md: handle_stripe5 - add request/completion logic for async write ops
After handle_stripe5 decides whether it wants to perform a read-modify-write, or a reconstruct write it calls handle_write_operations5. A read-modify-write operation will perform an xor subtraction of the blocks marked with the R5_Wantprexor flag, copy the new data into the stripe (biodrain) and perform a postxor operation across all up-to-date blocks to generate the new parity. A reconstruct write is run when all blocks are already up-to-date in the cache so all that is needed is a biodrain and postxor. On the completion path STRIPE_OP_PREXOR will be set if the operation was a read-modify-write. The STRIPE_OP_BIODRAIN flag is used in the completion path to differentiate write-initiated postxor operations versus expansion-initiated postxor operations. Completion of a write triggers i/o to the drives. Changelog: * make the 'rcw' parameter to handle_write_operations5 a simple flag, Neil Brown * remove test_and_set/test_and_clear BUG_ONs, Neil Brown Signed-off-by: Dan Williams <dan.j.williams@intel.com> Acked-By: NeilBrown <neilb@suse.de>
This commit is contained in:
Dan Williams
parent
d84e0f10d3
commit
e33129d841
1 changed files with 138 additions and 23 deletions
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@ -1822,7 +1822,79 @@ static void compute_block_2(struct stripe_head *sh, int dd_idx1, int dd_idx2)
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}
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}
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static int
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handle_write_operations5(struct stripe_head *sh, int rcw, int expand)
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{
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int i, pd_idx = sh->pd_idx, disks = sh->disks;
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int locked = 0;
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if (rcw) {
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/* if we are not expanding this is a proper write request, and
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* there will be bios with new data to be drained into the
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* stripe cache
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*/
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if (!expand) {
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set_bit(STRIPE_OP_BIODRAIN, &sh->ops.pending);
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sh->ops.count++;
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}
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set_bit(STRIPE_OP_POSTXOR, &sh->ops.pending);
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sh->ops.count++;
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for (i = disks; i--; ) {
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struct r5dev *dev = &sh->dev[i];
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if (dev->towrite) {
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set_bit(R5_LOCKED, &dev->flags);
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if (!expand)
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clear_bit(R5_UPTODATE, &dev->flags);
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locked++;
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}
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}
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} else {
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BUG_ON(!(test_bit(R5_UPTODATE, &sh->dev[pd_idx].flags) ||
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test_bit(R5_Wantcompute, &sh->dev[pd_idx].flags)));
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set_bit(STRIPE_OP_PREXOR, &sh->ops.pending);
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set_bit(STRIPE_OP_BIODRAIN, &sh->ops.pending);
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set_bit(STRIPE_OP_POSTXOR, &sh->ops.pending);
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sh->ops.count += 3;
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for (i = disks; i--; ) {
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struct r5dev *dev = &sh->dev[i];
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if (i == pd_idx)
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continue;
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/* For a read-modify write there may be blocks that are
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* locked for reading while others are ready to be
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* written so we distinguish these blocks by the
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* R5_Wantprexor bit
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*/
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if (dev->towrite &&
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(test_bit(R5_UPTODATE, &dev->flags) ||
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test_bit(R5_Wantcompute, &dev->flags))) {
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set_bit(R5_Wantprexor, &dev->flags);
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set_bit(R5_LOCKED, &dev->flags);
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clear_bit(R5_UPTODATE, &dev->flags);
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locked++;
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}
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}
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}
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/* keep the parity disk locked while asynchronous operations
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* are in flight
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*/
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set_bit(R5_LOCKED, &sh->dev[pd_idx].flags);
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clear_bit(R5_UPTODATE, &sh->dev[pd_idx].flags);
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locked++;
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pr_debug("%s: stripe %llu locked: %d pending: %lx\n",
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__FUNCTION__, (unsigned long long)sh->sector,
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locked, sh->ops.pending);
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return locked;
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}
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/*
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* Each stripe/dev can have one or more bion attached.
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@ -2217,27 +2289,8 @@ static void handle_issuing_new_write_requests5(raid5_conf_t *conf,
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* we can start a write request
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*/
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if (s->locked == 0 && (rcw == 0 || rmw == 0) &&
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!test_bit(STRIPE_BIT_DELAY, &sh->state)) {
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pr_debug("Computing parity...\n");
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compute_parity5(sh, rcw == 0 ?
