[Qemu-devel] [PATCH V13 0/5] support MAP_SYNC for memory-backend-file

Zhang, Yi posted 5 patches 10 weeks ago
Failed in applying to current master (apply log)
docs/nvdimm.txt                            |  25 ++++++-
exec.c                                     |   2 +-
include/qemu/mmap-alloc.h                  |  21 +++++-
linux-headers/asm-arm/mman.h               |   4 ++
linux-headers/asm-arm64/mman.h             |   1 +
linux-headers/asm-generic/hugetlb_encode.h |  36 ++++++++++
linux-headers/asm-generic/mman-common.h    |  77 ++++++++++++++++++++
linux-headers/asm-generic/mman.h           |  24 +++++++
linux-headers/asm-mips/mman.h              | 108 +++++++++++++++++++++++++++++
linux-headers/asm-powerpc/mman.h           |  39 +++++++++++
linux-headers/asm-s390/mman.h              |   1 +
linux-headers/asm-x86/mman.h               |  31 +++++++++
linux-headers/linux/mman.h                 |  38 ++++++++++
qemu-options.hx                            |   5 ++
scripts/update-linux-headers.sh            |   6 +-
util/mmap-alloc.c                          |  51 +++++++++++++-
util/oslib-posix.c                         |   2 +-
17 files changed, 460 insertions(+), 11 deletions(-)
create mode 100644 linux-headers/asm-arm/mman.h
create mode 100644 linux-headers/asm-arm64/mman.h
create mode 100644 linux-headers/asm-generic/hugetlb_encode.h
create mode 100644 linux-headers/asm-generic/mman-common.h
create mode 100644 linux-headers/asm-generic/mman.h
create mode 100644 linux-headers/asm-mips/mman.h
create mode 100644 linux-headers/asm-powerpc/mman.h
create mode 100644 linux-headers/asm-s390/mman.h
create mode 100644 linux-headers/asm-x86/mman.h
create mode 100644 linux-headers/linux/mman.h

[Qemu-devel] [PATCH V13 0/5] support MAP_SYNC for memory-backend-file

Posted by Zhang, Yi 10 weeks ago
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.

We will pass MAP_SYNC to mmap(2); if MAP_SYNC is supported and
'share=on' & 'pmem=on'. 
Or QEMU will not pass this flag to mmap(2)

Test with below cases:
1. pmem=on is set, shared=on is set, MAP_SYNC supported:
   a: backend is a dax supporting file.
   1) start VM1 with options:
   -object memory-backend-file,id=nv_be4,share,mem-path=${DAX_FILE_1},size=${DAX_FILE_SIZE_1},align=128M,pmem=on,share=on
   -device nvdimm,id=nv4,memdev=nv_be4,label-size=2M.
   
   2) start VM2 with options:
   -object memory-backend-file,id=nv_be4,share,mem-path=${DAX_FILE_2,size=${DAX_FILE_SIZE_2},align=128M,pmem=on,share=on
   -device nvdimm,id=nv4,memdev=nv_be4,label-size=2M.

   3) live migrate from VM1 to VM2.
   
   4) Suddly let Host crash or power failure.

   5) check DAX_FILE_1 and DAX_FILE_2, no corrupt.

   b: backend is a regular file.
   1) start with options
   -object memory-backend-file,id=nv_be4,share,mem-path=${REG_FILE},size=${REG_FILE_SIZE},align=128M,pmem=on,share=on
   -device nvdimm,id=nv4,memdev=nv_be4,label-size=2M.

   will warning "failed to validate with mapping flags: Operation not supported"
   FILE_1 and FILE_2 random corrupt.

2. Other cases:
   FILE_1 and FILE_2 random corrupt.

Changes in V13:
 * 4/5 Micheal: move the inlcude to mmap_alloc.c.
 * 4/5 Micheal: refine the warning message.
 * 5/5 Micheal: refine the Documentations.

