md: allow a maximum extent to be set for resyncing
This allows userspace to control resync/reshape progress and synchronise it
with other activities, such as shared access in a SAN, or backing up critical
sections during a tricky reshape.
Writing a number of sectors (which must be a multiple of the chunk size if
such is meaningful) causes a resync to pause when it gets to that point.
Signed-off-by: Neil Brown <neilb@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/Documentation/md.txt b/Documentation/md.txt
index 5818628..396cdd9 100644
--- a/Documentation/md.txt
+++ b/Documentation/md.txt
@@ -416,6 +416,16 @@
sectors in total that could need to be processed. The two
numbers are separated by a '/' thus effectively showing one
value, a fraction of the process that is complete.
+ A 'select' on this attribute will return when resync completes,
+ when it reaches the current sync_max (below) and possibly at
+ other times.
+
+ sync_max
+ This is a number of sectors at which point a resync/recovery
+ process will pause. When a resync is active, the value can
+ only ever be increased, never decreased. The value of 'max'
+ effectively disables the limit.
+
sync_speed
This shows the current actual speed, in K/sec, of the current