Re: kern/59924: NetBSD improperly does not update FAT0 on FAT12 MSDOS filesystem

["Michael Cheponis via gnats" <gnats-admin%NetBSD.org@localhost>]

The following reply was made to PR kern/59924; it has been noted by GNATS.

From: Michael Cheponis <michael.cheponis%gmail.com@localhost>
To: gnats-bugs%netbsd.org@localhost
Cc: mac%culver.net@localhost
Subject: Re: kern/59924: NetBSD improperly does not update FAT0 on FAT12 MSDOS filesystem
Date: Sat, 17 Jan 2026 12:58:46 -0800

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 If you do:
 
 # mount_mdos /dev/sd3a /a
 # disklabel -W sd3
 
 THEN you access files on /a normally: add/rm etc, when finished:
 
 # umount /a
 # disklabel -N sd3
 
 # fsck_msdos /dev/sd3a
 ** /dev/rsd3a
 ** Phase 1 - Read and Compare FATs
 ** Phase 2 - Check Cluster Chains
 ** Phase 3 - Checking Directories
 ** Phase 4 - Checking for Lost Files
 81 files, 0 free (0 clusters)
 
 Everything works.
 
 Maybe documentation needs to be updated to show this?  Or maybe protection
 of cluster 0 needs to be removed when mounting msdos?
 
 
 
 On Fri, Jan 16, 2026 at 2:45=E2=80=AFPM <gnats-admin%netbsd.org@localhost> wrote:
 
 > Thank you very much for your problem report.
 > It has the internal identification `kern/59924'.
 > The individual assigned to look at your
 > report is: kern-bug-people.
 >
 > >Category:       kern
 > >Responsible:    kern-bug-people
 > >Synopsis:       when files are created/removed from MSDOS FAT12
 > filesystem, FAT0 is not updated
 > >Arrival-Date:   Fri Jan 16 22:45:00 +0000 2026
 >
 >
 
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 <div dir=3D"ltr"><div class=3D"gmail_default" style=3D"font-family:arial,he=
 lvetica,sans-serif;font-size:small">If you do:</div><div class=3D"gmail_def=
 ault" style=3D"font-family:arial,helvetica,sans-serif;font-size:small"><br>=
 </div><div class=3D"gmail_default" style=3D"font-size:small"><font face=3D"=
 monospace"># mount_mdos /dev/sd3a /a</font></div><div class=3D"gmail_defaul=
 t" style=3D"font-size:small"><font face=3D"monospace"># disklabel -W sd3</f=
 ont></div><div class=3D"gmail_default" style=3D"font-family:arial,helvetica=
 ,sans-serif;font-size:small"><br></div><div class=3D"gmail_default" style=
 =3D"font-family:arial,helvetica,sans-serif;font-size:small">THEN you access=
  files on /a normally: add/rm etc, when finished:</div><div class=3D"gmail_=
 default" style=3D"font-family:arial,helvetica,sans-serif;font-size:small"><=
 br></div><div class=3D"gmail_default" style=3D"font-size:small"><font face=
 =3D"monospace"># umount /a</font></div><div class=3D"gmail_default" style=
 =3D"font-size:small"><font face=3D"monospace"># disklabel -N sd3</font></di=
 v><div class=3D"gmail_default" style=3D"font-size:small"><font face=3D"mono=
 space"><br></font></div><div class=3D"gmail_default" style=3D"font-size:sma=
 ll"><font face=3D"monospace"># fsck_msdos /dev/sd3a</font></div><div class=
 =3D"gmail_default" style=3D"font-size:small"><font face=3D"monospace">** /d=
 ev/rsd3a<br>** Phase 1 - Read and Compare FATs<br>** Phase 2 - Check Cluste=
 r Chains<br>** Phase 3 - Checking Directories<br>** Phase 4 - Checking for =
 Lost Files<br>81 files, 0 free (0 clusters)</font><br></div><div class=3D"g=
 mail_default" style=3D"font-family:arial,helvetica,sans-serif;font-size:sma=
 ll"><br></div><div class=3D"gmail_default" style=3D"font-family:arial,helve=
 tica,sans-serif;font-size:small">Everything works.</div><div class=3D"gmail=
 _default" style=3D"font-family:arial,helvetica,sans-serif;font-size:small">=
 <br></div><div class=3D"gmail_default" style=3D"font-family:arial,helvetica=
 ,sans-serif;font-size:small">Maybe documentation needs to be updated to sho=
 w this?=C2=A0 Or maybe protection of cluster 0 needs to be removed when mou=
 nting msdos?</div><div class=3D"gmail_default" style=3D"font-family:arial,h=
 elvetica,sans-serif;font-size:small"><br></div><div class=3D"gmail_default"=
  style=3D"font-family:arial,helvetica,sans-serif;font-size:small"><br></div=
 ></div><br><div class=3D"gmail_quote gmail_quote_container"><div dir=3D"ltr=
 " class=3D"gmail_attr">On Fri, Jan 16, 2026 at 2:45=E2=80=AFPM &lt;<a href=
 =3D"mailto:gnats-admin%netbsd.org@localhost";>gnats-admin%netbsd.org@localhost</a>&gt; wrote:<br=
 ></div><blockquote class=3D"gmail_quote" style=3D"margin:0px 0px 0px 0.8ex;=
 border-left:1px solid rgb(204,204,204);padding-left:1ex">Thank you very muc=
 h for your problem report.<br>
 It has the internal identification `kern/59924&#39;.<br>
 The individual assigned to look at your<br>
 report is: kern-bug-people. <br>
 <br>
 &gt;Category:=C2=A0 =C2=A0 =C2=A0 =C2=A0kern<br>
 &gt;Responsible:=C2=A0 =C2=A0 kern-bug-people<br>
 &gt;Synopsis:=C2=A0 =C2=A0 =C2=A0 =C2=A0when files are created/removed from=
  MSDOS FAT12 filesystem, FAT0 is not updated<br>
 &gt;Arrival-Date:=C2=A0 =C2=A0Fri Jan 16 22:45:00 +0000 2026<br>
 <br>
 </blockquote></div>
 
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