From: "Daniel Xu" <dxu@dxuuu.xyz>
To: "Joe Perches" <joe@perches.com>, <cgroups@vger.kernel.org>,
<tj@kernel.org>, <lizefan@huawei.com>, <hannes@cmpxchg.org>
Cc: <shakeelb@google.com>, <linux-kernel@vger.kernel.org>,
<gregkh@linuxfoundation.org>, <kernel-team@fb.com>
Subject: Re: [PATCH v2 1/4] kernfs: kvmalloc xattr value instead of kmalloc
Date: Mon, 09 Mar 2020 11:21:33 -0700 [thread overview]
Message-ID: <C16IH7NEXW4J.440OGTNY7CWX@dlxu-fedora-R90QNFJV> (raw)
In-Reply-To: <58c6e6dafabea52e5b030d18b83c13e4f43ab8e3.camel@perches.com>
Hi Joe,
On Fri Mar 6, 2020 at 12:49 AM, Joe Perches wrote:
> On Thu, 2020-03-05 at 13:16 -0800, Daniel Xu wrote:
> > It's not really necessary to have contiguous physical memory for xattr
> > values. We no longer need to worry about higher order allocations
> > failing with kvmalloc, especially because the xattr size limit is at
> > 64K.
>
>
> So why use vmalloc memory at all?
>
>
> > diff --git a/fs/xattr.c b/fs/xattr.c
> ']
> > @@ -817,7 +817,7 @@ struct simple_xattr *simple_xattr_alloc(const void *value, size_t size)
> > if (len < sizeof(*new_xattr))
> > return NULL;
> >
> > - new_xattr = kmalloc(len, GFP_KERNEL);
> > + new_xattr = kvmalloc(len, GFP_KERNEL);
>
>
> Why is this sensible?
> vmalloc memory is a much more limited resource.
What would be the alternative? As Greg said, contiguous memory should be
more scarce.
> Also, it seems as if the function should set
> new_xattr->name to NULL before the return.
>
Will add and send in a different patch.
Thanks,
Daniel
next prev parent reply other threads:[~2020-03-09 18:21 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-03-05 21:16 [PATCH v2 0/4] Support user xattrs in cgroupfs Daniel Xu
2020-03-05 21:16 ` [PATCH v2 1/4] kernfs: kvmalloc xattr value instead of kmalloc Daniel Xu
2020-03-06 8:49 ` Joe Perches
2020-03-06 9:37 ` Greg KH
2020-03-09 18:21 ` Daniel Xu [this message]
2020-03-09 19:41 ` Joe Perches
2020-03-09 19:51 ` Tejun Heo
2020-03-09 19:58 ` Joe Perches
2020-03-09 20:05 ` Tejun Heo
2020-03-10 19:40 ` Shakeel Butt
2020-03-10 20:40 ` Daniel Xu
2020-03-10 20:41 ` Shakeel Butt
2020-03-05 21:16 ` [PATCH v2 2/4] kernfs: Add removed_size out param for simple_xattr_set Daniel Xu
2020-03-10 18:20 ` Daniel Xu
2020-03-05 21:16 ` [PATCH v2 3/4] kernfs: Add option to enable user xattrs Daniel Xu
2020-03-05 21:16 ` [PATCH v2 4/4] cgroupfs: Support " Daniel Xu
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