Re: PR/42782 CVS commit: src/sys/ufs/ffs

[Michael van Elst <mlelstv%serpens.de@localhost>]

The following reply was made to PR kern/42782; it has been noted by GNATS.

From: Michael van Elst <mlelstv%serpens.de@localhost>
To: Izumi Tsutsui <tsutsui%ceres.dti.ne.jp@localhost>
Cc: gnats-bugs%NetBSD.org@localhost, kern-bug-people%NetBSD.org@localhost, 
gnats-admin%NetBSD.org@localhost,
        martin%NetBSD.org@localhost, mlelstv%NetBSD.org@localhost
Subject: Re: PR/42782 CVS commit: src/sys/ufs/ffs
Date: Thu, 11 Feb 2010 20:15:04 +0100

 On Fri, Feb 12, 2010 at 12:42:12AM +0900, Izumi Tsutsui wrote:
 > >  Module Name:      src
 > >  Committed By:     mlelstv
 > >  Date:             Thu Feb 11 00:06:16 UTC 2010
 > >  
 > >  Modified Files:
 > >    src/sys/ufs/ffs: ffs_vfsops.c
 > >  
 > >  Log Message:
 > >  There is no code left that uses disk size data, so don't query it.
 > >  This also failed when querying the simulated block device from mfs.
 > >  Fixes PR kern/42782.
 > 
 >  * ext2fs has the similar code.
 
 mfs fails because mfs is a hack that simulates only the block device
 without the underlying disk driver. As such it does not provide
 information about disk size or physical sector size.
 
 Fortunately mfs is ffs in disguise and ffs does not need real information
 about the physical disk on NetBSD because it can rely on DEV_BSIZE when
 talking to device drivers and stores disk size information in the
 superblock.
 
 ext2fs isn't used with such a hack but only with real device drivers,
 so it doesn't matter. However, it also doesn't need information about
 the physical disk on NetBSD (for the same reason as ffs),
 so the query can go away.
 
 >  * msdosfs still uses getdisksize() and secsize, and
 >    mountfs fails if getdisksize() returns error.
 
 msdosfs is also used with real device drivers. So far it does
 require information about the physical disk and it would have
 failed the same way before I encapsulated the ioctl's into
 getdisksize(). Why do you think that's bad now?
 
 
 Greetings,
 -- 
                                 Michael van Elst
 Internet: mlelstv%serpens.de@localhost
                                 "A potential Snark may lurk in every tree."