lightnvm: pblk: simplify path on REQ_PREFLUSH

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>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/drivers/lightnvm/pblk-cache.c b/drivers/lightnvm/pblk-cache.c
index 1d6b8e3..0d227ef 100644 (file)
--- a/drivers/lightnvm/pblk-cache.c
+++ b/drivers/lightnvm/pblk-cache.c
@@ -43,8 +43,10 @@ retry:
        if (unlikely(!bio_has_data(bio)))
                goto out;
 
-       w_ctx.flags = flags;
        pblk_ppa_set_empty(&w_ctx.ppa);
+       w_ctx.flags = flags;
+       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 (file)
--- 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;
 }