Date: Wed, 25 Feb 2004 07:45:07 -0800 (PST) From: Aaron Peterson <aaron@alpete.com> To: freebsd-gnats-submit@FreeBSD.org Subject: ports/63354: bcwipe does not act successfully on raw devices Message-ID: <200402251545.i1PFj76E042358@www.freebsd.org> Resent-Message-ID: <200402251550.i1PFoBFL005768@freefall.freebsd.org>
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>Number: 63354 >Category: ports >Synopsis: bcwipe does not act successfully on raw devices >Confidential: no >Severity: non-critical >Priority: low >Responsible: freebsd-ports-bugs >State: open >Quarter: >Keywords: >Date-Required: >Class: sw-bug >Submitter-Id: current-users >Arrival-Date: Wed Feb 25 07:50:11 PST 2004 >Closed-Date: >Last-Modified: >Originator: Aaron Peterson >Release: 5.2 >Organization: KY Cabinet for Health Services >Environment: FreeBSD fbsd52.state.ky.us 5.2-RELEASE FreeBSD 5.2-RELEASE #0: Sun Jan 11 04:21:45 GMT 2004 root@wv1u.btc.adaptec.com:/usr/obj/usr/src/sys/GENERIC i386 >Description: the bcwipe port seems to work as expected on files, but errors when asked to act on a raw device. Discussion on freebsd-current mailing list suggests this has to do with bcwipe expecting to act on a block device, when freebsd 5.2 no longer has block devices, only character devices. I don't even know the difference between the two, so I'm just repeating here. the subject of mail in this thread on freebsd-current was "bcwipe won't wipe a block device" >How-To-Repeat: ask bcwipe to wipe a block device per the example in the man page: bcwipe -bvmd /dev/fd0 or in my case, acting on a portable usb drive: bcwipe -bvmd /dev/da0 kdump/ktrace of this command on my system can be found here: http://alpete.com/bcwipe.kdump.txt >Fix: The final post in this thread on freebsd-current suggested the following: On Fri, 20 Feb 2004, John-Mark Gurney wrote: > Peter Jeremy wrote this message on Fri, Feb 20, 2004 at 18:23 +1100: > > Summary: bcwipe is trying to read 1 byte from an offset of 2^N-1. > > FreeBSD no longer has block devices (since 4.0) - /dev/da0 is a > > character device. Character devices can only be read in blocksize > > units (typically 512 bytes for disks). You need to fix bcwipe to > > handle character devices. > > this can be done by using the fstat call on the device node.. it will > provide both the proper block size (so it'll work w/ md swap backed > devices that have a 4k block size) and device size... Um, this can not be done by using the fstat call on the device node. fstat() on devices always gives 0 for the device size and is little better for the block size. The block size is always the nominal value PAGE_SIZE for non-disk devices and is not always the nominal value BLKDEV_IOSIZE for disk devices. From vfs_vnops.c: % } else if (vn_isdisk(vp, NULL)) { % sb->st_blksize = vp->v_rdev->si_bsize_best; % if (sb->st_blksize < vp->v_rdev->si_bsize_phys) % sb->st_blksize = vp->v_rdev->si_bsize_phys; % if (sb->st_blksize < BLKDEV_IOSIZE) % sb->st_blksize = BLKDEV_IOSIZE; % } else { % sb->st_blksize = PAGE_SIZE; % } Here si_bsize_phys is the sector size of drivers or GEOM set it, else it is defaulted to DEV_BSIZE in spec_open(). si_bsize_bestt is fully rotted garbage -- it is only used above, but never set except using bzero() to 0. Since sector sizes are normally smaller than BLKDEV_IOSIZE and BLKDEV_IOSIZE is normally PAGE_SIZE, the above normally sets st_blksize to PAGE_SIZE for all devices. Bruce >Release-Note: >Audit-Trail: >Unformatted:
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