From: Phillip Lougher <phillip@lougher.demon.co.uk>
To: Nick Piggin <nickpiggin@yahoo.com.au>
Cc: linuxram@us.ibm.com, linux-kernel@vger.kernel.org,
Andrew Morton <akpm@osdl.org>,
viro@parcelfarce.linux.theplanet.co.uk
Subject: Re: [PATCH] VFS readahead bug in 2.6.8-rc[1-3]
Date: Fri, 06 Aug 2004 18:05:41 +0100 [thread overview]
Message-ID: <4113BA65.8050901@lougher.demon.co.uk> (raw)
In-Reply-To: <411322E8.4000503@yahoo.com.au>
Nick Piggin wrote:
> Ram Pai wrote:
>
>>
>> there is a check in __do_page_cache_readahead() that validates this.
>> But it is still not guaranteed to work correctly against races.
>> The filesystem has to handle such out-of-bound requests gracefully.
>>
>> However with Nick's fix in do_generic_mapping_read() the filesystem is
>> gauranteed to be called with out-of-bound index, if the file size is a
>> multiple of 4k. Without the fix, the filesystem might get
>> called with out-of-bound index only in racy conditions.
>>
>
> How's this?
>
It doesn't work. It correctly handles the case where *ppos is equal
to i_size on entry to the function (and this does work for files 0, 4k
and n * 4k in length), but it doesn't handle readahead inside the for
loop. The check needs to be in the for loop.
next prev parent reply other threads:[~2004-08-06 17:14 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <Pine.LNX.4.44.0408052104420.2241-100000@dyn319181.beaverton.ibm.com>
[not found] ` <411322E8.4000503@yahoo.com.au>
2004-08-06 10:47 ` [PATCH] VFS readahead bug in 2.6.8-rc[1-3] Ram
2004-08-06 17:05 ` Phillip Lougher [this message]
2004-08-06 18:02 ` Ram Pai
2004-08-06 19:09 ` Nick Piggin
2004-08-06 19:39 ` Phillip Lougher
2004-08-06 20:21 ` Nick Piggin
2004-08-05 17:50 Phillip Lougher
2004-08-06 0:55 ` Nick Piggin
2004-08-06 2:19 ` Nick Piggin
2004-08-06 16:58 ` Phillip Lougher
2004-08-06 18:58 ` Nick Piggin
2004-08-06 19:14 ` Phillip Lougher
2004-08-06 19:31 ` viro
2004-08-06 19:18 ` Phillip Lougher
2004-08-06 19:46 ` Andrew Morton
2004-08-07 14:21 ` Pozsar Balazs
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