[dpdk-dev] [RFC PATCH 5/9] eal: introduce internal wrappers for file operations

[Dmitry Kozlyuk <dmitry.kozliuk@gmail.com>]

EAL common code uses file locking and truncation. Introduce
OS-independent wrapeprs in order to support both POSIX and Windows:

* eal_file_lock: lock or unlock an open file.
* eal_file_truncate: enforce a given size for an open file.

Wrappers follow POSIX semantics, but interface is not POSIX,
so that it can be made more clean, e.g. by not mixing locking
operation and behaviour on conflict.

Signed-off-by: Dmitry Kozlyuk <dmitry.kozliuk@gmail.com>

WIP2
---
 lib/librte_eal/common/eal_private.h | 45 ++++++++++++++++
 lib/librte_eal/freebsd/eal/eal.c    | 40 ++++++++++++++
 lib/librte_eal/linux/eal/eal.c      | 40 ++++++++++++++
 lib/librte_eal/windows/eal/eal.c    | 83 +++++++++++++++++++++++++++++
 4 files changed, 208 insertions(+)

diff --git a/lib/librte_eal/common/eal_private.h b/lib/librte_eal/common/eal_private.h
index ddcfbe2e4..0130571e8 100644
--- a/lib/librte_eal/common/eal_private.h
+++ b/lib/librte_eal/common/eal_private.h
@@ -443,4 +443,49 @@ rte_option_usage(void);
 uint64_t
 eal_get_baseaddr(void);
 
+/** File locking operation. */
+enum rte_flock_op {
+	RTE_FLOCK_SHARED,    /**< Acquire a shared lock. */
+	RTE_FLOCK_EXCLUSIVE, /**< Acquire an exclusive lock. */
+	RTE_FLOCK_UNLOCK     /**< Release a previously taken lock. */
+};
+
+/** Behavior on file locking conflict. */
+enum rte_flock_mode {
+	RTE_FLOCK_WAIT,  /**< Wait until the file gets unlocked to lock it. */
+	RTE_FLOCK_RETURN /**< Return immediately if the file is locked. */
+};
+
+/**
+ * Lock or unlock the file.
+ *
+ * On failure @code rte_errno @endcode is set to the error code
+ * specified by POSIX flock(3) description.
+ *
+ * @param fd
+ *  Opened file descriptor.
+ * @param op
+ *  Operation to perform.
+ * @param mode
+ *  Behavior on conflict.
+ * @return
+ *  0 on success, (-1) on failure.
+ */
+int eal_file_lock(int fd, enum rte_flock_op op, enum rte_flock_mode mode);
+
+/**
+ * Truncate or extend the file to the specified size.
+ *
+ * On failure @code rte_errno @endcode is set to the error code
+ * specified by POSIX ftruncate(3) description.
+ *
+ * @param fd
+ *  Opened file descriptor.
+ * @param size
+ *  Desired file size.
+ * @return
+ *  0 on success, (-1) on failure.
+ */
+int eal_file_truncate(int fd, ssize_t size);
+
 #endif /* _EAL_PRIVATE_H_ */
diff --git a/lib/librte_eal/freebsd/eal/eal.c b/lib/librte_eal/freebsd/eal/eal.c
index 6ae37e7e6..4bbcc7ab7 100644
--- a/lib/librte_eal/freebsd/eal/eal.c
+++ b/lib/librte_eal/freebsd/eal/eal.c
@@ -697,6 +697,46 @@ static void rte_eal_init_alert(const char *msg)
 	RTE_LOG(ERR, EAL, "%s\n", msg);
 }
 
+int
+eal_file_truncate(int fd, ssize_t size)
+{
+	int ret;
+
+	ret = ftruncate(fd, size);
+	if (ret)
+		rte_errno = errno;
+
+	return ret;
+}
+
+int
+eal_file_lock(int fd, enum rte_flock_op op, enum rte_flock_mode mode)
+{
+	int sys_flags = 0;
+	int ret;
+
+	if (mode == RTE_FLOCK_RETURN)
+		sys_flags |= LOCK_NB;
+
+	switch (op) {
+	case RTE_FLOCK_EXCLUSIVE:
+		sys_flags |= LOCK_EX;
+		break;
+	case RTE_FLOCK_SHARED:
+		sys_flags |= LOCK_SH;
+		break;
+	case RTE_FLOCK_UNLOCK:
+		sys_flags |= LOCK_UN;
+		break;
+	}
+
+	ret = flock(fd, sys_flags);
+	if (ret)
+		rte_errno = errno;
+
+	return ret;
+}
+
 /* Launch threads, called at application init(). */
 int
 rte_eal_init(int argc, char **argv)
diff --git a/lib/librte_eal/linux/eal/eal.c b/lib/librte_eal/linux/eal/eal.c
index 9530ee55f..d75c162c1 100644
--- a/lib/librte_eal/linux/eal/eal.c
+++ b/lib/librte_eal/linux/eal/eal.c
@@ -956,6 +956,46 @@ is_iommu_enabled(void)
 	return n > 2;
 }
 
