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block: raw: Implement punch_hole and write_zeroes

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Implement punch_hole() and write_zeroes() for raw file backends using
io_uring and fallocate.

punch_hole() uses FALLOC_FL_PUNCH_HOLE to deallocate storage.
write_zeroes() uses FALLOC_FL_ZERO_RANGE to write zeros efficiently.

Both use FALLOC_FL_KEEP_SIZE to maintain file size.

Signed-off-by: Anatol Belski <anbelski@linux.microsoft.com>
This commit is contained in:
Anatol Belski 2026-01-29 15:48:36 +01:00 • committed by Rob Bradford
parent 6c94975c80
commit 45b115aeb0
2 changed files with 94 additions and 16 deletions
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58
block/src/raw_async.rs
View file

@ -258,15 +258,57 @@ impl AsyncIo for RawFileAsync {
Ok(())
}
fn punch_hole(&mut self, _offset: u64, _length: u64, _user_data: u64) -> AsyncIoResult<()> {
Err(AsyncIoError::PunchHole(std::io::Error::other(
"punch_hole not supported for raw async backend",
)))
fn punch_hole(&mut self, offset: u64, length: u64, user_data: u64) -> AsyncIoResult<()> {
let (submitter, mut sq, _) = self.io_uring.split();
const FALLOC_FL_PUNCH_HOLE: i32 = 0x02;
const FALLOC_FL_KEEP_SIZE: i32 = 0x01;
let mode = FALLOC_FL_PUNCH_HOLE | FALLOC_FL_KEEP_SIZE;
// SAFETY: The file descriptor is known to be valid.
unsafe {
sq.push(
&opcode::Fallocate::new(types::Fd(self.fd), length)
.offset(offset)
.mode(mode)
.build()
.user_data(user_data),
)
.map_err(|e| {
AsyncIoError::PunchHole(Error::other(format!("Submission queue is full: {e:?}")))
})?;
};
sq.sync();
submitter.submit().map_err(AsyncIoError::PunchHole)?;
Ok(())
}
fn write_zeroes(&mut self, _offset: u64, _length: u64, _user_data: u64) -> AsyncIoResult<()> {
Err(AsyncIoError::WriteZeroes(std::io::Error::other(
"write_zeroes not supported for raw async backend",
)))
fn write_zeroes(&mut self, offset: u64, length: u64, user_data: u64) -> AsyncIoResult<()> {
let (submitter, mut sq, _) = self.io_uring.split();
const FALLOC_FL_ZERO_RANGE: i32 = 0x10;
const FALLOC_FL_KEEP_SIZE: i32 = 0x01;
let mode = FALLOC_FL_ZERO_RANGE | FALLOC_FL_KEEP_SIZE;
// SAFETY: The file descriptor is known to be valid.
unsafe {
sq.push(
&opcode::Fallocate::new(types::Fd(self.fd), length)
.offset(offset)
.mode(mode)
.build()
.user_data(user_data),
)
.map_err(|e| {
AsyncIoError::WriteZeroes(Error::other(format!("Submission queue is full: {e:?}")))
})?;
};
sq.sync();
submitter.submit().map_err(AsyncIoError::WriteZeroes)?;
Ok(())
}
}

52
block/src/raw_sync.rs
View file

@ -151,15 +151,51 @@ impl AsyncIo for RawFileSync {
self.completion_list.pop_front()
}
fn punch_hole(&mut self, _offset: u64, _length: u64, _user_data: u64) -> AsyncIoResult<()> {
Err(AsyncIoError::PunchHole(std::io::Error::other(
"punch_hole not supported for raw sync backend",
)))
fn punch_hole(&mut self, offset: u64, length: u64, user_data: u64) -> AsyncIoResult<()> {
const FALLOC_FL_PUNCH_HOLE: i32 = 0x02;
const FALLOC_FL_KEEP_SIZE: i32 = 0x01;
let mode = FALLOC_FL_PUNCH_HOLE | FALLOC_FL_KEEP_SIZE;
// SAFETY: FFI call with valid arguments
let result = unsafe {
libc::fallocate(
self.fd as libc::c_int,
mode,
offset as libc::off_t,
length as libc::off_t,
)
};
if result < 0 {
return Err(AsyncIoError::PunchHole(std::io::Error::last_os_error()));
}
self.completion_list.push_back((user_data, result));
self.eventfd.write(1).unwrap();
Ok(())
}
fn write_zeroes(&mut self, _offset: u64, _length: u64, _user_data: u64) -> AsyncIoResult<()> {
Err(AsyncIoError::WriteZeroes(std::io::Error::other(
"write_zeroes not supported for raw sync backend",
)))
fn write_zeroes(&mut self, offset: u64, length: u64, user_data: u64) -> AsyncIoResult<()> {
const FALLOC_FL_ZERO_RANGE: i32 = 0x10;
const FALLOC_FL_KEEP_SIZE: i32 = 0x01;
let mode = FALLOC_FL_ZERO_RANGE | FALLOC_FL_KEEP_SIZE;
// SAFETY: FFI call with valid arguments
let result = unsafe {
libc::fallocate(
self.fd as libc::c_int,
mode,
offset as libc::off_t,
length as libc::off_t,
)
};
if result < 0 {
return Err(AsyncIoError::WriteZeroes(std::io::Error::last_os_error()));
}
self.completion_list.push_back((user_data, result));
self.eventfd.write(1).unwrap();
Ok(())
}
}