From: Jeffle Xu <jefflexu@linux.alibaba.com>
To: vgoyal@redhat.com, stefanha@redhat.com, miklos@szeredi.hub
Cc: linux-fsdevel@vger.kernel.org, virtio-fs@redhat.com,
bo.liu@linux.alibaba.com, joseph.qi@linux.alibaba.com
Subject: [PATCH v6 7/7] Documentation/filesystem/dax: record DAX on virtiofs
Date: Mon, 11 Oct 2021 11:00:52 +0800 [thread overview]
Message-ID: <20211011030052.98923-8-jefflexu@linux.alibaba.com> (raw)
In-Reply-To: <20211011030052.98923-1-jefflexu@linux.alibaba.com>
Record DAX on virtiofs and the semantic difference with that on ext4
and xfs.
Signed-off-by: Jeffle Xu <jefflexu@linux.alibaba.com>
---
Documentation/filesystems/dax.rst | 20 ++++++++++++++++++--
1 file changed, 18 insertions(+), 2 deletions(-)
diff --git a/Documentation/filesystems/dax.rst b/Documentation/filesystems/dax.rst
index 9a1b8fd9e82b..e3b30429d703 100644
--- a/Documentation/filesystems/dax.rst
+++ b/Documentation/filesystems/dax.rst
@@ -23,8 +23,8 @@ on it as usual. The `DAX` code currently only supports files with a block
size equal to your kernel's `PAGE_SIZE`, so you may need to specify a block
size when creating the filesystem.
-Currently 3 filesystems support `DAX`: ext2, ext4 and xfs. Enabling `DAX` on them
-is different.
+Currently 4 filesystems support `DAX`: ext2, ext4, xfs and virtiofs.
+Enabling `DAX` on them is different.
Enabling DAX on ext2
--------------------
@@ -168,6 +168,22 @@ if the underlying media does not support dax and/or the filesystem is
overridden with a mount option.
+Enabling DAX on virtiofs
+----------------------------
+The semantic of DAX on virtiofs is basically equal to that on ext4 and xfs,
+except that when '-o dax=inode' is specified, virtiofs client derives the hint
+whether DAX shall be enabled or not from virtiofs server through FUSE protocol,
+rather than the persistent `FS_XFLAG_DAX` flag. That is, whether DAX shall be
+enabled or not is completely determined by virtiofs server, while virtiofs
+server itself may deploy various algorithm making this decision, e.g. depending
+on the persistent `FS_XFLAG_DAX` flag on the host.
+
+It is still supported to set or clear persistent `FS_XFLAG_DAX` flag inside
+guest, but it is not guaranteed that DAX will be enabled or disabled for
+corresponding file then. Users inside guest still need to call statx(2) and
+check the statx flag `STATX_ATTR_DAX` to see if DAX is enabled for this file.
+
+
Implementation Tips for Block Driver Writers
--------------------------------------------
--
2.27.0
WARNING: multiple messages have this Message-ID (diff)
From: Jeffle Xu <jefflexu@linux.alibaba.com>
To: vgoyal@redhat.com, stefanha@redhat.com, miklos@szeredi.hub
Cc: linux-fsdevel@vger.kernel.org, virtio-fs@redhat.com,
joseph.qi@linux.alibaba.com
Subject: [Virtio-fs] [PATCH v6 7/7] Documentation/filesystem/dax: record DAX on virtiofs
Date: Mon, 11 Oct 2021 11:00:52 +0800 [thread overview]
Message-ID: <20211011030052.98923-8-jefflexu@linux.alibaba.com> (raw)
In-Reply-To: <20211011030052.98923-1-jefflexu@linux.alibaba.com>
Record DAX on virtiofs and the semantic difference with that on ext4
and xfs.
Signed-off-by: Jeffle Xu <jefflexu@linux.alibaba.com>
---
Documentation/filesystems/dax.rst | 20 ++++++++++++++++++--
1 file changed, 18 insertions(+), 2 deletions(-)
diff --git a/Documentation/filesystems/dax.rst b/Documentation/filesystems/dax.rst
index 9a1b8fd9e82b..e3b30429d703 100644
--- a/Documentation/filesystems/dax.rst
+++ b/Documentation/filesystems/dax.rst
@@ -23,8 +23,8 @@ on it as usual. The `DAX` code currently only supports files with a block
size equal to your kernel's `PAGE_SIZE`, so you may need to specify a block
size when creating the filesystem.
-Currently 3 filesystems support `DAX`: ext2, ext4 and xfs. Enabling `DAX` on them
-is different.
+Currently 4 filesystems support `DAX`: ext2, ext4, xfs and virtiofs.
+Enabling `DAX` on them is different.
Enabling DAX on ext2
--------------------
@@ -168,6 +168,22 @@ if the underlying media does not support dax and/or the filesystem is
overridden with a mount option.
+Enabling DAX on virtiofs
+----------------------------
+The semantic of DAX on virtiofs is basically equal to that on ext4 and xfs,
+except that when '-o dax=inode' is specified, virtiofs client derives the hint
+whether DAX shall be enabled or not from virtiofs server through FUSE protocol,
+rather than the persistent `FS_XFLAG_DAX` flag. That is, whether DAX shall be
+enabled or not is completely determined by virtiofs server, while virtiofs
+server itself may deploy various algorithm making this decision, e.g. depending
+on the persistent `FS_XFLAG_DAX` flag on the host.
+
+It is still supported to set or clear persistent `FS_XFLAG_DAX` flag inside
+guest, but it is not guaranteed that DAX will be enabled or disabled for
+corresponding file then. Users inside guest still need to call statx(2) and
+check the statx flag `STATX_ATTR_DAX` to see if DAX is enabled for this file.
