[PATCH v2 05/11] md/raid5: add scribble region for buffer lists

Dan Williams
2009-05-19T01:00:58Z

Hang some memory off of each stripe_head which can be used for storing
the buffer lists used in parity calculations. Include space for dma
address conversions and pass that to async_tx via the
async_submit_ctl.scribble pointer.

[ Impact: move memory pressure from stack to heap ]

Signed-off-by: Dan Williams <dan.j.williams@intel.com>
---
drivers/md/raid5.c | 61 ++++++++++++++++++++++++++++++++++++++++++----------
drivers/md/raid5.h | 5 ++++
2 files changed, 54 insertions(+), 12 deletions(-)

diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c
index e1920f2..0e456a6 100644
--- a/drivers/md/raid5.c
+++ b/drivers/md/raid5.c
@@ -275,6 +275,9 @@ static void shrink_buffers(struct stripe_head *sh, int num)
struct page *p;
int i;

+ kfree(sh->scribble);
+ sh->scribble = NULL;
+
for (i=0; i<num ; i++) {
p = sh->dev[i].page;
if (!p)
@@ -284,10 +287,26 @@ static void shrink_buffers(struct stripe_head *sh, int num)
}
}

+static size_t scribble_len(int num)
+{
+ size_t len;
+
+ /* return enough space for an array of page pointers and dma
+ * addresses for the ddf raid6 layout
+ */
+ len = sizeof(struct page *) * (num+2) + sizeof(addr_conv_t) * (num+2);
+
+ return len;
+}
+
static int grow_buffers(struct stripe_head *sh, int num)
{
int i;

+ sh->scribble = kmalloc(scribble_len(num), GFP_KERNEL);
+ if (!sh->scribble)
+ return 1;
+
for (i=0; i<num; i++) {
struct page *page;

@@ -641,11 +660,16 @@ static void ops_complete_compute5(void *stripe_head_ref)
release_stripe(sh);
}

+/* return a pointer to the address conversion region of the scribble buffer */
+static addr_conv_t *sh_to_addr_conv(struct stripe_head *sh)
+{
+ return sh->scribble + sizeof(struct page *) * (sh->disks + 2);
+}
+
static struct dma_async_tx_descriptor *ops_run_compute5(struct stripe_head *sh)
{
- /* kernel stack size limits the total number of disks */
int disks = sh->disks;
- struct page *xor_srcs[disks];
+ struct page **xor_srcs = sh->scribble;
int target = sh->ops.target;
struct r5dev *tgt = &sh->dev[target];
struct page *xor_dest = tgt->page;
@@ -665,7 +689,7 @@ static struct dma_async_tx_descriptor *ops_run_compute5(struct stripe_head *sh)
atomic_inc(&sh->count);

init_async_submit(&submit, ASYNC_TX_XOR_ZERO_DST, NULL,
- ops_complete_compute5, sh, NULL);
+ ops_complete_compute5, sh, sh_to_addr_conv(sh));
if (unlikely(count == 1))
tx = async_memcpy(xor_dest, xor_srcs[0], 0, 0, STRIPE_SIZE, &submit);
else
@@ -685,9 +709,8 @@ static void ops_complete_prexor(void *stripe_head_ref)
static struct dma_async_tx_descriptor *
ops_run_prexor(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];
+ struct page **xor_srcs = sh->scribble;
int count = 0, pd_idx = sh->pd_idx, i;
struct async_submit_ctl submit;

@@ -705,7 +728,7 @@ ops_run_prexor(struct stripe_head *sh, struct dma_async_tx_descriptor *tx)
}

init_async_submit(&submit, ASYNC_TX_XOR_DROP_DST, tx,
- ops_complete_prexor, sh, NULL);
+ ops_complete_prexor, sh, sh_to_addr_conv(sh));
tx = async_xor(xor_dest, xor_srcs, 0, count, STRIPE_SIZE, &submit);

return tx;
@@ -776,9 +799,8 @@ static void ops_complete_postxor(void *stripe_head_ref)
static void
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];
+ struct page **xor_srcs = sh->scribble;
struct async_submit_ctl submit;
int count = 0, pd_idx = sh->pd_idx, i;
struct page *xor_dest;
@@ -818,7 +840,8 @@ ops_run_postxor(struct stripe_head *sh, struct dma_async_tx_descriptor *tx)

atomic_inc(&sh->count);

