linux-kernel - Re: [PATCH] NFS: allow name_to_handle

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Message-ID: <CA+55aFxHmVi-PuAWWrZqQzrich1QS9NR35DbdGpMts=y9uMAVA@mail.gmail.com>
Date:   Wed, 6 Dec 2017 18:07:01 -0800
From:   Linus Torvalds <torvalds@...ux-foundation.org>
To:     NeilBrown <neilb@...e.com>
Cc:     Trond Myklebust <trond.myklebust@...marydata.com>,
        Anna Schumaker <Anna.Schumaker@...app.com>,
        Al Viro <viro@...iv.linux.org.uk>,
        Andrew Morton <akpm@...ux-foundation.org>,
        lkml <linux-kernel@...r.kernel.org>,
        "linux-nfs@...r.kernel.org" <linux-nfs@...r.kernel.org>,
        linux-fsdevel <linux-fsdevel@...r.kernel.org>,
        Lennart Poettering <lennart@...ttering.net>
Subject: Re: [PATCH] NFS: allow name_to_handle_at() to work for Amazon EFS.

On Thu, Nov 30, 2017 at 12:56 PM, NeilBrown <neilb@...e.com> wrote:
>
> -/* limit the handle size to NFSv4 handle size now */
> -#define MAX_HANDLE_SZ 128
> +/* Must be larger than NFSv4 file handle, but small
> + * enough for an on-stack allocation. overlayfs doesn't
> + * want this too close to 255.
> + */
> +#define MAX_HANDLE_SZ 200

This really smells for so many reasons.

Also, that really is starting to be a fairly big stack allocation, and
it seems to be used in exactly one place (show_mark_fhandle), which
makes me go "why is that on the stack anyway?".

Could we just allocate a buffer at open time or something?

               Linus