From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:47240) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1gX65h-0002sx-MQ for qemu-devel@nongnu.org; Wed, 12 Dec 2018 10:06:31 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1gX65c-0004Vc-9Y for qemu-devel@nongnu.org; Wed, 12 Dec 2018 10:06:25 -0500 Received: from mx1.redhat.com ([209.132.183.28]:46588) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1gX65b-0004VA-V3 for qemu-devel@nongnu.org; Wed, 12 Dec 2018 10:06:20 -0500 Date: Wed, 12 Dec 2018 10:06:13 -0500 From: "Michael S. Tsirkin" Message-ID: <20181212100106-mutt-send-email-mst@kernel.org> References: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Subject: Re: [Qemu-devel] [PATCH V6 0/6] nvdimm: support MAP_SYNC for memory-backend-file List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Zhang Yi Cc: xiaoguangrong.eric@gmail.com, dan.j.williams@intel.com, stefanha@redhat.com, pbonzini@redhat.com, pagupta@redhat.com, yu.c.zhang@linux.intel.com, qemu-devel@nongnu.org, imammedo@redhat.com, ehabkost@redhat.com 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