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vhost_user_fs: add a flag to disable extended attributes

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Extended attributes (xattr) support has a huge impact on write
performance. The reason for this is that, if enabled, FUSE sends a
setxattr request after each write operation, and due to the inode
locking inside the kernel during said request, the ability to execute
the operations in parallel becomes heavily limited.

Signed-off-by: Sergio Lopez <slp@redhat.com>
This commit is contained in:
Sergio Lopez
2020-03-12 15:22:06 +01:00
committed by Rob Bradford
parent 710520e9a1
commit 07cc73bddc
2 changed files with 31 additions and 0 deletions
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24
vhost_user_fs/src/passthrough.rs
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@@ -231,6 +231,13 @@ pub struct Config {
///
/// The default is `/`.
pub root_dir: String,
/// Whether the file system should support Extended Attributes (xattr). Enabling this feature may
/// have a significant impact on performance, especially on write parallelism. This is the result
/// of FUSE attempting to remove the special file privileges after each write request.
///
/// The default value for this options is `false`.
pub xattr: bool,
}
impl Default for Config {
@@ -241,6 +248,7 @@ impl Default for Config {
cache_policy: Default::default(),
writeback: false,
root_dir: String::from("/"),
xattr: false,
}
}
}
@@ -1461,6 +1469,10 @@ impl FileSystem for PassthroughFs {
value: &[u8],
flags: u32,
) -> io::Result<()> {
if !self.cfg.xattr {
return Err(io::Error::from_raw_os_error(libc::ENOSYS));
}
// The f{set,get,remove,list}xattr functions don't work on an fd opened with `O_PATH` so we
// need to get a new fd.
let file = self.open_inode(inode, libc::O_RDONLY | libc::O_NONBLOCK)?;
@@ -1489,6 +1501,10 @@ impl FileSystem for PassthroughFs {
name: &CStr,
size: u32,
) -> io::Result<GetxattrReply> {
if !self.cfg.xattr {
return Err(io::Error::from_raw_os_error(libc::ENOSYS));
}
// The f{set,get,remove,list}xattr functions don't work on an fd opened with `O_PATH` so we
// need to get a new fd.
let file = self.open_inode(inode, libc::O_RDONLY | libc::O_NONBLOCK)?;
@@ -1517,6 +1533,10 @@ impl FileSystem for PassthroughFs {
}
fn listxattr(&self, _ctx: Context, inode: Inode, size: u32) -> io::Result<ListxattrReply> {
if !self.cfg.xattr {
return Err(io::Error::from_raw_os_error(libc::ENOSYS));
}
// The f{set,get,remove,list}xattr functions don't work on an fd opened with `O_PATH` so we
// need to get a new fd.
let file = self.open_inode(inode, libc::O_RDONLY | libc::O_NONBLOCK)?;
@@ -1544,6 +1564,10 @@ impl FileSystem for PassthroughFs {
}
fn removexattr(&self, _ctx: Context, inode: Inode, name: &CStr) -> io::Result<()> {
if !self.cfg.xattr {
return Err(io::Error::from_raw_os_error(libc::ENOSYS));
}
// The f{set,get,remove,list}xattr functions don't work on an fd opened with `O_PATH` so we
// need to get a new fd.
let file = self.open_inode(inode, libc::O_RDONLY | libc::O_NONBLOCK)?;