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Subject[GIT PULL 28/58] lightnvm: pblk: simplify path on REQ_PREFLUSH
Date
From: Javier González <javier@cnexlabs.com>

On REQ_PREFLUSH, directly tag the I/O context flags to signal a flush in
the write to cache path, instead of finding the correct entry context
and imposing a memory barrier. This simplifies the code and might
potentially prevent race conditions when adding functionality to the
write path.

Signed-off-by: Javier González <javier@cnexlabs.com>
Signed-off-by: Matias Bjørling <m@bjorling.me>
---
drivers/lightnvm/pblk-cache.c | 4 +++-
drivers/lightnvm/pblk-rb.c | 8 +-------
2 files changed, 4 insertions(+), 8 deletions(-)

diff --git a/drivers/lightnvm/pblk-cache.c b/drivers/lightnvm/pblk-cache.c
index 1d6b8e3..0d227ef 100644
--- a/drivers/lightnvm/pblk-cache.c
+++ b/drivers/lightnvm/pblk-cache.c
@@ -43,8 +43,10 @@ int pblk_write_to_cache(struct pblk *pblk, struct bio *bio, unsigned long flags)
if (unlikely(!bio_has_data(bio)))
goto out;

+ pblk_ppa_set_empty(&w_ctx.ppa);
w_ctx.flags = flags;
- pblk_ppa_set_empty(&w_ctx.ppa);
+ if (bio->bi_opf & REQ_PREFLUSH)
+ w_ctx.flags |= PBLK_FLUSH_ENTRY;

for (i = 0; i < nr_entries; i++) {
void *data = bio_data(bio);
diff --git a/drivers/lightnvm/pblk-rb.c b/drivers/lightnvm/pblk-rb.c
index 74c768c..05e6b2e 100644
--- a/drivers/lightnvm/pblk-rb.c
+++ b/drivers/lightnvm/pblk-rb.c
@@ -355,7 +355,6 @@ static int pblk_rb_sync_point_set(struct pblk_rb *rb, struct bio *bio,
{
struct pblk_rb_entry *entry;
unsigned int subm, sync_point;
- int flags;

subm = READ_ONCE(rb->subm);

@@ -369,12 +368,6 @@ static int pblk_rb_sync_point_set(struct pblk_rb *rb, struct bio *bio,
sync_point = (pos == 0) ? (rb->nr_entries - 1) : (pos - 1);
entry = &rb->entries[sync_point];

- flags = READ_ONCE(entry->w_ctx.flags);
- flags |= PBLK_FLUSH_ENTRY;
-
- /* Release flags on context. Protect from writes */
- smp_store_release(&entry->w_ctx.flags, flags);
-
/* Protect syncs */
smp_store_release(&rb->sync_point, sync_point);

@@ -454,6 +447,7 @@ static int pblk_rb_may_write_flush(struct pblk_rb *rb, unsigned int nr_entries,

/* Protect from read count */
smp_store_release(&rb->mem, mem);
+
return 1;
}

--
2.9.3
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