- init_async_submit(&submit, flags, tx, ops_complete_postxor, sh, NULL);
+ init_async_submit(&submit, flags, tx, ops_complete_postxor, sh,
+ sh_to_addr_conv(sh));
if (unlikely(count == 1))
tx = async_memcpy(xor_dest, xor_srcs[0], 0, 0, STRIPE_SIZE, &submit);
else
@@ -839,9 +862,8 @@ static void ops_complete_check(void *stripe_head_ref)

static void ops_run_check(struct stripe_head *sh)
{
- /* kernel stack size limits the total number of disks */
int disks = sh->disks;
- struct page *xor_srcs[disks];
+ struct page **xor_srcs = sh->scribble;
struct dma_async_tx_descriptor *tx;
struct async_submit_ctl submit;

@@ -857,7 +879,7 @@ static void ops_run_check(struct stripe_head *sh)
xor_srcs[count++] = dev->page;
}

- init_async_submit(&submit, 0, NULL, NULL, NULL, NULL);
+ init_async_submit(&submit, 0, NULL, NULL, NULL, sh_to_addr_conv(sh));
tx = async_xor_val(xor_dest, xor_srcs, 0, count, STRIPE_SIZE,
&sh->ops.zero_sum_result, &submit);

@@ -871,6 +893,7 @@ static void raid5_run_ops(struct stripe_head *sh, unsigned long ops_request)
int overlap_clear = 0, i, disks = sh->disks;
struct dma_async_tx_descriptor *tx = NULL;

+ mutex_lock(&sh->scribble_lock);
if (test_bit(STRIPE_OP_BIOFILL, &ops_request)) {
ops_run_biofill(sh);
overlap_clear++;
@@ -903,6 +926,7 @@ static void raid5_run_ops(struct stripe_head *sh, unsigned long ops_request)
if (test_and_clear_bit(R5_Overlap, &dev->flags))
wake_up(&sh->raid_conf->wait_for_overlap);
}
+ mutex_unlock(&sh->scribble_lock);
}

static int grow_one_stripe(raid5_conf_t *conf)
@@ -914,6 +938,7 @@ static int grow_one_stripe(raid5_conf_t *conf)
memset(sh, 0, sizeof(*sh) + (conf->raid_disks-1)*sizeof(struct r5dev));
sh->raid_conf = conf;
spin_lock_init(&sh->lock);
+ mutex_init(&sh->scribble_lock);

if (grow_buffers(sh, conf->raid_disks)) {
shrink_buffers(sh, conf->raid_disks);
@@ -1007,6 +1032,7 @@ static int resize_stripes(raid5_conf_t *conf, int newsize)

nsh->raid_conf = conf;
spin_lock_init(&nsh->lock);
+ mutex_init(&nsh->scribble_lock);

list_add(&nsh->lru, &newstripes);
}
@@ -1038,6 +1064,7 @@ static int resize_stripes(raid5_conf_t *conf, int newsize)
nsh->dev[i].page = osh->dev[i].page;
for( ; i<newsize; i++)
nsh->dev[i].page = NULL;
+ nsh->scribble = osh->scribble;
kmem_cache_free(conf->slab_cache, osh);
}
kmem_cache_destroy(conf->slab_cache);
@@ -1058,8 +1085,18 @@ static int resize_stripes(raid5_conf_t *conf, int newsize)

/* Step 4, return new stripes to service */
while(!list_empty(&newstripes)) {
+ void *scribble;
+
nsh = list_entry(newstripes.next, struct stripe_head, lru);
list_del_init(&nsh->lru);
+
+ scribble = kmalloc(scribble_len(newsize), GFP_NOIO);
+ if (scribble) {
+ kfree(nsh->scribble);
+ nsh->scribble = scribble;
+ } else
+ err = -ENOMEM;
+
for (i=conf->raid_disks; i < newsize; i++)
if (nsh->dev[i].page == NULL) {
struct page *p = alloc_page(GFP_NOIO);
diff --git a/drivers/md/raid5.h b/drivers/md/raid5.h
index 52ba999..6ab0ccd 100644
--- a/drivers/md/raid5.h
+++ b/drivers/md/raid5.h
@@ -211,6 +211,11 @@ struct stripe_head {
int disks; /* disks in stripe */
enum check_states check_state;
enum reconstruct_states reconstruct_state;
+ void *scribble; /* space for constructing buffer
+ * lists and performing address
+ * conversions
+ */
+ struct mutex scribble_lock; /* no concurrent scribbling */
/* stripe_operations
* @target - STRIPE_OP_COMPUTE_BLK target
*/