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From: Al Viro <viro@zeniv.linux.org.uk>
To: David Laight <David.Laight@aculab.com>
Cc: 'Josef Bacik' <josef@toxicpanda.com>, "hch@lst.de" <hch@lst.de>,
	"linux-fsdevel@vger.kernel.org" <linux-fsdevel@vger.kernel.org>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	"kernel-team@fb.com" <kernel-team@fb.com>
Subject: Re: [PATCH] proc: use vmalloc for our kernel buffer
Date: Thu, 13 Aug 2020 17:21:41 +0100	[thread overview]
Message-ID: <20200813162141.GY1236603@ZenIV.linux.org.uk> (raw)
In-Reply-To: <714c8baabe1a4d0191f8cdaf6e28a32d@AcuMS.aculab.com>

On Thu, Aug 13, 2020 at 04:19:27PM +0000, David Laight wrote:
> From: Josef Bacik
> > Sent: 13 August 2020 15:53
> > 
> >   sysctl: pass kernel pointers to ->proc_handler
> > 
> > we have been pre-allocating a buffer to copy the data from the proc
> > handlers into, and then copying that to userspace.  The problem is this
> > just blind kmalloc()'s the buffer size passed in from the read, which in
> > the case of our 'cat' binary was 64kib.  Order-4 allocations are not
> > awesome, and since we can potentially allocate up to our maximum order,
> > use vmalloc for these buffers.
> 
> What happens if I run 'dd bs=16M ...' ?

Try it.

  reply	other threads:[~2020-08-13 16:21 UTC|newest]

Thread overview: 19+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-08-13 14:53 Josef Bacik
2020-08-13 14:59 ` Matthew Wilcox
2020-08-13 15:08   ` Josef Bacik
2020-08-13 15:33 ` [PATCH][v2] " Josef Bacik
2020-08-13 15:37   ` Christoph Hellwig
2020-08-13 15:40     ` Josef Bacik
2020-08-13 15:41       ` Christoph Hellwig
2020-08-13 16:20         ` Al Viro
2020-08-13 17:19           ` Josef Bacik
2020-08-13 17:31             ` Al Viro
2020-08-13 17:36               ` Josef Bacik
2020-08-13 21:10             ` David Laight
2020-08-13 21:31               ` Josef Bacik
2020-08-13 16:19 ` [PATCH] " David Laight
2020-08-13 16:21   ` Al Viro [this message]
2020-08-13 17:08   ` Josef Bacik
2021-02-10 15:54 Josef Bacik
2021-02-10 17:16 ` Vlastimil Babka
2021-02-10 18:15 ` Matthew Wilcox

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