linux-kernel - Re: [PATCH v2 2/4] mm/vmalloc: add support for __GFP

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Message-ID: <YaC7jij1hHtdOJdE@dhcp22.suse.cz>
Date:   Fri, 26 Nov 2021 11:48:46 +0100
From:   Michal Hocko <mhocko@...e.com>
To:     Andrew Morton <akpm@...ux-foundation.org>
Cc:     Dave Chinner <david@...morbit.com>, Neil Brown <neilb@...e.de>,
        Christoph Hellwig <hch@....de>,
        Uladzislau Rezki <urezki@...il.com>,
        linux-fsdevel@...r.kernel.org, linux-mm@...ck.org,
        LKML <linux-kernel@...r.kernel.org>,
        Ilya Dryomov <idryomov@...il.com>,
        Jeff Layton <jlayton@...nel.org>
Subject: Re: [PATCH v2 2/4] mm/vmalloc: add support for __GFP_NOFAIL

On Mon 22-11-21 16:32:31, Michal Hocko wrote:
> From: Michal Hocko <mhocko@...e.com>
> 
> Dave Chinner has mentioned that some of the xfs code would benefit from
> kvmalloc support for __GFP_NOFAIL because they have allocations that
> cannot fail and they do not fit into a single page.
> 
> The large part of the vmalloc implementation already complies with the
> given gfp flags so there is no work for those to be done. The area
> and page table allocations are an exception to that. Implement a retry
> loop for those.
> 
> Add a short sleep before retrying. 1 jiffy is a completely random
> timeout. Ideally the retry would wait for an explicit event - e.g.
> a change to the vmalloc space change if the failure was caused by
> the space fragmentation or depletion. But there are multiple different
> reasons to retry and this could become much more complex. Keep the retry
> simple for now and just sleep to prevent from hogging CPUs.
> 
> Signed-off-by: Michal Hocko <mhocko@...e.com>

Are there still any concerns around this patch or the approach in
general?
-- 
Michal Hocko
SUSE Labs