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Subject[PATCH 2.6.21-rc4 07/15] md: move raid5 compute block operations to raid5_run_ops
Date
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@intel.com>
---
drivers/md/raid5.c | 125 +++++++++++++++++++++++++++++++++++++++-------------
1 files changed, 93 insertions(+), 32 deletions(-)
diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c
index 4d1adb5..9856742 100644
--- a/drivers/md/raid5.c
+++ b/drivers/md/raid5.c
@@ -1980,7 +1980,7 @@ static void handle_stripe5(struct stripe_head *sh)
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;
unsigned long pending=0;
@@ -2032,8 +2032,8 @@ static void handle_stripe5(struct stripe_head *sh)
/* 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++;
@@ -2188,31 +2188,82 @@ static void handle_stripe5(struct stripe_head *sh)
* 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);
- locked++;
- PRINTK("Reading block %d (sync=%d)\n",
- i, syncing);
+ 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
+ * raid5_run_ops 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++;
+ locked++;
+ PRINTK("Reading block %d (sync=%d)\n",
+ i, syncing);
+ }
}
}
}
@@ -2287,7 +2338,7 @@ static void handle_stripe5(struct stripe_head *sh)
if ((dev->towrite || i == sh->pd_idx) &&
(!test_bit(R5_LOCKED, &dev->flags)
) &&
- !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) */
)
@@ -2298,7 +2349,7 @@ static void handle_stripe5(struct stripe_head *sh)
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_UPTODATE, &dev->flags) || test_bit(R5_Wantcompute, &dev->flags))) {
if (test_bit(R5_Insync, &dev->flags)) rcw++;
else rcw += 2*disks;
}
@@ -2311,7 +2362,8 @@ static void handle_stripe5(struct stripe_head *sh)
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))
{
@@ -2330,7 +2382,8 @@ static void handle_stripe5(struct stripe_head *sh)
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))
{
@@ -2345,8 +2398,16 @@ static void handle_stripe5(struct stripe_head *sh)
}
}
/* 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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