On Nov 24 2016, Miklos Szeredi <miklos@xxxxxxxxxx> wrote: > On Thu, Nov 24, 2016 at 12:11 AM, Nikolaus Rath <Nikolaus@xxxxxxxx> 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. I trust that this is a good plan, but from the description I can't quite tell how the filesystem would make the distinction between umount/abort based on this. Would FUSE_DESTROY be send only for unmount, but not for abort? > 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. Already done at https://github.com/libfuse/libfuse/issues/122. Thanks! -Nikolaus -- GPG encrypted emails preferred. Key id: 0xD113FCAC3C4E599F Fingerprint: ED31 791B 2C5C 1613 AF38 8B8A D113 FCAC 3C4E 599F »Time flies like an arrow, fruit flies like a Banana.« -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
