Btrfs, scrub: repair the common data on RAID5/6 if it is corrupted

This patch implement the RAID5/6 common data repair function, the
implementation is similar to the scrub on the other RAID such as
RAID1, the differentia is that we don't read the data from the
mirror, we use the data repair function of RAID5/6.

Signed-off-by: Miao Xie <miaox@cn.fujitsu.com>

1 files changed, 176 insertions, 18 deletions

diff --git a/fs/btrfs/scrub.c b/fs/btrfs/scrub.c
index efa0831..ca4b9eb 100644
--- a/fs/btrfs/scrub.c
+++ b/fs/btrfs/scrub.c
@@ -63,6 +63,13 @@ struct scrub_ctx;
  */
 #define SCRUB_MAX_PAGES_PER_BLOCK	16	/* 64k per node/leaf/sector */
 
+struct scrub_recover {
+	atomic_t		refs;
+	struct btrfs_bio	*bbio;
+	u64			*raid_map;
+	u64			map_length;
+};
+
 struct scrub_page {
 	struct scrub_block	*sblock;
 	struct page		*page;
@@ -79,6 +86,8 @@ struct scrub_page {
 		unsigned int	io_error:1;
 	};
 	u8			csum[BTRFS_CSUM_SIZE];
+
+	struct scrub_recover	*recover;
 };
 
 struct scrub_bio {
@@ -196,7 +205,7 @@ static int scrub_setup_recheck_block(struct scrub_ctx *sctx,
 static void scrub_recheck_block(struct btrfs_fs_info *fs_info,
 				struct scrub_block *sblock, int is_metadata,
 				int have_csum, u8 *csum, u64 generation,
-				u16 csum_size);
+				u16 csum_size, int retry_failed_mirror);
 static void scrub_recheck_block_checksum(struct btrfs_fs_info *fs_info,
 					 struct scrub_block *sblock,
 					 int is_metadata, int have_csum,
@@ -790,6 +799,20 @@ out:
 	scrub_pending_trans_workers_dec(sctx);
 }
 
+static inline void scrub_get_recover(struct scrub_recover *recover)
+{
+	atomic_inc(&recover->refs);
+}
+
+static inline void scrub_put_recover(struct scrub_recover *recover)
+{
+	if (atomic_dec_and_test(&recover->refs)) {
+		kfree(recover->bbio);
+		kfree(recover->raid_map);
+		kfree(recover);
+	}
+}
+
 /*
  * scrub_handle_errored_block gets called when either verification of the
  * pages failed or the bio failed to read, e.g. with EIO. In the latter
@@ -906,7 +929,7 @@ static int scrub_handle_errored_block(struct scrub_block *sblock_to_check)
 
 	/* build and submit the bios for the failed mirror, check checksums */
 	scrub_recheck_block(fs_info, sblock_bad, is_metadata, have_csum,
-			    csum, generation, sctx->csum_size);
+			    csum, generation, sctx->csum_size, 1);
 
 	if (!sblock_bad->header_error && !sblock_bad->checksum_error &&
 	    sblock_bad->no_io_error_seen) {
@@ -1019,7 +1042,7 @@ nodatasum_case:
 		/* build and submit the bios, check checksums */
 		scrub_recheck_block(fs_info, sblock_other, is_metadata,
 				    have_csum, csum, generation,
-				    sctx->csum_size);
+				    sctx->csum_size, 0);
 
 		if (!sblock_other->header_error &&
 		    !sblock_other->checksum_error &&
@@ -1169,7 +1192,7 @@ nodatasum_case:
 			 */
 			scrub_recheck_block(fs_info, sblock_bad,
 					    is_metadata, have_csum, csum,
-					    generation, sctx->csum_size);
+					    generation, sctx->csum_size, 1);
 			if (!sblock_bad->header_error &&
 			    !sblock_bad->checksum_error &&
 			    sblock_bad->no_io_error_seen)
@@ -1201,11 +1224,18 @@ out:
 		     mirror_index++) {
 			struct scrub_block *sblock = sblocks_for_recheck +
 						     mirror_index;
+			struct scrub_recover *recover;
 			int page_index;
 
 			for (page_index = 0; page_index < sblock->page_count;
 			     page_index++) {
 				sblock->pagev[page_index]->sblock = NULL;
+				recover = sblock->pagev[page_index]->recover;
+				if (recover) {
+					scrub_put_recover(recover);
+					sblock->pagev[page_index]->recover =
+									NULL;
+				}
 				scrub_page_put(sblock->pagev[page_index]);
 			}
 		}
@@ -1215,14 +1245,63 @@ out:
 	return 0;
 }
 
