coredump: cn_vprintf() has no reason to call vsnprintf() twice
cn_vprintf() looks really overcomplicated and sub-optimal. We do not need
vsnprintf(NULL) to calculate the size we need, we can simply try to print
into the current buffer and expand/retry only if necessary.
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Cc: Andi Kleen <andi@firstfloor.org>
Cc: Colin Walters <walters@verbum.org>
Cc: Denys Vlasenko <vda.linux@googlemail.com>
Cc: Jiri Slaby <jslaby@suse.cz>
Cc: Lennart Poettering <mzxreary@0pointer.de>
Cc: Lucas De Marchi <lucas.de.marchi@gmail.com>
Acked-by: Neil Horman <nhorman@tuxdriver.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/fs/coredump.c b/fs/coredump.c
index c10a43a..2b1d1f5 100644
--- a/fs/coredump.c
+++ b/fs/coredump.c
@@ -71,26 +71,20 @@
static int cn_vprintf(struct core_name *cn, const char *fmt, va_list arg)
{
- char *cur;
- int need;
- int ret;
+ int free, need;
- need = vsnprintf(NULL, 0, fmt, arg);
- if (likely(need < cn->size - cn->used - 1))
- goto out_printf;
+again:
+ free = cn->size - cn->used;
+ need = vsnprintf(cn->corename + cn->used, free, fmt, arg);
+ if (need < free) {
+ cn->used += need;
+ return 0;
+ }
- ret = expand_corename(cn);
- if (ret)
- goto expand_fail;
+ if (!expand_corename(cn))
+ goto again;
-out_printf:
- cur = cn->corename + cn->used;
- vsnprintf(cur, need + 1, fmt, arg);
- cn->used += need;
- return 0;
-
-expand_fail:
- return ret;
+ return -ENOMEM;
}
static int cn_printf(struct core_name *cn, const char *fmt, ...)