[RFC v4 2/3] fs: btrfs: Extends btrfs/raid56 to support up to six parities

From: Andrea Mazzoleni
Date: Sat Jan 25 2014 - 03:13:55 EST

This patch makes btrfs/raid56.c to use the new raid interface and
extends its support to an arbitrary number of parities.

More in details, the two faila/failb failure indexes are now replaced
with a fail[] vector that keeps track of up to six failures.
The new raid_gen() and raid_rec() functions are now used to handle
all the RAID6 P/Q logic.

For kernel 3.13.

WARNING! This patch is not tested, and it's NOT meant for inclusion at
this stage. It's only example code to show how the new raid library could
be integrated in existing code.

Signed-off-by: Andrea Mazzoleni <amadvance@xxxxxxxxx>
---
fs/btrfs/Kconfig | 1 +
fs/btrfs/raid56.c | 273 +++++++++++++++++------------------------------------
fs/btrfs/raid56.h | 12 ++-
fs/btrfs/volumes.c | 4 +-
4 files changed, 97 insertions(+), 193 deletions(-)

diff --git a/fs/btrfs/Kconfig b/fs/btrfs/Kconfig
index aa976ec..173fabe 100644
--- a/fs/btrfs/Kconfig
+++ b/fs/btrfs/Kconfig
@@ -5,6 +5,7 @@ config BTRFS_FS
select ZLIB_DEFLATE
select LZO_COMPRESS
select LZO_DECOMPRESS
+ select RAID_CAUCHY
select RAID6_PQ
select XOR_BLOCKS

diff --git a/fs/btrfs/raid56.c b/fs/btrfs/raid56.c
index 24ac218..52a56ff 100644
--- a/fs/btrfs/raid56.c
+++ b/fs/btrfs/raid56.c
@@ -27,10 +27,10 @@
#include <linux/capability.h>
#include <linux/ratelimit.h>
#include <linux/kthread.h>
-#include <linux/raid/pq.h>
+#include <linux/raid/raid.h>
+#include <linux/raid/helper.h>
#include <linux/hash.h>
#include <linux/list_sort.h>
-#include <linux/raid/xor.h>
#include <linux/vmalloc.h>
#include <asm/div64.h>
#include "ctree.h"
@@ -125,11 +125,11 @@ struct btrfs_raid_bio {
*/
int read_rebuild;

- /* first bad stripe */
- int faila;
+ /* bad stripes */
+ int fail[RAID_PARITY_MAX];

- /* second bad stripe (for raid6 use) */
- int failb;
+ /* number of bad stripes in fail[] */
+ int nr_fail;

/*
* number of pages needed to represent the full
@@ -496,26 +496,6 @@ static void cache_rbio(struct btrfs_raid_bio *rbio)
}

/*
- * helper function to run the xor_blocks api. It is only
- * able to do MAX_XOR_BLOCKS at a time, so we need to
- * loop through.
- */
-static void run_xor(void **pages, int src_cnt, ssize_t len)
-{
- int src_off = 0;
- int xor_src_cnt = 0;
- void *dest = pages[src_cnt];
-
- while(src_cnt > 0) {
- xor_src_cnt = min(src_cnt, MAX_XOR_BLOCKS);
- xor_blocks(xor_src_cnt, len, dest, pages + src_off);
-
- src_cnt -= xor_src_cnt;
- src_off += xor_src_cnt;
- }
-}
-
-/*
* returns true if the bio list inside this rbio
* covers an entire stripe (no rmw required).
* Must be called with the bio list lock held, or
@@ -587,25 +567,18 @@ static int rbio_can_merge(struct btrfs_raid_bio *last,
}

/*
- * helper to index into the pstripe
- */
-static struct page *rbio_pstripe_page(struct btrfs_raid_bio *rbio, int index)
-{
- index += (rbio->nr_data * rbio->stripe_len) >> PAGE_CACHE_SHIFT;
- return rbio->stripe_pages[index];
-}
-
-/*
- * helper to index into the qstripe, returns null
- * if there is no qstripe
+ * helper to index into the parity stripe
+ * returns null if there is no stripe
*/
-static struct page *rbio_qstripe_page(struct btrfs_raid_bio *rbio, int index)
+static struct page *rbio_pstripe_page(struct btrfs_raid_bio *rbio,
+ int index, int parity)
{
- if (rbio->nr_data + 1 == rbio->bbio->num_stripes)
+ if (rbio->nr_data + parity >= rbio->bbio->num_stripes)
return NULL;

