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 ad9e423f836d25ef88e24287cb0daf040f0939cf..4da30cf17d98af6667d2a0421d714c31f8a112b2 100644 (file)
--- 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);
 }