USB storage question (was Re: CD Eject)

Pete Zaitcev zaitcev at redhat.com
Fri Jan 6 20:54:13 UTC 2006


> From: Cam <camilo at mesias.co.uk>
> References: <1cef3e950601050604g484b26cdo2b27de665fc9d6c2 at mail.gmail.com>
> 	<1136488717.22333.42.camel at remedyz.boston.redhat.com>

> > First, never yank a mounted USB device.
> [...]

Cam didn't quote relevant headers, so I cannot be sure with whom
I am disagreeing here, and I do not see the original message in
the thread. Remedyz.boston is J5's box.

Anyway, it's completely safe to yank a mounted USB device, as far as
system is concerned. If someone disagrees, we'll meet at dawn. :-)
Your data on it may suffer, but hey, that's called "freedom" (to hurt
yourself).

Current VFS orphans necessary files and inodes just fine in case of
a forced umount. Even if there was no umount, ub correctly orphans
the block device (actually, I think usb-storage and sd_mod try too).
So you are "guaranteed" that the system won't oops.

What is left is the filesystem integrity and delayed writes. Mounting
with "sync" is harmful and slow, but I think we do not delay writes
these days. So, it should be safe to look at LEDs and pull the device
when they stop flashing.

Seriously, people, USB devices are designed to be hotpluggable.

-- Pete




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