- index += ((rbio->nr_data + 1) * rbio->stripe_len) >>
- PAGE_CACHE_SHIFT;
+ index += ((rbio->nr_data + parity) * rbio->stripe_len)
+ >> PAGE_CACHE_SHIFT;
+
return rbio->stripe_pages[index];
}

@@ -946,8 +919,7 @@ static struct btrfs_raid_bio *alloc_rbio(struct btrfs_root *root,
rbio->fs_info = root->fs_info;
rbio->stripe_len = stripe_len;
rbio->nr_pages = num_pages;
- rbio->faila = -1;
- rbio->failb = -1;
+ rbio->nr_fail = 0;
atomic_set(&rbio->refs, 1);

/*
@@ -958,10 +930,10 @@ static struct btrfs_raid_bio *alloc_rbio(struct btrfs_root *root,
rbio->stripe_pages = p;
rbio->bio_pages = p + sizeof(struct page *) * num_pages;

- if (raid_map[bbio->num_stripes - 1] == RAID6_Q_STRIPE)
- nr_data = bbio->num_stripes - 2;
- else
- nr_data = bbio->num_stripes - 1;
+ /* get the number of data stripes removing all the parities */
+ nr_data = bbio->num_stripes;
+ while (nr_data > 0 && is_parity_stripe(raid_map[nr_data - 1]))
+ --nr_data;

rbio->nr_data = nr_data;
return rbio;
@@ -1072,8 +1044,7 @@ static int rbio_add_io_page(struct btrfs_raid_bio *rbio,
*/
static void validate_rbio_for_rmw(struct btrfs_raid_bio *rbio)
{
- if (rbio->faila >= 0 || rbio->failb >= 0) {
- BUG_ON(rbio->faila == rbio->bbio->num_stripes - 1);
+ if (rbio->nr_fail > 0) {
__raid56_parity_recover(rbio);
} else {
finish_rmw(rbio);
@@ -1137,10 +1108,10 @@ static noinline void finish_rmw(struct btrfs_raid_bio *rbio)
void *pointers[bbio->num_stripes];
int stripe_len = rbio->stripe_len;
int nr_data = rbio->nr_data;
+ int nr_parity;
+ int parity;
int stripe;
int pagenr;
- int p_stripe = -1;
- int q_stripe = -1;
struct bio_list bio_list;
struct bio *bio;
int pages_per_stripe = stripe_len >> PAGE_CACHE_SHIFT;
@@ -1148,14 +1119,7 @@ static noinline void finish_rmw(struct btrfs_raid_bio *rbio)

bio_list_init(&bio_list);

- if (bbio->num_stripes - rbio->nr_data == 1) {
- p_stripe = bbio->num_stripes - 1;
- } else if (bbio->num_stripes - rbio->nr_data == 2) {
- p_stripe = bbio->num_stripes - 2;
- q_stripe = bbio->num_stripes - 1;
- } else {
- BUG();
- }
+ nr_parity = bbio->num_stripes - rbio->nr_data;

/* at this point we either have a full stripe,
* or we've read the full stripe from the drive.
@@ -1194,29 +1158,15 @@ static noinline void finish_rmw(struct btrfs_raid_bio *rbio)
pointers[stripe] = kmap(p);
}

- /* then add the parity stripe */
- p = rbio_pstripe_page(rbio, pagenr);
- SetPageUptodate(p);
- pointers[stripe++] = kmap(p);
-
- if (q_stripe != -1) {
-
- /*
- * raid6, add the qstripe and call the
- * library function to fill in our p/q
- */
- p = rbio_qstripe_page(rbio, pagenr);
+ /* then add the parity stripes */
+ for (parity = 0; parity < nr_parity; ++parity) {
+ p = rbio_pstripe_page(rbio, pagenr, parity);
SetPageUptodate(p);
pointers[stripe++] = kmap(p);
-
- raid6_call.gen_syndrome(bbio->num_stripes, PAGE_SIZE,
- pointers);
- } else {
- /* raid5 */
- memcpy(pointers[nr_data], pointers[0], PAGE_SIZE);
- run_xor(pointers + 1, nr_data - 1, PAGE_CACHE_SIZE);
}

