Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
Date:   Wed, 20 Oct 2021 11:18:15 +0200
From:   Michal Hocko <mhocko@suse.com>
To:     Uladzislau Rezki <urezki@gmail.com>
Cc:     linux-mm@kvack.org, Dave Chinner <david@fromorbit.com>,
        Neil Brown <neilb@suse.de>,
        Andrew Morton <akpm@linux-foundation.org>,
        Christoph Hellwig <hch@infradead.org>,
        linux-fsdevel@vger.kernel.org, LKML <linux-kernel@vger.kernel.org>,
        Ilya Dryomov <idryomov@gmail.com>,
        Jeff Layton <jlayton@kernel.org>
Subject: Re: [RFC 2/3] mm/vmalloc: add support for __GFP_NOFAIL
Message-ID: <YW/e19fLyUy7ohR6@dhcp22.suse.cz>
References: <20211018114712.9802-1-mhocko@kernel.org>
 <20211018114712.9802-3-mhocko@kernel.org>
 <20211019110649.GA1933@pc638.lan>
 <YW6xZ7vi/7NVzRH5@dhcp22.suse.cz>
 <20211019194658.GA1787@pc638.lan>
 <YW/SYl/ZKp7W60mg@dhcp22.suse.cz>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <YW/SYl/ZKp7W60mg@dhcp22.suse.cz>
Precedence: bulk

On Wed 20-10-21 10:25:06, Michal Hocko wrote:
[...]
> > > The flag itself is not really necessary down there as long as we
> > > guarantee that the high level logic doesn't fail. In this case we keep
> > > retrying at __vmalloc_node_range level which should be possible to cover
> > > all callers that can control gfp mask. I was thinking to put it into
> > > __get_vm_area_node but that was slightly more hairy and we would be
> > > losing the warning which might turn out being helpful in cases where the
> > > failure is due to lack of vmalloc space or similar constrain. Btw. do we
> > > want some throttling on a retry?
> > > 
> > I think adding kind of schedule() will not make things worse and in corner
> > cases could prevent a power drain by CPU. It is important for mobile devices. 
> 
> I suspect you mean schedule_timeout here? Or cond_resched? I went with a
> later for now, I do not have a good idea for how to long to sleep here.
> I am more than happy to change to to a sleep though.

Forgot to paste the follow up I have staged currently
--- 
commit 66fea55e5543fa234692a70144cd63c7a1bca32f
Author: Michal Hocko <mhocko@suse.com>
Date:   Wed Oct 20 10:12:45 2021 +0200

    fold me "mm/vmalloc: add support for __GFP_NOFAIL"
    
    - add cond_resched

diff --git a/mm/vmalloc.c b/mm/vmalloc.c
index 0fb5413d9239..f7098e616883 100644
--- a/mm/vmalloc.c
+++ b/mm/vmalloc.c
@@ -2944,6 +2944,7 @@ static void *__vmalloc_area_node(struct vm_struct *area, gfp_t gfp_mask,
 	do {
 		ret = vmap_pages_range(addr, addr + size, prot, area->pages,
 			page_shift);
+		cond_resched();
 	} while ((gfp_mask & __GFP_NOFAIL) && (ret < 0));
 
 	if ((gfp_mask & (__GFP_FS | __GFP_IO)) == __GFP_IO)
@@ -3034,8 +3035,10 @@ void *__vmalloc_node_range(unsigned long size, unsigned long align,
 		warn_alloc(gfp_mask, NULL,
 			"vmalloc error: size %lu, vm_struct allocation failed",
 			real_size);
-		if (gfp_mask & __GFP_NOFAIL)
+		if (gfp_mask & __GFP_NOFAIL) {
+			cond_resched();
 			goto again;
+		}
 		goto fail;
 	}
 

-- 
Michal Hocko
SUSE Labs