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authorDaniel Baumann <daniel.baumann@progress-linux.org>2024-04-11 08:27:49 +0000
committerDaniel Baumann <daniel.baumann@progress-linux.org>2024-04-11 08:27:49 +0000
commitace9429bb58fd418f0c81d4c2835699bddf6bde6 (patch)
treeb2d64bc10158fdd5497876388cd68142ca374ed3 /drivers/md/dm-zero.c
parentInitial commit. (diff)
downloadlinux-ace9429bb58fd418f0c81d4c2835699bddf6bde6.tar.xz
linux-ace9429bb58fd418f0c81d4c2835699bddf6bde6.zip
Adding upstream version 6.6.15.upstream/6.6.15
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
Diffstat (limited to 'drivers/md/dm-zero.c')
-rw-r--r--drivers/md/dm-zero.c82
1 files changed, 82 insertions, 0 deletions
diff --git a/drivers/md/dm-zero.c b/drivers/md/dm-zero.c
new file mode 100644
index 0000000000..3b13e6eb1a
--- /dev/null
+++ b/drivers/md/dm-zero.c
@@ -0,0 +1,82 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (C) 2003 Jana Saout <jana@saout.de>
+ *
+ * This file is released under the GPL.
+ */
+
+#include <linux/device-mapper.h>
+
+#include <linux/module.h>
+#include <linux/init.h>
+#include <linux/bio.h>
+
+#define DM_MSG_PREFIX "zero"
+
+/*
+ * 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 = "No arguments required";
+ return -EINVAL;
+ }
+
+ /*
+ * Silently drop discards, avoiding -EOPNOTSUPP.
+ */
+ ti->num_discard_bios = 1;
+ ti->discards_supported = true;
+
+ return 0;
+}
+
+/*
+ * Return zeros only on reads
+ */
+static int zero_map(struct dm_target *ti, struct bio *bio)
+{
+ switch (bio_op(bio)) {
+ case REQ_OP_READ:
+ if (bio->bi_opf & REQ_RAHEAD) {
+ /* readahead of null bytes only wastes buffer cache */
+ return DM_MAPIO_KILL;
+ }
+ zero_fill_bio(bio);
+ break;
+ case REQ_OP_WRITE:
+ case REQ_OP_DISCARD:
+ /* writes get silently dropped */
+ break;
+ default:
+ return DM_MAPIO_KILL;
+ }
+
+ bio_endio(bio);
+
+ /* accepted bio, don't make new request */
+ return DM_MAPIO_SUBMITTED;
+}
+
+static void zero_io_hints(struct dm_target *ti, struct queue_limits *limits)
+{
+ limits->max_discard_sectors = UINT_MAX;
+ limits->max_hw_discard_sectors = UINT_MAX;
+ limits->discard_granularity = 512;
+}
+
+static struct target_type zero_target = {
+ .name = "zero",
+ .version = {1, 2, 0},
+ .features = DM_TARGET_NOWAIT,
+ .module = THIS_MODULE,
+ .ctr = zero_ctr,
+ .map = zero_map,
+ .io_hints = zero_io_hints,
+};
+module_dm(zero);
+
+MODULE_AUTHOR("Jana Saout <jana@saout.de>");
+MODULE_DESCRIPTION(DM_NAME " dummy target returning zeros");
+MODULE_LICENSE("GPL");