[PATCH] md: Core of raid5 resize process

This patch provides the core of the resize/expand process.

sync_request notices if a 'reshape' is happening and acts accordingly.

It allocated new stripe_heads for the next chunk-wide-stripe in the target
geometry, marking them STRIPE_EXPANDING.

Then it finds which stripe heads in the old geometry can provide data needed
by these and marks them STRIPE_EXPAND_SOURCE.  This causes stripe_handle to
read all blocks on those stripes.

Once all blocks on a STRIPE_EXPAND_SOURCE stripe_head are read, any that are
needed are copied into the corresponding STRIPE_EXPANDING stripe_head.  Once a
STRIPE_EXPANDING stripe_head is full, it is marks STRIPE_EXPAND_READY and then
is written out and released.

Signed-off-by: Neil Brown <neilb@suse.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 3 insertions, 1 deletions

diff --git a/include/linux/raid/raid5.h b/include/linux/raid/raid5.h
index 6fa274aea2a0..55c738d50508 100644
--- a/include/linux/raid/raid5.h
+++ b/include/linux/raid/raid5.h
@@ -157,6 +157,7 @@ struct stripe_head {
 #define R5_ReadError    8       /* seen a read error here recently */
 #define R5_ReWrite      9       /* have tried to over-write the readerror */
 
+#define R5_Expanded     10      /* This block now has post-expand data */
 /*
  * Write method
  */
@@ -176,7 +177,8 @@ struct stripe_head {
 #define STRIPE_DEGRADED         7
 #define STRIPE_BIT_DELAY        8
 #define STRIPE_EXPANDING        9
-
+#define STRIPE_EXPAND_SOURCE    10
+#define STRIPE_EXPAND_READY     11
 /*
  * Plugging:
  *