From a9ed3aa9b87ee41e8ab3ff471b1331c154767e45 Mon Sep 17 00:00:00 2001 From: Dave Airlie Date: Sat, 26 Sep 2026 07:57:59 +1000 Subject: Merge tag 'drm-misc-fixes-2026-09-24' of https://gitlab.freedesktop.org/drm/misc/kernel into drm-fixes A number of fixes: - bridge: - samsung-dsim: fix GPIO lifetime - client: Null pointer dereference fix - imagination: error handling fix, page handling fix - nouveau: fix reference leaks, double-frees, out-of-bounds accesses, use-after-frees, don't reject config without SCDC, a number of workarounds - virtio: fix memory leak, reference leaks, null pointer dereference, add pixel blend mode, cache coherency fix Signed-off-by: Dave Airlie From: Maxime Ripard Link: https://patch.msgid.link/arU22zzqUGDEco1y@houat --- drivers/md/dm-zero.c | 81 ++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 81 insertions(+) create mode 100644 drivers/md/dm-zero.c (limited to 'drivers/md/dm-zero.c') diff --git a/drivers/md/dm-zero.c b/drivers/md/dm-zero.c new file mode 100644 index 000000000..9a0bb623e --- /dev/null +++ b/drivers/md/dm-zero.c @@ -0,0 +1,81 @@ +// SPDX-License-Identifier: GPL-2.0-only +/* + * Copyright (C) 2003 Jana Saout + * + * This file is released under the GPL. + */ + +#include + +#include +#include +#include + +#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 "); +MODULE_DESCRIPTION(DM_NAME " dummy target returning zeros"); +MODULE_LICENSE("GPL"); -- cgit v1.3.1