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polyfill io_uring_{setup,free}_buf_ring #142

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Merged
wokron merged 1 commit into from
Jun 18, 2026
Merged

polyfill io_uring_{setup,free}_buf_ring #142

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51 changes: 50 additions & 1 deletion include/condy/condy_uring.hpp
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Original file line number Diff line number Diff line change
Expand Up @@ -4,7 +4,11 @@

#pragma once

#include <liburing.h> // IWYU pragma: export
#include <liburing.h>

#include <cerrno>
#include <cstring>
#include <sys/mman.h>

// liburing <= 2.3 has no version macros, define them here

Expand Down Expand Up @@ -35,3 +39,48 @@ inline void io_uring_prep_uring_cmd(struct io_uring_sqe *sqe, int cmd_op,
sqe->len = 0;
}
#endif

// Polyfill for io_uring_setup_buf_ring / io_uring_free_buf_ring
// (added in liburing 2.4)
#if IO_URING_CHECK_VERSION(2, 4) // < 2.4
inline struct io_uring_buf_ring *
io_uring_setup_buf_ring(struct io_uring *ring, unsigned int nentries, int bgid,
unsigned int flags, int *err) noexcept {
size_t ring_size = nentries * sizeof(struct io_uring_buf);
auto *br = static_cast<struct io_uring_buf_ring *>(
mmap(nullptr, ring_size, PROT_READ | PROT_WRITE,
MAP_ANONYMOUS | MAP_PRIVATE, -1, 0));
if (br == MAP_FAILED) {
*err = -errno;
return nullptr;
}

io_uring_buf_ring_init(br);

struct io_uring_buf_reg reg = {};
reg.ring_addr = reinterpret_cast<uint64_t>(br);
reg.ring_entries = nentries;
reg.bgid = bgid;

*err = 0;
int ret = io_uring_register_buf_ring(ring, &reg, flags);
if (ret != 0) {
munmap(br, ring_size);
*err = ret;
return nullptr;
}

return br;
}

inline int io_uring_free_buf_ring(struct io_uring *ring,
struct io_uring_buf_ring *br,
unsigned int nentries, int bgid) noexcept {
int ret = io_uring_unregister_buf_ring(ring, bgid);
if (ret != 0) {
return ret;
}
munmap(br, nentries * sizeof(struct io_uring_buf));
return 0;
}
#endif
72 changes: 19 additions & 53 deletions include/condy/provided_buffers.hpp
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Original file line number Diff line number Diff line change
Expand Up @@ -56,40 +56,23 @@ class BundledProvidedBufferQueue {
br_flags_(flags) {
auto &bgid_pool = runtime_->bgid_pool();

size_t data_size = capacity_ * sizeof(io_uring_buf);
void *data = mmap(nullptr, data_size, PROT_READ | PROT_WRITE,
MAP_ANONYMOUS | MAP_PRIVATE, 0, 0);
if (data == MAP_FAILED) [[unlikely]] {
throw detail::make_system_error("mmap");
}
auto d1 = detail::defer([&]() { munmap(data, data_size); });

bgid_ = bgid_pool.allocate();
auto d2 = detail::defer([&]() { bgid_pool.recycle(bgid_); });

br_ = reinterpret_cast<io_uring_buf_ring *>(data);
io_uring_buf_ring_init(br_);

io_uring_buf_reg reg = {};
reg.ring_addr = reinterpret_cast<uint64_t>(br_);
reg.ring_entries = capacity_;
reg.bgid = bgid_;
int r = io_uring_register_buf_ring(runtime_->ring().ring(), &reg,
br_flags_);
if (r != 0) [[unlikely]] {
throw detail::make_system_error("io_uring_register_buf_ring", -r);
auto d = detail::defer([&]() { bgid_pool.recycle(bgid_); });

int err = 0;
br_ = io_uring_setup_buf_ring(runtime_->ring().ring(), capacity_, bgid_,
br_flags_, &err);
if (br_ == nullptr) [[unlikely]] {
throw detail::make_system_error("io_uring_setup_buf_ring", -err);
}

d1.dismiss();
d2.dismiss();
d.dismiss();
}

~BundledProvidedBufferQueue() {
assert(br_ != nullptr);
size_t data_size = capacity_ * sizeof(io_uring_buf);
munmap(br_, data_size);
[[maybe_unused]] int r =
io_uring_unregister_buf_ring(runtime_->ring().ring(), bgid_);
[[maybe_unused]] int r = io_uring_free_buf_ring(runtime_->ring().ring(),
br_, capacity_, bgid_);
assert(r == 0);
if (r == 0) {
runtime_->bgid_pool().recycle(bgid_);
Expand Down Expand Up @@ -274,26 +257,13 @@ class BundledProvidedBufferPool {
auto &bgid_pool = runtime_->bgid_pool();

bgid_ = bgid_pool.allocate();
auto d2 = detail::defer([&]() { bgid_pool.recycle(bgid_); });
auto d = detail::defer([&]() { bgid_pool.recycle(bgid_); });

size_t ring_size = num_buffers_ * sizeof(io_uring_buf);
void *ring_data = mmap(nullptr, ring_size, PROT_READ | PROT_WRITE,
MAP_ANONYMOUS | MAP_PRIVATE, 0, 0);
if (ring_data == MAP_FAILED) [[unlikely]] {
throw detail::make_system_error("mmap");
}
auto d1 = detail::defer([&]() { munmap(ring_data, ring_size); });
br_ = reinterpret_cast<io_uring_buf_ring *>(ring_data);
io_uring_buf_ring_init(br_);

io_uring_buf_reg reg = {};
reg.ring_addr = reinterpret_cast<uint64_t>(br_);
reg.ring_entries = num_buffers_;
reg.bgid = bgid_;
int r = io_uring_register_buf_ring(runtime_->ring().ring(), &reg,
br_flags_);
if (r != 0) [[unlikely]] {
throw detail::make_system_error("io_uring_register_buf_ring", -r);
int err = 0;
br_ = io_uring_setup_buf_ring(runtime_->ring().ring(), num_buffers_,
bgid_, br_flags_, &err);
if (br_ == nullptr) [[unlikely]] {
throw detail::make_system_error("io_uring_setup_buf_ring", -err);
}

for (size_t bid = 0; bid < num_buffers_; bid++) {
Expand All @@ -303,21 +273,17 @@ class BundledProvidedBufferPool {
}
io_uring_buf_ring_advance(br_, static_cast<int>(num_buffers_));

d1.dismiss();
d2.dismiss();
d.dismiss();
}

~BundledProvidedBufferPool() {
assert(br_ != nullptr);
[[maybe_unused]] int r =
io_uring_unregister_buf_ring(runtime_->ring().ring(), bgid_);
[[maybe_unused]] int r = io_uring_free_buf_ring(
runtime_->ring().ring(), br_, num_buffers_, bgid_);
assert(r == 0);
if (r == 0) {
runtime_->bgid_pool().recycle(bgid_);
}

size_t ring_size = num_buffers_ * sizeof(io_uring_buf);
munmap(br_, ring_size);
}

public:
Expand Down
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