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

Oliver O'Halloran oohall at gmail.com
Tue Feb 25 08:20:45 AEDT 2020

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.

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