linux-kernel - Re: [PATCH 01/17] pramfs: documentation

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Message-ID: <AANLkTi=DbZ8eU05Sq0jxpCTNKm7rW52FWVNbR16U3Zse@mail.gmail.com>
Date:	Mon, 10 Jan 2011 09:14:29 +0100
From:	Marco Stornelli <marco.stornelli@...il.com>
To:	Pavel Machek <pavel@....cz>
Cc:	Tony Luck <tony.luck@...el.com>,
	Linux Kernel <linux-kernel@...r.kernel.org>,
	Linux Embedded <linux-embedded@...r.kernel.org>,
	Linux FS Devel <linux-fsdevel@...r.kernel.org>,
	Tim Bird <tim.bird@...sony.com>
Subject: Re: [PATCH 01/17] pramfs: documentation

2011/1/10 Pavel Machek <pavel@....cz>:
>> On 07/01/2011 22:59, Tony Luck wrote:
>> > On Fri, Jan 7, 2011 at 12:30 PM, Marco Stornelli
>> > <marco.stornelli@...il.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?
>
> Ask it the other way around.
>
> What is persistent filesystem good for when it is only persistent
> sometimes?
>
> You'd be better running ext2 over special block device, it is quite simple.
>

Ok I can work on it. However can an userspace tool prevent the insert
of fs in linux next?

Marco
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