by Hans Holmberg

[permalink] [raw]

Subject: [PATCH v2] lightnvm: pblk: clear flush point on completed writes

Move completion of syncs and clearing of flush points to the
write completion path - this ensures that the data has been
comitted to the media before completing bios containing syncs.

Signed-off-by: Hans Holmberg <[email protected]>
Signed-off-by: Javier González <[email protected]>
---

Changes since v1:

* Fixed an off-by one issue when clearing flush points

drivers/lightnvm/pblk-rb.c | 58 +++++++++++++++++++++----------------------
drivers/lightnvm/pblk-write.c | 17 ++++++++++++-
2 files changed, 44 insertions(+), 31 deletions(-)

diff --git a/drivers/lightnvm/pblk-rb.c b/drivers/lightnvm/pblk-rb.c
index 2c61d74..fe5465d 100644
--- a/drivers/lightnvm/pblk-rb.c
+++ b/drivers/lightnvm/pblk-rb.c
@@ -353,17 +353,17 @@ static int pblk_rb_flush_point_set(struct pblk_rb *rb, struct bio *bio,
unsigned int pos)
{
struct pblk_rb_entry *entry;
- unsigned int subm, flush_point;
+ unsigned int sync, flush_point;

- subm = READ_ONCE(rb->subm);
+ sync = READ_ONCE(rb->sync);
+
+ if (pos == sync)
+ return 0;

#ifdef CONFIG_NVM_DEBUG
atomic_inc(&rb->inflight_flush_point);
#endif

- if (pos == subm)
- return 0;
-
flush_point = (pos == 0) ? (rb->nr_entries - 1) : (pos - 1);
entry = &rb->entries[flush_point];

@@ -604,22 +604,6 @@ unsigned int pblk_rb_read_to_bio(struct pblk_rb *rb, struct nvm_rq *rqd,
return NVM_IO_ERR;
}

- if (flags & PBLK_FLUSH_ENTRY) {
- unsigned int flush_point;
-
- flush_point = READ_ONCE(rb->flush_point);
- if (flush_point == pos) {
- /* Protect flush points */
- smp_store_release(&rb->flush_point,
- EMPTY_ENTRY);
- }
-
- flags &= ~PBLK_FLUSH_ENTRY;
-#ifdef CONFIG_NVM_DEBUG
- atomic_dec(&rb->inflight_flush_point);
-#endif
- }
-
flags &= ~PBLK_WRITTEN_DATA;
flags |= PBLK_SUBMITTED_ENTRY;

@@ -735,15 +719,24 @@ void pblk_rb_sync_end(struct pblk_rb *rb, unsigned long *flags)

unsigned int pblk_rb_sync_advance(struct pblk_rb *rb, unsigned int nr_entries)
{
- unsigned int sync;
- unsigned int i;
-
+ unsigned int sync, flush_point;
lockdep_assert_held(&rb->s_lock);

sync = READ_ONCE(rb->sync);
+ flush_point = READ_ONCE(rb->flush_point);

- for (i = 0; i < nr_entries; i++)
- sync = (sync + 1) & (rb->nr_entries - 1);
+ if (flush_point != EMPTY_ENTRY) {
+ unsigned int secs_to_flush;
+
+ secs_to_flush = pblk_rb_ring_count(flush_point, sync,
+ rb->nr_entries);
+ if (secs_to_flush < nr_entries) {
+ /* Protect flush points */
+ smp_store_release(&rb->flush_point, EMPTY_ENTRY);
+ }
+ }
+
+ sync = (sync + nr_entries) & (rb->nr_entries - 1);

/* Protect from counts */
smp_store_release(&rb->sync, sync);
@@ -751,22 +744,27 @@ unsigned int pblk_rb_sync_advance(struct pblk_rb *rb, unsigned int nr_entries)
return sync;
}

+/* Calculate how many sectors to submit up to the current flush point. */
unsigned int pblk_rb_flush_point_count(struct pblk_rb *rb)
{
- unsigned int subm, flush_point;
- unsigned int count;
+ unsigned int subm, sync, flush_point;
+ unsigned int submitted, to_flush;

/* Protect flush points */
flush_point = smp_load_acquire(&rb->flush_point);
if (flush_point == EMPTY_ENTRY)
return 0;

+ /* Protect syncs */
+ sync = smp_load_acquire(&rb->sync);
+
subm = READ_ONCE(rb->subm);
+ submitted = pblk_rb_ring_count(subm, sync, rb->nr_entries);

/* The sync point itself counts as a sector to sync */
- count = pblk_rb_ring_count(flush_point, subm, rb->nr_entries) + 1;
+ to_flush = pblk_rb_ring_count(flush_point, sync, rb->nr_entries) + 1;

- return count;
+ return (submitted < to_flush) ? (to_flush - submitted) : 0;
}

/*
diff --git a/drivers/lightnvm/pblk-write.c b/drivers/lightnvm/pblk-write.c
index 018af87..aae86ed 100644
--- a/drivers/lightnvm/pblk-write.c
+++ b/drivers/lightnvm/pblk-write.c
@@ -21,13 +21,28 @@ static unsigned long pblk_end_w_bio(struct pblk *pblk, struct nvm_rq *rqd,
struct pblk_c_ctx *c_ctx)
{
struct bio *original_bio;
+ struct pblk_rb *rwb = &pblk->rwb;
unsigned long ret;
int i;

for (i = 0; i < c_ctx->nr_valid; i++) {
struct pblk_w_ctx *w_ctx;
+ int pos = c_ctx->sentry + i;
+ int flags;
+
+ w_ctx = pblk_rb_w_ctx(rwb, pos);
+ flags = READ_ONCE(w_ctx->flags);
+
+ if (flags & PBLK_FLUSH_ENTRY) {
+ flags &= ~PBLK_FLUSH_ENTRY;
+ /* Release flags on context. Protect from writes */
+ smp_store_release(&w_ctx->flags, flags);
+
+#ifdef CONFIG_NVM_DEBUG
+ atomic_dec(&rwb->inflight_flush_point);
+#endif
+ }

- w_ctx = pblk_rb_w_ctx(&pblk->rwb, c_ctx->sentry + i);
while ((original_bio = bio_list_pop(&w_ctx->bios)))
bio_endio(original_bio);
}
--
2.7.4