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Date:	Mon, 04 Apr 2011 15:11:52 -0400
From:	Eric Sandeen <sandeen@...hat.com>
To:	ext4 development <linux-ext4@...r.kernel.org>
CC:	Zeev Tarantov <zeev.tarantov@...il.com>
Subject: [PATCH] e2fsprogs: don't set stripe/stride to 1 block in mkfs

Block devices may set minimum or optimal IO hints equal to
blocksize; in this case there is really nothing for ext4
to do with this information (i.e. search for a block-aligned
allocation?) so don't set fs geometry with single-block
values.

Zeev also reported that with a block-sized stripe, the
ext4 allocator spends time spinning in ext4_mb_scan_aligned(),
oddly enough.

Reported-by: Zeev Tarantov <zeev.tarantov@...il.com>
Signed-off-by: Eric Sandeen <sandeen@...hat.com>
---

diff --git a/misc/mke2fs.c b/misc/mke2fs.c
index 9798b88..74b838c 100644
--- a/misc/mke2fs.c
+++ b/misc/mke2fs.c
@@ -1135,8 +1135,11 @@ static int get_device_geometry(const char *file,
 	if ((opt_io == 0) && (psector_size > blocksize))
 		opt_io = psector_size;
 
-	fs_param->s_raid_stride = min_io / blocksize;
-	fs_param->s_raid_stripe_width = opt_io / blocksize;
+	/* setting stripe/stride to blocksize is pointless */
+	if (min_io > blocksize)
+		fs_param->s_raid_stride = min_io / blocksize;
+	if (opt_io > blocksize)
+		fs_param->s_raid_stripe_width = opt_io / blocksize;
 
 	rc = blkid_topology_get_alignment_offset(tp);
 out:

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