From: Namjae Jeon <linkinjeon@kernel.org>
To: Eric Sandeen <sandeen@sandeen.net>
Cc: linux-fsdevel <linux-fsdevel@vger.kernel.org>,
Namjae Jeon <namjae.jeon@samsung.com>,
Pavel Reichl <preichl@redhat.com>,
chritophe.vu-brugier@seagate.com,
Hyeoncheol Lee <hyc.lee@gmail.com>
Subject: Re: problem with exfat on 4k logical sector devices
Date: Wed, 12 May 2021 06:21:36 +0900 [thread overview]
Message-ID: <CAKYAXd_5hBRZkCfj6YAgb1D2ONkpZMeN_KjAQ_7c+KxHouLHuw@mail.gmail.com> (raw)
In-Reply-To: <372ffd94-d1a2-04d6-ac38-a9b61484693d@sandeen.net>
> Hi Namjae -
Hi Eric,
>
> It seems that exfat is unhappy on 4k logical sector size devices:
Thanks for your report!
We have got same report from Christophe Vu-Brugier. And he sent us
the patch(https://github.com/exfatprogs/exfatprogs/pull/164) to fix it
yesterday.(Thanks Christophe!), I will check it today.
>
> [root@big18 exfatprogs]# modprobe scsi_debug sector_size=4096
> dev_size_mb=256
> [root@big18 exfatprogs]# dmesg | tail -n 1
> [933449.931608] sd 16:0:0:0: [sdh] Attached SCSI disk
> [root@big18 exfatprogs]# mkfs.exfat /dev/sdh
> exfatprogs version : 1.0.4
> Creating exFAT filesystem(/dev/sdh, cluster size=4096)
>
> Writing volume boot record: done
> Writing backup volume boot record: done
> Fat table creation: done
> Allocation bitmap creation: done
> Upcase table creation: done
> Writing root directory entry: done
> Synchronizing...
>
> exFAT format complete!
>
> [root@big18 exfatprogs]# fsck.exfat /dev/sdh
> exfatprogs version : 1.0.4
> checksums of boot sector are not correct. 0x44e6c5, but expected 0xda55694.
> Fix (y/N)? n
>
> [root@big18 exfatprogs]# mount /dev/sdh /mnt/test
> mount: /mnt/test: wrong fs type, bad option, bad superblock on /dev/sdh,
> missing codepage or helper program, or other error.
> [root@big18 exfatprogs]# dmesg
> <...>
> [933485.685102] exFAT-fs (sdh): Invalid exboot-signature(sector = 1):
> 0x00000000
> [933485.686134] exFAT-fs (sdh): Invalid exboot-signature(sector = 2):
> 0x00000000
> [933485.687173] exFAT-fs (sdh): Invalid exboot-signature(sector = 3):
> 0x00000000
> [933485.688209] exFAT-fs (sdh): Invalid exboot-signature(sector = 4):
> 0x00000000
> [933485.689247] exFAT-fs (sdh): Invalid exboot-signature(sector = 5):
> 0x00000000
> [933485.690283] exFAT-fs (sdh): Invalid exboot-signature(sector = 6):
> 0x00000000
> [933485.691318] exFAT-fs (sdh): Invalid exboot-signature(sector = 7):
> 0x00000000
> [933485.692352] exFAT-fs (sdh): Invalid exboot-signature(sector = 8):
> 0x00000000
> [933485.695450] exFAT-fs (sdh): Invalid boot checksum (boot checksum :
> 0x0044e6c5, checksum : 0x04653cbf)
> [933485.695452] exFAT-fs (sdh): invalid boot region
> [933485.695453] exFAT-fs (sdh): failed to recognize exfat type
>
> I think the primary problem here is that the boot sector disk structures are
> always 512 bytes, even if the underlying disk sectors are 4k. There is a
> mismatch between mkfs, fsck, and the kernel in this respect. mkfs calculates
> checksums using 512 bytes for all but the OEM and reserved sectors, where it
> uses sector_size instead (which may be 4k)
Right.
>
> 3 mkfs/mkfs.c exfat_write_boot_sector 129
> boot_calc_checksum((unsigned char *)ppbr, sizeof(struct pbr),
> 4 mkfs/mkfs.c exfat_write_extended_boot_sectors 155
> boot_calc_checksum((unsigned char *) &eb, sizeof(struct exbs),
> 5 mkfs/mkfs.c exfat_write_oem_sector 184
> boot_calc_checksum((unsigned char *)oem, bd->sector_size, false,
> 6 mkfs/mkfs.c exfat_write_oem_sector 196
> boot_calc_checksum((unsigned char *)oem, bd->sector_size, false,
>
> but fsck uses the disk sector size (4k) for everything, so there is a
> checksum mismatch and failure.
>
> exfat_update_boot_checksum()
> ...
> int sector_size = bd->sector_size;
> ...
> boot_calc_checksum(buf, sector_size, is_boot_sec,
> &checksum);
>
> The kernel has similar problems at mount time.
>
> (the kernel also has an issue where exfat_verify_boot_region is looking at 4
> bytes from the end of the sector for EXBOOT_SIGNATURE, rather than 4 bytes
> from the end of the boot_sector. Also, s_blocksize_bits never gets set...)
>
> Anyway, this can all be fixed, but first there is a question about what is
> proper:
Okay.
>
> For these 11 regions (main boot sector, main extended boot sectors, OEM, and
> reserved, I think?) should the checksums be calculated on the full sector
> size (possibly 4k) or 512, or is it calculated on 512 (structure size) for
> all but the OEM sector as mkfs does? It's not clear to me from a quick read
> of the spec.
>
> (But from the example at
> https://docs.microsoft.com/en-us/windows/win32/fileio/exfat-specification#figure-1-boot-checksum-computation
> it almost looks like the checksum calculation should cover the entire 4k for
> all these regions, even if the disk structure itself is smaller?)
In this case, We can check a dump of boot sectors formatted from Windows.
Let me check it more.
Thanks Eric!
>
> Thanks,
> -Eric
>
next prev parent reply other threads:[~2021-05-11 21:21 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-05-11 17:28 problem with exfat on 4k logical sector devices Eric Sandeen
2021-05-11 21:21 ` Namjae Jeon [this message]
2021-05-11 23:33 ` Eric Sandeen
2021-05-11 23:53 ` Namjae Jeon
2021-05-11 23:57 ` Eric Sandeen
2021-05-12 14:09 ` Hyunchul Lee
2021-05-12 16:44 ` Eric Sandeen
2021-05-12 17:56 ` Eric Sandeen
2021-05-13 6:53 ` Namjae Jeon
2021-05-13 6:52 ` Namjae Jeon
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=CAKYAXd_5hBRZkCfj6YAgb1D2ONkpZMeN_KjAQ_7c+KxHouLHuw@mail.gmail.com \
--to=linkinjeon@kernel.org \
--cc=chritophe.vu-brugier@seagate.com \
--cc=hyc.lee@gmail.com \
--cc=linux-fsdevel@vger.kernel.org \
--cc=namjae.jeon@samsung.com \
--cc=preichl@redhat.com \
--cc=sandeen@sandeen.net \
/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 an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.