Commit 9cf79d11 authored Jun 25, 2015 by Sudeep Holla Committed by Linus Torvalds Jun 25, 2015

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()

[akpm@linux-foundation.org: tweak comment]
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>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

parent ca96ab85

lib/bitmap.c

+8 −7

Original line number	Diff line number	Diff line
		@@ -462,19 +462,20 @@ 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 @buf is a pointer into a PAGE_SIZE area and that
		* sufficient storage remains at @buf to accommodate the
		* bitmap_print_to_pagebuf() output.
		*/
		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);

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