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. > > > 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.
