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From: "Valdis Klētnieks" <valdis.kletnieks@vt.edu>
To: "Pali Rohár" <pali.rohar@gmail.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	devel@driverdev.osuosl.org, linux-fsdevel@vger.kernel.org,
	linux-kernel@vger.kernel.org,
	Sasha Levin <alexander.levin@microsoft.com>,
	Christoph Hellwig <hch@infradead.org>
Subject: Re: [PATCH] staging: exfat: add exfat filesystem code to staging
Date: Thu, 29 Aug 2019 08:34:04 -0400
Message-ID: <81682.1567082044@turing-police> (raw)
In-Reply-To: <20190829121435.bsl5cnx7yqgakpgb@pali>

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On Thu, 29 Aug 2019 14:14:35 +0200, Pali Rohár said:
> On Wednesday 28 August 2019 18:08:17 Greg Kroah-Hartman wrote:
> > The full specification of the filesystem can be found at:
> >   https://docs.microsoft.com/en-us/windows/win32/fileio/exfat-specification
>
> This is not truth. This specification is not "full". There are missing
> important details, like how is TexFAT implemented. 

Well..given that the spec says it's an extension used by Windows CE...

> 1.5 Windows CE and TexFAT

> TexFAT is an extension to exFAT that adds transaction-safe operational
> semantics on top of the base file system. TexFAT is used by Windows CE. TexFAT
> requires the use of the two FATs and allocation bitmaps for use in
> transactions. It also defines several additional structures including padding
> descriptors and security descriptors.

And these two pieces of info:

> 3.1.13.1 ActiveFat Field

> The ActiveFat field shall describe which FAT and Allocation Bitmap are active
> (and implementations shall use), as follows:

> 0, which means the First FAT and First Allocation Bitmap are active

> 1, which means the Second FAT and Second Allocation Bitmap are active and is
> possible only when the NumberOfFats field contains the value 2

> Implementations shall consider the inactive FAT and Allocation Bitmap as stale.
> Only TexFAT-aware implementations shall switch the active FAT and Allocation
> Bitmaps (see Section 7.1).

> 3.1.16 NumberOfFats Field
> The NumberOfFats field shall describe the number of FATs and Allocation Bitmaps
> the volume contains.

> The valid range of values for this field shall be:

> 1, which indicates the volume only contains the First FAT and First Allocation Bitmap

> 2, which indicates the volume contains the First FAT, Second FAT, First
> Allocation Bitmap, and Second Allocation Bitmap; this value is only valid for
> TexFAT volumes

I think we're OK if we just set ActiveFat to 0 and NumberOfFats to 1.

Unless somebody has actual evidence of a non-WindowsCE extfat that has
NumberOfFats == 2....

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  reply index

Thread overview: 70+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-08-28 16:08 Greg Kroah-Hartman
2019-08-28 17:00 ` Greg Kroah-Hartman
2019-08-29  6:23   ` Christoph Hellwig
2019-08-29  6:39     ` Greg Kroah-Hartman
2019-08-29  9:41       ` Christoph Hellwig
2019-08-29  9:50         ` Greg Kroah-Hartman
2019-08-29 10:37           ` Christoph Hellwig
2019-08-29 11:04             ` Gao Xiang
2019-08-29 11:18               ` Greg Kroah-Hartman
2019-08-29 11:18             ` Greg Kroah-Hartman
2019-08-29 15:11               ` Dan Carpenter
2019-08-29 15:27                 ` Gao Xiang
2019-08-29 15:43                   ` Dan Carpenter
2019-08-29 15:51                     ` Gao Xiang
2019-08-29 16:04                       ` Gao Xiang
2019-08-30  8:34                         ` Dan Carpenter
2019-08-30  8:43                           ` Gao Xiang
2019-08-30 11:26                             ` Dan Carpenter
2019-08-30 12:04                               ` Gao Xiang
2019-08-29 16:44                     ` Gao Xiang
2019-08-29 16:59                       ` Joe Perches
2019-08-29 17:02                         ` Gao Xiang
2019-08-30  2:06                     ` Chao Yu
2019-08-30  6:38                       ` Gao Xiang
2019-08-30 12:00                         ` Checking usage of likeliness annotations Markus Elfring
2019-08-30 11:51                       ` [PATCH] staging: exfat: add exfat filesystem code to staging David Sterba
2019-08-31  3:50                         ` Chao Yu
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
2019-08-29  7:01     ` Gao Xiang
2019-08-29  8:24       ` Gao Xiang
2019-08-29  9:51         ` Christoph Hellwig
2019-08-29 12:14 ` Pali Rohár
2019-08-29 12:34   ` Valdis Klētnieks [this message]
2019-08-29 12:46     ` Pali Rohár
2019-08-29 14:08 ` Markus Elfring
2019-08-29 15:44 ` Markus Elfring
2019-08-29 20:56 ` Pali Rohár
2019-08-29 23:18   ` Valdis Klētnieks
2019-08-29 23:35     ` Sasha Levin
2019-08-30  7:56       ` Pali Rohár
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
2019-10-16 16:05             ` Valdis Klētnieks
2019-08-30  8:03     ` Pali Rohár
2019-08-30 15:40   ` Christoph Hellwig
2019-08-30 15:43     ` Pali Rohár
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

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