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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>
This commit is contained in:
Qu Wenruo 2016-09-30 13:04:56 +08:00 committed by David Sterba
parent 144a19145e
commit ef67f448c7
2 changed files with 64 additions and 0 deletions
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1
disk-io.h
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@ -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

63
raid56.c
View File

@ -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;
}