Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
Date:   Fri, 1 Apr 2022 15:26:00 +0200
From:   David Sterba <dsterba@suse.cz>
To:     Sweet Tea Dorminy <sweettea-kernel@dorminy.me>
Cc:     dsterba@suse.cz, Chris Mason <clm@fb.com>,
        Josef Bacik <josef@toxicpanda.com>,
        David Sterba <dsterba@suse.com>,
        Nick Terrell <terrelln@fb.com>, linux-kernel@vger.kernel.org,
        linux-btrfs@vger.kernel.org, kernel-team@fb.com,
        Nikolay Borisov <nborisov@suse.com>
Subject: Re: [PATCH v3 2/2] btrfs: allocate page arrays using bulk page
 allocator
Message-ID: <20220401132600.GI15609@twin.jikos.cz>
Reply-To: dsterba@suse.cz
Mail-Followup-To: dsterba@suse.cz,
        Sweet Tea Dorminy <sweettea-kernel@dorminy.me>,
        Chris Mason <clm@fb.com>, Josef Bacik <josef@toxicpanda.com>,
        David Sterba <dsterba@suse.com>, Nick Terrell <terrelln@fb.com>,
        linux-kernel@vger.kernel.org, linux-btrfs@vger.kernel.org,
        kernel-team@fb.com, Nikolay Borisov <nborisov@suse.com>
References: <cover.1648669832.git.sweettea-kernel@dorminy.me>
 <ede1d39f7878ee2ed12c1526cc2ec358a2d862cf.1648669832.git.sweettea-kernel@dorminy.me>
 <20220331173525.GF15609@twin.jikos.cz>
 <f9493291-9981-d684-bf49-a551aaf08061@dorminy.me>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <f9493291-9981-d684-bf49-a551aaf08061@dorminy.me>
User-Agent: Mutt/1.5.23.1-rc1 (2014-03-12)
Precedence: bulk

On Thu, Mar 31, 2022 at 02:19:07PM -0400, Sweet Tea Dorminy wrote:
> > Also in the xfs code there's memalloc_retry_wait() which is supposed to be
> > called when repeated memory allocation is retried. What was the reason
> > you removed it?
> 
> Trying to keep the behavior as close as possible to the existing behavior.

I see, makes sense.

> The current behavior of each alloc_page loop is to fail if alloc_page() 
> fails; in the worst case, alloc_pages_bulk_array() calls alloc_page() 
> after trying to get a batch, so I figured the worst case is still 
> basically a loop calling alloc_page() and failing if it ever fails.
> 
> Reading up on it, though, arguably the memalloc_retry_wait() should 
> already be in all the callsites, so maybe I should insert a patch in the 
> middle that just adds the memalloc_retry_wait() into 
> btrfs_alloc_page_array()? Since it's an orthogonal fixup to either the 
> refactoring or the conversion to alloc_pages_bulk_array()?

Yeah a separate patch with the reasonig about the potential effects is
better. The v3 is now in misc-next with the suggested loop refactoring,
so please send the memalloc_retry_wait() update on top of that. Thanks.