On Wed, Sep 09, 2015 at 04:41:34PM -0400, Anna Schumaker wrote: > On 09/09/2015 04:38 PM, Chris Mason wrote: > > On Wed, Sep 09, 2015 at 04:26:58PM -0400, Trond Myklebust wrote: > >> On Wed, Sep 9, 2015 at 4:09 PM, Chris Mason <clm@xxxxxx> wrote: > >>> On Tue, Sep 08, 2015 at 04:08:43PM -0700, Andy Lutomirski wrote: > >>>> On Tue, Sep 8, 2015 at 3:39 PM, Darrick J. Wong <darrick.wong@xxxxxxxxxx> wrote: > >>>>> On Tue, Sep 08, 2015 at 02:45:39PM -0700, Andy Lutomirski wrote: > >>>>>> What I meant by this was: if you ask for "regular copy", you may end > >>>>>> up with a reflink anyway. Anyway, how can you reflink a range and > >>>>>> have the contents *not* be the same? > >>>>> > >>>>> reflink forcibly remaps fd_dest's range to fd_src's range. If they didn't > >>>>> match before, they will afterwards. > >>>>> > >>>>> dedupe remaps fd_dest's range to fd_src's range only if they match, of course. > >>>>> > >>>>> Perhaps I should have said "...if the contents are the same before the call"? > >>>>> > >>>> > >>>> Oh, I see. > >>>> > >>>> Can we have a clean way to figure out whether two file ranges are the > >>>> same in a way that allows false negatives? I.e. return 1 if the > >>>> ranges are reflinks of each other and 0 if not? Pretty please? I've > >>>> implemented that in the past on btrfs by syncing the ranges and then > >>>> comparing FIEMAP output, but that's hideous. > >>> > >>> I'd almost rather have a separate call, maybe unshare_file_range()? > >>> > >> > >> Doesn't it make more sense to put that functionality in fallocate()? [slightly off-topic] How about FALLOC_FL_UNSHARE_RANGE? I've been looking for a place to land an unshare op that isn't chattr +C, and fallocate seems like a better fit anyway. --D > > > > That works too, I'm just hoping to keep the copy_file_range stuff > > simple. > > I agree with keeping copy_file_range() simple, especially for the initial > merge. Extra stuff can always be added in later :) > > Anna > > > > > -chris > > > > -- > To unsubscribe from this list: send the line "unsubscribe linux-api" in > the body of a message to majordomo@xxxxxxxxxxxxxxx > More majordomo info at http://vger.kernel.org/majordomo-info.html -- To unsubscribe from this list: send the line "unsubscribe linux-nfs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
