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coredump: cn_vprintf() has no reason to call vsnprintf() twice

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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>
This commit is contained in:
Oleg Nesterov 2013-07-03 15:08:19 -07:00 committed by Linus Torvalds
parent bc03c691aa
commit 5fe9d8ca21
1 changed files with 11 additions and 17 deletions
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28
fs/coredump.c
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@ -71,26 +71,20 @@ static int expand_corename(struct core_name *cn)
static int cn_vprintf(struct core_name *cn, const char *fmt, va_list arg) static int cn_vprintf(struct core_name *cn, const char *fmt, va_list arg)
{ {
char *cur; int free, need;
int need;
int ret;
need = vsnprintf(NULL, 0, fmt, arg); again:
if (likely(need < cn->size - cn->used - 1)) free = cn->size - cn->used;
goto out_printf; need = vsnprintf(cn->corename + cn->used, free, fmt, arg);
if (need < free) {
cn->used += need;
return 0;
}
ret = expand_corename(cn); if (!expand_corename(cn))
if (ret) goto again;
goto expand_fail;
out_printf: return -ENOMEM;
cur = cn->corename + cn->used;
vsnprintf(cur, need + 1, fmt, arg);
cn->used += need;
return 0;
expand_fail:
return ret;
} }
static int cn_printf(struct core_name *cn, const char *fmt, ...) static int cn_printf(struct core_name *cn, const char *fmt, ...)