From: Arnd Bergmann <arnd@arndb.de>
To: Ken'ichi Ohmichi <oomichi@mxs.nes.nec.co.jp>
Cc: CAI Qian <caiqian@redhat.com>,
fweisbec@gmail.com, mingo@elte.hu,
kexec <kexec@lists.infradead.org>,
viro@zeniv.linux.org.uk, jkacur@redhat.com,
akpm@linux-foundation.org, tglx@linutronix.de,
kamezawa hiroyu <kamezawa.hiroyu@jp.fujitsu.com>
Subject: Re: fix /proc/vmcore seek
Date: Fri, 3 Sep 2010 13:45:50 +0200 [thread overview]
Message-ID: <201009031345.50837.arnd@arndb.de> (raw)
In-Reply-To: <20100903100050.1943c4c3.oomichi@mxs.nes.nec.co.jp>
On Friday 03 September 2010, Ken'ichi Ohmichi wrote:
> Thank you for investigating.
> IIUC, this problem may happen if using "cp" command instead of
> makedumpfile.
>
> Does the following method in generic_file_llseek_unlocked() fail ?
> Is inode->i_sb->s_maxbytes too small ?
>
> 65 if (offset < 0 || offset > inode->i_sb->s_maxbytes)
> 66 return -EINVAL;
>
Yes, that is the main difference between generic_file_llseek and
default_llseek, besides the use of the BKL. We have discussed
changing this before, but so far without a conclusive answer.
If we can come up with a better test here, we might be able
to just kill default_llseek in favor of generic_file_llseek.
The problem is handling the special cases here. For a /proc file,
s_maxbytes is probably always zero, but that could be changed,
same for file systems using get_sb_single.
For some reason, get_sb_pseudo sets does set s_maxbytes while
get_sb_single/simple_fill_super does not.
Character devices are also special, because the s_maxbytes for
them AFAICT is the one from the file system holding the device,
so using generic_file_llseek would definitely be incorrect for them.
Arnd
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next prev parent reply other threads:[~2010-09-03 11:46 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <839326586.1621551283237394919.JavaMail.root@zmail06.collab.prod.int.phx2.redhat.com>
2010-08-31 6:50 ` makedumpfile failed for 2.6.36-rc2 caiqian
2010-08-31 7:28 ` Ken'ichi Ohmichi
2010-08-31 8:29 ` CAI Qian
2010-09-01 4:33 ` Ken'ichi Ohmichi
2010-09-01 5:16 ` CAI Qian
2010-09-02 11:51 ` CAI Qian
2010-09-02 12:20 ` fix /proc/vmcore seek Arnd Bergmann
2010-09-02 14:23 ` CAI Qian
2010-09-03 1:00 ` Ken'ichi Ohmichi
2010-09-03 11:45 ` Arnd Bergmann [this message]
2010-09-03 20:58 ` Andrew Morton
2010-09-03 21:10 ` Frederic Weisbecker
2010-09-06 1:10 ` [PATCH][mmotm] unsigned offset llseek support (Was " KAMEZAWA Hiroyuki
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