[git commit] ash: memalloc: Avoid looping in growstackto

[Denys Vlasenko]

commit: https://git.busybox.net/busybox/commit/?id=da2e46dff6576c29fa1d379c943bb7943aa6e7ce
branch: https://git.busybox.net/busybox/commit/?id=refs/heads/master

Upstream commit:

    Date: Thu, 31 May 2018 01:51:48 +0800
    memalloc: Avoid looping in growstackto

    Currently growstackto will repeatedly call growstackblock until
    the requisite size is obtained.  This is wasteful.  This patch
    changes growstackblock to take a minimum size instead.

    Signed-off-by: Herbert Xu <herbert at gondor.apana.org.au>

Signed-off-by: Denys Vlasenko <vda.linux at googlemail.com>
---
 shell/ash.c | 14 +++++++-------
 1 file changed, 7 insertions(+), 7 deletions(-)

diff --git a/shell/ash.c b/shell/ash.c
index fd2fc9f23..8d1822847 100644
--- a/shell/ash.c
+++ b/shell/ash.c
@@ -1678,15 +1678,16 @@ popstackmark(struct stackmark *mark)
  * part of the block that has been used.
  */
 static void
-growstackblock(void)
+growstackblock(size_t min)
 {
 	size_t newlen;
 
 	newlen = g_stacknleft * 2;
 	if (newlen < g_stacknleft)
 		ash_msg_and_raise_error(bb_msg_memory_exhausted);
-	if (newlen < 128)
-		newlen += 128;
+	min = SHELL_ALIGN(min | 128);
+	if (newlen < min)
+		newlen += min;
 
 	if (g_stacknxt == g_stackp->space && g_stackp != &stackbase) {
 		struct stack_block *sp;
@@ -1736,16 +1737,15 @@ static void *
 growstackstr(void)
 {
 	size_t len = stackblocksize();
-	growstackblock();
+	growstackblock(0);
 	return (char *)stackblock() + len;
 }
 
 static char *
 growstackto(size_t len)
 {
-	while (stackblocksize() < len)
-		growstackblock();
-
+	if (stackblocksize() < len)
+		growstackblock(len);
 	return stackblock();
 }