btrfs-progs: raid56: Introduce new function to calculate raid5 parity or data stripe

Introduce new function raid5_gen_result() to calculate parity or data
stripe.

Signed-off-by: Qu Wenruo <quwenruo@cn.fujitsu.com>
Signed-off-by: David Sterba <dsterba@suse.com>

diff --git a/disk-io.h b/disk-io.h
index d4a0e7f..1c8387e 100644 (file)
--- a/disk-io.h
+++ b/disk-io.h
@@ -199,5 +199,6 @@ int write_and_map_eb(struct btrfs_trans_handle *trans, struct btrfs_root *root,
 
 /* raid56.c */
 void raid6_gen_syndrome(int disks, size_t bytes, void **ptrs);
+int raid5_gen_result(int nr_devs, size_t stripe_len, int dest, void **data);
 
 #endif

diff --git a/raid56.c b/raid56.c
index 833df5f..8c79c45 100644 (file)
--- a/raid56.c
+++ b/raid56.c
@@ -26,6 +26,8 @@
 #include "kerncompat.h"
 #include "ctree.h"
 #include "disk-io.h"
+#include "volumes.h"
+#include "utils.h"
 
 /*
  * This is the C data type to use
@@ -107,3 +109,64 @@ void raid6_gen_syndrome(int disks, size_t bytes, void **ptrs)
        }
 }
 
+static void xor_range(char *dst, const char*src, size_t size)
+{
+       /* Move to DWORD aligned */
+       while (size && ((unsigned long)dst & sizeof(unsigned long))) {
+               *dst++ ^= *src++;
+               size--;
+       }
+
+       /* DWORD aligned part */
+       while (size >= sizeof(unsigned long)) {
+               *(unsigned long *)dst ^= *(unsigned long *)src;
+               src += sizeof(unsigned long);
+               dst += sizeof(unsigned long);
+               size -= sizeof(unsigned long);
+       }
+       /* Remaining */
+       while (size) {
+               *dst++ ^= *src++;
+               size--;
+       }
+}
+
+/*
+ * Generate desired data/parity stripe for RAID5
+ *
+ * @nr_devs:   Total number of devices, including parity
+ * @stripe_len:        Stripe length
+ * @data:      Data, with special layout:
+ *             data[0]:         Data stripe 0
+ *             data[nr_devs-2]: Last data stripe
+ *             data[nr_devs-1]: RAID5 parity
+ * @dest:      To generate which data. should follow above data layout
+ */
+int raid5_gen_result(int nr_devs, size_t stripe_len, int dest, void **data)
+{
+       int i;
+       char *buf = data[dest];
+
+       /* Validation check */
+       if (stripe_len <= 0 || stripe_len != BTRFS_STRIPE_LEN) {
+               error("invalid parameter for %s", __func__);
+               return -EINVAL;
+       }
+
+       if (dest >= nr_devs || nr_devs < 2) {
+               error("invalid parameter for %s", __func__);
+               return -EINVAL;
+       }
+       /* Shortcut for 2 devs RAID5, which is just RAID1 */
+       if (nr_devs == 2) {
+               memcpy(data[dest], data[1 - dest], stripe_len);
+               return 0;
+       }
+       memset(buf, 0, stripe_len);
+       for (i = 0; i < nr_devs; i++) {
+               if (i == dest)
+                       continue;
+               xor_range(buf, data[i], stripe_len);
+       }
+       return 0;
+}