[Skiboot] [PATCH] external/mambo: support mambo COW mode for PMEM disk

[Oliver O'Halloran]

On Tue, Feb 25, 2020 at 2:51 PM Stewart Smith <stewart at flamingspork.com> wrote:
>
> On Mon, Feb 24, 2020, at 1:20 PM, Oliver O'Halloran wrote:
> > On Tue, Feb 25, 2020 at 8:15 AM Michael Neuling <mikey at neuling.org> wrote:
> > >
> > > On Tue, 2020-02-18 at 14:16 -0600, Aaron Sawdey wrote:
> > > > I've added support in mambo's "memory mmap" command to have a "cow" mode
> > > > which just uses MAP_PRIVATE instead of MAP_SHARED on the file so that writes
> > > > to the memory region are not sent back to the file. This allows multiple
> > > > mambo instances to share the same filesystem image.
> > > >
> > > > This is implemented by having a PMEM_MODES environment variable. If this
> > > > is set, it is expected to contain a comma separated list of modes (rw or cow)
> > > > for the list of files in PMEM_DISK. If there are fewer modes than files, the
> > > > remaining files default to "rw".
> > >
> > > I'm not a big fan of the COW name. It suggests the writes are going somewhere. I
> > > realise this is the name used in mambo, but I'm not super keen on it. "PRIVATE"
> > > might be a better name.
> > >
> > > Can we call this (singular) PMEM_MODE since we have PMEM_DISK?
> > >
> > > Can you also include an example ie
> > >
> > >    export PMEM_DISK="mydisk1, mydisk2"
> > >    export PMEM_MODE="rw, cow"
> > >
> > >    Other than that, the code looks good.
> > >
> > >    Mikey
> >
> > Jokes on you. I already merged it.
>
> Didn't anyone tell you you're only meant to merge RFC patches? :)

Merging RFC patches is only permitted on fridays.

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