From 71a9c4885e1dec0f8ec5e4b05ecd6fddd27fc6c1 Mon Sep 17 00:00:00 2001 From: David Sterba Date: Fri, 31 May 2019 17:22:59 +0200 Subject: 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 --- fs/btrfs/ctree.h | 11 ++++++++++- 1 file changed, 10 insertions(+), 1 deletion(-) 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 -- cgit v1.2.3