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Merge pull request #774 from stlankes/fs
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feat: allow mounting a virtiofsd share to `/`
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@mkroening
mkroening authored Apr 24, 2024
2 parents 5fa96eb + d29dec6 commit 97c3e33
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Showing 2 changed files with 220 additions and 41 deletions.
245 changes: 213 additions & 32 deletions src/fs/fuse.rs
View file
Original file line number Diff line number Diff line change
Expand Up @@ -847,11 +847,13 @@ impl Clone for FuseFileHandle {
}

#[derive(Debug)]
pub(crate) struct FuseDirectory;
pub(crate) struct FuseDirectory {
prefix: Option<String>,
}

impl FuseDirectory {
pub const fn new() -> Self {
FuseDirectory {}
pub const fn new(prefix: Option<String>) -> Self {
FuseDirectory { prefix }
}
}

Expand All @@ -863,13 +865,23 @@ impl VfsNode for FuseDirectory {

fn traverse_readdir(&self, components: &mut Vec<&str>) -> Result<Vec<DirectoryEntry>, IoError> {
let path: String = if components.is_empty() {
"/".to_string()
if let Some(prefix) = &self.prefix {
"/".to_string() + prefix
} else {
"/".to_string()
}
} else {
components
let path: String = components
.iter()
.rev()
.map(|v| "/".to_owned() + v)
.collect()
.collect();

if let Some(prefix) = &self.prefix {
"/".to_owned() + &prefix.to_owned() + &path
} else {
path
}
};

debug!("FUSE opendir: {}", path);
Expand Down Expand Up @@ -925,7 +937,7 @@ impl VfsNode for FuseDirectory {
unsafe { &*(rsp.payload.as_ptr().byte_add(offset) as *const fuse_abi::Dirent) };

offset += core::mem::size_of::<fuse_abi::Dirent>() + dirent.d_namelen as usize;
// Allign to dirent struct
// Align to dirent struct
offset = ((offset) + U64_SIZE - 1) & (!(U64_SIZE - 1));

let name: &'static [u8] = unsafe {
Expand All @@ -950,13 +962,23 @@ impl VfsNode for FuseDirectory {

fn traverse_stat(&self, components: &mut Vec<&str>) -> Result<FileAttr, IoError> {
let path: String = if components.is_empty() {
"/".to_string()
if let Some(prefix) = &self.prefix {
"/".to_string() + prefix
} else {
"/".to_string()
}
} else {
components
let path: String = components
.iter()
.rev()
.map(|v| "/".to_owned() + v)
.collect()
.collect();

if let Some(prefix) = &self.prefix {
"/".to_owned() + &prefix.to_owned() + &path
} else {
path
}
};

debug!("FUSE stat: {}", path);
Expand Down Expand Up @@ -987,13 +1009,23 @@ impl VfsNode for FuseDirectory {

fn traverse_lstat(&self, components: &mut Vec<&str>) -> Result<FileAttr, IoError> {
let path: String = if components.is_empty() {
"/".to_string()
if let Some(prefix) = &self.prefix {
"/".to_string() + prefix
} else {
"/".to_string()
}
} else {
components
let path: String = components
.iter()
.rev()
.map(|v| "/".to_owned() + v)
.collect()
.collect();

if let Some(prefix) = &self.prefix {
"/".to_owned() + &prefix.to_owned() + &path
} else {
path
}
};

debug!("FUSE lstat: {}", path);
Expand All @@ -1015,13 +1047,23 @@ impl VfsNode for FuseDirectory {
mode: AccessPermission,
) -> Result<Arc<dyn ObjectInterface>, IoError> {
let path: String = if components.is_empty() {
"/".to_string()
if let Some(prefix) = &self.prefix {
"/".to_string() + prefix
} else {
"/".to_string()
}
} else {
components
let path: String = components
.iter()
.rev()
.map(|v| "/".to_owned() + v)
.collect()
.collect();

if let Some(prefix) = &self.prefix {
"/".to_owned() + &prefix.to_owned() + &path
} else {
path
}
};

debug!("FUSE open: {}, {:?} {:?}", path, opt, mode);
Expand Down Expand Up @@ -1071,13 +1113,23 @@ impl VfsNode for FuseDirectory {

