Re: Add a mountlist iterator

["J. Hannken-Illjes" <hannken%eis.cs.tu-bs.de@localhost>]

> On 30. Mar 2017, at 17:20, Christos Zoulas <christos%astron.com@localhost> wrote:
> 
> In article <534552FB-AF29-4219-8390-7514A2665CD0%eis.cs.tu-bs.de@localhost>,
> J. Hannken-Illjes <hannken%eis.cs.tu-bs.de@localhost> wrote:
>> Currently vfs_busy() / vfs_unbusy() get used to
>> 
>> - Enter/leave a critical section against unmounting
>> 
>> - Add a reference to the mount
>> 
>> - return the next mount from the mountlist on error
>> 
>> Plan is to untangle the mountlist processing from vfs_busy() / vfs_unbusy()
>> and add an iterator for the mountlist:
>> 
>> - void mountlist_iterator_init(mount_iterator_t **)
>> to initialize an iterator in mounted order.
>> 
>> - void mountlist_iterator_init_reverse(mount_iterator_t **)
>> to initialize an iterator in reverse mounted order.
>> 
>> - void mountlist_iterator_destroy(mount_iterator_t *)
>> to destroy an iterator aquired with one of the above.
>> 
>> - struct mount *mountlist_iterator_next(mount_iterator_t *, int)
>> to retrieve the next mount from an iterator or NULL if done.
>> The mount is returned vfs_busy'd, caller has to vfs_unbusy.
>> Accepts a flag MNT_NOWAIT to skip mounts whose unmount is in progress.
>> 
>> - struct mount *_mountlist_next(struct mount *)
>> a lockless variant to be used from DDB only.
>> 
>> Diffs are here: https://www.netbsd.org/~hannken/ml_iterator/
>> 
>> Comments or objections anyone?
> 
> LGTM, but can't all the copies of the dostatvfs iteration be merged
> together and utilize a converter function to handle the data massaging?

Looks like vfs_syscalls.c::do_sys_getvfsstat() - iterate over the
mountlist and call a copyfn() function on the stat buffer - already
does it.

--
J. Hannken-Illjes - hannken%eis.cs.tu-bs.de@localhost - TU Braunschweig (Germany)