drivers/md/dm-zero.c

Source file repositories/reference/linux-study-clean/drivers/md/dm-zero.c

File Facts

System
Linux kernel
Corpus path
drivers/md/dm-zero.c
Extension
.c
Size
1659 bytes
Lines
82
Domain
Driver Families
Bucket
drivers/md
Inferred role
Driver Families: implementation source
Status
source implementation candidate

Why This File Exists

Repeatable hardware-adapter layer. Deep compatibility for every driver is out of scope; this atlas records patterns, probe lifecycles, bus glue, IRQ/DMA usage, and links back to core abstractions.

Dependency Surface

Detected Declarations

Annotated Snippet

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");

Annotation

Implementation Notes