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Re: [RFC PATCH 26/26] UBIFS: include FS to compilation

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To: Christoph Hellwig <hch@...>
Cc: Pekka Enberg <penberg@...>, <Artem.Bityutskiy@...>, Artem Bityutskiy <dedekind@...>, LKML <linux-kernel@...>, David Woodhouse <dwmw2@...>
Date: Wednesday, April 30, 2008 - 3:04 am

Christoph Hellwig wrote:

What would make them more readable?  We (ok mostly me) are not enthusiastic
about BUG_ON for the following reasons:
	1. When testing and debugging you lose the opportunity to get more
	information and have to reboot the test platform
	2. When the system is in the hands of consumers we don't want it
	to oops under any circumstances.  This is particularly the case
	when looking at things like BUG_ON(!PageLocked(page)).  In an
	embedded system, single CPU, preemption disabled, even in the
	unlikely event this happens, the system would probably get away
	with it.
	3. We don't have many people using UBIFS so hoping they catch
	BUGs is less realistic.  It is also bad for us as we try to
	persuade people of the merits of UBIFS.  Consequently our focus
	is on our own testing (which brings us back to point 1).
	4. We have had a couple of situations with JFFS2 where BUG_ON was
	used incorrectly to handle errors that didn't look like they
	could happen but it turned out they could.  I.e. an error code
	should have been returned and the system allowed to continue.
	In short BUG_ON can be bad all by itself.

Perhaps if we called it dbg_check() instead of ubifs_assert() ?

As for things getting out of sync, anyone making changes to UBIFS, either
without testing or testing without the debug checks turned on, is taking
a much much bigger risk than just letting the checks get out of sync.

I am not sure it is really reasonable to compare the debugging needs of
SLUB with those of UBIFS because UBIFS has a much lower visibility and
usage.  There are far fewer eyes looking at the code and far fewer people
using it.  Since the burden of testing really falls on just a few of us,
we are keen to have lots of checks.


We use both PagePrivate and PageChecked differently to EXT3 etc.

From the original example, that just leaves PageLocked, but lots of kernel
functions seem to check that, so why not UBIFS too?