fn traverse_unlink(&self, components: &mut Vec<&str>) -> core::result::Result<(), IoError> {
let path: String = if components.is_empty() {
"/".to_string()
if let Some(prefix) = &self.prefix {
"/".to_string() + prefix
} else {
"/".to_string()
}
} else {
components
let path: String = components
.iter()
.rev()
.map(|v| "/".to_owned() + v)
.collect()
.collect();

if let Some(prefix) = &self.prefix {
"/".to_owned() + &prefix.to_owned() + &path
} else {
path
}
};

let (cmd, mut rsp) = ops::Unlink::create(&path);
Expand All @@ -1092,13 +1144,23 @@ impl VfsNode for FuseDirectory {

fn traverse_rmdir(&self, components: &mut Vec<&str>) -> core::result::Result<(), IoError> {
let path: String = if components.is_empty() {
"/".to_string()
if let Some(prefix) = &self.prefix {
"/".to_string() + prefix
} else {
"/".to_string()
}
} else {
components
let path: String = components
.iter()
.rev()
.map(|v| "/".to_owned() + v)
.collect()
.collect();

if let Some(prefix) = &self.prefix {
"/".to_owned() + &prefix.to_owned() + &path
} else {
path
}
};

let (cmd, mut rsp) = ops::Rmdir::create(&path);
Expand All @@ -1117,13 +1179,23 @@ impl VfsNode for FuseDirectory {
mode: AccessPermission,
) -> Result<(), IoError> {
let path: String = if components.is_empty() {
"/".to_string()
if let Some(prefix) = &self.prefix {
"/".to_string() + prefix
} else {
"/".to_string()
}
} else {
components
let path: String = components
.iter()
.rev()
.map(|v| "/".to_owned() + v)
.collect()
.collect();

if let Some(prefix) = &self.prefix {
"/".to_owned() + &prefix.to_owned() + &path
} else {
path
}
};
let (cmd, mut rsp) = ops::Mkdir::create(&path, mode.bits());

Expand Down Expand Up @@ -1153,12 +1225,121 @@ pub(crate) fn init() {
.unwrap();
trace!("fuse init answer: {:?}", rsp);

let mount_point = format!("/{}", driver.lock().get_mount_point());
info!("Mounting virtio-fs at {}", mount_point);
fs::FILESYSTEM
.get()
.unwrap()
.mount(mount_point.as_str(), Box::new(FuseDirectory::new()))
.expect("Mount failed. Duplicate mount_point?");
let mount_point = driver.lock().get_mount_point().to_string();
if mount_point == "/" {
let fuse_nid = lookup("/").unwrap();
// Opendir
// Flag 0x10000 for O_DIRECTORY might not be necessary
let (mut cmd, mut rsp) = ops::Open::create(fuse_nid, 0x10000);
cmd.in_header.opcode = fuse_abi::Opcode::Opendir as u32;
get_filesystem_driver()
.unwrap()
.lock()
.send_command(cmd.as_ref(), rsp.as_mut())
.unwrap();
let fuse_fh = unsafe { rsp.op_header.assume_init_ref().fh };

// Linux seems to allocate a single page to store the dirfile
let len = MAX_READ_LEN as u32;
let mut offset: usize = 0;

// read content of the directory
let (mut cmd, mut rsp) = ops::Read::create(fuse_nid, fuse_fh, len, 0);
cmd.in_header.opcode = fuse_abi::Opcode::Readdir as u32;
get_filesystem_driver()
.unwrap()
.lock()
.send_command(cmd.as_ref(), rsp.as_mut())
.unwrap();

let len: usize = if unsafe { rsp.out_header.assume_init_ref().len } as usize
- ::core::mem::size_of::<fuse_abi::OutHeader>()
- ::core::mem::size_of::<fuse_abi::ReadOut>()
>= len.try_into().unwrap()
{
len.try_into().unwrap()
} else {
(unsafe { rsp.out_header.assume_init_ref().len } as usize)
- ::core::mem::size_of::<fuse_abi::OutHeader>()
- ::core::mem::size_of::<fuse_abi::ReadOut>()
};

if len <= core::mem::size_of::<fuse_abi::Dirent>() {
panic!("FUSE no new dirs");
}

