On Thu, Mar 8, 2018 at 4:38 AM, yangerkun <yangerkun@xxxxxxxxxx> wrote: > [...] >>>> >>>> In fsck.overlay, lower layer file/dir may be modified with there is not >>>> I_OVL_INUSE in lower layer, but we cannot check does lower layer mounted >>>> with I_OVL_INUSE. >>>> >>> [...] >> Also, if we follow my suggestion above for upperdir/workdir >> fsck.overlay may still >> try to aquire I_OVL_INUSE on lowerdir with O_EXCL|O_DIRECTORY and kernel >> can test I_OVL_INUSE flag on lowerdir without trying to set it on mount. > > > It's good when we want to mount overlayfs with fsck.overlay is running; But > when there is a mounted overlayfs before fsck.overlay, we cannot use this > way to check if the lower layer has already been used. Perhaps we should acquire a shared POSIX lock from kernel on lower/upper/work dirs and fsck.overlay should acquire an exclusive POSIX lock. I'm not sure how acquiring a POSIX lock from kernel should work and which task should be the owner of the lock, but generally overlayfs could either have a single owner task in the kernel for all super blocks or one owner per sb, in which case, we could acquire an exclusive lock on work/upper dirs instead of using the custom I_OVL_INUSE lock. Just a thought - not sure if this makes sense. CC'ing Jeff for reality check. Thanks, Amir. -- To unsubscribe from this list: send the line "unsubscribe linux-unionfs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
