projects / linux-block.git / blame
| Commit | Line | Data |
|---|---|---|
| 3bd94003 | 1 | // SPDX-License-Identifier: GPL-2.0-only |
| 1da177e4 | 2 | /* |
| bf14299f | 3 | * Copyright (C) 2003 Jana Saout <jana@saout.de> |
| 1da177e4 LT |
4 | * |
| 5 | * This file is released under the GPL. | |
| 6 | */ | |
| 7 | ||
| 586e80e6 | 8 | #include <linux/device-mapper.h> |
| 1da177e4 LT |
9 | |
| 10 | #include <linux/module.h> | |
| 11 | #include <linux/init.h> | |
| 12 | #include <linux/bio.h> | |
| 13 | ||
| 72d94861 AK |
14 | #define DM_MSG_PREFIX "zero" |
| 15 | ||
| 1da177e4 LT |
16 | /* |
| 17 | * Construct a dummy mapping that only returns zeros | |
| 18 | */ | |
| 19 | static int zero_ctr(struct dm_target *ti, unsigned int argc, char **argv) | |
| 20 | { | |
| 21 | if (argc != 0) { | |
| 72d94861 | 22 | ti->error = "No arguments required"; |
| 1da177e4 LT |
23 | return -EINVAL; |
| 24 | } | |
| 25 | ||
| f8facb61 MS |
26 | /* |
| 27 | * Silently drop discards, avoiding -EOPNOTSUPP. | |
| 28 | */ | |
| 55a62eef | 29 | ti->num_discard_bios = 1; |
| 00065f92 | 30 | ti->discards_supported = true; |
| f8facb61 | 31 | |
| 1da177e4 LT |
32 | return 0; |
| 33 | } | |
| 34 | ||
| 35 | /* | |
| 36 | * Return zeros only on reads | |
| 37 | */ | |
| 7de3ee57 | 38 | static int zero_map(struct dm_target *ti, struct bio *bio) |
| 1da177e4 | 39 | { |
| 70246286 CH |
40 | switch (bio_op(bio)) { |
| 41 | case REQ_OP_READ: | |
| 1eff9d32 | 42 | if (bio->bi_opf & REQ_RAHEAD) { |
| 70246286 | 43 | /* readahead of null bytes only wastes buffer cache */ |
| 846785e6 | 44 | return DM_MAPIO_KILL; |
| 70246286 | 45 | } |
| 1da177e4 LT |
46 | zero_fill_bio(bio); |
| 47 | break; | |
| 70246286 | 48 | case REQ_OP_WRITE: |
| 00065f92 | 49 | case REQ_OP_DISCARD: |
| 1da177e4 LT |
50 | /* writes get silently dropped */ |
| 51 | break; | |
| 70246286 | 52 | default: |
| 846785e6 | 53 | return DM_MAPIO_KILL; |
| 1da177e4 LT |
54 | } |
| 55 | ||
| 4246a0b6 | 56 | bio_endio(bio); |
| 1da177e4 LT |
57 | |
| 58 | /* accepted bio, don't make new request */ | |
| d2a7ad29 | 59 | return DM_MAPIO_SUBMITTED; |
| 1da177e4 LT |
60 | } |
| 61 | ||
| 00065f92 MP |
62 | static void zero_io_hints(struct dm_target *ti, struct queue_limits *limits) |
| 63 | { | |
| 64 | limits->max_discard_sectors = UINT_MAX; | |
| 65 | limits->max_hw_discard_sectors = UINT_MAX; | |
| 66 | limits->discard_granularity = 512; | |
| 67 | } | |
| 68 | ||
| 1da177e4 LT |
69 | static struct target_type zero_target = { |
| 70 | .name = "zero", | |
| 00065f92 | 71 | .version = {1, 2, 0}, |
| 410fe220 | 72 | .features = DM_TARGET_NOWAIT, |
| 1da177e4 LT |
73 | .module = THIS_MODULE, |
| 74 | .ctr = zero_ctr, | |
| 75 | .map = zero_map, | |
| 00065f92 | 76 | .io_hints = zero_io_hints, |
| 1da177e4 | 77 | }; |
| 3664ff82 | 78 | module_dm(zero); |
| 1da177e4 | 79 | |
| bf14299f | 80 | MODULE_AUTHOR("Jana Saout <jana@saout.de>"); |
| 1da177e4 LT |
81 | MODULE_DESCRIPTION(DM_NAME " dummy target returning zeros"); |
| 82 | MODULE_LICENSE("GPL"); |