[PATCHSET v1 RFC liburing 4/6] Add `liburing_madvise()`

[Ammar Faizi <ammar.faizi@xxxxxxxxxxxxxxxxxxxxx>]

Do not use `madvise()` directly from the libc in the liburing internal
sources. Wrap them in `src/syscall.c`. This is the part of implementing
the kernel style return value (which later is supposed to support no
libc environment).

`liburing_madvise()` does the same thing with `madvise()` from the libc.
The only different is when error happens, the return value is of
`liburing_madvise()` will be a negative error code.

Signed-off-by: Ammar Faizi <ammar.faizi@xxxxxxxxxxxxxxxxxxxxx>
---
 src/setup.c   | 18 +++++++++---------
 src/syscall.c |  8 ++++++++
 src/syscall.h |  1 +
 3 files changed, 18 insertions(+), 9 deletions(-)

diff --git a/src/setup.c b/src/setup.c
index 01cb151..52f3557 100644
--- a/src/setup.c
+++ b/src/setup.c
@@ -120,20 +120,20 @@ int io_uring_ring_dontfork(struct io_uring *ring)
 		return -EINVAL;
 
 	len = *ring->sq.kring_entries * sizeof(struct io_uring_sqe);
-	ret = madvise(ring->sq.sqes, len, MADV_DONTFORK);
-	if (ret == -1)
-		return -errno;
+	ret = liburing_madvise(ring->sq.sqes, len, MADV_DONTFORK);
+	if (uring_unlikely(ret))
+		return ret;
 
 	len = ring->sq.ring_sz;
-	ret = madvise(ring->sq.ring_ptr, len, MADV_DONTFORK);
-	if (ret == -1)
-		return -errno;
+	ret = liburing_madvise(ring->sq.ring_ptr, len, MADV_DONTFORK);
+	if (uring_unlikely(ret))
+		return ret;
 
 	if (ring->cq.ring_ptr != ring->sq.ring_ptr) {
 		len = ring->cq.ring_sz;
-		ret = madvise(ring->cq.ring_ptr, len, MADV_DONTFORK);
-		if (ret == -1)
-			return -errno;
+		ret = liburing_madvise(ring->cq.ring_ptr, len, MADV_DONTFORK);
+		if (uring_unlikely(ret))
+			return ret;
 	}
 
 	return 0;
diff --git a/src/syscall.c b/src/syscall.c
index cb48a94..44861f6 100644
--- a/src/syscall.c
+++ b/src/syscall.c
@@ -133,3 +133,11 @@ int liburing_munmap(void *addr, size_t length)
 	ret = munmap(addr, length);
 	return (ret < 0) ? -errno : ret;
 }
+
+int liburing_madvise(void *addr, size_t length, int advice)
+{
+	int ret;
+
+	ret = madvise(addr, length, advice);
+	return (ret < 0) ? -errno : ret;
+}
diff --git a/src/syscall.h b/src/syscall.h
index feccf67..32381ce 100644
--- a/src/syscall.h
+++ b/src/syscall.h
@@ -29,5 +29,6 @@ int ____sys_io_uring_register(int fd, unsigned int opcode, const void *arg,
 void *liburing_mmap(void *addr, size_t length, int prot, int flags, int fd,
 		    off_t offset);
 int liburing_munmap(void *addr, size_t length);
+int liburing_madvise(void *addr, size_t length, int advice);
 
 #endif
-- 
2.30.2