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RECONSTRUCT_WRITE : READ_MODIFY_WRITE);
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/* now every locked buffer is ready to be written */
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for (i = disks; i--; )
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if (test_bit(R5_LOCKED, &sh->dev[i].flags)) {
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pr_debug("Writing block %d\n", i);
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s->locked++;
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set_bit(R5_Wantwrite, &sh->dev[i].flags);
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if (!test_bit(R5_Insync, &sh->dev[i].flags)
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|| (i == sh->pd_idx && s->failed == 0))
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set_bit(STRIPE_INSYNC, &sh->state);
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}
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if (test_and_clear_bit(STRIPE_PREREAD_ACTIVE, &sh->state)) {
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atomic_dec(&conf->preread_active_stripes);
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if (atomic_read(&conf->preread_active_stripes) <
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IO_THRESHOLD)
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md_wakeup_thread(conf->mddev->thread);
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}
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}
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!test_bit(STRIPE_BIT_DELAY, &sh->state))
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s->locked += handle_write_operations5(sh, rcw == 0, 0);
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}
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static void handle_issuing_new_write_requests6(raid5_conf_t *conf,
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@ -2656,8 +2709,70 @@ static void handle_stripe5(struct stripe_head *sh)
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(s.syncing && (s.uptodate < disks)) || s.expanding)
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handle_issuing_new_read_requests5(sh, &s, disks);
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/* now to consider writing and what else, if anything should be read */
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if (s.to_write)
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/* Now we check to see if any write operations have recently
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* completed
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*/
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/* leave prexor set until postxor is done, allows us to distinguish
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* a rmw from a rcw during biodrain
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*/
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if (test_bit(STRIPE_OP_PREXOR, &sh->ops.complete) &&
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test_bit(STRIPE_OP_POSTXOR, &sh->ops.complete)) {
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clear_bit(STRIPE_OP_PREXOR, &sh->ops.complete);
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clear_bit(STRIPE_OP_PREXOR, &sh->ops.ack);
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clear_bit(STRIPE_OP_PREXOR, &sh->ops.pending);
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for (i = disks; i--; )
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clear_bit(R5_Wantprexor, &sh->dev[i].flags);
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}
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/* if only POSTXOR is set then this is an 'expand' postxor */
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if (test_bit(STRIPE_OP_BIODRAIN, &sh->ops.complete) &&
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test_bit(STRIPE_OP_POSTXOR, &sh->ops.complete)) {
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clear_bit(STRIPE_OP_BIODRAIN, &sh->ops.complete);
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clear_bit(STRIPE_OP_BIODRAIN, &sh->ops.ack);
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clear_bit(STRIPE_OP_BIODRAIN, &sh->ops.pending);
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clear_bit(STRIPE_OP_POSTXOR, &sh->ops.complete);
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clear_bit(STRIPE_OP_POSTXOR, &sh->ops.ack);
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clear_bit(STRIPE_OP_POSTXOR, &sh->ops.pending);
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/* All the 'written' buffers and the parity block are ready to
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* be written back to disk
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*/
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BUG_ON(!test_bit(R5_UPTODATE, &sh->dev[sh->pd_idx].flags));
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for (i = disks; i--; ) {
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dev = &sh->dev[i];
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if (test_bit(R5_LOCKED, &dev->flags) &&
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(i == sh->pd_idx || dev->written)) {
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pr_debug("Writing block %d\n", i);
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set_bit(R5_Wantwrite, &dev->flags);
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if (!test_and_set_bit(
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STRIPE_OP_IO, &sh->ops.pending))
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sh->ops.count++;
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if (!test_bit(R5_Insync, &dev->flags) ||
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(i == sh->pd_idx && s.failed == 0))
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set_bit(STRIPE_INSYNC, &sh->state);
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}
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}
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if (test_and_clear_bit(STRIPE_PREREAD_ACTIVE, &sh->state)) {
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atomic_dec(&conf->preread_active_stripes);
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if (atomic_read(&conf->preread_active_stripes) <
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IO_THRESHOLD)
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md_wakeup_thread(conf->mddev->thread);
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}
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}
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/* Now to consider new write requests and what else, if anything
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* should be read. We do not handle new writes when:
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* 1/ A 'write' operation (copy+xor) is already in flight.
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* 2/ A 'check' operation is in flight, as it may clobber the parity
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* block.
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*/
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if (s.to_write && !test_bit(STRIPE_OP_POSTXOR, &sh->ops.pending) &&
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!test_bit(STRIPE_OP_CHECK, &sh->ops.pending))
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handle_issuing_new_write_requests5(conf, sh, &s, disks);
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/* maybe we need to check and possibly fix the parity for this stripe
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