From: Brian Behlendorf <behlendorf1@llnl.gov>
Date: Thu, 26 Aug 2010 17:58:19 +0000 (-0700)
Subject: Fix stack lzjb
X-Git-Url: https://git.camperquake.de/gitweb.cgi?a=commitdiff_plain;h=18a89ba43d3e5e8a31d50838c93ec26d1cb27429;p=zfs.git

Fix stack lzjb

Reduce kernel stack usage by lzjb_compress() by moving uint16 array
off the stack and on to the heap.  The exact performance implications
of this I have not measured but we absolutely need to keep stack
usage to a minimum.  If/when this becomes and issue we optimize.

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
---

diff --git a/module/zfs/lzjb.c b/module/zfs/lzjb.c
index ad9e423..4da30cf 100644
--- a/module/zfs/lzjb.c
+++ b/module/zfs/lzjb.c
@@ -36,7 +36,7 @@
  * source length if compression would overflow the destination buffer.
  */
 
-#include <sys/types.h>
+#include <sys/zfs_context.h>
 
 #define	MATCH_BITS	6
 #define	MATCH_MIN	3
@@ -54,12 +54,15 @@ lzjb_compress(void *s_start, void *d_start, size_t s_len, size_t d_len, int n)
 	int copymask = 1 << (NBBY - 1);
 	int mlen, offset, hash;
 	uint16_t *hp;
-	uint16_t lempel[LEMPEL_SIZE] = { 0 };
+	uint16_t *lempel;
 
+	lempel = kmem_zalloc(LEMPEL_SIZE * sizeof (uint16_t), KM_SLEEP);
 	while (src < (uchar_t *)s_start + s_len) {
 		if ((copymask <<= 1) == (1 << NBBY)) {
-			if (dst >= (uchar_t *)d_start + d_len - 1 - 2 * NBBY)
+			if (dst >= (uchar_t *)d_start + d_len - 1 - 2 * NBBY) {
+				kmem_free(lempel, LEMPEL_SIZE*sizeof(uint16_t));
 				return (s_len);
+			}
 			copymask = 1;
 			copymap = dst;
 			*dst++ = 0;
@@ -89,6 +92,8 @@ lzjb_compress(void *s_start, void *d_start, size_t s_len, size_t d_len, int n)
 			*dst++ = *src++;
 		}
 	}
+
+	kmem_free(lempel, LEMPEL_SIZE * sizeof (uint16_t));
 	return (dst - (uchar_t *)d_start);
 }