[PATCH 22/27] aio: batch aio_kiocb allocation

[Jens Axboe <axboe@kernel.dk>]

Similarly to how we use the state->ios_left to know how many references
to get to a file, we can use it to allocate the aio_kiocb's we need in
bulk.

Signed-off-by: Jens Axboe <axboe@kernel.dk>
---
 fs/aio.c | 42 +++++++++++++++++++++++++++++++++++++-----
 1 file changed, 37 insertions(+), 5 deletions(-)

diff --git a/fs/aio.c b/fs/aio.c
index 341eb1b19319..426939f1dae9 100644
--- a/fs/aio.c
+++ b/fs/aio.c
@@ -230,6 +230,8 @@ struct aio_kiocb {
 	};
 };
 
+#define AIO_IOPOLL_BATCH	8
+
 struct aio_submit_state {
 	struct kioctx *ctx;
 
@@ -244,6 +246,13 @@ struct aio_submit_state {
 	struct list_head req_list;
 	unsigned int req_count;
 
+	/*
+	 * aio_kiocb alloc cache
+	 */
+	void *iocbs[AIO_IOPOLL_BATCH];
+	unsigned int free_iocbs;
+	unsigned int cur_iocb;
+
 	/*
 	 * File reference cache
 	 */
@@ -1102,11 +1111,32 @@ static void aio_iocb_init(struct kioctx *ctx, struct aio_kiocb *req)
  *	Allocate a slot for an aio request.
  * Returns NULL if no requests are free.
  */
-static inline struct aio_kiocb *aio_get_req(struct kioctx *ctx)
+static struct aio_kiocb *aio_get_req(struct kioctx *ctx,
+				     struct aio_submit_state *state)
 {
 	struct aio_kiocb *req;
 
-	req = kmem_cache_alloc(kiocb_cachep, GFP_KERNEL);
+	if (!state)
+		req = kmem_cache_alloc(kiocb_cachep, GFP_KERNEL);
+	else if (!state->free_iocbs) {
+		size_t size;
+
+		size = min_t(size_t, state->ios_left, ARRAY_SIZE(state->iocbs));
+		size = kmem_cache_alloc_bulk(kiocb_cachep, GFP_KERNEL, size,
+						state->iocbs);
+		if (size < 0)
+			return ERR_PTR(size);
+		else if (!size)
+			return ERR_PTR(-ENOMEM);
+		state->free_iocbs = size - 1;
+		state->cur_iocb = 1;
+		req = state->iocbs[0];
+	} else {
+		req = state->iocbs[state->cur_iocb];
+		state->free_iocbs--;
+		state->cur_iocb++;
+	}
+
 	if (req)
 		aio_iocb_init(ctx, req);
 
@@ -1347,8 +1377,6 @@ static bool aio_read_events(struct kioctx *ctx, long min_nr, long nr,
 	return ret < 0 || *i >= min_nr;
 }
 
-#define AIO_IOPOLL_BATCH	8
-
 /*
  * Process completed iocb iopoll entries, copying the result to userspace.
  */
@@ -2320,7 +2348,7 @@ static int __io_submit_one(struct kioctx *ctx, const struct iocb *iocb,
 		return -EAGAIN;
 
 	ret = -EAGAIN;
-	req = aio_get_req(ctx);
+	req = aio_get_req(ctx, state);
 	if (unlikely(!req))
 		goto out_put_reqs_available;
 
@@ -2452,6 +2480,9 @@ static void aio_submit_state_end(struct aio_submit_state *state)
 	if (!list_empty(&state->req_list))
 		aio_flush_state_reqs(state->ctx, state);
 	aio_file_put(state);
+	if (state->free_iocbs)
+		kmem_cache_free_bulk(kiocb_cachep, state->free_iocbs,
+					&state->iocbs[state->cur_iocb]);
 }
 
 /*
@@ -2463,6 +2494,7 @@ static void aio_submit_state_start(struct aio_submit_state *state,
 	state->ctx = ctx;
 	INIT_LIST_HEAD(&state->req_list);
 	state->req_count = 0;
+	state->free_iocbs = 0;
 	state->file = NULL;
 	state->ios_left = max_ios;
 #ifdef CONFIG_BLOCK
-- 
2.17.1