Changes in V12:
 * 2/5: Micheal: Update update-linux-headers.sh
 * 3/5: Micheal: Use script update add linux/mman.h
 * 4/5: Pankaj,Micheal: 1) fallback to mmap without
        MAP_SYNC & MAP_SHARED_VALIDATE if sync not supported or failed
	2) Replace the include with 3/5 added linux/mman.h
 * 5/5: Micheal: Refine the Documentations.

Changes in V11:
 * 1/3: Micheal: Change to just add a bool is_pmem in qemu_ram_mmap.
 * 2/3: Micheal: Fix the compatibility for old kernel.
 * 2/3&3/3: Micheal&Eduardo :Update the behavior below: 
   Waning at no-dax and continue without MAP_SYNC.
   Test if fails again for compatibility, then remove the MAP_VALIDATE and
   silently proceed.

Changes in V10:
 * 4/4: refine the document.
 * 3/4: Reviewed-by: Stefano Garzarella <sgarzare@redhat.com>
 * 2/4: refine the commit message, Added MAP_SHARED_VALIDATE.
 * 2/4: Fix the wrong include header

Changes in V9:
 * 1/6: Reviewed-by: Eduardo Habkost <ehabkost@redhat.com>
 * 2/6: New Added: Micheal: use sparse feature define RAM_FLAG. 
 since I don't have much knowledge about the sparse feature, @Micheal Could you 
 add some documentation/commit message on this patch? Thank you very much.
 * 3/6: from 2/5: Eduardo: updated the commit message. 
 * 4/6: from 3/5: Micheal: don't ignore MAP_SYNC failures silently.
 * 5/6: from 4/5: Eduardo: updated the commit message.
 * 6/6: from 5/5: Micheal: Drop the sync option, document the MAP_SYNC.

Changes in v8:
 * Micheal: 3/5, remove the duplicated define in the os_dep.h
 * Micheal: 2/5, make type define safety.
 * Micheal: 2/5, fixed the incorrect define MAP_SHARE on qemu_anon_ram_alloc.
 * 4/6 removed, we remove the on/off/auto define of sync,  as by now,
   MAP_SYNC only worked with pmem=on.
 * @Micheal, I still reuse the RAM_SYNC flag, it is much straightforward to parse 
   all the flags in one parameter.

Changes in v7:
 * Micheal: [3,4,6]/6 limited the "sync" flag only on a nvdimm backend.(pmem=on)

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 (5):
  util/mmap-alloc: Add a 'is_pmem' parameter to qemu_ram_mmap
  scripts/update-linux-headers: add linux/mman.h
  linux-headers: add linux/mman.h.
  util/mmap-alloc: support MAP_SYNC in qemu_ram_mmap()
  docs: Added MAP_SYNC documentation

Zhang Yi (5):
  util/mmap-alloc: Add a 'is_pmem' parameter to qemu_ram_mmap
  scripts/update-linux-headers: add linux/mman.h
  linux-headers: add linux/mman.h.
  util/mmap-alloc: support MAP_SYNC in qemu_ram_mmap()
  docs: Added MAP_SYNC documentation

 docs/nvdimm.txt                            |  25 ++++++-
 exec.c                                     |   2 +-
 include/qemu/mmap-alloc.h                  |  21 +++++-
 linux-headers/asm-arm/mman.h               |   4 ++
 linux-headers/asm-arm64/mman.h             |   1 +
 linux-headers/asm-generic/hugetlb_encode.h |  36 ++++++++++
 linux-headers/asm-generic/mman-common.h    |  77 ++++++++++++++++++++
 linux-headers/asm-generic/mman.h           |  24 +++++++
 linux-headers/asm-mips/mman.h              | 108 +++++++++++++++++++++++++++++
 linux-headers/asm-powerpc/mman.h           |  39 +++++++++++
 linux-headers/asm-s390/mman.h              |   1 +
 linux-headers/asm-x86/mman.h               |  31 +++++++++
 linux-headers/linux/mman.h                 |  38 ++++++++++
 qemu-options.hx                            |   5 ++
 scripts/update-linux-headers.sh            |   6 +-
 util/mmap-alloc.c                          |  51 +++++++++++++-
 util/oslib-posix.c                         |   2 +-
 17 files changed, 460 insertions(+), 11 deletions(-)
 create mode 100644 linux-headers/asm-arm/mman.h
 create mode 100644 linux-headers/asm-arm64/mman.h
 create mode 100644 linux-headers/asm-generic/hugetlb_encode.h
 create mode 100644 linux-headers/asm-generic/mman-common.h
 create mode 100644 linux-headers/asm-generic/mman.h
 create mode 100644 linux-headers/asm-mips/mman.h
 create mode 100644 linux-headers/asm-powerpc/mman.h
 create mode 100644 linux-headers/asm-s390/mman.h
 create mode 100644 linux-headers/asm-x86/mman.h
 create mode 100644 linux-headers/linux/mman.h

