suspending threads before devices

[Benjamin Kaduk]

On Wed, 19 Nov 2014, John Baldwin wrote:

> Yes, there should have been quotes around unmount.  I want a
> VFS_SUSPEND/VFS_RESUME that for local filesystems (e.g. UFS) does the on-disk
> equivalent of unmount.  (Flush dirty buffers and mark filesystem as clean.)
> You really want this for S4 and even for S3 so you don't have to fsck if
> resume fails.  BTW, I think for network or userland filesystems you just punt
> on this (i.e. VFS_SUSPEND is a no-op or best-effort at most)

Well, some network filesystems have things that could be done in this
vein, but that would have to be at the filesystem layer, not in the VFS, I
think.  (E.g., OpenAFS has "disconnected mode".)

-Ben