On Thu, Feb 06, 2025 at 04:42:46PM +1100, NeilBrown wrote: > These "_async" versions of various inode operations are only guaranteed > a shared lock on the directory but if the directory isn't exclusively > locked then they are guaranteed an exclusive lock on the dentry within > the directory (which will be implemented in a later patch). > > This will allow a graceful transition from exclusive to shared locking > for directory updates, and even to async updates which can complete with > no lock on the directory - only on the dentry. I'm sorry, but I don't buy the "complete with no lock on directory" part - not without a verifiable proof of correctness of the locking scheme. Especially if you are putting rename into the mix. And your method prototypes pretty much bake that in. *IF* we intend to try going that way (and I'm not at all convinced that it's feasible - locking aside, there's also a shitload of fun with fsnotify, audit, etc.), let's make those new methods take a single argument - something like struct mkdir_args, etc., with inlines for extracting individual arguments out of that. Yes, it's ugly, but it allows later changes without a massive headache on each calling convention modification. Said that, an explicit description of locking scheme and a proof of correctness (at least on the "it can't deadlock" level) is, IMO, a hard requirement for the entire thing, async or no async. We *do* have such for the current locking scheme.
