From: "Valdis Klētnieks" <valdis.kletnieks@vt.edu>
To: "Pali Rohár" <pali.rohar@gmail.com>
Cc: Sasha Levin <sashal@kernel.org>,
devel@driverdev.osuosl.org, Christoph Hellwig <hch@infradead.org>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
linux-kernel@vger.kernel.org,
Sasha Levin <alexander.levin@microsoft.com>,
linux-fsdevel@vger.kernel.org
Subject: Re: [PATCH] staging: exfat: add exfat filesystem code to staging
Date: Fri, 14 Feb 2020 18:25:38 -0500 [thread overview]
Message-ID: <89492.1581722738@turing-police> (raw)
In-Reply-To: <20200214224357.yv2lwyusi3gwolp3@pali>
[-- Attachment #1.1: Type: text/plain, Size: 1362 bytes --]
> Idea is simple. Expects that we have a clean filesystem in correct
> state. We load primary/active/main FAT table (just call it FAT1) and all
> changes to filesystem would be done via second non-active FAT table
> (FAT2). At unmount or sync or flush buffer times, FAT2 would be copied
> back to the FAT1 and filesystem would be back in clean state.
Somehow, scribbling on the non-active table for actual changes sounds like a
bad idea waiting to happen (partly because if you do that and crash, after the
reboot you remount, and it starts up with the now-stale FAT1 because you never
flagged that FAT as stale.
That means that if we started using the secondary FAT, we'd change the
ActiveFAT variable to indicate that. And if we do that, we need to also set
num_fat to 2 because num_fat 1 and ActiveFAT pointing at the second FAT is
*definitely* bogus.
And that could result in us crashing and leaving the device with a header that
says 'num_fat == 2', ActiveFAT == second, and the dirty bit set - and the user
next uses the filesystem on a system/device that hard-codes that there's only 1 FAT,
so it blindly goes on its merry way using a FAT that's stale and never realizing it.
And that's actually the same failure mode as in the first paragraph - you start
off using FAT1 because you don't see an indication that it's stale.
[-- Attachment #1.2: Type: application/pgp-signature, Size: 832 bytes --]
[-- Attachment #2: Type: text/plain, Size: 169 bytes --]
_______________________________________________
devel mailing list
devel@linuxdriverproject.org
http://driverdev.linuxdriverproject.org/mailman/listinfo/driverdev-devel
next prev parent reply other threads:[~2020-02-14 23:25 UTC|newest]
Thread overview: 40+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20190828160817.6250-1-gregkh@linuxfoundation.org>
[not found] ` <20190829205631.uhz6jdboneej3j3c@pali>
2019-08-30 15:40 ` [PATCH] staging: exfat: add exfat filesystem code to staging Christoph Hellwig
2019-08-30 15:43 ` Pali Rohár
[not found] ` <184209.1567120696@turing-police>
[not found] ` <20190829233506.GT5281@sasha-vm>
[not found] ` <20190830075647.wvhrx4asnkrfkkwk@pali>
2019-10-16 14:03 ` Pali Rohár
2019-10-16 14:31 ` Sasha Levin
2019-10-16 16:03 ` Pali Rohár
2019-10-16 16:20 ` Sasha Levin
2019-10-16 16:22 ` Greg Kroah-Hartman
2019-10-16 16:32 ` Pali Rohár
2019-10-16 16:50 ` Greg Kroah-Hartman
2019-10-16 20:33 ` Sasha Levin
2019-10-16 21:53 ` Valdis Klētnieks
2019-10-17 7:53 ` Pali Rohár
2019-10-17 7:50 ` Pali Rohár
2020-02-13 0:06 ` Pali Rohár
2020-02-13 21:18 ` Sasha Levin
2020-02-14 22:16 ` Valdis Klētnieks
2020-02-14 22:43 ` Pali Rohár
2020-02-14 23:25 ` Valdis Klētnieks [this message]
2020-04-21 21:30 ` exfat upcase table for code points above U+FFFF (Was: Re: [PATCH] staging: exfat: add exfat filesystem code to staging) Pali Rohár
2020-04-27 15:49 ` Sasha Levin
2020-04-28 7:46 ` Pali Rohár
2019-10-16 16:05 ` [PATCH] staging: exfat: add exfat filesystem code to staging Valdis Klētnieks
[not found] ` <20190828170022.GA7873@kroah.com>
[not found] ` <20190829062340.GB3047@infradead.org>
[not found] ` <20190829063955.GA30193@kroah.com>
[not found] ` <20190829094136.GA28643@infradead.org>
[not found] ` <20190829095019.GA13557@kroah.com>
[not found] ` <20190829103749.GA13661@infradead.org>
[not found] ` <20190829111810.GA23393@kroah.com>
2019-08-30 15:36 ` Christoph Hellwig
2019-08-30 21:54 ` Dave Chinner
2019-08-31 10:31 ` Valdis Klētnieks
2019-09-01 0:04 ` Dave Chinner
[not found] ` <20190829151144.GJ23584@kadam>
[not found] ` <20190829152757.GA125003@architecture4>
[not found] ` <20190829154346.GK23584@kadam>
[not found] ` <cd38b645-2930-3e02-6c6a-5972ea02b537@huawei.com>
[not found] ` <20190830115142.GM2752@twin.jikos.cz>
2019-08-31 3:50 ` Chao Yu
2019-09-14 13:39 ` [PATCH] staging: exfat: add exfat filesystem code to Park Ju Hyung
2019-09-15 13:54 ` Greg KH
2019-09-15 16:11 ` Ju Hyung Park
[not found] ` <20190918195920.25210-1-qkrwngud825@gmail.com>
2019-09-18 20:12 ` [PATCH] staging: exfat: rebase to sdFAT v2.2.0 Greg KH
2019-09-18 20:13 ` Greg KH
2019-09-18 20:22 ` Ju Hyung Park
2019-09-18 20:26 ` Greg KH
2019-09-18 20:31 ` Ju Hyung Park
2019-09-18 20:46 ` Valdis Klētnieks
2019-09-18 21:31 ` kbuild test robot
2019-09-18 21:31 ` kbuild test robot
2019-09-18 22:17 ` Ju Hyung Park
2019-10-24 9:39 ` [PATCH] staging: exfat: add exfat filesystem code to staging Pali Rohár
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=89492.1581722738@turing-police \
--to=valdis.kletnieks@vt.edu \
--cc=alexander.levin@microsoft.com \
--cc=devel@driverdev.osuosl.org \
--cc=gregkh@linuxfoundation.org \
--cc=hch@infradead.org \
--cc=linux-fsdevel@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=pali.rohar@gmail.com \
--cc=sashal@kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).