linux-ext4 - Re: [PATCH] mm: introduce kv[mz]alloc helpers

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Date:   Mon, 02 Jan 2017 07:55:22 -0800
From:   Joe Perches <joe@...ches.com>
To:     Michal Hocko <mhocko@...nel.org>,
        Andrew Morton <akpm@...ux-foundation.org>
Cc:     Vlastimil Babka <vbabka@...e.cz>,
        David Rientjes <rientjes@...gle.com>,
        Mel Gorman <mgorman@...e.de>,
        Johannes Weiner <hannes@...xchg.org>,
        Al Viro <viro@...iv.linux.org.uk>, linux-mm@...ck.org,
        LKML <linux-kernel@...r.kernel.org>, kvm@...r.kernel.org,
        linux-f2fs-devel@...ts.sourceforge.net,
        linux-security-module@...r.kernel.org, linux-ext4@...r.kernel.org,
        Michal Hocko <mhocko@...e.com>,
        Anatoly Stepanov <astepanov@...udlinux.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Mike Snitzer <snitzer@...hat.com>,
        "Michael S. Tsirkin" <mst@...hat.com>,
        Theodore Ts'o <tytso@....edu>,
        Andreas Dilger <adilger@...ger.ca>
Subject: Re: [PATCH] mm: introduce kv[mz]alloc helpers

On Mon, 2017-01-02 at 14:37 +0100, Michal Hocko wrote:
> From: Michal Hocko <mhocko@...e.com>
> 
> Using kmalloc with the vmalloc fallback for larger allocations is a
> common pattern in the kernel code. Yet we do not have any common helper
> for that and so users have invented their own helpers. Some of them are
> really creative when doing so. Let's just add kv[mz]alloc and make sure
> it is implemented properly. This implementation makes sure to not make
> a large memory pressure for > PAGE_SZE requests (__GFP_NORETRY) and also
> to not warn about allocation failures. This also rules out the OOM
> killer as the vmalloc is a more approapriate fallback than a disruptive
> user visible action.
> 
> This patch also changes some existing users and removes helpers which
> are specific for them. In some cases this is not possible (e.g.
> ext4_kvmalloc, libcfs_kvzalloc, __aa_kvmalloc) because those seems to be
> broken and require GFP_NO{FS,IO} context which is not vmalloc compatible
> in general (note that the page table allocation is GFP_KERNEL). Those
> need to be fixed separately.
> 
> apparmor has already claimed kv[mz]alloc so remove those and use
> __aa_kvmalloc instead to prevent from the naming clashes.

I have no real objection but perhaps this would
be better done as 3 or more patches

o rename apparmor uses
o introduce generic
o conversions to generic

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