+ /* compute the parity */
+ raid_gen(rbio->nr_data, nr_parity, PAGE_SIZE, pointers);

for (stripe = 0; stripe < bbio->num_stripes; stripe++)
kunmap(page_in_rbio(rbio, stripe, pagenr, 0));
@@ -1321,24 +1271,25 @@ static int fail_rbio_index(struct btrfs_raid_bio *rbio, int failed)
{
unsigned long flags;
int ret = 0;
+ int i;

spin_lock_irqsave(&rbio->bio_list_lock, flags);

/* we already know this stripe is bad, move on */
- if (rbio->faila == failed || rbio->failb == failed)
- goto out;
+ for (i = 0; i < rbio->nr_fail; ++i)
+ if (rbio->fail[i] == failed)
+ goto out;

- if (rbio->faila == -1) {
- /* first failure on this rbio */
- rbio->faila = failed;
- atomic_inc(&rbio->bbio->error);
- } else if (rbio->failb == -1) {
- /* second failure on this rbio */
- rbio->failb = failed;
- atomic_inc(&rbio->bbio->error);
- } else {
+ if (rbio->nr_fail == RAID_PARITY_MAX) {
ret = -EIO;
+ goto out;
}
+
+ /* new failure on this rbio */
+ raid_insert(rbio->nr_fail, rbio->fail, failed);
+ ++rbio->nr_fail;
+ atomic_inc(&rbio->bbio->error);
+
out:
spin_unlock_irqrestore(&rbio->bio_list_lock, flags);

@@ -1724,8 +1675,10 @@ static void __raid_recover_end_io(struct btrfs_raid_bio *rbio)
{
int pagenr, stripe;
void **pointers;
- int faila = -1, failb = -1;
+ int ifail;
int nr_pages = (rbio->stripe_len + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
+ int nr_parity;
+ int nr_fail;
struct page *page;
int err;
int i;
@@ -1737,8 +1690,8 @@ static void __raid_recover_end_io(struct btrfs_raid_bio *rbio)
goto cleanup_io;
}

- faila = rbio->faila;
- failb = rbio->failb;
+ nr_parity = rbio->bbio->num_stripes - rbio->nr_data;
+ nr_fail = rbio->nr_fail;

if (rbio->read_rebuild) {
spin_lock_irq(&rbio->bio_list_lock);
@@ -1752,98 +1705,30 @@ static void __raid_recover_end_io(struct btrfs_raid_bio *rbio)
/* setup our array of pointers with pages
* from each stripe
*/
+ ifail = 0;
for (stripe = 0; stripe < rbio->bbio->num_stripes; stripe++) {
/*
* if we're rebuilding a read, we have to use
* pages from the bio list
*/
if (rbio->read_rebuild &&
- (stripe == faila || stripe == failb)) {
+ rbio->fail[ifail] == stripe) {
page = page_in_rbio(rbio, stripe, pagenr, 0);
+ ++ifail;
} else {
page = rbio_stripe_page(rbio, stripe, pagenr);
}
pointers[stripe] = kmap(page);
}

