linux-kernel - Re: [PATCH v3 2/2] vfs: avoid duplicating creds in faccessat if possible

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Message-ID: <CAGudoHFUkchB93rvOSFgBxkLJWT59hyGs==uTcvtO3pKyekxvQ@mail.gmail.com>
Date:   Thu, 2 Mar 2023 19:51:55 +0100
From:   Mateusz Guzik <mjguzik@...il.com>
To:     Al Viro <viro@...iv.linux.org.uk>
Cc:     Linus Torvalds <torvalds@...ux-foundation.org>,
        Christian Brauner <brauner@...nel.org>, serge@...lyn.com,
        paul@...l-moore.com, linux-fsdevel@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-security-module@...r.kernel.org
Subject: Re: [PATCH v3 2/2] vfs: avoid duplicating creds in faccessat if possible

On 3/2/23, Al Viro <viro@...iv.linux.org.uk> wrote:
> On Thu, Mar 02, 2023 at 07:22:17PM +0100, Mateusz Guzik wrote:
>
>> Ops, I meant "names_cache", here:
>> 	names_cachep = kmem_cache_create_usercopy("names_cache", PATH_MAX, 0,
>> 			SLAB_HWCACHE_ALIGN|SLAB_PANIC, 0, PATH_MAX, NULL);
>>
>> it is fs/dcache.c and I brainfarted into the above.
>
> So you mean __getname() stuff?
>

yes. do some lookups in a loop on a kernel built with
CONFIG_INIT_ON_ALLOC_DEFAULT_ON=y (there may be a runtime switch for
it?) and  you will see memset using most time in perf top

-- 
Mateusz Guzik <mjguzik gmail.com>