From patchwork Mon Apr 20 07:55:08 2009
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Subject: [5/17] bottom-layer barrier support
Date: Mon, 20 Apr 2009 07:55:08 -0000
From: Mikulas Patocka <mpatocka@redhat.com>
X-Patchwork-Id: 18986
dm-target-flush-option.patch
Two variables for targets.
Target driver can change num_flush_requests and signal that it wants
to receive flushes. It receives num_flush_requests flushes, individual
flushes are differentiated by map_info->flush_request (which goes from
0 to num_flush_requests - 1).
Old targets without flush support won't receive any flush requests.
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
---
include/linux/device-mapper.h | 11 +++++++++++
1 file changed, 11 insertions(+)
--
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Index: linux-2.6.30-rc1-devel/include/linux/device-mapper.h
===================================================================
--- linux-2.6.30-rc1-devel.orig/include/linux/device-mapper.h 2009-04-10 06:32:54.000000000 +0200
+++ linux-2.6.30-rc1-devel/include/linux/device-mapper.h 2009-04-10 06:33:26.000000000 +0200
@@ -21,6 +21,7 @@ typedef enum { STATUSTYPE_INFO, STATUSTY
union map_info {
void *ptr;
unsigned long long ll;
+ unsigned flush_request;
};
/*
@@ -168,6 +169,16 @@ struct dm_target {
sector_t split_io;
/*
+ * A number of zero-length barrier requests that will be submitted
+ * to the target for the purpose of flushing cache.
+ *
+ * The request number will be placed in union map_info->flush_request.
+ * It is a responsibility of the target driver to remap these requests
+ * to the real underlying devices.
+ */
+ unsigned num_flush_requests;
+
+ /*
* These are automatically filled in by
* dm_table_get_device.
*/