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Messages in current thread:
[RFC PATCH] UBIFS - new flash file system, Artem Bityutskiy, (Thu Mar 27, 10:55 am)
Re: [RFC PATCH] UBIFS - new flash file system, Thomas Gleixner, (Fri Apr 18, 5:05 am)
Re: [RFC PATCH] UBIFS - new flash file system, Jan Engelhardt, (Mon Mar 31, 8:29 am)
Re: [RFC PATCH] UBIFS - new flash file system, Jörn, (Mon Mar 31, 9:40 am)
Re: [RFC PATCH] UBIFS - new flash file system, Adrian Hunter, (Mon Mar 31, 8:47 am)
Re: [RFC PATCH] UBIFS - new flash file system, Jörn, (Mon Mar 31, 9:20 am)
Re: [RFC PATCH] UBIFS - new flash file system, Artem Bityutskiy, (Mon Mar 31, 10:00 am)
Re: [RFC PATCH] UBIFS - new flash file system, Jörn, (Mon Mar 31, 1:17 pm)
Re: [RFC PATCH] UBIFS - new flash file system, Pekka Enberg, (Mon Mar 31, 4:49 pm)
Re: [RFC PATCH] UBIFS - new flash file system, Jörn, (Mon Mar 31, 5:21 pm)
Re: [RFC PATCH] UBIFS - new flash file system, Artem Bityutskiy, (Tue Apr 1, 2:00 am)
Re: [RFC PATCH] UBIFS - new flash file system, Artem Bityutskiy, (Fri Mar 28, 2:45 am)
Re: [RFC PATCH] UBIFS - new flash file system, Josh Boyer, (Thu Mar 27, 12:20 pm)
Re: [RFC PATCH] UBIFS - new flash file system, Artem Bityutskiy, (Fri Mar 28, 2:17 am)
[RFC PATCH 09/26] UBIFS: add key helpers, Artem Bityutskiy, (Thu Mar 27, 10:55 am)
[RFC PATCH 26/26] UBIFS: include FS to compilation, Artem Bityutskiy, (Thu Mar 27, 10:55 am)
Re: [RFC PATCH 26/26] UBIFS: include FS to compilation, Pekka Enberg, (Tue Apr 1, 3:39 am)
Re: [RFC PATCH 26/26] UBIFS: include FS to compilation, Artem Bityutskiy, (Tue Apr 1, 4:51 am)
Re: [RFC PATCH 26/26] UBIFS: include FS to compilation, Christoph Hellwig, (Sat Apr 26, 5:35 am)
Re: [RFC PATCH 26/26] UBIFS: include FS to compilation, Adrian Hunter, (Mon Apr 28, 3:09 am)
Re: [RFC PATCH 26/26] UBIFS: include FS to compilation, ext Christoph Hellwig, (Mon Apr 28, 5:00 am)
Re: [RFC PATCH 26/26] UBIFS: include FS to compilation, Adrian Hunter, (Mon Apr 28, 7:23 am)
Re: [RFC PATCH 26/26] UBIFS: include FS to compilation, ext ext Christoph Hellwig..., (Mon Apr 28, 7:39 am)
Re: [RFC PATCH 26/26] UBIFS: include FS to compilation, Adrian Hunter, (Mon Apr 28, 8:25 am)
Re: [RFC PATCH 26/26] UBIFS: include FS to compilation, Christoph Hellwig, (Mon Apr 28, 9:02 am)
Re: [RFC PATCH 26/26] UBIFS: include FS to compilation, Pekka Enberg, (Tue Apr 1, 5:15 am)
Re: [RFC PATCH 26/26] UBIFS: include FS to compilation, Artem Bityutskiy, (Tue Apr 1, 5:25 am)
Re: [RFC PATCH 26/26] UBIFS: include FS to compilation, Pekka Enberg, (Tue Apr 1, 6:04 am)
Re: [RFC PATCH 26/26] UBIFS: include FS to compilation, Artem Bityutskiy, (Tue Apr 1, 6:26 am)
Re: [RFC PATCH 26/26] UBIFS: include FS to compilation, Pekka Enberg, (Tue Apr 1, 7:33 am)
Re: [RFC PATCH 26/26] UBIFS: include FS to compilation, Christoph Hellwig, (Sat Apr 26, 5:37 am)
Re: [RFC PATCH 26/26] UBIFS: include FS to compilation, Adrian Hunter, (Mon Apr 28, 3:10 am)
Re: [RFC PATCH 26/26] UBIFS: include FS to compilation, ext Christoph Hellwig, (Mon Apr 28, 5:03 am)
Re: [RFC PATCH 26/26] UBIFS: include FS to compilation, Adrian Hunter, (Wed Apr 30, 3:04 am)
Re: [RFC PATCH 26/26] UBIFS: include FS to compilation, Artem Bityutskiy, (Tue Apr 1, 7:56 am)
[RFC PATCH 22/26] UBIFS: add extended attribute support, Artem Bityutskiy, (Thu Mar 27, 10:55 am)
[RFC PATCH 04/26] UBIFS: add journal replay, Artem Bityutskiy, (Thu Mar 27, 10:55 am)
[RFC PATCH 03/26] UBIFS: add flash scanning, Artem Bityutskiy, (Thu Mar 27, 10:55 am)
