io_uring_prep_cmd_discard(3)

NAME
io_uring_prep_cmd_discard - prepare a discard command

SYNOPSIS
#include <liburing.h>

void io_uring_prep_cmd_discard(struct io_uring_sqe *sqe,
                          int fd,
                          uint64_t offset,
                          uint64_t nbytes);

DESCRIPTION
The io_uring_prep_cmd_discard(3) function prepares a discard command request. The submission queue entry sqe is setup to use the file descriptor fd to start discarding nbytes at the specified offset.

The command is an asynchronous equivalent of BLOCK_URING_CMD_DISCARD ioctl with a few differences. It allows multiple parallel discards, and it does not exclude concurrent writes and reads. As a result, it may lead to races for the data on the disk, if the application has IO inflight for the same ranges that the discard operates on. It's the user's responsibility to account for that. Furthermore, only best efforts are done to invalidate page caches. The user has to make sure that no other inflight requests are modifying or reading the range(s). If that is the case, it might result in stale page cache and data inconsistencies.

Available since 6.12.

RETURN VALUE
None

ERRORS
The CQE res field will contain the result of the operation. On success, this field will be set to 0 . On error, a negative error value is returned. Note that where synchronous system calls will return -1 on failure and set errno to the actual error value, io_uring never uses errno. Instead it returns the negated errno directly in the CQE res field.

SEE ALSO
io_uring_get_sqe(3), io_uring_submit(3),