-- 
2.7.4


Re: [Qemu-devel] [PATCH V13 0/5] support MAP_SYNC for memory-backend-file

Posted by Michael S. Tsirkin 10 weeks ago
On Fri, Feb 08, 2019 at 06:10:23PM +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.
> 
> We will pass MAP_SYNC to mmap(2); if MAP_SYNC is supported and
> 'share=on' & 'pmem=on'. 
> Or QEMU will not pass this flag to mmap(2)

Overall this looks reasonable to me.
Besides the documentation nit:

Reviewed-by: Michael S. Tsirkin <mst@redhat.com>


> Test with below cases:
> 1. pmem=on is set, shared=on is set, MAP_SYNC supported:
>    a: backend is a dax supporting file.
>    1) start VM1 with options:
>    -object memory-backend-file,id=nv_be4,share,mem-path=${DAX_FILE_1},size=${DAX_FILE_SIZE_1},align=128M,pmem=on,share=on
>    -device nvdimm,id=nv4,memdev=nv_be4,label-size=2M.
>    
>    2) start VM2 with options:
>    -object memory-backend-file,id=nv_be4,share,mem-path=${DAX_FILE_2,size=${DAX_FILE_SIZE_2},align=128M,pmem=on,share=on
>    -device nvdimm,id=nv4,memdev=nv_be4,label-size=2M.
> 
>    3) live migrate from VM1 to VM2.
>    
>    4) Suddly let Host crash or power failure.
> 
>    5) check DAX_FILE_1 and DAX_FILE_2, no corrupt.
> 
>    b: backend is a regular file.
>    1) start with options
>    -object memory-backend-file,id=nv_be4,share,mem-path=${REG_FILE},size=${REG_FILE_SIZE},align=128M,pmem=on,share=on
>    -device nvdimm,id=nv4,memdev=nv_be4,label-size=2M.
> 
>    will warning "failed to validate with mapping flags: Operation not supported"
>    FILE_1 and FILE_2 random corrupt.
> 
> 2. Other cases:
>    FILE_1 and FILE_2 random corrupt.
> 
> Changes in V13:
>  * 4/5 Micheal: move the inlcude to mmap_alloc.c.
>  * 4/5 Micheal: refine the warning message.
>  * 5/5 Micheal: refine the Documentations.
> 
> Changes in V12:
>  * 2/5: Micheal: Update update-linux-headers.sh
>  * 3/5: Micheal: Use script update add linux/mman.h
>  * 4/5: Pankaj,Micheal: 1) fallback to mmap without
>         MAP_SYNC & MAP_SHARED_VALIDATE if sync not supported or failed
> 	2) Replace the include with 3/5 added linux/mman.h
>  * 5/5: Micheal: Refine the Documentations.
> 
> Changes in V11:
>  * 1/3: Micheal: Change to just add a bool is_pmem in qemu_ram_mmap.
>  * 2/3: Micheal: Fix the compatibility for old kernel.
>  * 2/3&3/3: Micheal&Eduardo :Update the behavior below: 
>    Waning at no-dax and continue without MAP_SYNC.
>    Test if fails again for compatibility, then remove the MAP_VALIDATE and
>    silently proceed.
> 
> Changes in V10:
>  * 4/4: refine the document.
>  * 3/4: Reviewed-by: Stefano Garzarella <sgarzare@redhat.com>
>  * 2/4: refine the commit message, Added MAP_SHARED_VALIDATE.
>  * 2/4: Fix the wrong include header
> 
> Changes in V9:
>  * 1/6: Reviewed-by: Eduardo Habkost <ehabkost@redhat.com>
>  * 2/6: New Added: Micheal: use sparse feature define RAM_FLAG. 
>  since I don't have much knowledge about the sparse feature, @Micheal Could you 
>  add some documentation/commit message on this patch? Thank you very much.