[RFC PATCH 18/26] UBIFS: add LEB find subsystem, Artem Bityutskiy, (Thu Mar 27, 10:55 am)
[RFC PATCH 16/26] UBIFS: add LEB properties tree, Artem Bityutskiy, (Thu Mar 27, 10:55 am)
[RFC PATCH 08/26] UBIFS: add compression support, Artem Bityutskiy, (Thu Mar 27, 10:55 am)
[RFC PATCH 07/26] UBIFS: add file-system recovery, Artem Bityutskiy, (Thu Mar 27, 10:55 am)
[RFC PATCH 06/26] UBIFS: add superblock and master node, Artem Bityutskiy, (Thu Mar 27, 10:55 am)
[RFC PATCH 05/26] UBIFS: add file-system build, Artem Bityutskiy, (Thu Mar 27, 10:55 am)
Re: [RFC PATCH 05/26] UBIFS: add file-system build, Andrew Morton, (Fri Mar 28, 6:12 am)
Re: [RFC PATCH 05/26] UBIFS: add file-system build, Artem Bityutskiy, (Fri Mar 28, 7:04 am)
[RFC PATCH 02/26] UBIFS: add I/O sub-system, Artem Bityutskiy, (Thu Mar 27, 10:55 am)
[RFC PATCH 25/26] UBIFS: add debugging stuff, Artem Bityutskiy, (Thu Mar 27, 10:55 am)
Re: [RFC PATCH 25/26] UBIFS: add debugging stuff, Pekka Enberg, (Mon Mar 31, 5:00 pm)
Re: [RFC PATCH 25/26] UBIFS: add debugging stuff, Artem Bityutskiy, (Tue Apr 1, 2:20 am)
Re: [RFC PATCH 25/26] UBIFS: add debugging stuff, Pekka Enberg, (Tue Apr 1, 3:43 am)
Re: [RFC PATCH 25/26] UBIFS: add debugging stuff, Pekka Enberg, (Tue Apr 1, 3:33 am)
Re: [RFC PATCH 25/26] UBIFS: add debugging stuff, Adrian Hunter, (Tue Apr 1, 4:34 am)
Re: [RFC PATCH 25/26] UBIFS: add debugging stuff, Artem Bityutskiy, (Tue Apr 1, 4:32 am)
Re: [RFC PATCH 25/26] UBIFS: add debugging stuff, Pekka Enberg, (Tue Apr 1, 5:00 am)
Re: [RFC PATCH 25/26] UBIFS: add debugging stuff, Artem Bityutskiy, (Tue Apr 1, 5:04 am)
[RFC PATCH 24/26] UBIFS: add header files, Artem Bityutskiy, (Thu Mar 27, 10:55 am)
[RFC PATCH 23/26] UBIFS: add orphans handling sub-system, Artem Bityutskiy, (Thu Mar 27, 10:55 am)
[RFC PATCH 21/26] UBIFS: add budgeting, Artem Bityutskiy, (Thu Mar 27, 10:55 am)
[RFC PATCH 20/26] UBIFS: add VFS operations, Artem Bityutskiy, (Thu Mar 27, 10:55 am)
Re: [RFC PATCH 20/26] UBIFS: add VFS operations, Pekka Enberg, (Tue Apr 1, 8:08 am)
Re: [RFC PATCH 20/26] UBIFS: add VFS operations, Artem Bityutskiy, (Tue Apr 1, 8:42 am)
Re: [RFC PATCH 20/26] UBIFS: add VFS operations, Pekka Enberg, (Tue Apr 1, 9:12 am)
Re: [RFC PATCH 20/26] UBIFS: add VFS operations, Artem Bityutskiy, (Tue Apr 1, 10:04 am)
Re: [RFC PATCH 20/26] UBIFS: add VFS operations, Adrian Hunter, (Tue Apr 1, 11:14 am)
Re: [RFC PATCH 20/26] UBIFS: add VFS operations, Andi Kleen, (Thu Mar 27, 9:36 am)
Re: [RFC PATCH 20/26] UBIFS: add VFS operations, Artem Bityutskiy, (Thu Mar 27, 9:42 am)
[RFC PATCH 19/26] UBIFS: add Garbage Collector, Artem Bityutskiy, (Thu Mar 27, 10:55 am)
Re: [RFC PATCH 19/26] UBIFS: add Garbage Collector, Arnd Bergmann, (Mon Mar 31, 10:11 pm)
[RFC PATCH 01/26] VFS: introduce writeback_inodes_sb(), Artem Bityutskiy, (Thu Mar 27, 10:55 am)
[RFC PATCH 17/26] UBIFS: add LEB properties tree, Artem Bityutskiy, (Thu Mar 27, 10:55 am)
[RFC PATCH 15/26] UBIFS: add LEB properties, Artem Bityutskiy, (Thu Mar 27, 10:55 am)
[RFC PATCH 14/26] UBIFS: add TNC shrinker, Artem Bityutskiy, (Thu Mar 27, 10:55 am)
[RFC PATCH 13/26] UBIFS: add TNC commit implementation, Artem Bityutskiy, (Thu Mar 27, 10:55 am)
[RFC PATCH 12/26] UBIFS: add TNC implementation, Artem Bityutskiy, (Thu Mar 27, 10:55 am)
[RFC PATCH 11/26] UBIFS: add commit functionality, Artem Bityutskiy, (Thu Mar 27, 10:55 am)
[RFC PATCH 10/26] UBIFS: add the journal, Artem Bityutskiy, (Thu Mar 27, 10:55 am)
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