From: "Roberto A. Foglietta" <roberto.foglietta@gmail.com>
To: Marco Stornelli <marco.stornelli@gmail.com>
Cc: Tony Luck <tony.luck@intel.com>,
Linux Kernel <linux-kernel@vger.kernel.org>,
Linux Embedded <linux-embedded@vger.kernel.org>,
Linux FS Devel <linux-fsdevel@vger.kernel.org>,
Tim Bird <tim.bird@am.sony.com>
Subject: Re: [PATCH 01/17] pramfs: documentation
Date: Tue, 11 Jan 2011 16:42:57 +0100 [thread overview]
Message-ID: <AANLkTi=fF_hskZ7kDEby0Uga0eaU_stM9qs890mUpxWd@mail.gmail.com> (raw)
In-Reply-To: <4D281D65.1070102@gmail.com>
2011/1/8 Marco Stornelli <marco.stornelli@gmail.com>:
> On 07/01/2011 22:59, Tony Luck wrote:
>> On Fri, Jan 7, 2011 at 12:30 PM, Marco Stornelli
>> <marco.stornelli@gmail.com> wrote:
>>> constraint). About the errors: pramfs does not maintain file data in the
>>> page caches for normal file I/O, so no writeback, the read/write
>>> operation are done with direct io and they are always sync. The data are
>>> write protected in hw when the arch provide this facility (x86 does).
>>> Inode contains a checksum and when there are problems they are marked as
>>> bad. Superblock contains checksum and there is a redundant superblock.
>>
>> But you can still get pramfs inconsistencies if the system crashes at an
>> inopportune moment. E.g. when making files you write the new inode to
>> pramfs, and then you insert the entry into the directory. A crash between
>> these two operations leaves an allocated inode that doesn't appear in
>> any directory. Without a fsck option, it will be hard to see that you have
>> this problem, and your only recovery option is to wipe *all* files by making
>> a new filesystem.
>
> Is it a problem if you lost some logs? However do you expect that fsck
> in this case will drop the inode?
IF there could be some inconsistencies in the file-system AND as long
as there is no way to fixup these inconsistencies than purging their
allocated space THEN I think the best approach would be clearing these
inconsistencies at the mount time and printing a WARNING message for
debug/stats purpose. Otherwise a user-space tool would be better
because it could be used in interactive mode, also.
Obviously the best would be to not have any inconsistencies at all.
However, in a real world, the thread-off between a journaling fs and a
simpler one in terms of code and memory usage could make acceptable
adopting a simpler fs than a journaled one. Kernel documentation
should inform clearly the user about pro/cons of adopting a simpler fs
especially about data loss conditions.
-RAF
prev parent reply other threads:[~2011-01-11 15:42 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-01-06 12:01 [PATCH 01/17] pramfs: documentation Marco Stornelli
2011-01-07 18:42 ` Tony Luck
2011-01-07 20:30 ` Marco Stornelli
2011-01-07 21:59 ` Tony Luck
2011-01-08 8:16 ` Marco Stornelli
2011-01-10 8:08 ` Pavel Machek
2011-01-10 8:14 ` Marco Stornelli
2011-01-10 17:35 ` Luck, Tony
2011-01-10 18:17 ` Marco Stornelli
2011-01-11 15:42 ` Roberto A. Foglietta [this message]
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