>  * 3/6: from 2/5: Eduardo: updated the commit message. 
>  * 4/6: from 3/5: Micheal: don't ignore MAP_SYNC failures silently.
>  * 5/6: from 4/5: Eduardo: updated the commit message.
>  * 6/6: from 5/5: Micheal: Drop the sync option, document the MAP_SYNC.
> 
> Changes in v8:
>  * Micheal: 3/5, remove the duplicated define in the os_dep.h
>  * Micheal: 2/5, make type define safety.
>  * Micheal: 2/5, fixed the incorrect define MAP_SHARE on qemu_anon_ram_alloc.
>  * 4/6 removed, we remove the on/off/auto define of sync,  as by now,
>    MAP_SYNC only worked with pmem=on.
>  * @Micheal, I still reuse the RAM_SYNC flag, it is much straightforward to parse 
>    all the flags in one parameter.
> 
> Changes in v7:
>  * Micheal: [3,4,6]/6 limited the "sync" flag only on a nvdimm backend.(pmem=on)
> 
> 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 (5):
>   util/mmap-alloc: Add a 'is_pmem' parameter to qemu_ram_mmap
>   scripts/update-linux-headers: add linux/mman.h
>   linux-headers: add linux/mman.h.
>   util/mmap-alloc: support MAP_SYNC in qemu_ram_mmap()
>   docs: Added MAP_SYNC documentation
> 
> Zhang Yi (5):
>   util/mmap-alloc: Add a 'is_pmem' parameter to qemu_ram_mmap
>   scripts/update-linux-headers: add linux/mman.h
>   linux-headers: add linux/mman.h.
>   util/mmap-alloc: support MAP_SYNC in qemu_ram_mmap()
>   docs: Added MAP_SYNC documentation
> 
>  docs/nvdimm.txt                            |  25 ++++++-
>  exec.c                                     |   2 +-
>  include/qemu/mmap-alloc.h                  |  21 +++++-
>  linux-headers/asm-arm/mman.h               |   4 ++
>  linux-headers/asm-arm64/mman.h             |   1 +
>  linux-headers/asm-generic/hugetlb_encode.h |  36 ++++++++++
>  linux-headers/asm-generic/mman-common.h    |  77 ++++++++++++++++++++
>  linux-headers/asm-generic/mman.h           |  24 +++++++
>  linux-headers/asm-mips/mman.h              | 108 +++++++++++++++++++++++++++++
>  linux-headers/asm-powerpc/mman.h           |  39 +++++++++++
>  linux-headers/asm-s390/mman.h              |   1 +
>  linux-headers/asm-x86/mman.h               |  31 +++++++++
>  linux-headers/linux/mman.h                 |  38 ++++++++++
>  qemu-options.hx                            |   5 ++
>  scripts/update-linux-headers.sh            |   6 +-
>  util/mmap-alloc.c                          |  51 +++++++++++++-
>  util/oslib-posix.c                         |   2 +-
>  17 files changed, 460 insertions(+), 11 deletions(-)
>  create mode 100644 linux-headers/asm-arm/mman.h
>  create mode 100644 linux-headers/asm-arm64/mman.h
>  create mode 100644 linux-headers/asm-generic/hugetlb_encode.h
>  create mode 100644 linux-headers/asm-generic/mman-common.h
>  create mode 100644 linux-headers/asm-generic/mman.h
>  create mode 100644 linux-headers/asm-mips/mman.h
>  create mode 100644 linux-headers/asm-powerpc/mman.h
>  create mode 100644 linux-headers/asm-s390/mman.h
>  create mode 100644 linux-headers/asm-x86/mman.h
>  create mode 100644 linux-headers/linux/mman.h
> 
> -- 
> 2.7.4

