From 57f0f512b273f60d52568b8c6b77e17f5636edc0 Mon Sep 17 00:00:00 2001
From: André Fabian Silva Delgado <emulatorman@parabola.nu>
Date: Wed, 5 Aug 2015 17:04:01 -0300
Subject: Initial import

---
 drivers/md/dm-linear.c | 182 +++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 182 insertions(+)
 create mode 100644 drivers/md/dm-linear.c

(limited to 'drivers/md/dm-linear.c')

diff --git a/drivers/md/dm-linear.c b/drivers/md/dm-linear.c
new file mode 100644
index 000000000..53e848c10
--- /dev/null
+++ b/drivers/md/dm-linear.c
@@ -0,0 +1,182 @@
+/*
+ * Copyright (C) 2001-2003 Sistina Software (UK) Limited.
+ *
+ * This file is released under the GPL.
+ */
+
+#include "dm.h"
+#include <linux/module.h>
+#include <linux/init.h>
+#include <linux/blkdev.h>
+#include <linux/bio.h>
+#include <linux/slab.h>
+#include <linux/device-mapper.h>
+
+#define DM_MSG_PREFIX "linear"
+
+/*
+ * Linear: maps a linear range of a device.
+ */
+struct linear_c {
+	struct dm_dev *dev;
+	sector_t start;
+};
+
+/*
+ * Construct a linear mapping: <dev_path> <offset>
+ */
+static int linear_ctr(struct dm_target *ti, unsigned int argc, char **argv)
+{
+	struct linear_c *lc;
+	unsigned long long tmp;
+	char dummy;
+
+	if (argc != 2) {
+		ti->error = "Invalid argument count";
+		return -EINVAL;
+	}
+
+	lc = kmalloc(sizeof(*lc), GFP_KERNEL);
+	if (lc == NULL) {
+		ti->error = "dm-linear: Cannot allocate linear context";
+		return -ENOMEM;
+	}
+
+	if (sscanf(argv[1], "%llu%c", &tmp, &dummy) != 1) {
+		ti->error = "dm-linear: Invalid device sector";
+		goto bad;
+	}
+	lc->start = tmp;
+
+	if (dm_get_device(ti, argv[0], dm_table_get_mode(ti->table), &lc->dev)) {
+		ti->error = "dm-linear: Device lookup failed";
+		goto bad;
+	}
+
+	ti->num_flush_bios = 1;
+	ti->num_discard_bios = 1;
+	ti->num_write_same_bios = 1;
+	ti->private = lc;
+	return 0;
+
+      bad:
+	kfree(lc);
+	return -EINVAL;
+}
+
+static void linear_dtr(struct dm_target *ti)
+{
+	struct linear_c *lc = (struct linear_c *) ti->private;
+
+	dm_put_device(ti, lc->dev);
+	kfree(lc);
+}
+
+static sector_t linear_map_sector(struct dm_target *ti, sector_t bi_sector)
+{
+	struct linear_c *lc = ti->private;
+
+	return lc->start + dm_target_offset(ti, bi_sector);
+}
+
+static void linear_map_bio(struct dm_target *ti, struct bio *bio)
+{
+	struct linear_c *lc = ti->private;
+
+	bio->bi_bdev = lc->dev->bdev;
+	if (bio_sectors(bio))
+		bio->bi_iter.bi_sector =
+			linear_map_sector(ti, bio->bi_iter.bi_sector);
+}
+
+static int linear_map(struct dm_target *ti, struct bio *bio)
+{
+	linear_map_bio(ti, bio);
+
+	return DM_MAPIO_REMAPPED;
+}
+
+static void linear_status(struct dm_target *ti, status_type_t type,
+			  unsigned status_flags, char *result, unsigned maxlen)
+{
+	struct linear_c *lc = (struct linear_c *) ti->private;
+
+	switch (type) {
+	case STATUSTYPE_INFO:
+		result[0] = '\0';
+		break;
+
+	case STATUSTYPE_TABLE:
+		snprintf(result, maxlen, "%s %llu", lc->dev->name,
+				(unsigned long long)lc->start);
+		break;
+	}
+}
+
+static int linear_ioctl(struct dm_target *ti, unsigned int cmd,
+			unsigned long arg)
+{
+	struct linear_c *lc = (struct linear_c *) ti->private;
+	struct dm_dev *dev = lc->dev;
+	int r = 0;
+
+	/*
+	 * Only pass ioctls through if the device sizes match exactly.
+	 */
+	if (lc->start ||
+	    ti->len != i_size_read(dev->bdev->bd_inode) >> SECTOR_SHIFT)
+		r = scsi_verify_blk_ioctl(NULL, cmd);
+
+	return r ? : __blkdev_driver_ioctl(dev->bdev, dev->mode, cmd, arg);
+}
+
+static int linear_merge(struct dm_target *ti, struct bvec_merge_data *bvm,
+			struct bio_vec *biovec, int max_size)
+{
+	struct linear_c *lc = ti->private;
+	struct request_queue *q = bdev_get_queue(lc->dev->bdev);
+
+	if (!q->merge_bvec_fn)
+		return max_size;
+
+	bvm->bi_bdev = lc->dev->bdev;
+	bvm->bi_sector = linear_map_sector(ti, bvm->bi_sector);
+
+	return min(max_size, q->merge_bvec_fn(q, bvm, biovec));
+}
+
+static int linear_iterate_devices(struct dm_target *ti,
+				  iterate_devices_callout_fn fn, void *data)
+{
+	struct linear_c *lc = ti->private;
+
+	return fn(ti, lc->dev, lc->start, ti->len, data);
+}
+
+static struct target_type linear_target = {
+	.name   = "linear",
+	.version = {1, 2, 1},
+	.module = THIS_MODULE,
+	.ctr    = linear_ctr,
+	.dtr    = linear_dtr,
+	.map    = linear_map,
+	.status = linear_status,
+	.ioctl  = linear_ioctl,
+	.merge  = linear_merge,
+	.iterate_devices = linear_iterate_devices,
+};
+
+int __init dm_linear_init(void)
+{
+	int r = dm_register_target(&linear_target);
+
+	if (r < 0)
+		DMERR("register failed %d", r);
+
+	return r;
+}
+
+void dm_linear_exit(void)
+{
+	dm_unregister_target(&linear_target);
+}
-- 
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