Something went wrong. Try again.
(I'm so sorry!) Linux kernel mirror (for testing) git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
kernel os linux
Something went wrong. Try again.
12345678910111213141516171819202122232425262728293031323334353637383940414243444546474849505152535455565758596061626364656667686970717273747576777879808182// 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_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");