core-helper: add file read/discard helpers to read all data from a file

Add helpers to read and discard all the data in a file, useful for exercising the reading of large /proc and /sys files. Signed-off-by: Colin Ian King <[email protected]>
ColinIanKing · Oct 13, 2024 · 29a24a7 · 29a24a7
1 parent d0135ea
commit 29a24a7
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diff --git a/core-helper.c b/core-helper.c
@@ -2073,6 +2073,26 @@ ssize_t stress_system_write(
 	return ret;
 }
 
+/*
+ *  stress_system_discard()
+ *	read and discard contents of a given file
+ */
+ssize_t stress_system_discard(const char *path)
+{
+	int fd;
+	ssize_t ret;
+
+	if (UNLIKELY(!path))
+		return -EINVAL;
+	fd = open(path, O_RDONLY);
+	if (UNLIKELY(fd < 0))
+		return -errno;
+	ret = stress_read_discard(fd);
+	(void)close(fd);
+
+	return ret;
+}
+
 /*
  *  stress_system_read()
  *	read a buffer from a /sys or /proc entry
@@ -3295,6 +3315,25 @@ int stress_get_unused_uid(uid_t *uid)
 }
 #endif
 
+/*
+ *  stress_read_discard(cont int fd)
+ *	read and discard contents of file fd
+ */
+ssize_t stress_read_discard(const int fd)
+{
+	ssize_t rbytes = 0, ret;
+
+	do {
+		char buffer[4096];
+
+		ret = read(fd, buffer, sizeof(buffer));
+		if (ret > 0)
+			rbytes += ret;
+	} while (ret > 0);
+
+	return rbytes;
+}
+
 /*
  *  stress_read_buffer()
  *	In addition to read() this function makes sure all bytes have been

diff --git a/core-helper.h b/core-helper.h
@@ -103,6 +103,7 @@ extern WARN_UNUSED int stress_cache_alloc(const char *name) NONNULL(1);
 extern void stress_cache_free(void);
 extern ssize_t stress_system_write(const char *path, const char *buf,
 	const size_t buf_len);
+extern ssize_t stress_system_discard(const char *path);
 extern WARN_UNUSED ssize_t stress_system_read(const char *path, char *buf,
 	const size_t buf_len);
 extern WARN_UNUSED bool stress_is_prime64(const uint64_t n);
@@ -142,6 +143,7 @@ extern WARN_UNUSED int stress_dirent_list_prune(struct dirent **dlist, const int
 extern WARN_UNUSED bool stress_warn_once_hash(const char *filename, const int line) NONNULL(1);
 extern WARN_UNUSED uint16_t stress_ipv4_checksum(uint16_t *ptr, const size_t sz);
 extern WARN_UNUSED int stress_get_unused_uid(uid_t *uid);
+extern ssize_t stress_read_discard(const int fd);
 extern WARN_UNUSED ssize_t stress_read_buffer(const int fd, void* buffer,
 	const ssize_t size, const bool ignore_sig_eintr);
 extern WARN_UNUSED ssize_t stress_write_buffer(const int fd, const void* buffer,