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),

liburing-2.8                                      Oct 13, 2024                      io_uring_prep_cmd_discard(3)