initramfs: switch initramfs unpacking to struct file based APIs

There is no good reason to mess with file descriptors from in-kernel
code, switch the initramfs unpacking to struct file based write
instead.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Acked-by: Linus Torvalds <torvalds@linux-foundation.org>

init/initramfs.c

@@ -13,13 +13,14 @@
 #include <linux/memblock.h>
 #include <linux/namei.h>
 
-static ssize_t __init xwrite(int fd, const char *p, size_t count)
+static ssize_t __init xwrite(struct file *file, const char *p, size_t count,
+		loff_t *pos)
 {
 	ssize_t out = 0;
 
 	/* sys_write only can write MAX_RW_COUNT aka 2G-4K bytes at most */
 	while (count) {
-		ssize_t rv = ksys_write(fd, p, count);
+		ssize_t rv = kernel_write(file, p, count, pos);
 
 		if (rv < 0) {
 			if (rv == -EINTR || rv == -EAGAIN)
@@ -317,7 +318,8 @@ static int __init maybe_link(void)
 	return 0;
 }
 
-static __initdata int wfd;
+static __initdata struct file *wfile;
+static __initdata loff_t wfile_pos;
 
 static int __init do_name(void)
 {
@@ -334,16 +336,17 @@ static int __init do_name(void)
 			int openflags = O_WRONLY|O_CREAT;
 			if (ml != 1)
 				openflags |= O_TRUNC;
-			wfd = ksys_open(collected, openflags, mode);
-
-			if (wfd >= 0) {
-				ksys_fchown(wfd, uid, gid);
-				ksys_fchmod(wfd, mode);
-				if (body_len)
-					ksys_ftruncate(wfd, body_len);
-				vcollected = kstrdup(collected, GFP_KERNEL);
-				state = CopyFile;
-			}
+			wfile = filp_open(collected, openflags, mode);
+			if (IS_ERR(wfile))
+				return 0;
+			wfile_pos = 0;
+
+			vfs_fchown(wfile, uid, gid);
+			vfs_fchmod(wfile, mode);
+			if (body_len)
+				vfs_truncate(&wfile->f_path, body_len);
+			vcollected = kstrdup(collected, GFP_KERNEL);
+			state = CopyFile;
 		}
 	} else if (S_ISDIR(mode)) {
 		ksys_mkdir(collected, mode);
@@ -365,16 +368,16 @@ static int __init do_name(void)
 static int __init do_copy(void)
 {
 	if (byte_count >= body_len) {
-		if (xwrite(wfd, victim, body_len) != body_len)
+		if (xwrite(wfile, victim, body_len, &wfile_pos) != body_len)
 			error("write error");
-		ksys_close(wfd);
+		fput(wfile);
 		do_utime(vcollected, mtime);
 		kfree(vcollected);
 		eat(body_len);
 		state = SkipIt;
 		return 0;
 	} else {
-		if (xwrite(wfd, victim, byte_count) != byte_count)
+		if (xwrite(wfile, victim, byte_count, &wfile_pos) != byte_count)
 			error("write error");
 		body_len -= byte_count;
 		eat(byte_count);
@@ -576,21 +579,23 @@ static inline bool kexec_free_initrd(void)
 static void __init populate_initrd_image(char *err)
 {
 	ssize_t written;
-	int fd;
+	struct file *file;
+	loff_t pos = 0;
 
 	unpack_to_rootfs(__initramfs_start, __initramfs_size);
 
 	printk(KERN_INFO "rootfs image is not initramfs (%s); looks like an initrd\n",
 			err);
-	fd = ksys_open("/initrd.image", O_WRONLY | O_CREAT, 0700);
-	if (fd < 0)
+	file = filp_open("/initrd.image", O_WRONLY | O_CREAT, 0700);
+	if (IS_ERR(file))
 		return;
 
-	written = xwrite(fd, (char *)initrd_start, initrd_end - initrd_start);
+	written = xwrite(file, (char *)initrd_start, initrd_end - initrd_start,
+			&pos);
 	if (written != initrd_end - initrd_start)
 		pr_err("/initrd.image: incomplete write (%zd != %ld)\n",
 		       written, initrd_end - initrd_start);
-	ksys_close(fd);
+	fput(file);
 }
 #endif /* CONFIG_BLK_DEV_RAM */