io_uring: Add function to reserve file slots
This makes it possible to expand the file array prior to adding file
descriptors and perform the expensive registration function early in the
reservation process.
Change-Id: I34cf9fad41ea90ccfd6bc15b7b3b89bf80e8f600
Signed-off-by: William A. Kennington III <wak@google.com>
diff --git a/src/stdplus/io_uring.cpp b/src/stdplus/io_uring.cpp
index 357f4c9..c824597 100644
--- a/src/stdplus/io_uring.cpp
+++ b/src/stdplus/io_uring.cpp
@@ -53,6 +53,18 @@
ring->updateFile(slot, -1);
}
+void IoUring::reserveFiles(size_t num)
+{
+ auto new_size = std::max<size_t>(7, num + filesAllocated);
+ if (files.size() < new_size)
+ {
+ io_uring_unregister_files(&ring);
+ files.resize(new_size, -1);
+ CHECK_RET(io_uring_register_files(&ring, files.data(), files.size()),
+ "io_uring_register_files");
+ }
+}
+
[[nodiscard]] IoUring::FileHandle IoUring::registerFile(int fd)
{
unsigned slot = 0;
@@ -67,7 +79,7 @@
io_uring_unregister_files(&ring);
files.resize(std::max<size_t>(7, files.size() * 2 + 1), -1);
- files[slot] = fd;
+ setFile(slot, fd);
CHECK_RET(io_uring_register_files(&ring, files.data(), files.size()),
"io_uring_register_files");
return FileHandle(slot, *this);
@@ -168,9 +180,22 @@
h->handleCQE(cqe);
}
+void IoUring::setFile(unsigned slot, int fd) noexcept
+{
+ if (files[slot] == -1 && files[slot] != fd)
+ {
+ filesAllocated++;
+ }
+ else if (fd == -1 && files[slot] != fd)
+ {
+ filesAllocated--;
+ }
+ files[slot] = fd;
+}
+
void IoUring::updateFile(unsigned slot, int fd)
{
- files[slot] = fd;
+ setFile(slot, fd);
CHECK_RET(io_uring_register_files_update(&ring, slot, &files[slot], 1),
"io_uring_register_files_update");
}
diff --git a/src/stdplus/io_uring.hpp b/src/stdplus/io_uring.hpp
index 62539ea..5e9e778 100644
--- a/src/stdplus/io_uring.hpp
+++ b/src/stdplus/io_uring.hpp
@@ -57,6 +57,13 @@
IoUring& operator=(const IoUring&) = delete;
~IoUring();
+ /** @brief Reserves an additional number of file descriptor slots
+ *
+ * @param[in] num - The number of slots to register
+ * @throws std::system_error if the allocation fails
+ */
+ void reserveFiles(size_t num);
+
/** @brief Registers a file descriptor with a slot on the ring
*
* @param[in] fd - The file descriptor to register
@@ -65,6 +72,13 @@
*/
[[nodiscard]] FileHandle registerFile(int fd);
+ /** @brief Get current list of files descriptors registered on the ring.
+ * Note this view potentially expires when registrations change. */
+ inline stdplus::span<const int> getFiles() const noexcept
+ {
+ return files;
+ }
+
/** @brief Gets an unused SQE from the ring
*
* @throws std::system_error if the allocation fails
@@ -116,8 +130,10 @@
std::optional<stdplus::ManagedFd> event_fd;
std::vector<CQEHandler*> handlers;
std::vector<int> files;
+ size_t filesAllocated = 0;
void dropHandler(CQEHandler* h, io_uring_cqe& cqe) noexcept;
+ void setFile(unsigned slot, int fd) noexcept;
void updateFile(unsigned slot, int fd);
};
diff --git a/test/io_uring.cpp b/test/io_uring.cpp
index b50e519..c98462d 100644
--- a/test/io_uring.cpp
+++ b/test/io_uring.cpp
@@ -179,13 +179,16 @@
// Slots are always allocated linearly and re-used if invalidated
fh = ring.registerFile(0);
+ EXPECT_GT(ring.getFiles().size(), 1);
EXPECT_EQ(*fh, 0);
fh = ring.registerFile(1);
EXPECT_EQ(*fh, 1);
+ EXPECT_EQ(ring.getFiles()[1], 1);
// The first handle should have dropped and can be replaced
fh = ring.registerFile(2);
EXPECT_EQ(*fh, 0);
+ EXPECT_EQ(ring.getFiles()[0], 2);
// We should be able to write to stderr via the fixed file and regular fd
testFdWrite(2, 0);
@@ -197,11 +200,18 @@
testFdWrite(*fh, IOSQE_FIXED_FILE, -EBADF);
std::vector<IoUring::FileHandle> fhs;
- for (size_t i = 0; i < 10; ++i)
+ EXPECT_LT(ring.getFiles().size(), 9);
+ ring.reserveFiles(9);
+ EXPECT_EQ(ring.getFiles().size(), 9);
+ for (size_t i = 0; i < 9; ++i)
{
fhs.emplace_back(ring.registerFile(2));
testFdWrite(fhs.back(), IOSQE_FIXED_FILE);
}
+ EXPECT_EQ(ring.getFiles().size(), 9);
+ fhs.emplace_back(ring.registerFile(2));
+ testFdWrite(fhs.back(), IOSQE_FIXED_FILE);
+ EXPECT_GE(ring.getFiles().size(), 10);
}
} // namespace stdplus