Kyle Moffett wrote:
In this case they _are_ equivalent due to symmetry. If the other
device _may_ assume that the connection is broken, then you _must_
assume that the connection is broken. Since either device _may_
assume that, both devices therefore _must_ according to spec.
Only insofar as the kernel can not assume the device is still
connected. If the kernel sees that it is immediately reconnected and
has every reason to believe that the 'disconnect' was only a result of
momentary power loss, and it can probably continue to access the device
with no consequences, then it should do so.
No, as I said before, a good set of USB suspend scripts can solve this
problem. All of the ones I am aware of *now* already sync all data,
which is good enough to prevent data-loss in _every_ case where the
device is spontaneously unplugged. On the other hand, this is _never_
good enough if the device is accidentally switched underneath us while
suspended (and that's not so terribly uncommon, I know a lot of people
who would do that accidentally, myself included).
I suppose this is true. Syncing before suspend will (mostly) keep the
kernel from shooting the user in the foot.
I think most users prefer a system that works right when you use it
right to one that doesn't break quite as badly when you do something
stupid.
I think you just proved my point. Running the "sync" command a couple
times then unplugging the USB stick basically never results in data
loss even if the filesystem is mounted. Spontaneously switching block
devices under a mounted filesystem is guaranteed to either panic the
machine or cause massive data corruption or both.
But who cares? There are plenty of really stupid things users can do to
hose their system, it isn't right to prevent them from doing something
perfectly reasonable just because it reduces the damage done when they
do something completely unreasonable.
Also why is this argument more valid for USB than SCSI? I am just as
free to unplug a scsi disk and replace it with a different one while
hibernated, yet I don't suffer data loss when I don't do such
foolishness.
SCSI != USB. Users generally don't expect to hotplug SCSI devices
while booted and running (with the exception of some _really_
expensive hotplug-bays where we expect the admin to know what the hell
they're doing). On the other hand, users _do_ expect to hotplug
random USB devices whenever they feel like it.
So because SCSI is more expensive than USB, it is ok to assume it will
only be used by people who know what they are doing? And since USB will
be used by people who don't know what they are doing, we must assume
they will always do silly things ( swap or modify the drive while
suspended ), at the expense of those who don't?
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