DragonFlyBSD

This patch makes use of the new macro hammer_xlate_to_zone2() I've added in the previous patch in http://bugs.dragonflybsd.org/issues/2771

I see hammer source does not prefer to use bunch of macros over macros, but rather use raw and/or bitwise operation probably to keep simplicity of the code as well as its design. However a piece of code like (a) makes it difficult to understand what it's trying to do. Using this macro makes it look like (b) which to me makes better sense.

(a) base_off = (zone_offset & (~HAMMER_LARGEBLOCK_MASK64 & ~HAMMER_OFF_ZONE_MASK)) | HAMMER_ZONE_RAW_BUFFER;
(b) base_off = hammer_xlate_to_zone2(zone_offset & ~HAMMER_LARGEBLOCK_MASK64);

Since I've already sent a patch with such a macro to translate zones and the fact that zoneX-to-zone2 translation does have a meaning, I'd like to use that in other functions of blockmap code. There is no logical change here as following unittest shows.

----------
\# cat ./unittest.c
\#include <stdio.h>
\#include <assert.h>
\#include <vfs/hammer/hammer_disk.h>

/* new macro */
\#define hammer_xlate_to_zone2(offset) \
((offset & ~HAMMER_OFF_ZONE_MASK) | HAMMER_ZONE_RAW_BUFFER)

/* mimic blockmap translation */
static void assert_blockmap_translation(hammer_off_t next_offset) {
hammer_off_t base_off1, base_off2;

base_off1 = (next_offset &
            (~HAMMER_LARGEBLOCK_MASK64 & ~HAMMER_OFF_ZONE_MASK)) |
            HAMMER_ZONE_RAW_BUFFER;
    base_off2 = hammer_xlate_to_zone2(next_offset &
                     ~HAMMER_LARGEBLOCK_MASK64);

printf("next = 0x%08lX\n", next_offset);
    printf("off1 = 0x%08lX\n", base_off1);
    printf("off2 = 0x%08lX\n", base_off2);
    assert(base_off1  base_off2);
    assert(HAMMER_ZONE_DECODE(base_off1)  HAMMER_ZONE_RAW_BUFFER_INDEX);
    assert(HAMMER_ZONE_DECODE(base_off2) == HAMMER_ZONE_RAW_BUFFER_INDEX);
}

int main(void) {
assert_blockmap_translation(0xA011223344556677);
assert_blockmap_translation(0x8FFFFFFFFFFFFFFF);
printf("success\n");
return 0;
}
\# gcc Wall -g ./unittest.c -o unittest
\# ./unittest
next = 0xA011223344556677
off1 = 0x2011223344000000
off2 = 0x2011223344000000
next = 0x8FFFFFFFFFFFFFFF
off1 = 0x2FFFFFFFFF800000
off2 = 0x2FFFFFFFFF800000
success
---------

This patch goes on top of following two patches I've submitted. Sorry that the patch series # is disconnected from the previous two.
http://bugs.dragonflybsd.org/issues/2770
[PATCH 1/2] sys/vfs/hammer: make variable names up-to-date with code
http://bugs.dragonflybsd.org/issues/2771
[PATCH 2/2] sys/vfs/hammer: make hammer_blockmap_lookup() lightweight