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Subject[PATCH 027 of 29] md: md: replace R5_WantPrexor with R5_WantDrain, add 'prexor' reconstruct_states

From: Dan Williams <dan.j.williams@intel.com>

Currently ops_run_biodrain and other locations have extra logic to determine
which blocks are processed in the prexor and non-prexor cases. This can be
eliminated if handle_write_operations5 flags the blocks to be processed in all
cases via R5_Wantdrain. The presence of the prexor operation is tracked in
sh->reconstruct_state.

Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Signed-off-by: Neil Brown <neilb@suse.de>

### Diffstat output
./drivers/md/raid5.c | 89 ++++++++++++++-----------------------------
./include/linux/raid/raid5.h | 6 +-
2 files changed, 32 insertions(+), 63 deletions(-)
diff .prev/drivers/md/raid5.c ./drivers/md/raid5.c
--- .prev/drivers/md/raid5.c 2008-06-27 16:42:36.000000000 +1000
+++ ./drivers/md/raid5.c 2008-06-27 16:42:56.000000000 +1000
@@ -637,7 +637,7 @@ ops_run_prexor(struct stripe_head *sh, s
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))
+ if (test_bit(R5_Wantdrain, &dev->flags))
xor_srcs[count++] = dev->page;
}

@@ -649,16 +649,10 @@ ops_run_prexor(struct stripe_head *sh, s
}

static struct dma_async_tx_descriptor *
-ops_run_biodrain(struct stripe_head *sh, struct dma_async_tx_descriptor *tx,
- unsigned long ops_request)
+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, &ops_request);
+ int i;

pr_debug("%s: stripe %llu\n", __func__,
(unsigned long long)sh->sector);
@@ -666,20 +660,8 @@ ops_run_biodrain(struct stripe_head *sh,
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) {
+ if (test_and_clear_bit(R5_Wantdrain, &dev->flags)) {
struct bio *wbi;

spin_lock(&sh->lock);
@@ -704,18 +686,6 @@ ops_run_biodrain(struct stripe_head *sh,
static void ops_complete_postxor(void *stripe_head_ref)
{
struct stripe_head *sh = stripe_head_ref;
-
- pr_debug("%s: stripe %llu\n", __func__,
- (unsigned long long)sh->sector);
-
- sh->reconstruct_state = reconstruct_state_result;
- set_bit(STRIPE_HANDLE, &sh->state);
- release_stripe(sh);
-}
-
-static void ops_complete_write(void *stripe_head_ref)
-{
- struct stripe_head *sh = stripe_head_ref;
int disks = sh->disks, i, pd_idx = sh->pd_idx;

pr_debug("%s: stripe %llu\n", __func__,
@@ -727,14 +697,21 @@ static void ops_complete_write(void *str
set_bit(R5_UPTODATE, &dev->flags);
}

- sh->reconstruct_state = reconstruct_state_drain_result;
+ if (sh->reconstruct_state == reconstruct_state_drain_run)
+ sh->reconstruct_state = reconstruct_state_drain_result;
+ else if (sh->reconstruct_state == reconstruct_state_prexor_drain_run)
+ sh->reconstruct_state = reconstruct_state_prexor_drain_result;
+ else {
+ BUG_ON(sh->reconstruct_state != reconstruct_state_run);
+ sh->reconstruct_state = reconstruct_state_result;
+ }
+
set_bit(STRIPE_HANDLE, &sh->state);
release_stripe(sh);
}

static void
-ops_run_postxor(struct stripe_head *sh, struct dma_async_tx_descriptor *tx,
- unsigned long ops_request)
+ops_run_postxor(struct stripe_head *sh, struct dma_async_tx_descriptor *tx)
{
/* kernel stack size limits the total number of disks */
int disks = sh->disks;
@@ -742,9 +719,8 @@ ops_run_postxor(struct stripe_head *sh,

int count = 0, pd_idx = sh->pd_idx, i;
struct page *xor_dest;
- int prexor = test_bit(STRIPE_OP_PREXOR, &ops_request);
+ int prexor = 0;
unsigned long flags;
- dma_async_tx_callback callback;

pr_debug("%s: stripe %llu\n", __func__,
(unsigned long long)sh->sector);
@@ -752,7 +728,8 @@ ops_run_postxor(struct stripe_head *sh,
/* check if prexor is active which means only process blocks
* that are part of a read-modify-write (written)
*/
- if (prexor) {
+ if (sh->reconstruct_state == reconstruct_state_prexor_drain_run) {
+ prexor = 1;
xor_dest = xor_srcs[count++] = sh->dev[pd_idx].page;
for (i = disks; i--; ) {
struct r5dev *dev = &sh->dev[i];
@@ -768,10 +745,6 @@ ops_run_postxor(struct stripe_head *sh,
}
}

