Re: [Qemu-devel] fstrim & upstream kernel not working

["Richard W.M. Jones" <rjones@redhat.com>]

On Fri, Mar 14, 2014 at 02:28:24PM +0100, Paolo Bonzini wrote:
> Il 14/03/2014 14:24, Richard W.M. Jones ha scritto:
> >>> Could be a race condition (something going on in the background
> >>> between rm and fstrim).
> >Not much happens in the libguestfs appliance.  There are usually only
> >two processes (udev + guestfsd).
> 
> There's also the kernel.  The ext4 driver is probably doing
> something after rm returns, and hasn't finished yet when you invoke
> FITRIM.

Yup.  libguestfs has exposed a number of places where you can type
commands slowly by hand, but running them from a script would fail.
Check out the number of places we call 'udevadm --settle' or 'sync' --
each one has been discovered painfully over 5 years.

$ git grep -E 'udev_settle|sync_disks' daemon | wc -l
59

Rich.

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