Re: 2.6.13-rc6-mm1

[Jon Smirl]

On 8/22/05, Benoit Boissinot <benoit.boissinot@xxxxxxxxxxxx> wrote:
> On Sun, Aug 21, 2005 at 06:34:48PM -0400, Jon Smirl wrote:
> > This should fix it, but I'm not on a machine where I can test it. Can
> > you give it a try and let me know?
> >
> 
> it works ok.
> But there is still at least one problem: if ops->store returns an error,
> then there will be a substraction and the write will loop (i could do it
> with a store wich returned EINVAL and a 22 length string).
> 
> I don't know if you can put a '\0' at buffer->page[count] if
> count == PAGE_SIZE.
> 
> Moreover, i think it is more correct to add only the leading
> whitespace from the count because if the ops->store doesn't read
> everything it will do something weird:
> 
> For example, if we have ' 123    ' and ops->store read only one char,
> then the function will return 7 (1 leading + 4 trailing + 1 read).  For
> the next call the buffer will be filled only by spaces which is
> incorrect (it should be '23    ').

The attached version tries to fix these issues. I am still not
somewhere where I can test, so please check it out.

-- 
Jon Smirl
jonsmirl@xxxxxxxxx
diff --git a/fs/sysfs/file.c b/fs/sysfs/file.c
--- a/fs/sysfs/file.c
+++ b/fs/sysfs/file.c
@@ -6,6 +6,7 @@
 #include <linux/fsnotify.h>
 #include <linux/kobject.h>
 #include <linux/namei.h>
+#include <linux/ctype.h>
 #include <asm/uaccess.h>
 #include <asm/semaphore.h>
 
@@ -207,8 +208,41 @@ flush_write_buffer(struct dentry * dentr
 	struct attribute * attr = to_attr(dentry);
 	struct kobject * kobj = to_kobj(dentry->d_parent);
 	struct sysfs_ops * ops = buffer->ops;
+	size_t ws_count = count, leading = 0;
+	int ret = 0;
+	char *x;
 
-	return ops->store(kobj,attr,buffer->page,count);
+	/* locate trailing white space */
+	while ((ws_count > 0) && isspace(buffer->page[ws_count - 1]))
+		ws_count--;
+	if (ws_count == 0)
+		return count;
+
+	/* locate leading white space */
+	x = buffer->page;
+	while (isspace(*x))
+		x++;
+	leading = x - buffer->page;
+	ws_count -= leading;
+
+	/* interface is still ambigous about this */
+	/* string is both passed by length and terminated */
+	if (ws_count != PAGE_SIZE)
+		x[ws_count] = '\0';
+
+	ret = ops->store(kobj, attr, x, ws_count);
+
+	/* is it an error? */
+	if (ret < 0) 
+		return ret;
+
+	/* the whole string was consumed */
+	if (ret == ws_count)
+		return count;
+
+	/* only part of the string was consumed */
+	/* return count can not include trailing space */
+	return leading + ret;
 }