linux-kernel - [PATCH 4.19 068/100] aio: separate out ring reservation from req allocation

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Date:   Tue, 30 Apr 2019 13:38:37 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Christoph Hellwig <hch@....de>,
        Jens Axboe <axboe@...nel.dk>,
        Guenter Roeck <linux@...ck-us.net>
Subject: [PATCH 4.19 068/100] aio: separate out ring reservation from req allocation

From: Christoph Hellwig <hch@....de>

commit 432c79978c33ecef91b1b04cea6936c20810da29 upstream.

This is in preparation for certain types of IO not needing a ring
reserveration.

Signed-off-by: Christoph Hellwig <hch@....de>
Signed-off-by: Jens Axboe <axboe@...nel.dk>
Cc: Guenter Roeck <linux@...ck-us.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 fs/aio.c |   30 +++++++++++++++++-------------
 1 file changed, 17 insertions(+), 13 deletions(-)

--- a/fs/aio.c
+++ b/fs/aio.c
@@ -902,7 +902,7 @@ static void put_reqs_available(struct ki
 	local_irq_restore(flags);
 }
 
-static bool get_reqs_available(struct kioctx *ctx)
+static bool __get_reqs_available(struct kioctx *ctx)
 {
 	struct kioctx_cpu *kcpu;
 	bool ret = false;
@@ -994,6 +994,14 @@ static void user_refill_reqs_available(s
 	spin_unlock_irq(&ctx->completion_lock);
 }
 
+static bool get_reqs_available(struct kioctx *ctx)
+{
+	if (__get_reqs_available(ctx))
+		return true;
+	user_refill_reqs_available(ctx);
+	return __get_reqs_available(ctx);
+}
+
 /* aio_get_req
  *	Allocate a slot for an aio request.
  * Returns NULL if no requests are free.
@@ -1002,24 +1010,15 @@ static inline struct aio_kiocb *aio_get_
 {
 	struct aio_kiocb *req;
 
-	if (!get_reqs_available(ctx)) {
-		user_refill_reqs_available(ctx);
-		if (!get_reqs_available(ctx))
-			return NULL;
-	}
-
 	req = kmem_cache_alloc(kiocb_cachep, GFP_KERNEL|__GFP_ZERO);
 	if (unlikely(!req))
-		goto out_put;
+		return NULL;
 
 	percpu_ref_get(&ctx->reqs);
 	INIT_LIST_HEAD(&req->ki_list);
 	refcount_set(&req->ki_refcnt, 0);
 	req->ki_ctx = ctx;
 	return req;
-out_put:
-	put_reqs_available(ctx, 1);
-	return NULL;
 }
 
 static struct kioctx *lookup_ioctx(unsigned long ctx_id)
@@ -1813,9 +1812,13 @@ static int io_submit_one(struct kioctx *
 		return -EINVAL;
 	}
 
+	if (!get_reqs_available(ctx))
+		return -EAGAIN;
+
+	ret = -EAGAIN;
 	req = aio_get_req(ctx);
 	if (unlikely(!req))
-		return -EAGAIN;
+		goto out_put_reqs_available;
 
 	if (iocb.aio_flags & IOCB_FLAG_RESFD) {
 		/*
@@ -1878,11 +1881,12 @@ static int io_submit_one(struct kioctx *
 		goto out_put_req;
 	return 0;
 out_put_req:
-	put_reqs_available(ctx, 1);
 	percpu_ref_put(&ctx->reqs);
 	if (req->ki_eventfd)
 		eventfd_ctx_put(req->ki_eventfd);
 	kmem_cache_free(kiocb_cachep, req);
+out_put_reqs_available:
+	put_reqs_available(ctx, 1);
 	return ret;
 }