Re: [Qemu-devel] [PATCH V13 0/5] support MAP_SYNC for memory-backend-file

Posted by Pankaj Gupta 10 weeks ago

> 
> 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.
> 
> We will pass MAP_SYNC to mmap(2); if MAP_SYNC is supported and
> 'share=on' & 'pmem=on'.
> Or QEMU will not pass this flag to mmap(2)
> 
> Test with below cases:
> 1. pmem=on is set, shared=on is set, MAP_SYNC supported:
>    a: backend is a dax supporting file.
>    1) start VM1 with options:
>    -object
>    memory-backend-file,id=nv_be4,share,mem-path=${DAX_FILE_1},size=${DAX_FILE_SIZE_1},align=128M,pmem=on,share=on
>    -device nvdimm,id=nv4,memdev=nv_be4,label-size=2M.
>    
>    2) start VM2 with options:
>    -object
>    memory-backend-file,id=nv_be4,share,mem-path=${DAX_FILE_2,size=${DAX_FILE_SIZE_2},align=128M,pmem=on,share=on
>    -device nvdimm,id=nv4,memdev=nv_be4,label-size=2M.
> 
>    3) live migrate from VM1 to VM2.
>    
>    4) Suddly let Host crash or power failure.
> 
>    5) check DAX_FILE_1 and DAX_FILE_2, no corrupt.
> 
>    b: backend is a regular file.
>    1) start with options
>    -object
>    memory-backend-file,id=nv_be4,share,mem-path=${REG_FILE},size=${REG_FILE_SIZE},align=128M,pmem=on,share=on
>    -device nvdimm,id=nv4,memdev=nv_be4,label-size=2M.
> 
>    will warning "failed to validate with mapping flags: Operation not
>    supported"
>    FILE_1 and FILE_2 random corrupt.
> 
> 2. Other cases:
>    FILE_1 and FILE_2 random corrupt.
> 
> Changes in V13:
>  * 4/5 Micheal: move the inlcude to mmap_alloc.c.
>  * 4/5 Micheal: refine the warning message.
>  * 5/5 Micheal: refine the Documentations.
> 
> Changes in V12:
>  * 2/5: Micheal: Update update-linux-headers.sh
>  * 3/5: Micheal: Use script update add linux/mman.h
>  * 4/5: Pankaj,Micheal: 1) fallback to mmap without
>         MAP_SYNC & MAP_SHARED_VALIDATE if sync not supported or failed
> 	2) Replace the include with 3/5 added linux/mman.h
>  * 5/5: Micheal: Refine the Documentations.
> 
> Changes in V11:
>  * 1/3: Micheal: Change to just add a bool is_pmem in qemu_ram_mmap.
>  * 2/3: Micheal: Fix the compatibility for old kernel.
>  * 2/3&3/3: Micheal&Eduardo :Update the behavior below:
>    Waning at no-dax and continue without MAP_SYNC.
>    Test if fails again for compatibility, then remove the MAP_VALIDATE and
>    silently proceed.
> 
> Changes in V10:
>  * 4/4: refine the document.
>  * 3/4: Reviewed-by: Stefano Garzarella <sgarzare@redhat.com>
>  * 2/4: refine the commit message, Added MAP_SHARED_VALIDATE.
>  * 2/4: Fix the wrong include header
> 
> Changes in V9:
>  * 1/6: Reviewed-by: Eduardo Habkost <ehabkost@redhat.com>
>  * 2/6: New Added: Micheal: use sparse feature define RAM_FLAG.
>  since I don't have much knowledge about the sparse feature, @Micheal Could
>  you
>  add some documentation/commit message on this patch? Thank you very much.
>  * 3/6: from 2/5: Eduardo: updated the commit message.
>  * 4/6: from 3/5: Micheal: don't ignore MAP_SYNC failures silently.
