Re: [Qemu-devel] [PATCH v3 0/3] nvdimm: support MAP_SYNC for memory-backend-file

[Haozhong Zhang]

ping?

On 01/17/18 16:13 +0800, Haozhong Zhang wrote:
> v3 is based on Eduardo's machine-next tree. Changes of
> memory-backend-file are based on my previous patches in that tree.
> 
> 
> Linux 4.15 introduces a new mmap flag MAP_SYNC, which can be used to
> guarantee the write persistence to mmap'ed files supporting DAX (e.g.,
> files on ext4/xfs file system mounted with '-o dax').
> 
> A description of MAP_SYNC and MAP_SHARED_VALIDATE can be found at
>     https://patchwork.kernel.org/patch/10028151/
> 
> This patchset enables QEMU to use MAP_SYNC flag for memory-backend-file,
> in order to guarantee the guest write persistence to backend files
> supporting DAX.
> 
> A new auto on/off option 'sync' is added to memory-backend-file:
>  - on:  try to pass MAP_SYNC to mmap(2); if MAP_SYNC is not supported or
>         'share=off', QEMU will abort
>  - off: never pass MAP_SYNC to mmap(2)
>  - auto (default): if MAP_SYNC is supported and 'share=on', work as if
>         'sync=on'; otherwise, work as if 'sync=off'
> 
> Changes in v3:
>  * Patch 1: add MAP_SHARED_VALIDATE in both sync=on and sync=auto
>    cases, and add back the retry mechanism. MAP_SYNC will be ignored
>    by Linux kernel 4.15 if MAP_SHARED_VALIDATE is missed.
>  * Patch 1: define MAP_SYNC and MAP_SHARED_VALIDATE as 0 on non-Linux
>    platforms in order to make qemu_ram_mmap() compile on those platforms.
>  * Patch 2&3: include more information in error messages of
>    memory-backend in hope to help user to identify the error.
>    (Dr. David Alan Gilbert)
>  * Patch 3: fix typo in the commit message. (Dr. David Alan Gilbert)
> 
> Changes in v2:
>  * Add 'sync' option to control the use of MAP_SYNC. (Eduardo Habkost)
>  * Remove the unnecessary set of MAP_SHARED_VALIDATE in some cases and
>    the retry mechanism in qemu_ram_mmap(). (Michael S. Tsirkin)
>  * Move OS dependent definitions of MAP_SYNC and MAP_SHARED_VALIDATE
>    to osdep.h. (Michael S. Tsirkin)
> 
> Haozhong Zhang (3):
>   util/mmap-alloc: support MAP_SYNC in qemu_ram_mmap()
>   hostmem: add hostmem type name and id in error messages
>   hostmem-file: add 'sync' option
> 
>  backends/hostmem-file.c   | 49 
> +++++++++++++++++++++++++++++++++++++++++++----
>  backends/hostmem.c        | 11 +++++++----
>  docs/nvdimm.txt           | 15 ++++++++++++++-
>  exec.c                    | 13 ++++++++-----
>  include/exec/memory.h     |  4 ++++
>  include/exec/ram_addr.h   |  6 +++---
>  include/qemu/mmap-alloc.h |  3 ++-
>  include/qemu/osdep.h      | 18 +++++++++++++++++
>  memory.c                  |  6 ++++--
>  numa.c                    |  2 +-
>  qemu-options.hx           | 21 +++++++++++++++++++-
>  util/mmap-alloc.c         | 24 +++++++++++++++++++++--
>  util/oslib-posix.c        |  2 +-
>  13 files changed, 149 insertions(+), 25 deletions(-)
> 
> -- 
> 2.14.1
>