Received-SPF: softfail (google.com: domain of transitioning linux-kernel-owner@vger.kernel.org does not designate 23.128.96.19 as permitted sender) client-ip=23.128.96.19;
Date:   Tue, 17 May 2022 16:39:16 -0700
From:   Andrew Morton <akpm@linux-foundation.org>
To:     Miaohe Lin <linmiaohe@huawei.com>
Cc:     NeilBrown <neilb@suse.de>, <willy@infradead.org>, <vbabka@suse.cz>,
        <dhowells@redhat.com>, <apopple@nvidia.com>, <david@redhat.com>,
        <surenb@google.com>, <peterx@redhat.com>,
        <naoya.horiguchi@nec.com>, <linux-mm@kvack.org>,
        <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH 11/15] mm/swap: add helper swap_offset_available()
Message-Id: <20220517163916.71ab9aa1ec095bbc57b82f98@linux-foundation.org>
In-Reply-To: <9319a62b-f43d-8ee9-77b9-a1afee7dbc10@huawei.com>
References: <20220509131416.17553-1-linmiaohe@huawei.com>
        <20220509131416.17553-12-linmiaohe@huawei.com>
        <165214355418.14782.13896859043718755300@noble.neil.brown.name>
        <9319a62b-f43d-8ee9-77b9-a1afee7dbc10@huawei.com>
Mime-Version: 1.0
Content-Type: text/plain; charset=US-ASCII
Content-Transfer-Encoding: 7bit
Precedence: bulk

On Tue, 10 May 2022 10:03:19 +0800 Miaohe Lin <linmiaohe@huawei.com> wrote:

> On 2022/5/10 8:45, NeilBrown wrote:
> > On Mon, 09 May 2022, Miaohe Lin wrote:
> >> Add helper swap_offset_available() to remove some duplicated codes.
> >> Minor readability improvement.
> > 
> > I don't think that putting the spin_lock() inside the inline helper is
> > good for readability.
> > If the function was called
> >    swap_offset_available_and_locked()
> 
> Yes, swap_offset_available_and_locked should be more suitable as we do the spin_lock
> inside it. Will do this in next version.
> 

--- a/mm/swapfile.c~mm-swap-add-helper-swap_offset_available-fix
+++ a/mm/swapfile.c
@@ -775,7 +775,8 @@ static void set_cluster_next(struct swap
 	this_cpu_write(*si->cluster_next_cpu, next);
 }
 
-static inline bool swap_offset_available(struct swap_info_struct *si, unsigned long offset)
+static bool swap_offset_available_and_locked(struct swap_info_struct *si,
+					     unsigned long offset)
 {
 	if (data_race(!si->swap_map[offset])) {
 		spin_lock(&si->lock);
@@ -967,7 +968,7 @@ done:
 scan:
 	spin_unlock(&si->lock);
 	while (++offset <= READ_ONCE(si->highest_bit)) {
-		if (swap_offset_available(si, offset))
+		if (swap_offset_available_and_locked(si, offset))
 			goto checks;
 		if (unlikely(--latency_ration < 0)) {
 			cond_resched();
@@ -977,7 +978,7 @@ scan:
 	}
 	offset = si->lowest_bit;
 	while (offset < scan_base) {
-		if (swap_offset_available(si, offset))
+		if (swap_offset_available_and_locked(si, offset))
 			goto checks;
 		if (unlikely(--latency_ration < 0)) {
 			cond_resched();
_