From: David Sterba <dsterba@suse.com>
Date: Fri, 31 May 2019 15:22:59 +0000 (+0200)
Subject: btrfs: document BTRFS_MAX_MIRRORS
X-Git-Url: http://git.cdn.openwrt.org/?a=commitdiff_plain;h=71a9c4885e1dec0f8ec5e4b05ecd6fddd27fc6c1;p=openwrt%2Fstaging%2Fblogic.git

btrfs: document BTRFS_MAX_MIRRORS

The real meaning of that constant is not clear from the context due to
the target device inclusion.

Signed-off-by: David Sterba <dsterba@suse.com>
---

diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
index fb7435533478..31198499f175 100644
--- a/fs/btrfs/ctree.h
+++ b/fs/btrfs/ctree.h
@@ -46,7 +46,16 @@ struct btrfs_ref;
 
 #define BTRFS_MAGIC 0x4D5F53665248425FULL /* ascii _BHRfS_M, no null */
 
-#define BTRFS_MAX_MIRRORS 3
+/*
+ * 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 RAID1 with 2 copies.
+ */
+#define BTRFS_MAX_MIRRORS (2 + 1)
 
 #define BTRFS_MAX_LEVEL 8