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virtio-balloon: use fallocate when balloon inflated

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For vhost-user devices, memory should be shared between CLH and
vhost-user backend. However, madvise DONTNEED doesn't working in
this case. So, let's use fallocate PUNCH_HOLE to discard those
memory regions instead.

Signed-off-by: Li Hangjing <lihangjing@bytedance.com>
This commit is contained in:
Li Hangjing 2021-01-28 15:56:42 +08:00 committed by Sebastien Boeuf
parent aa27f0e743
commit 3fed07419a
2 changed files with 26 additions and 1 deletions
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26
virtio-devices/src/balloon.rs
View File

@ -62,6 +62,8 @@ pub enum Error {
UnexpectedWriteOnlyDescriptor,
// Guest sent us invalid request.
InvalidRequest,
// Fallocate fail.
FallocateFail(std::io::Error),
// Madvise fail.
MadviseFail(std::io::Error),
// Failed to EventFd write.
@ -203,7 +205,29 @@ impl BalloonEpollHandler {
let gpa = (pfn as u64) << VIRTIO_BALLOON_PFN_SHIFT;
if let Ok(hva) = mem.get_host_address(GuestAddress(gpa)) {
let advice = match ev_type {
INFLATE_QUEUE_EVENT => libc::MADV_DONTNEED,
INFLATE_QUEUE_EVENT => {
let region =
mem.find_region(GuestAddress(gpa))
.ok_or(Error::GuestMemory(
GuestMemoryError::InvalidGuestAddress(GuestAddress(gpa)),
))?;
if let Some(f_off) = region.file_offset() {
let offset = hva as usize - region.as_ptr() as usize;
let res = unsafe {
libc::fallocate64(
f_off.file().as_raw_fd(),
libc::FALLOC_FL_PUNCH_HOLE | libc::FALLOC_FL_KEEP_SIZE,
(offset as u64 + f_off.start()) as libc::off64_t,
(1 << VIRTIO_BALLOON_PFN_SHIFT) as libc::off64_t,
)
};
if res != 0 {
return Err(Error::FallocateFail(io::Error::last_os_error()));
}
}
libc::MADV_DONTNEED
}
DEFLATE_QUEUE_EVENT => libc::MADV_WILLNEED,
_ => return Err(Error::ProcessQueueWrongEvType(ev_type)),
};

1
virtio-devices/src/seccomp_filters.rs
View File

@ -86,6 +86,7 @@ fn virtio_balloon_thread_rules() -> Vec<SyscallRuleSet> {
allow_syscall(libc::SYS_epoll_wait),
allow_syscall(libc::SYS_exit),
allow_syscall(libc::SYS_futex),
allow_syscall(libc::SYS_fallocate),
allow_syscall(libc::SYS_madvise),
allow_syscall(libc::SYS_munmap),
allow_syscall(libc::SYS_read),