Help troubleshooting...

[Kostik Belousov]

On Sun, Oct 25, 2009 at 01:34:37PM -0600, M. Warner Losh wrote:
> I have a usb stick (8GB) on it.  This stick has about 5GB of junk on
> it at this point.
> 
> I tried to do 'cat * > /dev/null' recently, to measure how fast it
> goes.  It got about 1GB into the drive and then I got device missing
> messages.
> 
> Here's the dmesg messages:
> 
> # Plug it in
> da0 at umass-sim0 bus 0 scbus2 target 0 lun 0
> da0: <HP v125w PMAP> Removable Direct Access SCSI-0 device 
> da0: 40.000MB/s transfers
> da0: 7660MB (15687680 512 byte sectors: 255H 63S/T 976C)
> # mount it, etc
> # run the cat command
> Device da0s1 went missing before all of the data could be written to it; expect data loss.
> # get error messages
> # Remove the drive
> ugen2.2: <HP> at usbus2 (disconnected)
> umass0: at uhub2, port 1, addr 2 (disconnected)
> (da0:umass-sim0:0:0:0): lost device
> (da0:umass-sim0:0:0:0): removing device entry
> 
> So devfs thinks the device went missing:
> 
> static int
> devfs_fsync(struct vop_fsync_args *ap)
> {
> ...
> 	if (!vn_isdisk(ap->a_vp, &error)) {
> 		bo = &ap->a_vp->v_bufobj;
> 		de = ap->a_vp->v_data;
> 		if (error == ENXIO && bo->bo_dirty.bv_cnt > 0) {
> 			printf("Device %s went missing before all of the data "
> 			    "could be written to it; expect data loss.\n",
> 			    de->de_dirent->d_name);
> ...
> 
> So it thinks that it isn't a disk.  vn_isdisk is return ENXIO because
> either vp->v_rdev == NULL or the v_rdev->si_devsw == NULL.
si_devsw is cleared in kern_conf.c:destroy_devl, line 835.
I think USB subsystem called either destroy_dev() or destroy_dev_sched().

> 
> So how the heck can that happen without other warnings?  It appears
> the only place it is set like this is in devfs_reclaim.  But I'm
> having trouble tracking down where *THAT* is called.
Reclaim might be called if devfs mount point is forcibly unmounted
special vnode from which you used to mount pendrive.

> 
> This is with the following system:
> 
> FreeBSD lighthouse 9.0-CURRENT FreeBSD 9.0-CURRENT #41 r185338:198411M: Fri Oct 23 10:08:48 MDT 2009     imp at lighthouse:/cache/svn/head/sys/amd64/compile/LIGHTHOUSE  amd64
> 
> Warner
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