[PATCH v2 3/4] btrfs-progs: raid56: Introduce new function to calculate raid5 parity or data stripe

[Qu Wenruo]

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

Signed-off-by: Qu Wenruo 
Signed-off-by: David Sterba 
---
Changelog:
v2:
  None
---
 disk-io.h |  1 +
 raid56.c  | 63 +++
 2 files changed, 64 insertions(+)

diff --git a/disk-io.h b/disk-io.h
index 8ab36aa..245626c 100644
--- a/disk-io.h
+++ b/disk-io.h
@@ -192,5 +192,6 @@ 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
--- 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;
+}
-- 
2.10.1



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[PATCH v2 3/4] btrfs-progs: raid56: Introduce new function to calculate raid5 parity or data stripe

[Qu Wenruo]

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

Signed-off-by: Qu Wenruo 
---
v2:
  Patch split
  Change parameter type from void* to char* for xor_range()
  Change parameter order for xxor_range()
  Handle unaligned memory address for xor_range()
---
 disk-io.h |  1 +
 raid56.c  | 63 +++
 2 files changed, 64 insertions(+)

diff --git a/disk-io.h b/disk-io.h
index 440baa9..9fc7e92 100644
--- a/disk-io.h
+++ b/disk-io.h
@@ -192,5 +192,6 @@ 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
--- 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;
+}
-- 
2.10.0



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