btrfs: move BTRFS_MAX_MIRRORS into scrub.c

This is only used locally in scrub.c, move it out of ctree.h into
scrub.c.

Reviewed-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

1 files changed, 11 insertions, 0 deletions

diff --git a/fs/btrfs/scrub.c b/fs/btrfs/scrub.c
index 196c4c6ed1ed..cdda4b2f20f2 100644
--- a/fs/btrfs/scrub.c
+++ b/fs/btrfs/scrub.c
@@ -56,6 +56,17 @@ struct scrub_ctx;
 
 #define SCRUB_MAX_PAGES			(DIV_ROUND_UP(BTRFS_MAX_METADATA_BLOCKSIZE, PAGE_SIZE))
 
+/*
+ * Maximum number of mirrors that can be available for all profiles counting
+ * the target device of dev-replace as one. During an active device replace
+ * procedure, the target device of the copy operation is a mirror for the
+ * filesystem data as well that can be used to read data in order to repair
+ * read errors on other disks.
+ *
+ * Current value is derived from RAID1C4 with 4 copies.
+ */
+#define BTRFS_MAX_MIRRORS (4 + 1)
+
 struct scrub_recover {
 	refcount_t		refs;
 	struct btrfs_io_context	*bioc;