On 02/28/2017 12:45 AM, Shaohua Li wrote:
> On Tue, Feb 21, 2017 at 08:43:56PM +0100, Artur Paszkiewicz wrote:
>> Attach a page for holding the partial parity data to stripe_head.
>> Allocate it only if mddev has the MD_HAS_PPL flag set.
>>
>> Partial parity is the xor of not modified data chunks of a stripe and is
>> calculated as follows:
>>
>> - reconstruct-write case:
>> xor data from all not updated disks in a stripe
>>
>> - read-modify-write case:
>> xor old data and parity from all updated disks in a stripe
>>
>> Implement it using the async_tx API and integrate into raid_run_ops().
>> It must be called when we still have access to old data, so do it when
>> STRIPE_OP_BIODRAIN is set, but before ops_run_prexor5(). The result is
>> stored into sh->ppl_page.
>>
>> Partial parity is not meaningful for full stripe write and is not stored
>> in the log or used for recovery, so don't attempt to calculate it when
>> stripe has STRIPE_FULL_WRITE.
>>
>> Signed-off-by: Artur Paszkiewicz <artur.paszkiewicz@xxxxxxxxx>
>> ---
>> drivers/md/raid5.c | 100 +++++++++++++++++++++++++++++++++++++++++++++++++++++
>> drivers/md/raid5.h | 3 ++
>> 2 files changed, 103 insertions(+)
>>
>> diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c
>> index 7b7722bb2e8d..02e02fe5b04e 100644
>> --- a/drivers/md/raid5.c
>> +++ b/drivers/md/raid5.c
>> @@ -463,6 +463,11 @@ static void shrink_buffers(struct stripe_head *sh)
>> sh->dev[i].page = NULL;
>> put_page(p);
>> }
>> +
>> + if (sh->ppl_page) {
>> + put_page(sh->ppl_page);
>> + sh->ppl_page = NULL;
>> + }
>> }
>>
>> static int grow_buffers(struct stripe_head *sh, gfp_t gfp)
>> @@ -479,6 +484,13 @@ static int grow_buffers(struct stripe_head *sh, gfp_t gfp)
>> sh->dev[i].page = page;
>> sh->dev[i].orig_page = page;
>> }
>> +
>> + if (test_bit(MD_HAS_PPL, &sh->raid_conf->mddev->flags)) {
>> + sh->ppl_page = alloc_page(gfp);
>> + if (!sh->ppl_page)
>> + return 1;
>> + }
>> +
>> return 0;
>> }
>>
>> @@ -1974,6 +1986,55 @@ static void ops_run_check_pq(struct stripe_head *sh, struct raid5_percpu *percpu
>> &sh->ops.zero_sum_result, percpu->spare_page, &submit);
>> }
>>
>> +static struct dma_async_tx_descriptor *
>> +ops_run_partial_parity(struct stripe_head *sh, struct raid5_percpu *percpu,
>> + struct dma_async_tx_descriptor *tx)
>> +{
>> + int disks = sh->disks;
>> + struct page **xor_srcs = flex_array_get(percpu->scribble, 0);
>> + int count = 0, pd_idx = sh->pd_idx, i;
>> + struct async_submit_ctl submit;
>> +
>> + pr_debug("%s: stripe %llu\n", __func__, (unsigned long long)sh->sector);
>> +
>> + /*
>> + * Partial parity is the XOR of stripe data chunks that are not changed
>> + * during the write request. Depending on available data
>> + * (read-modify-write vs. reconstruct-write case) we calculate it
>> + * differently.
>> + */
>> + if (sh->reconstruct_state == reconstruct_state_prexor_drain_run) {
>> + /* rmw: xor old data and parity from updated disks */
>> + for (i = disks; i--;) {
>> + struct r5dev *dev = &sh->dev[i];
>> + if (test_bit(R5_Wantdrain, &dev->flags) || i == pd_idx)
>> + xor_srcs[count++] = dev->page;
>> + }
>> + } else if (sh->reconstruct_state == reconstruct_state_drain_run) {
>> + /* rcw: xor data from all not updated disks */
>> + for (i = disks; i--;) {
>> + struct r5dev *dev = &sh->dev[i];
>> + if (test_bit(R5_UPTODATE, &dev->flags))
>> + xor_srcs[count++] = dev->page;
>> + }
>> + } else {
>> + return tx;
>> + }
>> +
>> + init_async_submit(&submit, ASYNC_TX_XOR_ZERO_DST, tx, NULL, sh,
>> + flex_array_get(percpu->scribble, 0)
>> + + sizeof(struct page *) * (sh->disks + 2));
>> +
>> + if (count == 1)
>> + tx = async_memcpy(sh->ppl_page, xor_srcs[0], 0, 0, PAGE_SIZE,
>> + &submit);
>> + else
>> + tx = async_xor(sh->ppl_page, xor_srcs, 0, count, PAGE_SIZE,
>> + &submit);
>> +
>> + return tx;
>> +}
>
> Can you put this function to raid5-ppl.c? I'd like to keep all the log related
> out raid5.c if possible.
Sure, I'll move it if you prefer that, but I thought that it's good to
have all the ops_run_ functions in one place.
Thanks,
Artur
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