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md: replace R5_WantPrexor with R5_WantDrain, add 'prexor' reconstruct…
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…_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>
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Dan Williams authored and Neil Brown committed Jun 27, 2008
1 parent 600aa10 commit d8ee072
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Showing 2 changed files with 32 additions and 63 deletions.
89 changes: 29 additions & 60 deletions drivers/md/raid5.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -637,7 +637,7 @@ ops_run_prexor(struct stripe_head *sh, struct dma_async_tx_descriptor *tx)
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;
}

Expand All @@ -649,37 +649,19 @@ ops_run_prexor(struct stripe_head *sh, struct dma_async_tx_descriptor *tx)
}

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);

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);
Expand All @@ -702,18 +684,6 @@ ops_run_biodrain(struct stripe_head *sh, struct dma_async_tx_descriptor *tx,
}

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;
Expand All @@ -727,32 +697,39 @@ static void ops_complete_write(void *stripe_head_ref)
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;
struct page *xor_srcs[disks];

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);

/* 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];
Expand All @@ -768,10 +745,6 @@ ops_run_postxor(struct stripe_head *sh, struct dma_async_tx_descriptor *tx,
}
}

/* 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
Expand All @@ -785,10 +758,10 @@ ops_run_postxor(struct stripe_head *sh, struct dma_async_tx_descriptor *tx,
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)
Expand Down Expand Up @@ -847,12 +820,12 @@ static void raid5_run_ops(struct stripe_head *sh, unsigned long ops_request)
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);
Expand Down Expand Up @@ -1669,6 +1642,7 @@ handle_write_operations5(struct stripe_head *sh, struct stripe_head_state *s,

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++;
Expand All @@ -1681,7 +1655,7 @@ handle_write_operations5(struct stripe_head *sh, struct stripe_head_state *s,
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);
Expand All @@ -1691,15 +1665,10 @@ handle_write_operations5(struct stripe_head *sh, struct stripe_head_state *s,
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++;
Expand Down Expand Up @@ -2660,11 +2629,11 @@ static void handle_stripe5(struct stripe_head *sh)
* 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
Expand Down
6 changes: 3 additions & 3 deletions include/linux/raid/raid5.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -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,
};
Expand Down Expand Up @@ -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
*/
Expand Down

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