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Re: [Qemu-devel] [PATCH V6 0/6] nvdimm: support MAP_SYNC for memory-back
From: |
Michael S. Tsirkin |
Subject: |
Re: [Qemu-devel] [PATCH V6 0/6] nvdimm: support MAP_SYNC for memory-backend-file |
Date: |
Wed, 12 Dec 2018 10:06:13 -0500 |
On Wed, Dec 12, 2018 at 04:11:44PM +0800, Zhang Yi wrote:
> 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/
>
> In order to make sure that the file metadata is in sync after a fault
> while we are writing a shared DAX supporting backend files, this
> patch-set enables QEMU to use MAP_SYNC flag for memory-backend-dax-file.
>
> As the DAX vs DMA truncated issue was solved, we refined the code and
> send out this feature for the v5 version.
>
> 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'
Can this change be limited to a real DAX device?
Then you won't need to bother with flags at all.
And am I mistaken in thinking that this will affect all
guest memory with share=on? Or do I misunderstand?
> Changes in v6:
> * Pankaj: 3/7 are squashed with 2/7
> * Pankaj: 7/7 update comments to "consistent filesystem metadata".
> * Pankaj, Igor: 1/7 Added Reviewed-by in patch-1/7
> * Stefan, 4/7 move the include header from "/linux/mman.h" to "osdep.h"
> * Stefan, 5/7 Add missing "munmap"
> * Stefan, 2/7 refine the shared/flag.
>
> Changes in v5:
> * Add patch 1 to fix a memory leak issue.
> * Refine the patch 4-6
> * Remove the patch 3 as we already change the parameter from "shared" to
> "flags"
>
> Changes in v4:
> * Add patch 1-3 to switch some functions to a single 'flags'
> parameters. (Michael S. Tsirkin)
> * v3 patch 1-3 become v4 patch 4-6.
> * Patch 4: move definitions of MAP_SYNC and MAP_SHARED_VALIDATE to a
> new header file under include/standard-headers/linux/. (Michael S. Tsirkin)
> * Patch 6: refine the description of the 'sync' option. (Michael S. Tsirkin)
>
> 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)
>
> Zhang Yi (6):
> numa: Fixed the memory leak of numa error message
> util/mmap-alloc: switch qemu_ram_mmap() to 'flags' parameter
> util/mmap-alloc: support MAP_SYNC in qemu_ram_mmap()
> util/mmap-alloc: Switch the RAM_SYNC flags to OnOffAuto
> hostmem: add more information in error messages
> hostmem-file: add 'sync' option
>
> backends/hostmem-file.c | 45 +++++++++++++++++++++++++++++++++++++++++++--
> backends/hostmem.c | 8 +++++---
> docs/nvdimm.txt | 20 +++++++++++++++++++-
> exec.c | 9 +++++----
> include/exec/memory.h | 18 ++++++++++++++++++
> include/exec/ram_addr.h | 1 +
> include/qemu/mmap-alloc.h | 20 +++++++++++++++++++-
> include/qemu/osdep.h | 29 +++++++++++++++++++++++++++++
> numa.c | 1 +
> qemu-options.hx | 22 +++++++++++++++++++++-
> util/mmap-alloc.c | 26 +++++++++++++++++++++-----
> util/oslib-posix.c | 8 +++++++-
> 12 files changed, 189 insertions(+), 18 deletions(-)
>
> --
> 2.7.4
- [Qemu-devel] [PATCH V6 0/6] nvdimm: support MAP_SYNC for memory-backend-file, Zhang Yi, 2018/12/12
- [Qemu-devel] [PATCH V6 1/6] numa: Fixed the memory leak of numa error message, Zhang Yi, 2018/12/12
- [Qemu-devel] [PATCH V6 2/6] util/mmap-alloc: switch qemu_ram_mmap() to 'flags' parameter, Zhang Yi, 2018/12/12
- [Qemu-devel] [PATCH V6 3/6] util/mmap-alloc: support MAP_SYNC in qemu_ram_mmap(), Zhang Yi, 2018/12/12
- [Qemu-devel] [PATCH V6 4/6] util/mmap-alloc: Switch the RAM_SYNC flags to OnOffAuto, Zhang Yi, 2018/12/12
- [Qemu-devel] [PATCH V6 5/6] hostmem: add more information in error messages, Zhang Yi, 2018/12/12
- [Qemu-devel] [PATCH V6 6/6] hostmem-file: add 'sync' option, Zhang Yi, 2018/12/12
- Re: [Qemu-devel] [PATCH V6 0/6] nvdimm: support MAP_SYNC for memory-backend-file,
Michael S. Tsirkin <=
- Re: [Qemu-devel] [PATCH V6 0/6] nvdimm: support MAP_SYNC for memory-backend-file, Stefan Hajnoczi, 2018/12/17