[PATCH] device-mapper: Record & restore bio state.

[Alasdair G Kergon]

Simple functions to record and restore bio state so we can
resubmit a bio that returned an error.

DM multipath (following shortly) uses this.

This patch has it private to device-mapper: is it any use elsewhere?

Signed-Off-By: Alasdair G Kergon <agk@xxxxxxxxxx>
--- diff/drivers/md/dm-bio-record.h	1970-01-01 01:00:00.000000000 +0100
+++ source/drivers/md/dm-bio-record.h	2005-02-08 16:40:42.000000000 +0000
@@ -0,0 +1,45 @@
+/*
+ * Copyright (C) 2004-2005 Red Hat, Inc. All rights reserved.
+ *
+ * This file is released under the GPL.
+ */
+
+#ifndef DM_BIO_RECORD_H
+#define DM_BIO_RECORD_H
+
+#include <linux/bio.h>
+
+/*
+ * There are lots of mutable fields in the bio struct that get
+ * changed by the lower levels of the block layer.  Some targets,
+ * such as multipath, may wish to resubmit a bio on error.  The
+ * functions in this file help the target record and restore the
+ * original bio state.
+ */
+struct dm_bio_details {
+	sector_t bi_sector;
+	struct block_device *bi_bdev;
+	unsigned int bi_size;
+	unsigned short bi_idx;
+	unsigned long bi_flags;
+};
+
+static inline void dm_bio_record(struct dm_bio_details *bd, struct bio *bio)
+{
+	bd->bi_sector = bio->bi_sector;
+	bd->bi_bdev = bio->bi_bdev;
+	bd->bi_size = bio->bi_size;
+	bd->bi_idx = bio->bi_idx;
+	bd->bi_flags = bio->bi_flags;
+}
+
+static inline void dm_bio_restore(struct dm_bio_details *bd, struct bio *bio)
+{
+	bio->bi_sector = bd->bi_sector;
+	bio->bi_bdev = bd->bi_bdev;
+	bio->bi_size = bd->bi_size;
+	bio->bi_idx = bd->bi_idx;
+	bio->bi_flags = bd->bi_flags;
+}
+
+#endif
-
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