- /* all raid6 handling here */
- if (rbio->raid_map[rbio->bbio->num_stripes - 1] ==
- RAID6_Q_STRIPE) {
-
- /*
- * single failure, rebuild from parity raid5
- * style
- */
- if (failb < 0) {
- if (faila == rbio->nr_data) {
- /*
- * Just the P stripe has failed, without
- * a bad data or Q stripe.
- * TODO, we should redo the xor here.
- */
- err = -EIO;
- goto cleanup;
- }
- /*
- * a single failure in raid6 is rebuilt
- * in the pstripe code below
- */
- goto pstripe;
- }
-
- /* make sure our ps and qs are in order */
- if (faila > failb) {
- int tmp = failb;
- failb = faila;
- faila = tmp;
- }
-
- /* if the q stripe is failed, do a pstripe reconstruction
- * from the xors.
- * If both the q stripe and the P stripe are failed, we're
- * here due to a crc mismatch and we can't give them the
- * data they want
- */
- if (rbio->raid_map[failb] == RAID6_Q_STRIPE) {
- if (rbio->raid_map[faila] == RAID5_P_STRIPE) {
- err = -EIO;
- goto cleanup;
- }
- /*
- * otherwise we have one bad data stripe and
- * a good P stripe. raid5!
- */
- goto pstripe;
- }
-
- if (rbio->raid_map[failb] == RAID5_P_STRIPE) {
- raid6_datap_recov(rbio->bbio->num_stripes,
- PAGE_SIZE, faila, pointers);
- } else {
- raid6_2data_recov(rbio->bbio->num_stripes,
- PAGE_SIZE, faila, failb,
- pointers);
- }
- } else {
- void *p;
-
- /* rebuild from P stripe here (raid5 or raid6) */
- BUG_ON(failb != -1);
-pstripe:
- /* Copy parity block into failed block to start with */
- memcpy(pointers[faila],
- pointers[rbio->nr_data],
- PAGE_CACHE_SIZE);
-
- /* rearrange the pointer array */
- p = pointers[faila];
- for (stripe = faila; stripe < rbio->nr_data - 1; stripe++)
- pointers[stripe] = pointers[stripe + 1];
- pointers[rbio->nr_data - 1] = p;
-
- /* xor in the rest */
- run_xor(pointers, rbio->nr_data - 1, PAGE_CACHE_SIZE);
+ /* if we have too many failure */
+ if (nr_fail > nr_parity) {
+ err = -EIO;
+ goto cleanup;
}
+ raid_rec(nr_fail, rbio->fail, rbio->nr_data, nr_parity,
+ PAGE_SIZE, pointers);
+
/* if we're doing this rebuild as part of an rmw, go through
* and set all of our private rbio pages in the
* failed stripes as uptodate. This way finish_rmw will
@@ -1852,24 +1737,23 @@ pstripe:
*/
if (!rbio->read_rebuild) {
for (i = 0; i < nr_pages; i++) {
- if (faila != -1) {
- page = rbio_stripe_page(rbio, faila, i);
- SetPageUptodate(page);
- }
- if (failb != -1) {
- page = rbio_stripe_page(rbio, failb, i);
+ for (ifail = 0; ifail < nr_fail; ++ifail) {
+ int sfail = rbio->fail[ifail];
+ page = rbio_stripe_page(rbio, sfail, i);
SetPageUptodate(page);
}
}
}
+ ifail = 0;
for (stripe = 0; stripe < rbio->bbio->num_stripes; stripe++) {
/*
* if we're rebuilding a read, we have to use
* pages from the bio list
*/
if (rbio->read_rebuild &&
- (stripe == faila || stripe == failb)) {
+ rbio->fail[ifail] == stripe) {
page = page_in_rbio(rbio, stripe, pagenr, 0);
+ ++ifail;
} else {
page = rbio_stripe_page(rbio, stripe, pagenr);
}
@@ -1891,8 +1775,7 @@ cleanup_io:

rbio_orig_end_io(rbio, err, err == 0);
} else if (err == 0) {
- rbio->faila = -1;
- rbio->failb = -1;
+ rbio->nr_fail = 0;
finish_rmw(rbio);
} else {
rbio_orig_end_io(rbio, err, 0);
@@ -1939,6 +1822,7 @@ static int __raid56_parity_recover(struct btrfs_raid_bio *rbio)
int bios_to_read = 0;
struct btrfs_bio *bbio = rbio->bbio;
struct bio_list bio_list;
+ int ifail;
int ret;
int nr_pages = (rbio->stripe_len + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
int pagenr;
@@ -1958,10 +1842,12 @@ static int __raid56_parity_recover(struct btrfs_raid_bio *rbio)
* stripe cache, it is possible that some or all of these
* pages are going to be uptodate.
*/
+ ifail = 0;
for (stripe = 0; stripe < bbio->num_stripes; stripe++) {
- if (rbio->faila == stripe ||
- rbio->failb == stripe)
+ if (rbio->fail[ifail] == stripe) {
+ ++ifail;
continue;
+ }

