From: Al Viro <viro@zeniv.linux.org.uk>
To: "J. R. Okajima" <hooanon05g@gmail.com>
Cc: linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org,
kolyshkin@gmail.com
Subject: Re: [PATCH] concrete /proc/mounts
Date: Sun, 26 May 2019 13:07:19 +0100 [thread overview]
Message-ID: <20190526120719.GQ17978@ZenIV.linux.org.uk> (raw)
In-Reply-To: <17910.1558861894@jrobl>
On Sun, May 26, 2019 at 06:11:34PM +0900, J. R. Okajima wrote:
> commit 1e83f8634c6efe7dd4e6036ee202ca10bdbca0b3
> Author: J. R. Okajima <hooanon05g@gmail.com>
> Date: Sat May 25 18:35:13 2019 +0900
>
> concrete /proc/mounts
>
> When the size of /proc/mounts exceeds PAGE_SIZE, seq_read() has to
> release namespace_sem via mounts_op.m_stop(). It means if someone else
> issues mount(2) or umount(2) and the mounts list got changed, then the
> continuous getmntent(3) calls show the incomplete mounts list and some
> entries may not appear in it.
>
> This patch generates the full mounts list when mounts_op.m_start() is
> called, and keep it in the seq_file buffer until the file is closed.
> The size of the buffer increases if necessary. Other operations m_next,
> m_stop, m_show become meaningless, but still necessary for the seq_file
> manner.
>
> I don't think the size of the buffer matters because many /proc entries
> already keep the similar PAGE_SIZE buffer. Increasing /proc/mounts
> buffer is to keep the correctness of the mount list.
>
> Reported-by: Kirill Kolyshkin <kolyshkin@gmail.com>
> See-also: https://github.com/kolyshkin/procfs-test
> Signed-off-by: J. R. Okajima <hooanon05g@gmail.com>
Translation: let's generate the entire contents on the first read() and keep
it until the sucker's closed; that way userland wont' see anything changing
under it. Oh, wait...
NAK.
next prev parent reply other threads:[~2019-05-26 12:07 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-05-26 9:11 [PATCH] concrete /proc/mounts J. R. Okajima
2019-05-26 12:07 ` Al Viro [this message]
2019-05-26 19:06 ` J. R. Okajima
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