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'
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