let mut entries: Vec<String> = Vec::new();
while (unsafe { rsp.out_header.assume_init_ref().len } as usize) - offset
> core::mem::size_of::<fuse_abi::Dirent>()
{
let dirent =
unsafe { &*(rsp.payload.as_ptr().byte_add(offset) as *const fuse_abi::Dirent) };

offset += core::mem::size_of::<fuse_abi::Dirent>() + dirent.d_namelen as usize;
// Allign to dirent struct
offset = ((offset) + U64_SIZE - 1) & (!(U64_SIZE - 1));

let name: &'static [u8] = unsafe {
core::slice::from_raw_parts(
dirent.d_name.as_ptr(),
dirent.d_namelen.try_into().unwrap(),
)
};
entries.push(unsafe { core::str::from_utf8_unchecked(name).to_string() });
}

let (cmd, mut rsp) = ops::Release::create(fuse_nid, fuse_fh);
get_filesystem_driver()
.unwrap()
.lock()
.send_command(cmd.as_ref(), rsp.as_mut())
.unwrap();

// remove predefined directories
entries.retain(|x| x != ".");
entries.retain(|x| x != "..");
entries.retain(|x| x != "tmp");
entries.retain(|x| x != "proc");
warn!("Fuse don't mount the host directories 'tmp' and 'proc' into the guest file system!");

for i in entries {
let (cmd, mut rsp) = ops::Lookup::create(&i);
get_filesystem_driver()
.unwrap()
.lock()
.send_command(cmd.as_ref(), rsp.as_mut())
.unwrap();

let attr = unsafe { rsp.op_header.assume_init().attr };
let attr = FileAttr::from(attr);

if attr.st_mode.contains(AccessPermission::S_IFDIR) {
info!("Fuse mount {} to /{}", i, i);
fs::FILESYSTEM
.get()
.unwrap()
.mount(
&("/".to_owned() + i.as_str()),
Box::new(FuseDirectory::new(Some(i))),
)
.expect("Mount failed. Invalid mount_point?");
} else {
warn!("Fuse don't mount {}. It isn't a directory!", i);
}
}
} else {
let mount_point = if mount_point.starts_with('/') {
mount_point
} else {
"/".to_owned() + &mount_point
};

info!("Mounting virtio-fs at {}", mount_point);
fs::FILESYSTEM
.get()
.unwrap()
.mount(mount_point.as_str(), Box::new(FuseDirectory::new(None)))
.expect("Mount failed. Invalid mount_point?");
}
}
}
16 changes: 7 additions & 9 deletions src/syscalls/mod.rs
View file
Original file line number Diff line number Diff line change
Expand Up @@ -430,7 +430,7 @@ pub unsafe extern "C" fn sys_getdents64(
return -crate::errno::EINVAL as i64;
}

let limit = dirp as usize + count;
const ALIGN_DIRENT: usize = core::mem::align_of::<Dirent64>();
let mut dirp: *mut Dirent64 = dirp;
let mut offset: i64 = 0;
let obj = get_object(fd);
Expand All @@ -442,18 +442,18 @@ pub unsafe extern "C" fn sys_getdents64(
|v| {
for i in v.iter() {
let len = i.name.len();
if dirp as usize + core::mem::size_of::<Dirent64>() + len + 1 >= limit {
let aligned_len = ((core::mem::size_of::<Dirent64>() + len + 1)
+ (ALIGN_DIRENT - 1)) & (!(ALIGN_DIRENT - 1));
if offset as usize + aligned_len >= count {
return -crate::errno::EINVAL as i64;
}

let dir = unsafe { &mut *dirp };

dir.d_ino = 0;
dir.d_type = 0;
dir.d_reclen = (core::mem::size_of::<Dirent64>() + len + 1)
.try_into()
.unwrap();
offset += i64::from(dir.d_reclen);
dir.d_reclen = aligned_len.try_into().unwrap();
offset += i64::try_from(aligned_len).unwrap();
dir.d_off = offset;

// copy null-terminated filename
Expand All @@ -463,9 +463,7 @@ pub unsafe extern "C" fn sys_getdents64(
s.add(len).write_bytes(0, 1);
}

dirp = unsafe {
(dirp as *mut u8).add(dir.d_reclen as usize) as *mut Dirent64
};
dirp = unsafe { (dirp as *mut u8).add(aligned_len) as *mut Dirent64 };
}

offset
Expand Down

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