+
+
Implementation Tips for Block Driver Writers
--------------------------------------------
--
2.27.0
next prev parent reply other threads:[~2021-10-11 3:01 UTC|newest]
Thread overview: 74+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-10-11 3:00 [PATCH v6 0/7] fuse,virtiofs: support per-file DAX Jeffle Xu
2021-10-11 3:00 ` [Virtio-fs] " Jeffle Xu
2021-10-11 3:00 ` [PATCH v6 1/7] fuse: add fuse_should_enable_dax() helper Jeffle Xu
2021-10-11 3:00 ` [Virtio-fs] " Jeffle Xu
2021-10-11 3:00 ` [PATCH v6 2/7] fuse: make DAX mount option a tri-state Jeffle Xu
2021-10-11 3:00 ` [Virtio-fs] " Jeffle Xu
2021-10-18 14:10 ` Vivek Goyal
2021-10-18 14:10 ` [Virtio-fs] " Vivek Goyal
2021-10-20 2:52 ` JeffleXu
2021-10-20 2:52 ` [Virtio-fs] " JeffleXu
2021-10-20 14:48 ` Vivek Goyal
2021-10-20 14:48 ` [Virtio-fs] " Vivek Goyal
2021-10-29 8:33 ` JeffleXu
2021-10-29 8:33 ` [Virtio-fs] " JeffleXu
2021-10-29 13:03 ` Vivek Goyal
2021-10-29 13:03 ` [Virtio-fs] " Vivek Goyal
2021-11-01 8:21 ` JeffleXu
2021-11-01 8:21 ` [Virtio-fs] " JeffleXu
2021-10-20 15:17 ` Vivek Goyal
2021-10-20 15:17 ` [Virtio-fs] " Vivek Goyal
2021-10-22 6:54 ` JeffleXu
2021-10-22 6:54 ` [Virtio-fs] " JeffleXu
2021-10-25 17:52 ` Ira Weiny
2021-10-25 17:52 ` [Virtio-fs] " Ira Weiny
2021-10-25 18:12 ` Vivek Goyal
2021-10-25 18:12 ` [Virtio-fs] " Vivek Goyal
2021-10-25 19:02 ` Ira Weiny
2021-10-25 19:02 ` [Virtio-fs] " Ira Weiny
2021-10-25 19:33 ` Vivek Goyal
2021-10-25 19:33 ` [Virtio-fs] " Vivek Goyal
2021-10-25 20:41 ` Ira Weiny
2021-10-25 20:41 ` [Virtio-fs] " Ira Weiny
2021-10-26 13:45 ` Vivek Goyal
2021-10-26 13:45 ` [Virtio-fs] " Vivek Goyal
2021-10-27 6:00 ` JeffleXu
2021-10-27 6:00 ` [Virtio-fs] " JeffleXu
2021-10-11 3:00 ` [PATCH v6 3/7] fuse: support per-file DAX in fuse protocol Jeffle Xu
2021-10-11 3:00 ` [Virtio-fs] " Jeffle Xu
2021-10-18 14:14 ` Vivek Goyal
2021-10-18 14:14 ` [Virtio-fs] " Vivek Goyal
2021-10-18 14:20 ` Vivek Goyal
2021-10-18 14:20 ` [Virtio-fs] " Vivek Goyal
2021-10-20 3:04 ` JeffleXu
2021-10-20 3:04 ` [Virtio-fs] " JeffleXu
2021-10-20 14:54 ` Vivek Goyal
2021-10-20 14:54 ` [Virtio-fs] " Vivek Goyal
2021-10-11 3:00 ` [PATCH v6 4/7] fuse: negotiate per-file DAX in FUSE_INIT Jeffle Xu
2021-10-11 3:00 ` [Virtio-fs] " Jeffle Xu
2021-10-18 14:30 ` Vivek Goyal
2021-10-18 14:30 ` [Virtio-fs] " Vivek Goyal
2021-10-20 3:10 ` JeffleXu
2021-10-20 3:10 ` [Virtio-fs] " JeffleXu
2021-10-20 15:44 ` Vivek Goyal
2021-10-20 15:44 ` [Virtio-fs] " Vivek Goyal
2021-10-11 3:00 ` [PATCH v6 5/7] fuse: enable per-file DAX Jeffle Xu
2021-10-11 3:00 ` [Virtio-fs] " Jeffle Xu
2021-10-18 15:11 ` Vivek Goyal
2021-10-18 15:11 ` [Virtio-fs] " Vivek Goyal
2021-10-11 3:00 ` [PATCH v6 6/7] fuse: mark inode DONT_CACHE when per-file DAX hint changes Jeffle Xu
2021-10-11 3:00 ` [Virtio-fs] " Jeffle Xu
2021-10-18 15:19 ` Vivek Goyal
2021-10-18 15:19 ` [Virtio-fs] " Vivek Goyal
2021-10-27 5:05 ` JeffleXu
2021-10-27 5:05 ` [Virtio-fs] " JeffleXu
2021-10-11 3:00 ` Jeffle Xu [this message]
2021-10-11 3:00 ` [Virtio-fs] [PATCH v6 7/7] Documentation/filesystem/dax: record DAX on virtiofs Jeffle Xu
2021-10-15 3:33 ` [PATCH v6 0/7] fuse,virtiofs: support per-file DAX JeffleXu
2021-10-15 3:33 ` [Virtio-fs] " JeffleXu
2021-10-18 15:21 ` Vivek Goyal
2021-10-18 15:21 ` [Virtio-fs] " Vivek Goyal
2021-10-20 5:22 ` JeffleXu
2021-10-20 5:22 ` [Virtio-fs] " JeffleXu
2021-10-20 16:06 ` Vivek Goyal
2021-10-20 16:06 ` [Virtio-fs] " Vivek Goyal
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