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;
+}
+
static void raid_run_ops(struct stripe_head *sh, unsigned long ops_request)
{
int overlap_clear = 0, i, disks = sh->disks;
@@ -2004,6 +2065,9 @@ static void raid_run_ops(struct stripe_head *sh, unsigned long ops_request)
async_tx_ack(tx);
}
+ if (test_bit(STRIPE_OP_PARTIAL_PARITY, &ops_request))
+ tx = ops_run_partial_parity(sh, percpu, tx);
+
if (test_bit(STRIPE_OP_PREXOR, &ops_request)) {
if (level < 6)
tx = ops_run_prexor5(sh, percpu, tx);
@@ -3079,6 +3143,12 @@ schedule_reconstruction(struct stripe_head *sh, struct stripe_head_state *s,
s->locked++;
}
+ if (level == 5 && sh->ppl_page &&
+ test_bit(STRIPE_OP_BIODRAIN, &s->ops_request) &&
+ !test_bit(STRIPE_FULL_WRITE, &sh->state) &&
+ test_bit(R5_Insync, &sh->dev[pd_idx].flags))
+ set_bit(STRIPE_OP_PARTIAL_PARITY, &s->ops_request);
+
pr_debug("%s: stripe %llu locked: %d ops_request: %lx\n",
__func__, (unsigned long long)sh->sector,
s->locked, s->ops_request);
@@ -3126,6 +3196,36 @@ static int add_stripe_bio(struct stripe_head *sh, struct bio *bi, int dd_idx,
if (*bip && (*bip)->bi_iter.bi_sector < bio_end_sector(bi))
goto overlap;
+ if (forwrite && sh->ppl_page) {
+ /*
+ * With PPL only writes to consecutive data chunks within a
+ * stripe are allowed because for a single stripe_head we can
+ * only have one PPL entry at a time, which describes one data
+ * range. Not really an overlap, but wait_for_overlap can be
+ * used to handle this.
+ */
+ sector_t sector;
+ sector_t first = 0;
+ sector_t last = 0;
+ int count = 0;
+ int i;
+
+ for (i = 0; i < sh->disks; i++) {
+ if (i != sh->pd_idx &&
+ (i == dd_idx || sh->dev[i].towrite)) {
+ sector = sh->dev[i].sector;
+ if (count == 0 || sector < first)
+ first = sector;
+ if (sector > last)
+ last = sector;
+ count++;
+ }
+ }
+
+ if (first + conf->chunk_sectors * (count - 1) != last)
+ goto overlap;
+ }
+
if (!forwrite || previous)
clear_bit(STRIPE_BATCH_READY, &sh->state);
diff --git a/drivers/md/raid5.h b/drivers/md/raid5.h
index 4bb27b97bf6b..3cc4cb28f7e6 100644
--- a/drivers/md/raid5.h
+++ b/drivers/md/raid5.h
@@ -228,6 +228,8 @@ struct stripe_head {
struct list_head log_list;
sector_t log_start; /* first meta block on the journal */
struct list_head r5c; /* for r5c_cache->stripe_in_journal */
+
+ struct page *ppl_page; /* partial parity of this stripe */
/**
* struct stripe_operations
* @target - STRIPE_OP_COMPUTE_BLK target
@@ -400,6 +402,7 @@ enum {
STRIPE_OP_BIODRAIN,
STRIPE_OP_RECONSTRUCT,
STRIPE_OP_CHECK,
+ STRIPE_OP_PARTIAL_PARITY,
};
/*
--
2.11.0
--
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