bitmap: remove explicit newline handling using scnprintf format string

bitmap_print_to_pagebuf uses scnprintf to copy the cpumask/list to page
buffer.  It handles the newline and trailing null character explicitly.

It's unnecessary and also partially duplicated as scnprintf already adds
trailing null character.  The newline can be passed through format string
to scnprintf.  This patch does that simplification.

However theoretically there's one behavior difference: when the buffer is
too small, the original code would still output '\n' at the end while the
new code(with this patch) would just continue to print the formatted
string.  Since this function is dealing with only page buffers, it's
highly unlikely to hit that corner case.

This patch will help in auditing the users of bitmap_print_to_pagebuf
to verify that the buffer passed is large enough and get rid of it
completely by replacing them with direct scnprintf()

Signed-off-by: Sudeep Holla <sudeep.holla@arm.com>
Suggested-by: Pawel Moll <Pawel.Moll@arm.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: "Peter Zijlstra (Intel)" <peterz@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

1 files changed, 6 insertions, 7 deletions

diff --git a/lib/bitmap.c b/lib/bitmap.c
index 40162f87ea2d7f..77bba6fbc0a159 100644
--- a/lib/bitmap.c
+++ b/lib/bitmap.c
@@ -462,19 +462,18 @@ EXPORT_SYMBOL(bitmap_parse_user);
  * Output format is a comma-separated list of decimal numbers and
  * ranges if list is specified or hex digits grouped into comma-separated
  * sets of 8 digits/set. Returns the number of characters written to buf.
+ * It is assumed that the buffer passed is atleast PAGE_SIZE and easily
+ * accommodate nmaskbits.
  */
 int bitmap_print_to_pagebuf(bool list, char *buf, const unsigned long *maskp,
 			    int nmaskbits)
 {
-	ptrdiff_t len = PTR_ALIGN(buf + PAGE_SIZE - 1, PAGE_SIZE) - buf - 2;
+	ptrdiff_t len = PTR_ALIGN(buf + PAGE_SIZE - 1, PAGE_SIZE) - buf;
 	int n = 0;
 
-	if (len > 1) {
-		n = list ? scnprintf(buf, len, "%*pbl", nmaskbits, maskp) :
-			   scnprintf(buf, len, "%*pb", nmaskbits, maskp);
-		buf[n++] = '\n';
-		buf[n] = '\0';
-	}
+	if (len > 1)
+		n = list ? scnprintf(buf, len, "%*pbl\n", nmaskbits, maskp) :
+			   scnprintf(buf, len, "%*pb\n", nmaskbits, maskp);
 	return n;
 }
 EXPORT_SYMBOL(bitmap_print_to_pagebuf);