# Upstream patch to fix broken glusterfs if you use ext4 as storage backend.
# This was introduced with the Linux 3.2.46-1+deb7u1 version.
# This patch has been backported by Salvatore Bonaccorso, thanks!
# Closes: #722694

diff -Naur glusterfs-3.2.7.orig/xlators/cluster/dht/src/dht-helper.c glusterfs-3.2.7/xlators/cluster/dht/src/dht-helper.c
--- glusterfs-3.2.7.orig/xlators/cluster/dht/src/dht-helper.c	2012-06-10 19:44:16.000000000 +0200
+++ glusterfs-3.2.7/xlators/cluster/dht/src/dht-helper.c	2013-09-27 21:05:25.895511703 +0200
@@ -49,6 +49,43 @@
 }
 
 
+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)
 {
@@ -56,6 +93,9 @@
         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;
@@ -69,7 +109,23 @@
         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)
@@ -147,16 +203,38 @@
         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)
@@ -165,7 +243,6 @@
         if (x_p)
                 *x_p = x;
 
-out:
         return 0;
 }