On 8/28/25 5:05 PM, Tobias Waldekranz wrote: > This target allows you to map in a region of another device as a > contiguous range of blocks of a dm device. > > This is the basic building block used by LVM to stitch together > logical volumes from one or more ranges of blocks from one or more > physical disks. > > Signed-off-by: Tobias Waldekranz <[email protected]> > --- > drivers/block/dm/Kconfig | 7 ++ > drivers/block/dm/Makefile | 1 + > drivers/block/dm/dm-linear.c | 123 +++++++++++++++++++++++++++++++++++ > 3 files changed, 131 insertions(+) > create mode 100644 drivers/block/dm/dm-linear.c > > diff --git a/drivers/block/dm/Kconfig b/drivers/block/dm/Kconfig > index f64c69e03d..e763e530d3 100644 > --- a/drivers/block/dm/Kconfig > +++ b/drivers/block/dm/Kconfig > @@ -5,3 +5,10 @@ menuconfig DM_BLK > other data sources. Modeled after, and intended to be > compatible with, the Linux kernel's device mapper subsystem. > > +config DM_BLK_LINEAR > + bool "Linear target" > + depends on DM_BLK
Tab/Spaces mix up. > + help > + Maps a contiguous region of an existing device into a dm > + device. > + > diff --git a/drivers/block/dm/Makefile b/drivers/block/dm/Makefile > index 9c045087c0..f52d19f9c4 100644 > --- a/drivers/block/dm/Makefile > +++ b/drivers/block/dm/Makefile > @@ -1,2 +1,3 @@ > # SPDX-License-Identifier: GPL-2.0-only > obj-$(CONFIG_DM_BLK) += dm-core.o > +obj-$(CONFIG_DM_BLK_LINEAR) += dm-linear.o > diff --git a/drivers/block/dm/dm-linear.c b/drivers/block/dm/dm-linear.c > new file mode 100644 > index 0000000000..d3415814cb > --- /dev/null > +++ b/drivers/block/dm/dm-linear.c > @@ -0,0 +1,123 @@ > +// SPDX-License-Identifier: GPL-2.0-only > +// SPDX-FileCopyrightText: © 2025 Tobias Waldekranz <[email protected]>, > Wires > + > +#include <block.h> > +#include <common.h> Nitpick: If possible, I'd like to avoid common.h in new code. It's a lot of unneeded stuff in there. > +#include <disks.h> > +#include <fcntl.h> > + > +#include "dm-target.h" > + > +struct dm_linear { > + struct cdev *cdev; > + loff_t offset; > +}; > + > +static int dm_linear_read(struct dm_target *ti, void *buf, > + sector_t block, blkcnt_t num_blocks) > +{ > + struct dm_linear *l = ti->private; > + > + block <<= SECTOR_SHIFT; > + num_blocks <<= SECTOR_SHIFT; > + > + if (cdev_read(l->cdev, buf, num_blocks, l->offset + block, 0) < > num_blocks) > + return -EIO; Why not propagate the underlying error code if it's negative? > + > + return 0; > +} > + > +static int dm_linear_write(struct dm_target *ti, const void *buf, > + sector_t block, blkcnt_t num_blocks) > +{ > + struct dm_linear *l = ti->private; > + > + block <<= SECTOR_SHIFT; > + num_blocks <<= SECTOR_SHIFT; > + > + if (cdev_write(l->cdev, buf, num_blocks, l->offset + block, 0) < > num_blocks) > + return -EIO; > + > + return 0; > +} > + > +static int dm_linear_create(struct dm_target *ti, unsigned int argc, char > **argv) > +{ > + struct dm_linear *l; > + int err; > + > + if (argc != 2) { > + dm_target_err(ti, "Expected 2 arguments (\"<dev> <offset>\"), > got %u\n", > + argc); > + err = -EINVAL; > + goto err; > + } > + > + l = xzalloc(sizeof(*l)); > + ti->private = l; > + > + if (kstrtoull(argv[1], 0, &l->offset)) { > + dm_target_err(ti, "Invalid offset: \"%s\"\n", argv[1]); > + err = -EINVAL; > + goto err_free; > + } > + l->offset <<= SECTOR_SHIFT; > + > + l->cdev = cdev_open_by_path_name(argv[0], O_RDWR); > + if (!l->cdev) { > + dm_target_err(ti, "Cannot open device %s: %m\n", argv[0]); > + err = -ENODEV; > + goto err_free; > + } > + > + l->cdev = cdev_readlink(l->cdev); > + > + if ((ti->size << SECTOR_SHIFT) > (l->cdev->size - l->offset)) { > + dm_target_err(ti, "%s is too small to map %llu blocks at %llu, > %llu available\n", > + argv[0], ti->size, l->offset >> SECTOR_SHIFT, > + (l->cdev->size - l->offset) >> SECTOR_SHIFT); > + err = -ENOSPC; > + goto err_close; > + } > + > + return 0; > + > +err_close: > + cdev_close(l->cdev); > +err_free: > + free(l); > +err: > + return err; > +} > + > +static int dm_linear_destroy(struct dm_target *ti) > +{ > + struct dm_linear *l = ti->private; > + > + cdev_close(l->cdev); > + free(l); > + return 0; > +} > + > +static char *dm_linear_asprint(struct dm_target *ti) > +{ > + struct dm_linear *l = ti->private; > + > + return xasprintf("dev:%s offset:%llu", > + cdev_name(l->cdev), l->offset >> SECTOR_SHIFT); > +} > + > +static struct dm_target_ops dm_linear_ops = { > + .name = "linear", > + .asprint = dm_linear_asprint, > + .create = dm_linear_create, > + .destroy = dm_linear_destroy, > + .read = dm_linear_read, > + .write = dm_linear_write, > +}; > + > +static int __init dm_linear_init(void) > +{ > + return dm_target_register(&dm_linear_ops); > +} > +device_initcall(dm_linear_init); -- Pengutronix e.K. | | Steuerwalder Str. 21 | http://www.pengutronix.de/ | 31137 Hildesheim, Germany | Phone: +49-5121-206917-0 | Amtsgericht Hildesheim, HRA 2686 | Fax: +49-5121-206917-5555 |
