
+ if ((uptodate == disks-1) && !test_bit(STRIPE_OP_CHECK, &sh->ops.pending)) {
+ set_bit(STRIPE_OP_COMPUTE_BLK, &sh->ops.pending);
+ set_bit(R5_Wantcompute, &dev->flags);
+ sh->ops.target = i;
+ BUG_ON(req_compute++);
+ sh->ops.count++;
+ /* Careful: from this point on 'uptodate' is in the eye of the
+ * workqueue which services 'compute' operations before writes.
+ * R5_Wantcompute flags a block that will be R5_UPTODATE
+ * by the time it is needed for a subsequent operation.
+ */
+ uptodate++;
+ } else if ((uptodate < disks-1) && test_bit(R5_Insync, &dev->flags)) {
+ /* Note: we hold off compute operations while checks are in flight,
+ * but we still prefer 'compute' over 'read' hence we only read if
+ * (uptodate < disks-1)
+ */
+ set_bit(R5_LOCKED, &dev->flags);
+ set_bit(R5_Wantread, &dev->flags);
+ if (!test_and_set_bit(STRIPE_OP_IO, &sh->ops.pending))
+ sh->ops.count++;
#if 0
- /* if I am just reading this block and we don't have
- a failed drive, or any pending writes then sidestep the cache */
- if (sh->bh_read[i] && !sh->bh_read[i]->b_reqnext &&
- ! syncing && !failed && !to_write) {
- sh->bh_cache[i]->b_page = sh->bh_read[i]->b_page;
- sh->bh_cache[i]->b_data = sh->bh_read[i]->b_data;
- }
+ /* if I am just reading this block and we don't have
+ a failed drive, or any pending writes then sidestep the cache */
+ if (sh->bh_read[i] && !sh->bh_read[i]->b_reqnext &&
+ ! syncing && !failed && !to_write) {
+ sh->bh_cache[i]->b_page = sh->bh_read[i]->b_page;
+ sh->bh_cache[i]->b_data = sh->bh_read[i]->b_data;
+ }
#endif
- locked++;
- PRINTK("Reading block %d (sync=%d)\n",
- i, syncing);
+ locked++;
+ PRINTK("Reading block %d (sync=%d)\n",
+ i, syncing);
+ }
}
}
}
@@ -2338,7 +2389,7 @@ #if 0
|| sh->bh_page[i]!=bh->b_page
#endif
) &&
- !test_bit(R5_UPTODATE, &dev->flags)) {
+ !(test_bit(R5_UPTODATE, &dev->flags) || test_bit(R5_Wantcompute, &dev->flags))) {
if (test_bit(R5_Insync, &dev->flags)
/* && !(!mddev->insync && i == sh->pd_idx) */
)
@@ -2352,7 +2403,7 @@ #if 0
|| sh->bh_page[i] != bh->b_page
#endif
) &&
- !test_bit(R5_UPTODATE, &dev->flags)) {
+ !(test_bit(R5_UPTODATE, &dev->flags) || test_bit(R5_Wantcompute, &dev->flags))) {
if (test_bit(R5_Insync, &dev->flags)) rcw++;
else rcw += 2*disks;
}
@@ -2365,7 +2416,8 @@ #endif
for (i=disks; i--;) {
dev = &sh->dev[i];
if ((dev->towrite || i == sh->pd_idx) &&
- !test_bit(R5_LOCKED, &dev->flags) && !test_bit(R5_UPTODATE, &dev->flags) &&
+ !test_bit(R5_LOCKED, &dev->flags) &&
+ !(test_bit(R5_UPTODATE, &dev->flags) || test_bit(R5_Wantcompute, &dev->flags)) &&
test_bit(R5_Insync, &dev->flags)) {
if (test_bit(STRIPE_PREREAD_ACTIVE, &sh->state))
{
@@ -2384,7 +2436,8 @@ #endif
for (i=disks; i--;) {
dev = &sh->dev[i];
if (!test_bit(R5_OVERWRITE, &dev->flags) && i != sh->pd_idx &&
- !test_bit(R5_LOCKED, &dev->flags) && !test_bit(R5_UPTODATE, &dev->flags) &&
+ !test_bit(R5_LOCKED, &dev->flags) &&
+ !(test_bit(R5_UPTODATE, &dev->flags) || test_bit(R5_Wantcompute, &dev->flags)) &&
test_bit(R5_Insync, &dev->flags)) {
if (test_bit(STRIPE_PREREAD_ACTIVE, &sh->state))
{
@@ -2399,8 +2452,16 @@ #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))
+ /* since handle_stripe can be called at any time we need to handle the case
+ * where a compute block operation has been submitted and then a subsequent
+ * call wants to start a write request. raid5_run_ops only handles the case where
+ * compute block and postxor are requested simultaneously. If this
+ * is not the case then new writes need to be held off until the compute
+ * completes.
+ */
+ if ((req_compute || !test_bit(STRIPE_OP_COMPUTE_BLK, &sh->ops.pending)) &&
+ (locked == 0 && (rcw == 0 ||rmw == 0) &&
+ !test_bit(STRIPE_BIT_DELAY, &sh->state)))
locked += handle_write_operations5(sh, rcw, 0);
}
-
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