+int
+eal_file_truncate(int fd, ssize_t size)
+{
+	int ret;
+
+	ret = ftruncate(fd, size);
+	if (ret)
+		rte_errno = errno;
+
+	return ret;
+}
+
+int
+eal_file_lock(int fd, enum rte_flock_op op, enum rte_flock_mode mode)
+{
+	int sys_flags = 0;
+	int ret;
+
+	if (mode == RTE_FLOCK_RETURN)
+		sys_flags |= LOCK_NB;
+
+	switch (op) {
+	case RTE_FLOCK_EXCLUSIVE:
+		sys_flags |= LOCK_EX;
+		break;
+	case RTE_FLOCK_SHARED:
+		sys_flags |= LOCK_SH;
+		break;
+	case RTE_FLOCK_UNLOCK:
+		sys_flags |= LOCK_UN;
+		break;
+	}
+
+	ret = flock(fd, sys_flags);
+	if (ret)
+		rte_errno = errno;
+
+	return ret;
+}
+
 /* Launch threads, called at application init(). */
 int
 rte_eal_init(int argc, char **argv)
diff --git a/lib/librte_eal/windows/eal/eal.c b/lib/librte_eal/windows/eal/eal.c
index a84b6147a..4932185ec 100644
--- a/lib/librte_eal/windows/eal/eal.c
+++ b/lib/librte_eal/windows/eal/eal.c
@@ -224,6 +224,89 @@ rte_eal_init_alert(const char *msg)
 	RTE_LOG(ERR, EAL, "%s\n", msg);
 }
 
+int
+eal_file_truncate(int fd, ssize_t size)
+{
+	HANDLE handle;
+	DWORD ret;
+	LONG low = (LONG)((size_t)size);
+	LONG high = (LONG)((size_t)size >> 32);
+
+	handle = (HANDLE)_get_osfhandle(fd);
+	if (handle == INVALID_HANDLE_VALUE) {
+		rte_errno = EBADF;
+		return -1;
+	}
+
+	ret = SetFilePointer(handle, low, &high, FILE_BEGIN);
+	if (ret == INVALID_SET_FILE_POINTER) {
+		RTE_LOG_WIN32_ERR("SetFilePointer()");
+		rte_errno = EINVAL;
+		return -1;
+	}
+
+	return 0;
+}
+
+static int
+lock_file(HANDLE handle, enum rte_flock_op op, enum rte_flock_mode mode)
+{
+	DWORD sys_flags = 0;
+	OVERLAPPED overlapped;
+
+	if (op == RTE_FLOCK_EXCLUSIVE)
+		sys_flags |= LOCKFILE_EXCLUSIVE_LOCK;
+	if (mode == RTE_FLOCK_RETURN)
+		sys_flags |= LOCKFILE_FAIL_IMMEDIATELY;
+
+	memset(&overlapped, 0, sizeof(overlapped));
+	if (!LockFileEx(handle, sys_flags, 0, 0, 0, &overlapped)) {
+		if ((sys_flags & LOCKFILE_FAIL_IMMEDIATELY) &&
+			(GetLastError() == ERROR_IO_PENDING)) {
+			rte_errno = EWOULDBLOCK;
+		} else {
+			RTE_LOG_WIN32_ERR("LockFileEx()");
+			rte_errno = EINVAL;
+		}
+		return -1;
+	}
+
+	return 0;
+}
+
+static int
+unlock_file(HANDLE handle)
+{
+	if (!UnlockFileEx(handle, 0, 0, 0, NULL)) {
+		RTE_LOG_WIN32_ERR("UnlockFileEx()");
+		rte_errno = EINVAL;
+		return -1;
+	}
+	return 0;
+}
+
+int
+eal_file_lock(int fd, enum rte_flock_op op, enum rte_flock_mode mode)
+{
+	HANDLE handle = (HANDLE)_get_osfhandle(fd);
+
+	if (handle == INVALID_HANDLE_VALUE) {
+		rte_errno = EBADF;
+		return -1;
+	}
+
+	switch (op) {
+	case RTE_FLOCK_EXCLUSIVE:
+	case RTE_FLOCK_SHARED:
+		return lock_file(handle, op, mode);
+	case RTE_FLOCK_UNLOCK:
+		return unlock_file(handle);
+	default:
+		rte_errno = EINVAL;
+		return -1;
+	}
+}
+
  /* Launch threads, called at application init(). */
 int
 rte_eal_init(int argc, char **argv)
-- 
2.25.1