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-rw-r--r--xlators/cluster/dht/src/dht-helper.c87
1 files changed, 82 insertions, 5 deletions
diff --git a/xlators/cluster/dht/src/dht-helper.c b/xlators/cluster/dht/src/dht-helper.c
index 4f50e214..e91352c4 100644
--- a/xlators/cluster/dht/src/dht-helper.c
+++ b/xlators/cluster/dht/src/dht-helper.c
@@ -40,6 +40,43 @@ dht_frame_return (call_frame_t *frame)
}
+static uint64_t
+dht_bits_for (uint64_t num)
+{
+ uint64_t bits = 0, ctrl = 1;
+
+ while (ctrl < num) {
+ ctrl *= 2;
+ bits ++;
+ }
+
+ return bits;
+}
+
+/*
+ * A slightly "updated" version of the algorithm described in the commit log
+ * is used here.
+ *
+ * The only enhancement is that:
+ *
+ * - The number of bits used by the backend filesystem for HUGE d_off which
+ * is described as 63, and
+ * - The number of bits used by the d_off presented by the transformation
+ * upwards which is described as 64, are both made "configurable."
+ */
+
+
+#define BACKEND_D_OFF_BITS 63
+#define PRESENT_D_OFF_BITS 63
+
+#define ONE 1ULL
+#define MASK (~0ULL)
+#define PRESENT_MASK (MASK >> (64 - PRESENT_D_OFF_BITS))
+#define BACKEND_MASK (MASK >> (64 - BACKEND_D_OFF_BITS))
+
+#define TOP_BIT (ONE << (PRESENT_D_OFF_BITS - 1))
+#define SHIFT_BITS (max (0, (BACKEND_D_OFF_BITS - PRESENT_D_OFF_BITS + 1)))
+
int
dht_itransform (xlator_t *this, xlator_t *subvol, uint64_t x, uint64_t *y_p)
{
@@ -47,6 +84,9 @@ dht_itransform (xlator_t *this, xlator_t *subvol, uint64_t x, uint64_t *y_p)
int cnt = 0;
int max = 0;
uint64_t y = 0;
+ uint64_t hi_mask = 0;
+ uint64_t off_mask = 0;
+ int max_bits = 0;
if (x == ((uint64_t) -1)) {
y = (uint64_t) -1;
@@ -60,7 +100,23 @@ dht_itransform (xlator_t *this, xlator_t *subvol, uint64_t x, uint64_t *y_p)
max = conf->subvolume_cnt;
cnt = dht_subvol_cnt (this, subvol);
- y = ((x * max) + cnt);
+ if (max == 1) {
+ y = x;
+ goto out;
+ }
+
+ max_bits = dht_bits_for (max);
+
+ hi_mask = ~(PRESENT_MASK >> (max_bits + 1));
+
+ if (x & hi_mask) {
+ /* HUGE d_off */
+ off_mask = MASK << max_bits;
+ y = TOP_BIT | ((x >> SHIFT_BITS) & off_mask) | cnt;
+ } else {
+ /* small d_off */
+ y = ((x * max) + cnt);
+ }
out:
if (y_p)
@@ -135,16 +191,38 @@ dht_deitransform (xlator_t *this, uint64_t y, xlator_t **subvol_p,
int max = 0;
uint64_t x = 0;
xlator_t *subvol = 0;
+ int max_bits = 0;
+ uint64_t off_mask = 0;
+ uint64_t host_mask = 0;
if (!this->private)
- goto out;
+ return -1;
conf = this->private;
max = conf->subvolume_cnt;
- cnt = y % max;
- x = y / max;
+ if (max == 1) {
+ x = y;
+ cnt = 0;
+ goto out;
+ }
+
+ if (y & TOP_BIT) {
+ /* HUGE d_off */
+ max_bits = dht_bits_for (max);
+ off_mask = (MASK << max_bits);
+ host_mask = ~(off_mask);
+
+ x = ((y & ~TOP_BIT) & off_mask) << SHIFT_BITS;
+
+ cnt = y & host_mask;
+ } else {
+ /* small d_off */
+ cnt = y % max;
+ x = y / max;
+ }
+out:
subvol = conf->subvolumes[cnt];
if (subvol_p)
@@ -153,7 +231,6 @@ dht_deitransform (xlator_t *this, uint64_t y, xlator_t **subvol_p,
if (x_p)
*x_p = x;
-out:
return 0;
}