lkml.org 
[lkml]   [2016]   [Nov]   [24]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
From
Date
SubjectRe: [fuse-devel] fuse: feasible to distinguish between umount and abort?
On Thu, Nov 24, 2016 at 12:11 AM, Nikolaus Rath <Nikolaus@rath.org> wrote:
> Hello,
>
> Currently, both a call to umount(2) and writing "1" to
> /sys/fs/fuse/connections/NNN/abort will put the /dev/fuse fd into the
> same state: reading from it returns ENODEV, and polling on it returns
> POLLERR.
>
> This causes problems for filesystems that want to ensure that the
> mountpoint is free when they exit. If accessing the device fd gives the
> above errors, they have to do an additional check to determine if they
> still need to unmount the mountpoint. This is difficult to do without
> race conditions (think of someone unmounting and immediately re-starting
> a new filesystem instance).
>
> Would it be possible to change the behavior of the /dev/fuse fd so that
> userspace can distinguish between a regular umount and use of the
> /sys/fs/fuse abort)?

Yes. My proposal would be for the kernel to send FUSE_DESTROY
asynchronously and only return ENODEV once that request was read by
userspace. Currently FUSE_DESTROY is sent synchronously for fuseblk
mounts, but not for plain fuse mounts.

Please file a bug somewhere. I don't mind if kernel bugs are also
kept at the github project as long as they can easily be found.

Thanks,
Miklos

\
 
 \ /
  Last update: 2016-11-24 10:11    [W:0.146 / U:0.224 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site