Bug 5893

Summary:	pdflush thread bomb on UDF writes
Product:	File System	Reporter:	Daniel Pouzzner (douzzer)
Component:	UDF	Assignee:	Ben Fennema (bfennema)
Status:	REJECTED WILL_NOT_FIX
Severity:	normal	CC:	diegocg, douzzer, fgroups, jack, kernel, protasnb
Priority:	P2
Hardware:	i386
OS:	Linux
Kernel Version:	2.6.18-rc4	Subsystem:
Regression:	---	Bisected commit-id:

Description Daniel Pouzzner 2006-01-14 18:43:51 UTC

Keywords: UDF, pdflush
Most recent kernel where this bug did not occur: unknown
Distribution: gentoo 2005.1
Hardware Environment: dual AMD Opteron 848 on Tyan S2895
Software Environment: not relevant
Problem Description:
Extracting a large tar archive into a UDF residing on a DVD-RAM results in
spawning of many pdflush threads (16 or more) each associated with the same UDF.
 A given device should have no more than one pdflush thread associated with it,
and multiple threads fighting for the same device grossly erodes system
responsiveness and results in a grossly inefficient pattern of access to the
underlying device over which they fight.
Steps to reproduce:
See above.

Comment 1 Diego Calleja 2006-01-15 10:51:13 UTC

2.6.12 is 7 months old, could you try 2.6.15 to check if it's reproduceable in
the lastest version?

Comment 2 Daniel Pouzzner 2006-01-15 15:16:26 UTC

I don't have the ability to install 2.6.15 just now, but when I do I'll attempt
to replicate this bug.  I know from research I did before posting, that pdflush
does not itself perform any checks to avert device contention.  It relies on the
caller to do it.  What I don't know is whether the responsibility for the checks
is specific to the device abstraction layer (right) or the filesystem layer (not
right).

The DVD-RAM drive is an ordinary ATAPI device, a Panasonic (Matsushita) SW-9574-C.

By the way, shortly after posting the bug, I realized the obvious workaround is
to use -o sync,dirsync with the mount.  This works perfectly for my purposes
(backup to DVD-RAM).

Comment 3 Frank Noack 2006-07-28 06:58:40 UTC

with 2.6.17-r4 on gentoo it also dont work. See please http://forums.gentoo.org/
viewtopic-t-481464-highlight-.html

Comment 4 Daniel Drake 2006-08-13 07:59:05 UTC

Frank has reproduced this on clean 2.6.18-rc4
http://bugs.gentoo.org/142007

Comment 5 Natalie Protasevich 2008-03-15 00:47:07 UTC

Has the issue been fixed? Any update on this please.
Thanks.

Comment 6 Natalie Protasevich 2008-03-15 13:28:17 UTC

Comment from Daniel Pouzzner:
ever since discovering the problem I've just always mounted UDF's sync+dirsync, and haven't had a problem set up that way.