- /* check whether this postxor is part of a write */
- callback = test_bit(STRIPE_OP_BIODRAIN, &ops_request) ?
- ops_complete_write : ops_complete_postxor;
-
/* 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
@@ -785,10 +758,10 @@ ops_run_postxor(struct stripe_head *sh,
if (unlikely(count == 1)) {
flags &= ~(ASYNC_TX_XOR_DROP_DST | ASYNC_TX_XOR_ZERO_DST);
tx = async_memcpy(xor_dest, xor_srcs[0], 0, 0, STRIPE_SIZE,
- flags, tx, callback, sh);
+ flags, tx, ops_complete_postxor, sh);
} else
tx = async_xor(xor_dest, xor_srcs, 0, count, STRIPE_SIZE,
- flags, tx, callback, sh);
+ flags, tx, ops_complete_postxor, sh);
}

static void ops_complete_check(void *stripe_head_ref)
@@ -847,12 +820,12 @@ static void raid5_run_ops(struct stripe_
tx = ops_run_prexor(sh, tx);

if (test_bit(STRIPE_OP_BIODRAIN, &ops_request)) {
- tx = ops_run_biodrain(sh, tx, ops_request);
+ tx = ops_run_biodrain(sh, tx);
overlap_clear++;
}

if (test_bit(STRIPE_OP_POSTXOR, &ops_request))
- ops_run_postxor(sh, tx, ops_request);
+ ops_run_postxor(sh, tx);

if (test_bit(STRIPE_OP_CHECK, &ops_request))
ops_run_check(sh);
@@ -1669,6 +1642,7 @@ handle_write_operations5(struct stripe_h

if (dev->towrite) {
set_bit(R5_LOCKED, &dev->flags);
+ set_bit(R5_Wantdrain, &dev->flags);
if (!expand)
clear_bit(R5_UPTODATE, &dev->flags);
s->locked++;
@@ -1681,7 +1655,7 @@ handle_write_operations5(struct stripe_h
BUG_ON(!(test_bit(R5_UPTODATE, &sh->dev[pd_idx].flags) ||
test_bit(R5_Wantcompute, &sh->dev[pd_idx].flags)));

- sh->reconstruct_state = reconstruct_state_drain_run;
+ sh->reconstruct_state = reconstruct_state_prexor_drain_run;
set_bit(STRIPE_OP_PREXOR, &s->ops_request);
set_bit(STRIPE_OP_BIODRAIN, &s->ops_request);
set_bit(STRIPE_OP_POSTXOR, &s->ops_request);
@@ -1691,15 +1665,10 @@ handle_write_operations5(struct stripe_h
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);
+ test_bit(R5_Wantcompute, &dev->flags))) {
+ set_bit(R5_Wantdrain, &dev->flags);
set_bit(R5_LOCKED, &dev->flags);
clear_bit(R5_UPTODATE, &dev->flags);
s->locked++;
@@ -2660,11 +2629,11 @@ static void handle_stripe5(struct stripe
* completed
*/
prexor = 0;
- if (sh->reconstruct_state == reconstruct_state_drain_result) {
+ if (sh->reconstruct_state == reconstruct_state_prexor_drain_result)
+ prexor = 1;
+ if (sh->reconstruct_state == reconstruct_state_drain_result ||
+ sh->reconstruct_state == reconstruct_state_prexor_drain_result) {
sh->reconstruct_state = reconstruct_state_idle;
- for (i = disks; i--; )
- prexor += test_and_clear_bit(R5_Wantprexor,
- &sh->dev[i].flags);

/* All the 'written' buffers and the parity block are ready to
* be written back to disk
diff .prev/include/linux/raid/raid5.h ./include/linux/raid/raid5.h
--- .prev/include/linux/raid/raid5.h 2008-06-27 16:42:36.000000000 +1000
+++ ./include/linux/raid/raid5.h 2008-06-27 16:42:56.000000000 +1000
@@ -187,8 +187,10 @@ enum check_states {
*/
enum reconstruct_states {
reconstruct_state_idle = 0,
+ reconstruct_state_prexor_drain_run, /* prexor-write */
reconstruct_state_drain_run, /* write */
reconstruct_state_run, /* expand */
+ reconstruct_state_prexor_drain_result,
reconstruct_state_drain_result,
reconstruct_state_result,
};
@@ -258,9 +260,7 @@ struct r6_state {
#define R5_Wantfill 12 /* dev->toread contains a bio that needs
* filling
*/
-#define R5_Wantprexor 13 /* distinguish blocks ready for rmw from
- * other "towrites"
- */
+#define R5_Wantdrain 13 /* dev->towrite needs to be drained */
/*
* Write method
*/

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