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From: Terry Lambert <tlambert@primenet.com>
Message-Id: <199802040716.AAA04564@usr08.primenet.com>
Subject: Re: sb being written to r/o disks.
To: julian@whistle.com (Julian Elischer)
Date: Wed, 4 Feb 1998 07:16:59 +0000 (GMT)
Cc: mckusick@mckusick.com, current@FreeBSD.ORG
In-Reply-To: <34D7B6B0.31DFF4F5@whistle.com> from "Julian Elischer" at Feb 3, 98 04:30:41 pm
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> something is doing syncronous writes to a r/o FS..
> who? that's easy..
> 
> # mount -u -ordonly /
> Breakpoint at   _mount: pushl   %ebp
> db> b bwrite
> db> c
> Breakpoint at   _bwrite:        pushl   %ebp
> db> tr
> _bwrite(f245ccf4,0) at _bwrite
> _ffs_sbupdate(f045f200,1) at _ffs_sbupdate+0xb0
> _ffs_mount(f045fc00,efbfd268,efbfd1cc,f3666eb8,f364e740) at
> _ffs_mount+0x1e5
> _mount(f364e740,f3666f94,0,efbfd268,1201) at _mount+0x416
> _syscall(27,27,1201,efbfd268,efbfd238) at _syscall+0x187
> _Xsyscall() at _Xsyscall+0x35
> --- syscall 0x15, eip = 0x6a95, esp = 0xefbfd188, ebp = 0xefbfd238 ---
> db> 
> 
> apparently _ffs_sbupdate() doesn't know to check if the fs is readonly..

This is kind of well known; this is because R/O FS's get their "last
mounted on" information updated.  This is probably a bad thing.
Probably the "last mounted on" information for a R/O FS should be
set by newfs.  It really means "please mount me here".


					Terry Lambert
					terry@lambert.org
---
Any opinions in this posting are my own and not those of my present
or previous employers.