From mboxrd@z Thu Jan 1 00:00:00 1970 From: Andreas Rohner Subject: Re: [PATCH 1/1] nilfs2: add mount option that reduces super block writes Date: Thu, 30 Jan 2014 07:52:44 +0100 Message-ID: <52E9F6BC.5090205@gmx.net> References: <75ceb45c464097ab556baacf2d15d6ae4b792bb2.1391048231.git.andreas.rohner@gmx.net> <127C78C3-9D47-439C-9639-263BC453D98D@dubeyko.com> <52E9EB06.1000504@gmx.net> <8DBE8E18-F678-44B0-A6A6-5AFEC227AA86@dubeyko.com> Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <8DBE8E18-F678-44B0-A6A6-5AFEC227AA86-yeENwD64cLxBDgjK7y7TUQ@public.gmane.org> Sender: linux-nilfs-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org List-ID: Content-Type: text/plain; charset="us-ascii" To: Vyacheslav Dubeyko Cc: linux-nilfs-u79uwXL29TY76Z2rM5mHXA@public.gmane.org On 2014-01-30 08:44, Vyacheslav Dubeyko wrote: > > On Jan 30, 2014, at 9:02 AM, Andreas Rohner wrote: > >> Hi Vyacheslav, >> >> On 2014-01-30 07:36, Vyacheslav Dubeyko wrote: >>> Hi Andreas, >>> >>> On Jan 30, 2014, at 5:47 AM, Andreas Rohner wrote: >>> >>>> This patch introduces a mount option bad_ftl that disables the >>>> periodic overwrites of the super block to make the file system better >>>> suitable for bad flash memory with a bad FTL. The super block is only >>>> written at umount time. So if there is a power outage the file system >>>> needs to be recovered by a linear scan of all segment summary blocks. >>>> >>>> The linear scan is only necessary if the file system wasn't umounted >>>> properly. So the normal mount time is not affected. >>>> >>>> Signed-off-by: Andreas Rohner >>>> --- >>>> fs/nilfs2/segbuf.c | 3 ++- >>>> fs/nilfs2/segment.c | 3 ++- >>>> fs/nilfs2/super.c | 10 +++++++-- >>>> fs/nilfs2/the_nilfs.c | 54 ++++++++++++++++++++++++++++++++++++++++++++--- >>>> include/linux/nilfs2_fs.h | 4 +++- >>>> 5 files changed, 66 insertions(+), 8 deletions(-) >>>> >>> >>> As far as I can judge, conceptually it is simply rollback of the fix [1]. >> >> The normal recovery mode checks all partial segments and computes the >> checksum over all the data. That takes significantly longer than my >> approach of just checking one block per segment, namely the segment >> summary block. >> > > I don't think that your suggestion changes situation significantly. > Because in the issue [1] you can go through the whole volume in the really > bad environment. Maybe you will mount volume 30 minutes instead of 1 hour > with technique that you suggest in the patch. Yes probably. It is still a simple scan. But you wouldn't use the mount option for 1 TB hard drives. I just thought it could be useful for small linux systems, like the raspberry pi that use a small SD card as root. But as I said it is just an experiment. Thanks for your comments. br, Andreas Rohner > With the best regards, > Vyacheslav Dubeyko. > >> br, >> Andreas Rohner >> >>> Thanks, >>> Vyacheslav Dubeyko. >>> >>> [1] https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=a9bae189542e71f91e61a4428adf6e5a7dfe8063 >>> >>> >> > > -- To unsubscribe from this list: send the line "unsubscribe linux-nilfs" in the body of a message to majordomo-u79uwXL29TY76Z2rM5mHXA@public.gmane.org More majordomo info at http://vger.kernel.org/majordomo-info.html