[PATCH 07/16] md: move write operations to raid5_run_ops

Dan Williams
2007-05-02T06:18:16Z

handle_stripe sets STRIPE_OP_PREXOR, STRIPE_OP_BIODRAIN, STRIPE_OP_POSTXOR
to request a write to the stripe cache. raid5_run_ops is triggerred to run
and executes the request outside the stripe lock.

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>
---

drivers/md/raid5.c | 151 +++++++++++++++++++++++++++++++++++++++++++++-------
1 files changed, 130 insertions(+), 21 deletions(-)

diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c
index 14e9f6a..03a435d 100644
--- a/drivers/md/raid5.c
+++ b/drivers/md/raid5.c
@@ -1807,7 +1807,74 @@ static void compute_block_2(struct stripe_head *sh, int dd_idx1, int dd_idx2)
}
}

+static int handle_write_operations5(struct stripe_head *sh, int rcw, int expand)
+{
+ int i, pd_idx = sh->pd_idx, disks = sh->disks;
+ int locked=0;
+
+ if (rcw) {
+ /* skip the drain operation on an expand */
+ if (!expand) {
+ set_bit(STRIPE_OP_BIODRAIN, &sh->ops.pending);
+ sh->ops.count++;
+ }
+
+ set_bit(STRIPE_OP_POSTXOR, &sh->ops.pending);
+ sh->ops.count++;
+
+ for (i=disks ; i-- ;) {
+ struct r5dev *dev = &sh->dev[i];
+
+ if (dev->towrite) {
+ set_bit(R5_LOCKED, &dev->flags);
+ if (!expand)
+ clear_bit(R5_UPTODATE, &dev->flags);
+ locked++;
+ }
+ }
+ } else {
+ BUG_ON(!(test_bit(R5_UPTODATE, &sh->dev[pd_idx].flags) ||
+ test_bit(R5_Wantcompute, &sh->dev[pd_idx].flags)));
+
+ set_bit(STRIPE_OP_PREXOR, &sh->ops.pending);
+ set_bit(STRIPE_OP_BIODRAIN, &sh->ops.pending);
+ set_bit(STRIPE_OP_POSTXOR, &sh->ops.pending);
+
+ sh->ops.count += 3;
+
+ for (i=disks ; i-- ;) {
+ struct r5dev *dev = &sh->dev[i];
+ if (i==pd_idx)
+ continue;

+ /* For a read-modify write there may be blocks that are
+ * locked for reading while others are ready to be written
+ * so we distinguish these blocks by the R5_Wantprexor bit
+ */
+ if (dev->towrite &&
+ (test_bit(R5_UPTODATE, &dev->flags) ||
+ test_bit(R5_Wantcompute, &dev->flags))) {
+ set_bit(R5_Wantprexor, &dev->flags);
+ set_bit(R5_LOCKED, &dev->flags);
+ clear_bit(R5_UPTODATE, &dev->flags);
+ locked++;
+ }
+ }
+ }
+
+ /* keep the parity disk locked while asynchronous operations
+ * are in flight
+ */
+ set_bit(R5_LOCKED, &sh->dev[pd_idx].flags);
+ clear_bit(R5_UPTODATE, &sh->dev[pd_idx].flags);
+ locked++;
+
+ PRINTK("%s: stripe %llu locked: %d pending: %lx\n",
+ __FUNCTION__, (unsigned long long)sh->sector,
+ locked, sh->ops.pending);
+
+ return locked;
+}

/*
* Each stripe/dev can have one or more bion attached.
@@ -2170,8 +2237,67 @@ static void handle_stripe5(struct stripe_head *sh)
set_bit(STRIPE_HANDLE, &sh->state);
}

- /* now to consider writing and what else, if anything should be read */
- if (to_write) {
+ /* Now we check to see if any write operations have recently
+ * completed
+ */
+
+ /* leave prexor set until postxor is done, allows us to distinguish
+ * a rmw from a rcw during biodrain
+ */
+ if (test_bit(STRIPE_OP_PREXOR, &sh->ops.complete) &&
+ test_bit(STRIPE_OP_POSTXOR, &sh->ops.complete)) {
+
+ clear_bit(STRIPE_OP_PREXOR, &sh->ops.complete);
+ clear_bit(STRIPE_OP_PREXOR, &sh->ops.ack);
+ clear_bit(STRIPE_OP_PREXOR, &sh->ops.pending);
+
+ for (i=disks; i--;)
+ clear_bit(R5_Wantprexor, &sh->dev[i].flags);
+ }
+
+ /* if only POSTXOR is set then this is an 'expand' postxor */
+ if (test_bit(STRIPE_OP_BIODRAIN, &sh->ops.complete) &&
+ test_bit(STRIPE_OP_POSTXOR, &sh->ops.complete)) {
+
+ clear_bit(STRIPE_OP_BIODRAIN, &sh->ops.complete);
+ clear_bit(STRIPE_OP_BIODRAIN, &sh->ops.ack);
+ clear_bit(STRIPE_OP_BIODRAIN, &sh->ops.pending);
+
+ clear_bit(STRIPE_OP_POSTXOR, &sh->ops.complete);
+ clear_bit(STRIPE_OP_POSTXOR, &sh->ops.ack);
+ clear_bit(STRIPE_OP_POSTXOR, &sh->ops.pending);
+
+ /* All the 'written' buffers and the parity block are ready to be
+ * written back to disk
+ */
+ BUG_ON(!test_bit(R5_UPTODATE, &sh->dev[sh->pd_idx].flags));
+ for (i=disks; i--;) {
+ dev = &sh->dev[i];
+ if (test_bit(R5_LOCKED, &dev->flags) &&
+ (i == sh->pd_idx || dev->written)) {
+ PRINTK("Writing block %d\n", i);
+ set_bit(R5_Wantwrite, &dev->flags);
+ if (!test_and_set_bit(STRIPE_OP_IO, &sh->ops.pending))
+ sh->ops.count++;
+ if (!test_bit(R5_Insync, &dev->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);
+ }
+ }
+
+ /* 1/ Now to consider new write requests and what else, if anything should be read
+ * 2/ Check operations clobber the parity block so do not start new writes while
+ * a check is in flight
+ * 3/ Write operations do not stack
+ */
+ if (to_write && !test_bit(STRIPE_OP_POSTXOR, &sh->ops.pending) &&
+ !test_bit(STRIPE_OP_CHECK, &sh->ops.pending)) {
int rmw=0, rcw=0;
for (i=disks ; i--;) {
/* would I have to read this buffer for read_modify_write */
@@ -2238,25 +2364,8 @@ 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)) {
- PRINTK("Computing parity...\n");
- compute_parity5(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);
- }
- 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);
- }
- }
+ !test_bit(STRIPE_BIT_DELAY, &sh->state))
+ locked += handle_write_operations5(sh, rcw == 0, 0);
}

/* maybe we need to check and possibly fix the parity for this stripe