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From: James W McMechan <mcmechanjw@juno.com>
To: maneesh@in.ibm.com
Cc: hugh@veritas.com, linux-kernel@vger.kernel.org,
	wli@holomorphy.com, viro@parcelfarce.linux.theplanet.co.uk,
	akpm@osdl.org
Subject: Re: Oops with tmpfs on both 2.4.22 & 2.6.0-test11
Date: Wed, 3 Dec 2003 03:06:14 -0800	[thread overview]
Message-ID: <20031203.030618.-346209.0.mcmechanjw@juno.com> (raw)

> Hi,
> 
> I hope nobody minds me jumping in this thread. I have been looking 
> at this code for some time and hope I have got the facts correct.
> 
Thank you, so far it is no longer crashing :)

> The two list_xxx macros as mentioned (fs/libfs.c:line 137) adjusts 
> the cursor dentry to the beginning of the d_subdirs list needed for 
> (file->f_pos == 2) as there can be additions in the d_subdirs list 
> after the open call and before ->lseek or ->readdir call.
> 
> The cursor adjustment in dcache_dir_lseek() (fs/libfs.c: line 90) 
> always puts the cursor just before the last looked dentry in the
> while loop. 
> 
> But it is problematic when we have an empty directory and 
> (file->f_pos == 2)
> In this case we have the loop counter p pointing to the cursor and 
> doing list_del and list_add_tail of the same list node results in oops.
> 
This is where I get mildly lost, from what you are saying here I
would have expected a test on list_empty rather than on
fpos==2 also this occurs in every file, will starting in a different
pos in the list cause problems?

With further testing it also Oops even when the dir is not empty
I did a "touch /dev/shm/1 /dev/shm/2 /dev/shm/3" to put some
entries in the dir first and the original still oops at offset 2

I should do more testing, to see if I can find out what happens
on non empty dirs, because I was thinking it was due to the
dir being empty, which now appears not to be true.

> The following patch takes (file->f_post == 2) as a special case and 
> adjusts the cursor dentry by putting it right at the beginning of the 
> d_subdirs list.
> 
Also is the new variable dentry needed or just a optimization?
It looks functionally equivalent, but perhaps it is needed for 
something I am not seeing at the moment.
> 
> Thanks
> Maneesh

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             reply	other threads:[~2003-12-03 11:15 UTC|newest]

Thread overview: 19+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2003-12-03 11:06 James W McMechan [this message]
2003-12-03 12:02 ` Maneesh Soni
     [not found] <20031207.140732.-1654081.3.mcmechanjw@juno.com>
2003-12-08  5:10 ` Maneesh Soni
  -- strict thread matches above, loose matches on Subject: below --
2003-12-07 22:48 James McMechan
2003-12-01  2:59 James W McMechan
2003-12-01 11:37 ` Maneesh Soni
2003-12-01  2:06 James W McMechan
2003-12-01  4:51 ` William Lee Irwin III
2003-12-01  1:06 James W McMechan
2003-12-01  3:43 ` William Lee Irwin III
2003-11-30 21:17 James W McMechan
2003-12-01  1:21 ` William Lee Irwin III
2003-12-01  7:58   ` Andries Brouwer
2003-12-01  8:00     ` William Lee Irwin III
2003-11-30 17:34 James W McMechan
2003-11-30 20:06 ` William Lee Irwin III
2003-11-30 21:21   ` Oleg Drokin
2003-11-30 16:57 James W McMechan
2003-11-30 19:27 ` William Lee Irwin III

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