+static inline int scrub_nr_raid_mirrors(struct btrfs_bio *bbio, u64 *raid_map)
+{
+	if (raid_map) {
+		if (raid_map[bbio->num_stripes - 1] == RAID6_Q_STRIPE)
+			return 3;
+		else
+			return 2;
+	} else {
+		return (int)bbio->num_stripes;
+	}
+}
+
+static inline void scrub_stripe_index_and_offset(u64 logical, u64 *raid_map,
+						 u64 mapped_length,
+						 int nstripes, int mirror,
+						 int *stripe_index,
+						 u64 *stripe_offset)
+{
+	int i;
+
+	if (raid_map) {
+		/* RAID5/6 */
+		for (i = 0; i < nstripes; i++) {
+			if (raid_map[i] == RAID6_Q_STRIPE ||
+			    raid_map[i] == RAID5_P_STRIPE)
+				continue;
+
+			if (logical >= raid_map[i] &&
+			    logical < raid_map[i] + mapped_length)
+				break;
+		}
+
+		*stripe_index = i;
+		*stripe_offset = logical - raid_map[i];
+	} else {
+		/* The other RAID type */
+		*stripe_index = mirror;
+		*stripe_offset = 0;
+	}
+}
+
 static int scrub_setup_recheck_block(struct scrub_ctx *sctx,
 				     struct btrfs_fs_info *fs_info,
 				     struct scrub_block *original_sblock,
 				     u64 length, u64 logical,
 				     struct scrub_block *sblocks_for_recheck)
 {
+	struct scrub_recover *recover;
+	struct btrfs_bio *bbio;
+	u64 *raid_map;
+	u64 sublen;
+	u64 mapped_length;
+	u64 stripe_offset;
+	int stripe_index;
 	int page_index;
 	int mirror_index;
+	int nmirrors;
 	int ret;
 
 	/*
@@ -1233,23 +1312,39 @@ static int scrub_setup_recheck_block(struct scrub_ctx *sctx,
 
 	page_index = 0;
 	while (length > 0) {
-		u64 sublen = min_t(u64, length, PAGE_SIZE);
-		u64 mapped_length = sublen;
-		struct btrfs_bio *bbio = NULL;
+		sublen = min_t(u64, length, PAGE_SIZE);
+		mapped_length = sublen;
+		bbio = NULL;
+		raid_map = NULL;
 
 		/*
 		 * with a length of PAGE_SIZE, each returned stripe
 		 * represents one mirror
 		 */
-		ret = btrfs_map_block(fs_info, REQ_GET_READ_MIRRORS, logical,
-				      &mapped_length, &bbio, 0);
+		ret = btrfs_map_sblock(fs_info, REQ_GET_READ_MIRRORS, logical,
+				       &mapped_length, &bbio, 0, &raid_map);
 		if (ret || !bbio || mapped_length < sublen) {
 			kfree(bbio);
+			kfree(raid_map);
 			return -EIO;
 		}
 
