uml: convert to seq_file/proc_fops

Convert code away from ->read_proc/->write_proc interfaces.  Switch to
proc_create()/proc_create_data() which make addition of proc entries
reliable wrt NULL ->proc_fops, NULL ->data and so on.

Problem with ->read_proc et al is described here commit
786d7e1612f0b0adb6046f19b906609e4fe8b1ba "Fix rmmod/read/write races in
/proc entries"

Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>
Cc: Jeff Dike <jdike@addtoit.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 23 insertions, 20 deletions

diff --git a/arch/um/kernel/exitcode.c b/arch/um/kernel/exitcode.c
index 6540d2c..829df49 100644
--- a/arch/um/kernel/exitcode.c
+++ b/arch/um/kernel/exitcode.c
@@ -6,7 +6,9 @@
 #include <linux/ctype.h>
 #include <linux/init.h>
 #include <linux/kernel.h>
+#include <linux/module.h>
 #include <linux/proc_fs.h>
+#include <linux/seq_file.h>
 #include <linux/types.h>
 #include <asm/uaccess.h>
 
@@ -16,30 +18,26 @@
  */
 int uml_exitcode = 0;
 
-static int read_proc_exitcode(char *page, char **start, off_t off,
-			      int count, int *eof, void *data)
+static int exitcode_proc_show(struct seq_file *m, void *v)
 {
-	int len, val;
+	int val;
 
 	/*
 	 * Save uml_exitcode in a local so that we don't need to guarantee
 	 * that sprintf accesses it atomically.
 	 */
 	val = uml_exitcode;
-	len = sprintf(page, "%d\n", val);
-	len -= off;
-	if (len <= off+count)
-		*eof = 1;
-	*start = page + off;
-	if (len > count)
-		len = count;
-	if (len < 0)
-		len = 0;
-	return len;
+	seq_printf(m, "%d\n", val);
+	return 0;
+}
+
+static int exitcode_proc_open(struct inode *inode, struct file *file)
+{
+	return single_open(file, exitcode_proc_show, NULL);
 }
 
-static int write_proc_exitcode(struct file *file, const char __user *buffer,
-			       unsigned long count, void *data)
+static ssize_t exitcode_proc_write(struct file *file,
+		const char __user *buffer, size_t count, loff_t *pos)
 {
 	char *end, buf[sizeof("nnnnn\0")];
 	int tmp;
@@ -55,20 +53,25 @@ static int write_proc_exitcode(struct file *file, const char __user *buffer,
 	return count;
 }
 
+static const struct file_operations exitcode_proc_fops = {
+	.owner		= THIS_MODULE,
+	.open		= exitcode_proc_open,
+	.read		= seq_read,
+	.llseek		= seq_lseek,
+	.release	= single_release,
+	.write		= exitcode_proc_write,
+};
+
 static int make_proc_exitcode(void)
 {
 	struct proc_dir_entry *ent;
 
-	ent = create_proc_entry("exitcode", 0600, NULL);
+	ent = proc_create("exitcode", 0600, NULL, &exitcode_proc_fops);
 	if (ent == NULL) {
 		printk(KERN_WARNING "make_proc_exitcode : Failed to register "
 		       "/proc/exitcode\n");
 		return 0;
 	}
-
-	ent->read_proc = read_proc_exitcode;
-	ent->write_proc = write_proc_exitcode;
-
 	return 0;
 }