Introduce function, recover_from_parities(), to recover data stripes.

It just wraps raid56_recov() with extra check functions to
scrub_full_stripe structure.

Signed-off-by: Qu Wenruo <quwen...@cn.fujitsu.com>
---
 scrub.c | 51 +++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 51 insertions(+)

diff --git a/scrub.c b/scrub.c
index ef391ad1..3163cacb 100644
--- a/scrub.c
+++ b/scrub.c
@@ -825,3 +825,54 @@ out:
        free(ptrs);
        return ret;
 }
+
+/*
+ * Try to recover data stripe from P or Q stripe
+ *
+ * Return >0 if it can't be require any more.
+ * Return 0 for successful repair or no need to repair at all
+ * Return <0 for fatal error
+ */
+static int recover_from_parities(struct btrfs_fs_info *fs_info,
+                                 struct btrfs_scrub_progress *scrub_ctx,
+                                 struct scrub_full_stripe *fstripe)
+{
+       void **ptrs;
+       int nr_stripes = fstripe->nr_stripes;
+       int stripe_len = BTRFS_STRIPE_LEN;
+       int max_tolerance;
+       int i;
+       int ret;
+
+       /* No need to recover */
+       if (!fstripe->nr_corrupted_stripes)
+               return 0;
+
+       /* Already recovered once, no more chance */
+       if (fstripe->recovered)
+               return 1;
+
+       if (fstripe->bg_type & BTRFS_BLOCK_GROUP_RAID5)
+               max_tolerance = 1;
+       else
+               max_tolerance = 2;
+
+       /* Out of repair */
+       if (fstripe->nr_corrupted_stripes > max_tolerance)
+               return 1;
+
+       ptrs = malloc(sizeof(void *) * fstripe->nr_stripes);
+       if (!ptrs)
+               return -ENOMEM;
+
+       /* Construct ptrs */
+       for (i = 0; i < nr_stripes; i++)
+               ptrs[i] = fstripe->stripes[i].data;
+
+       ret = raid56_recov(nr_stripes, stripe_len, fstripe->bg_type,
+                       fstripe->corrupted_index[0],
+                       fstripe->corrupted_index[1], ptrs);
+       fstripe->recovered = 1;
+       free(ptrs);
+       return ret;
+}
-- 
2.13.0



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