On Thu, Dec 19, 2024 at 06:50:59AM +0100, Christoph Hellwig wrote: > On Tue, Dec 17, 2024 at 08:59:55AM -0800, Darrick J. Wong wrote: > > Hrmm, they're rt extents that are available "now", or "for cheap"... > > > > XC_FREE_NOW_RTEXTENTS > > > > XC_FREE_RTEXTENTS_IMMED > > > > XC_FREE_RTEXTENTS_CHEAP > > > > Eh, I'm not enthusiastic about any of those. The best I can think of > > is: > > > > XC_FREE_RTEXTENTS_NOGC, /* space available without gc */ > > I really hate that, as it encodes the policy how to get (or not) the > blocks vs what they are. Yeah, me too. Want to leave it as XC_FREE_RTAVAILABLE? > > > > going to use the greedy algorithm. Later I see XFS_ZR_GREEDY gets used > > > > from the buffered write path, but there doesn't seem to be an obvious > > > > reason why? > > > > > > Posix/Linux semantics for buffered writes require us to implement > > > short writes. That is if a single (p)write(v) syscall for say 10MB > > > only find 512k of space it should write those instead of failing > > > with ENOSPC. The XFS_ZR_GREEDY implements that by backing down to > > > what we can allocate (and the current implementation for that is > > > a little ugly, I plan to find some time for changes to the core > > > percpu_counters to improve this after the code is merged). > > > > Ah, ok. Can you put that in the comments defining XFS_ZR_GREEDY? > > This is what I added earlier this week: > > /* > * Grab any available space, even if it is less than what the caller asked for. > */ > #define XFS_ZR_GREEDY (1U << 0) > > Do you want the glory details on why we're doing it here as well? > I guess it if can't be left as an exercise to the reader I'd probably > rather place it in the caller. Nah, that's enough to hint at what I should be looking for any time there's a branch involving XFS_ZR_GREEDY. --D
