The number of outstanding kiocbs is one of the few shared things left
that has to be touched for every kiocb - it'd be nice to make it percpu.
We can make it per cpu by treating it like an allocation problem: we
have a maximum number of kiocbs that can be outstanding (i.e. slots) -
then we just allocate and free slots, and we know how to write per cpu
allocators.
So as prep work for that, we convert reqs_active to reqs_available.
Signed-off-by: Kent Overstreet <koverstr...@google.com>
---
fs/aio.c | 29 ++++++++++++++---------------
1 file changed, 14 insertions(+), 15 deletions(-)
diff --git a/fs/aio.c b/fs/aio.c
index 7dee3aa..e6f29dc 100644
--- a/fs/aio.c
+++ b/fs/aio.c
@@ -79,7 +79,7 @@ struct kioctx {
long nr_pages;
struct {
- atomic_t reqs_active;
+ atomic_t reqs_available;
} ____cacheline_aligned;
struct {
@@ -301,17 +301,17 @@ static void free_ioctx(struct kioctx *ctx)
head = ring->head;
kunmap_atomic(ring);
- while (atomic_read(&ctx->reqs_active) > 0) {
+ while (atomic_read(&ctx->reqs_available) < ctx->nr) {
wait_event(ctx->wait, head != ctx->tail);
avail = (head < ctx->tail ? ctx->tail : ctx->nr) - head;
- atomic_sub(avail, &ctx->reqs_active);
+ atomic_add(avail, &ctx->reqs_available);
head += avail;
head %= ctx->nr;
}
- WARN_ON(atomic_read(&ctx->reqs_active) < 0);
+ WARN_ON(atomic_read(&ctx->reqs_available) > ctx->nr);
aio_free_ring(ctx);
@@ -368,6 +368,8 @@ static struct kioctx *ioctx_alloc(unsigned nr_events)
if (aio_setup_ring(ctx) < 0)
goto out_freectx;
+ atomic_set(&ctx->reqs_available, ctx->nr);
+
/* limit the number of system wide aios */
spin_lock(&aio_nr_lock);
if (aio_nr + nr_events > aio_max_nr ||
@@ -448,7 +450,7 @@ void exit_aio(struct mm_struct *mm)
"exit_aio:ioctx still alive: %d %d %d\n",
atomic_read(&ctx->users),
atomic_read(&ctx->dead),
- atomic_read(&ctx->reqs_active));
+ atomic_read(&ctx->reqs_available));
/*
* We don't need to bother with munmap() here -
* exit_mmap(mm) is coming and it'll unmap everything.
@@ -476,12 +478,9 @@ static inline struct kiocb *aio_get_req(struct kioctx *ctx)
{
struct kiocb *req;
- if (atomic_read(&ctx->reqs_active) >= ctx->nr)
+ if (atomic_dec_if_positive(&ctx->reqs_available) <= 0)
return NULL;
- if (atomic_inc_return(&ctx->reqs_active) > ctx->nr)
- goto out_put;
-
req = kmem_cache_alloc(kiocb_cachep, GFP_KERNEL|__GFP_ZERO);
if (unlikely(!req))
goto out_put;
@@ -491,7 +490,7 @@ static inline struct kiocb *aio_get_req(struct kioctx *ctx)
return req;
out_put:
- atomic_dec(&ctx->reqs_active);
+ atomic_inc(&ctx->reqs_available);
return NULL;
}
@@ -565,7 +564,7 @@ void aio_complete(struct kiocb *iocb, long res, long res2)
/*
* Take rcu_read_lock() in case the kioctx is being destroyed, as we
- * need to issue a wakeup after decrementing reqs_active.
+ * need to issue a wakeup after incrementing reqs_available.
*/
rcu_read_lock();
@@ -582,7 +581,7 @@ void aio_complete(struct kiocb *iocb, long res, long res2)
* when the event got cancelled.
*/
if (test_and_set_bit(KIF_CANCELLED, &iocb->ki_flags)) {
- atomic_dec(&ctx->reqs_active);
+ atomic_inc(&ctx->reqs_available);
/* Still need the wake_up in case free_ioctx is waiting */
goto put_rq;
}
@@ -707,7 +706,7 @@ static int aio_read_events(struct kioctx *ctx, struct
io_event __user *event,
ring->head = head;
kunmap_atomic(ring);
- atomic_sub(ret, &ctx->reqs_active);
+ atomic_add(ret, &ctx->reqs_available);
pr_debug("%d h%u t%u\n", ret, head, ctx->tail);
out:
@@ -770,7 +769,7 @@ static int read_events(struct kioctx *ctx,
break;
/* Try to only show up in io wait if there are ops in flight */
- if (atomic_read(&ctx->reqs_active))
+ if (atomic_read(&ctx->reqs_available) != ctx->nr)
io_schedule();
else
schedule();
@@ -1161,7 +1160,7 @@ static int io_submit_one(struct kioctx *ctx, struct iocb
__user *user_iocb,
return 0;
out_put_req:
- atomic_dec(&ctx->reqs_active);
+ atomic_inc(&ctx->reqs_available);
aio_put_req(req); /* drop extra ref to req */
aio_put_req(req); /* drop i/o ref to req */
return ret;
--
1.7.12
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