From: "Pali Rohár" <pali.rohar@gmail.com>
To: OGAWA Hirofumi <hirofumi@mail.parknet.co.jp>
Cc: linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org
Subject: Re: [PATCH] fat: Relax checks for sector size and media type
Date: Mon, 3 Sep 2018 10:04:22 +0200 [thread overview]
Message-ID: <20180903080422.ta3clnhr5bobv6il@pali> (raw)
In-Reply-To: <874lf7t3gg.fsf@mail.parknet.co.jp>
On Monday 03 September 2018 17:01:03 OGAWA Hirofumi wrote:
> Pali Rohár <pali.rohar@gmail.com> writes:
>
> >> Just relaxing validation doesn't work. The block layer doesn't support
> >> smaller than 512, and lager than PAGE_SIZE. (And in specification, fat
> >> doesn't support lager than 4096.)
> >
> > Hi! I just sent this patch for discussion, with links to (now open
> > source) Windows implementation. I guess that Windows driver
> > implementation is more "authoritative" then Microsoft's own
> > specification. It is known that Windows implementation does not match
> > Microsoft specification.
> >
> > I know at least 3 FAT specifications (MS EFI FAT, MS/SD card FAT,
> > ECMA-107) and you are right that Microsoft's one does not allow sector
> > sizes larger then 4096.
> >
> > If there is limitation by block layer, then:
> >
> > 1) Why we do not check for PAGE_SIZE?
>
> That source seems to check power_of_2(size) and 128 <= size <=
> 4096. Rather why do you want to support larger than 4096? Or I'm missing
> something?
I looked into (Linux) mkfs.fat and it supports formatting disk also with
sector size > 4096. Therefore I thought it may be good idea for ability
to mount and use it (on Linux).
I could check what other operating system would do with FAT sector size
larger then 4096.
> > 2) Is check in fat driver really needed (if block layer checks it)?
>
> Yes, isolating block layer error and fat format error to be better error
> report.
Ok.
--
Pali Rohár
pali.rohar@gmail.com
next prev parent reply other threads:[~2018-09-03 12:23 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-09-02 13:19 [PATCH] fat: Relax checks for sector size and media type Pali Rohár
2018-09-03 7:17 ` OGAWA Hirofumi
2018-09-03 7:40 ` Pali Rohár
2018-09-03 8:01 ` OGAWA Hirofumi
2018-09-03 8:04 ` Pali Rohár [this message]
2018-09-03 8:19 ` OGAWA Hirofumi
2018-09-12 10:17 ` Pali Rohár
2018-09-12 10:36 ` OGAWA Hirofumi
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