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[dm-devel] Maximum chunk size in dm-raid4-5.c



Hi,

Is there a particular reason why CHUNK_SIZE_MAX is set to 512 sectors in
the dm raid4/5 module?  I have a fakeraid controller that can create
rather huge (1MB!) RAID5 stripes that this module rejects.  I set it to
2048 and as far as I can tell there haven't been any adverse stability
effects, though I suspect that gigantic stripes do wonders for disk
throughput. :P

Attached is a patch to increase it to 2048 sectors.  Please apply if
it's ok.

--D

Signed-off-by: Darrick J. Wong <djwong us ibm com>
--- a/drivers/md/dm-raid4-5.c	2006-06-01 17:42:27.000000000 -0700
+++ b/drivers/md/dm-raid4-5.c	2006-06-01 17:42:32.000000000 -0700
@@ -70,7 +70,7 @@
 #define	CHUNK_SIZE		64

 /* Maximum setable chunk size in sectors */
-#define	CHUNK_SIZE_MAX		512
+#define	CHUNK_SIZE_MAX		2048

 /* Recover chunk size in sectors */
 #define	RECOVER_CHUNK_SIZE	CHUNK_SIZE_MAX
@@ -3114,7 +3114,7 @@ static int raid_ctr(struct dm_target *ti
 		    chunk_size > CHUNK_SIZE_MAX ||
 		    chunk_size & (chunk_size - 1))
 			TI_ERR("Invalid chunk size; must "
-			       "be 2^^n and less equal 512");
+			       "be 2^^n and less equal 2048");

 		/*
 		 * In case we've got 2 or more variable raid parameters,
--- a/drivers/md/dm-raid4-5.c	2006-06-01 17:42:27.000000000 -0700
+++ b/drivers/md/dm-raid4-5.c	2006-06-01 17:42:32.000000000 -0700
@@ -70,7 +70,7 @@
 #define	CHUNK_SIZE		64
 
 /* Maximum setable chunk size in sectors */
-#define	CHUNK_SIZE_MAX		512
+#define	CHUNK_SIZE_MAX		2048
 
 /* Recover chunk size in sectors */
 #define	RECOVER_CHUNK_SIZE	CHUNK_SIZE_MAX
@@ -3114,7 +3114,7 @@ static int raid_ctr(struct dm_target *ti
 		    chunk_size > CHUNK_SIZE_MAX ||
 		    chunk_size & (chunk_size - 1))
 			TI_ERR("Invalid chunk size; must "
-			       "be 2^^n and less equal 512");
+			       "be 2^^n and less equal 2048");
 
 		/*
 		 * In case we've got 2 or more variable raid parameters,

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