for (pagenr = 0; pagenr < nr_pages; pagenr++) {
struct page *p;
@@ -2037,6 +1923,7 @@ int raid56_parity_recover(struct btrfs_root *root, struct bio *bio,
{
struct btrfs_raid_bio *rbio;
int ret;
+ int i;

rbio = alloc_rbio(root, bbio, raid_map, stripe_len);
if (IS_ERR(rbio))
@@ -2046,21 +1933,33 @@ int raid56_parity_recover(struct btrfs_root *root, struct bio *bio,
bio_list_add(&rbio->bio_list, bio);
rbio->bio_list_bytes = bio->bi_size;

- rbio->faila = find_logical_bio_stripe(rbio, bio);
- if (rbio->faila == -1) {
+ rbio->fail[0] = find_logical_bio_stripe(rbio, bio);
+ if (rbio->fail[0] == -1) {
BUG();
kfree(raid_map);
kfree(bbio);
kfree(rbio);
return -EIO;
}
+ rbio->nr_fail = 1;

/*
- * reconstruct from the q stripe if they are
- * asking for mirror 3
+ * Reconstruct from other parity stripes if they are
+ * asking for different mirrors.
+ * For each mirror we disable one extra parity to trigger
+ * a different recovery.
+ * With mirror_num == 2 we disable nothing and we reconstruct
+ * with the first parity, with mirror_num == 3 we disable the
+ * first parity and then we reconstruct with the second,
+ * and so on, up to mirror_num == 7 where we disable the first 5
+ * parity levels and we recover with the 6 one.
*/
- if (mirror_num == 3)
- rbio->failb = bbio->num_stripes - 2;
+ if (mirror_num > 2 && mirror_num - 2 < RAID_PARITY_MAX) {
+ for (i = 0; i < mirror_num - 2; ++i) {
+ raid_insert(rbio->nr_fail, rbio->fail, rbio->nr_data + i);
+ ++rbio->nr_fail;
+ }
+ }

ret = lock_stripe_add(rbio);

diff --git a/fs/btrfs/raid56.h b/fs/btrfs/raid56.h
index ea5d73b..8adc48d 100644
--- a/fs/btrfs/raid56.h
+++ b/fs/btrfs/raid56.h
@@ -33,11 +33,15 @@ static inline int nr_data_stripes(struct map_lookup *map)
{
return map->num_stripes - nr_parity_stripes(map);
}
-#define RAID5_P_STRIPE ((u64)-2)
-#define RAID6_Q_STRIPE ((u64)-1)

-#define is_parity_stripe(x) (((x) == RAID5_P_STRIPE) || \
- ((x) == RAID6_Q_STRIPE))
+#define RAID_PAR1_STRIPE ((u64)-6)
+#define RAID_PAR2_STRIPE ((u64)-5)
+#define RAID_PAR3_STRIPE ((u64)-4)
+#define RAID_PAR4_STRIPE ((u64)-3)
+#define RAID_PAR5_STRIPE ((u64)-2)
+#define RAID_PAR6_STRIPE ((u64)-1)
+
+#define is_parity_stripe(x) (((u64)(x) >= RAID_PAR1_STRIPE))

int raid56_parity_recover(struct btrfs_root *root, struct bio *bio,
struct btrfs_bio *bbio, u64 *raid_map,
diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
index 92303f4..bf593f7 100644
--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -4918,10 +4918,10 @@ static int __btrfs_map_block(struct btrfs_fs_info *fs_info, int rw,
raid_map[(i+rot) % num_stripes] =
em->start + (tmp + i) * map->stripe_len;

- raid_map[(i+rot) % map->num_stripes] = RAID5_P_STRIPE;
+ raid_map[(i+rot) % map->num_stripes] = RAID_PAR1_STRIPE;
if (map->type & BTRFS_BLOCK_GROUP_RAID6)
raid_map[(i+rot+1) % num_stripes] =
- RAID6_Q_STRIPE;
+ RAID_PAR2_STRIPE;

*length = map->stripe_len;
stripe_index = 0;
--
1.7.12.1

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