+		recover = kzalloc(sizeof(struct scrub_recover), GFP_NOFS);
+		if (!recover) {
+			kfree(bbio);
+			kfree(raid_map);
+			return -ENOMEM;
+		}
+
+		atomic_set(&recover->refs, 1);
+		recover->bbio = bbio;
+		recover->raid_map = raid_map;
+		recover->map_length = mapped_length;
+
 		BUG_ON(page_index >= SCRUB_PAGES_PER_RD_BIO);
-		for (mirror_index = 0; mirror_index < (int)bbio->num_stripes;
+
+		nmirrors = scrub_nr_raid_mirrors(bbio, raid_map);
+		for (mirror_index = 0; mirror_index < nmirrors;
 		     mirror_index++) {
 			struct scrub_block *sblock;
 			struct scrub_page *page;
@@ -1265,26 +1360,38 @@ leave_nomem:
 				spin_lock(&sctx->stat_lock);
 				sctx->stat.malloc_errors++;
 				spin_unlock(&sctx->stat_lock);
-				kfree(bbio);
+				scrub_put_recover(recover);
 				return -ENOMEM;
 			}
 			scrub_page_get(page);
 			sblock->pagev[page_index] = page;
 			page->logical = logical;
-			page->physical = bbio->stripes[mirror_index].physical;
+
+			scrub_stripe_index_and_offset(logical, raid_map,
+						      mapped_length,
+						      bbio->num_stripes,
+						      mirror_index,
+						      &stripe_index,
+						      &stripe_offset);
+			page->physical = bbio->stripes[stripe_index].physical +
+					 stripe_offset;
+			page->dev = bbio->stripes[stripe_index].dev;
+
 			BUG_ON(page_index >= original_sblock->page_count);
 			page->physical_for_dev_replace =
 				original_sblock->pagev[page_index]->
 				physical_for_dev_replace;
 			/* for missing devices, dev->bdev is NULL */
-			page->dev = bbio->stripes[mirror_index].dev;
 			page->mirror_num = mirror_index + 1;
 			sblock->page_count++;
 			page->page = alloc_page(GFP_NOFS);
 			if (!page->page)
 				goto leave_nomem;
+
+			scrub_get_recover(recover);
+			page->recover = recover;
 		}
-		kfree(bbio);
+		scrub_put_recover(recover);
 		length -= sublen;
 		logical += sublen;
 		page_index++;
@@ -1293,6 +1400,51 @@ leave_nomem:
 	return 0;
 }
 
+struct scrub_bio_ret {
+	struct completion event;
+	int error;
+};
+
+static void scrub_bio_wait_endio(struct bio *bio, int error)
+{
+	struct scrub_bio_ret *ret = bio->bi_private;
+
+	ret->error = error;
+	complete(&ret->event);
+}
+
+static inline int scrub_is_page_on_raid56(struct scrub_page *page)
+{
+	return page->recover && page->recover->raid_map;
+}
+
+static int scrub_submit_raid56_bio_wait(struct btrfs_fs_info *fs_info,
+					struct bio *bio,
+					struct scrub_page *page)
+{
+	struct scrub_bio_ret done;
+	int ret;
+
+	init_completion(&done.event);
+	done.error = 0;
+	bio->bi_iter.bi_sector = page->logical >> 9;
+	bio->bi_private = &done;
+	bio->bi_end_io = scrub_bio_wait_endio;
+
+	ret = raid56_parity_recover(fs_info->fs_root, bio, page->recover->bbio,
+				    page->recover->raid_map,
+				    page->recover->map_length,
+				    page->mirror_num, 1);
+	if (ret)
+		return ret;
+
+	wait_for_completion(&done.event);
+	if (done.error)
+		return -EIO;
+
+	return 0;
+}
+
 /*
  * this function will check the on disk data for checksum errors, header
  * errors and read I/O errors. If any I/O errors happen, the exact pages
@@ -1303,7 +1455,7 @@ leave_nomem:
 static void scrub_recheck_block(struct btrfs_fs_info *fs_info,
 				struct scrub_block *sblock, int is_metadata,
 				int have_csum, u8 *csum, u64 generation,
-				u16 csum_size)
+				u16 csum_size, int retry_failed_mirror)
 {
 	int page_num;
 
@@ -1329,11 +1481,17 @@ static void scrub_recheck_block(struct btrfs_fs_info *fs_info,
 			continue;
 		}
 		bio->bi_bdev = page->dev->bdev;
-		bio->bi_iter.bi_sector = page->physical >> 9;
 
 		bio_add_page(bio, page->page, PAGE_SIZE, 0);
-		if (btrfsic_submit_bio_wait(READ, bio))
-			sblock->no_io_error_seen = 0;
+		if (!retry_failed_mirror && scrub_is_page_on_raid56(page)) {
+			if (scrub_submit_raid56_bio_wait(fs_info, bio, page))
+				sblock->no_io_error_seen = 0;
+		} else {
+			bio->bi_iter.bi_sector = page->physical >> 9;
+
+			if (btrfsic_submit_bio_wait(READ, bio))
+				sblock->no_io_error_seen = 0;
+		}
 
 		bio_put(bio);
 	}