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authorLinus Torvalds <torvalds@ppc970.osdl.org>2005-04-17 02:20:36 +0400
committerLinus Torvalds <torvalds@ppc970.osdl.org>2005-04-17 02:20:36 +0400
commit1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 (patch)
tree0bba044c4ce775e45a88a51686b5d9f90697ea9d /drivers/md/dm-zero.c
downloadlinux-1da177e4c3f41524e886b7f1b8a0c1fc7321cac2.tar.xz
Linux-2.6.12-rc2
Initial git repository build. I'm not bothering with the full history, even though we have it. We can create a separate "historical" git archive of that later if we want to, and in the meantime it's about 3.2GB when imported into git - space that would just make the early git days unnecessarily complicated, when we don't have a lot of good infrastructure for it. Let it rip!
Diffstat (limited to 'drivers/md/dm-zero.c')
-rw-r--r--drivers/md/dm-zero.c81
1 files changed, 81 insertions, 0 deletions
diff --git a/drivers/md/dm-zero.c b/drivers/md/dm-zero.c
new file mode 100644
index 000000000000..7febc2cac73d
--- /dev/null
+++ b/drivers/md/dm-zero.c
@@ -0,0 +1,81 @@
+/*
+ * Copyright (C) 2003 Christophe Saout <christophe@saout.de>
+ *
+ * This file is released under the GPL.
+ */
+
+#include "dm.h"
+
+#include <linux/module.h>
+#include <linux/init.h>
+#include <linux/bio.h>
+
+/*
+ * Construct a dummy mapping that only returns zeros
+ */
+static int zero_ctr(struct dm_target *ti, unsigned int argc, char **argv)
+{
+ if (argc != 0) {
+ ti->error = "dm-zero: No arguments required";
+ return -EINVAL;
+ }
+
+ return 0;
+}
+
+/*
+ * Return zeros only on reads
+ */
+static int zero_map(struct dm_target *ti, struct bio *bio,
+ union map_info *map_context)
+{
+ switch(bio_rw(bio)) {
+ case READ:
+ zero_fill_bio(bio);
+ break;
+ case READA:
+ /* readahead of null bytes only wastes buffer cache */
+ return -EIO;
+ case WRITE:
+ /* writes get silently dropped */
+ break;
+ }
+
+ bio_endio(bio, bio->bi_size, 0);
+
+ /* accepted bio, don't make new request */
+ return 0;
+}
+
+static struct target_type zero_target = {
+ .name = "zero",
+ .version = {1, 0, 0},
+ .module = THIS_MODULE,
+ .ctr = zero_ctr,
+ .map = zero_map,
+};
+
+int __init dm_zero_init(void)
+{
+ int r = dm_register_target(&zero_target);
+
+ if (r < 0)
+ DMERR("zero: register failed %d", r);
+
+ return r;
+}
+
+void __exit dm_zero_exit(void)
+{
+ int r = dm_unregister_target(&zero_target);
+
+ if (r < 0)
+ DMERR("zero: unregister failed %d", r);
+}
+
+module_init(dm_zero_init)
+module_exit(dm_zero_exit)
+
+MODULE_AUTHOR("Christophe Saout <christophe@saout.de>");
+MODULE_DESCRIPTION(DM_NAME " dummy target returning zeros");
+MODULE_LICENSE("GPL");