From: Tobias Stoeckmann <tobias@stoeckmann.org>
Date: Thu, 17 Oct 2024 21:55:06 +0000 (+0200)
Subject: libkmod: Use pread where appropriate
X-Git-Tag: v34~208
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=8d03b6c7d990af301950d3ecdc4b5c69fa525928;p=thirdparty%2Fkmod.git

libkmod: Use pread where appropriate

Since we do not want to modify the current position in file, use pread
instead of read + lseek. Removes one lseek call per module, which for
depmod on Arch Linux means 6143 calls.

Signed-off-by: Tobias Stoeckmann <tobias@stoeckmann.org>
Link: https://github.com/kmod-project/kmod/pull/189
Signed-off-by: Lucas De Marchi <lucas.de.marchi@gmail.com>
---

diff --git a/libkmod/libkmod-file.c b/libkmod/libkmod-file.c
index fe2bd05d..828522ec 100644
--- a/libkmod/libkmod-file.c
+++ b/libkmod/libkmod-file.c
@@ -95,8 +95,7 @@ struct kmod_file *kmod_file_open(const struct kmod_ctx *ctx, const char *filenam
 		return NULL;
 	}
 
-	sz = read_str_safe(file->fd, buf, sizeof(buf));
-	lseek(file->fd, 0, SEEK_SET);
+	sz = pread_str_safe(file->fd, buf, sizeof(buf), 0);
 	if (sz != (sizeof(buf) - 1)) {
 		if (sz < 0)
 			errno = -sz;
diff --git a/shared/util.c b/shared/util.c
index 5102879f..6d1cf420 100644
--- a/shared/util.c
+++ b/shared/util.c
@@ -183,6 +183,33 @@ bool path_ends_with_kmod_ext(const char *path, size_t len)
 
 /* read-like and fread-like functions                                       */
 /* ************************************************************************ */
+ssize_t pread_str_safe(int fd, char *buf, size_t buflen, off_t off)
+{
+	size_t todo = buflen - 1;
+	size_t done = 0;
+
+	assert_cc(EAGAIN == EWOULDBLOCK);
+
+	do {
+		ssize_t r = pread(fd, buf + done, todo, off + done);
+
+		if (r == 0)
+			break;
+		else if (r > 0) {
+			todo -= r;
+			done += r;
+		} else {
+			if (errno == EAGAIN || errno == EINTR)
+				continue;
+			else
+				return -errno;
+		}
+	} while (todo > 0);
+
+	buf[done] = '\0';
+	return done;
+}
+
 ssize_t read_str_safe(int fd, char *buf, size_t buflen)
 {
 	size_t todo = buflen - 1;
diff --git a/shared/util.h b/shared/util.h
index 974f1ddb..579217f3 100644
--- a/shared/util.h
+++ b/shared/util.h
@@ -35,6 +35,8 @@ _nonnull_all_ bool path_ends_with_kmod_ext(const char *path, size_t len);
 
 /* read-like and fread-like functions                                       */
 /* ************************************************************************ */
+_must_check_ _nonnull_(2) ssize_t pread_str_safe(int fd, char *buf, size_t buflen,
+						 off_t off);
 _must_check_ _nonnull_(2) ssize_t read_str_safe(int fd, char *buf, size_t buflen);
 _nonnull_(2) ssize_t write_str_safe(int fd, const char *buf, size_t buflen);
 _must_check_ _nonnull_(2) int read_str_long(int fd, long *value, int base);