>  * 5/6: from 4/5: Eduardo: updated the commit message.
>  * 6/6: from 5/5: Micheal: Drop the sync option, document the MAP_SYNC.
> 
> Changes in v8:
>  * Micheal: 3/5, remove the duplicated define in the os_dep.h
>  * Micheal: 2/5, make type define safety.
>  * Micheal: 2/5, fixed the incorrect define MAP_SHARE on qemu_anon_ram_alloc.
>  * 4/6 removed, we remove the on/off/auto define of sync,  as by now,
>    MAP_SYNC only worked with pmem=on.
>  * @Micheal, I still reuse the RAM_SYNC flag, it is much straightforward to
>  parse
>    all the flags in one parameter.
> 
> Changes in v7:
>  * Micheal: [3,4,6]/6 limited the "sync" flag only on a nvdimm
>  backend.(pmem=on)
> 
> 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 (5):
>   util/mmap-alloc: Add a 'is_pmem' parameter to qemu_ram_mmap
>   scripts/update-linux-headers: add linux/mman.h
>   linux-headers: add linux/mman.h.
>   util/mmap-alloc: support MAP_SYNC in qemu_ram_mmap()
>   docs: Added MAP_SYNC documentation
> 
> Zhang Yi (5):
>   util/mmap-alloc: Add a 'is_pmem' parameter to qemu_ram_mmap
>   scripts/update-linux-headers: add linux/mman.h
>   linux-headers: add linux/mman.h.
>   util/mmap-alloc: support MAP_SYNC in qemu_ram_mmap()
>   docs: Added MAP_SYNC documentation
> 
>  docs/nvdimm.txt                            |  25 ++++++-
>  exec.c                                     |   2 +-
>  include/qemu/mmap-alloc.h                  |  21 +++++-
>  linux-headers/asm-arm/mman.h               |   4 ++
>  linux-headers/asm-arm64/mman.h             |   1 +
>  linux-headers/asm-generic/hugetlb_encode.h |  36 ++++++++++
>  linux-headers/asm-generic/mman-common.h    |  77 ++++++++++++++++++++
>  linux-headers/asm-generic/mman.h           |  24 +++++++
>  linux-headers/asm-mips/mman.h              | 108
>  +++++++++++++++++++++++++++++
>  linux-headers/asm-powerpc/mman.h           |  39 +++++++++++
>  linux-headers/asm-s390/mman.h              |   1 +
>  linux-headers/asm-x86/mman.h               |  31 +++++++++
>  linux-headers/linux/mman.h                 |  38 ++++++++++
>  qemu-options.hx                            |   5 ++
>  scripts/update-linux-headers.sh            |   6 +-
>  util/mmap-alloc.c                          |  51 +++++++++++++-
>  util/oslib-posix.c                         |   2 +-
>  17 files changed, 460 insertions(+), 11 deletions(-)
>  create mode 100644 linux-headers/asm-arm/mman.h
>  create mode 100644 linux-headers/asm-arm64/mman.h
>  create mode 100644 linux-headers/asm-generic/hugetlb_encode.h
>  create mode 100644 linux-headers/asm-generic/mman-common.h
>  create mode 100644 linux-headers/asm-generic/mman.h
>  create mode 100644 linux-headers/asm-mips/mman.h
>  create mode 100644 linux-headers/asm-powerpc/mman.h
>  create mode 100644 linux-headers/asm-s390/mman.h
>  create mode 100644 linux-headers/asm-x86/mman.h
>  create mode 100644 linux-headers/linux/mman.h
> 
> --
> 2.7.4

This patch series look good to me. 
With updated patch 5, feel free to add.

Reviewed-by: Pankaj Gupta <pagupta@redhat.com>

> 
> 
>