Hello Goldwyn, On 06/05/2017 07:51 AM, Goldwyn Rodrigues wrote: > From: Goldwyn Rodrigues <rgoldwyn@xxxxxxxx> > > Add more information about the iocb structure. It explains the fields > of the I/O control block structure which is passed to the io_submit > call. > > The work also includes the nowait feature flags which is currently > posted at http://marc.info/?l=linux-fsdevel&m=149664103900715&w=2 Thanks for the patch. I've applied, and made a few small tweaks. Cheers, Michael > Signed-off-by: Goldwyn Rodrigues <rgoldwyn@xxxxxxxx> > --- > man2/io_submit.2 | 114 +++++++++++++++++++++++++++++++++++++++++++++++++++++++ > 1 file changed, 114 insertions(+) > > diff --git a/man2/io_submit.2 b/man2/io_submit.2 > index 6aae4efff..fc1290da9 100644 > --- a/man2/io_submit.2 > +++ b/man2/io_submit.2 > @@ -28,6 +28,120 @@ The > .I iocbpp > argument should be an array of \fInr\fP AIO control blocks, > which will be submitted to context \fIctx_id\fP. > +The > +.I iocb > +(I/O control block) structure defined in linux/aio_abi.h > +defines the parameters that control the I/O operation. > +.PP > +.in +4n > +.nf > + > +#include <linux/aio_abi.h> > + > +struct iocb { > + __u64 aio_data; > + __u32 PADDED(aio_key, aio_rw_flags); > + > + __u16 aio_lio_opcode; > + __s16 aio_reqprio; > + __u32 aio_fildes; > + > + __u64 aio_buf; > + __u64 aio_nbytes; > + __s64 aio_offset; > + > + __u64 aio_reserved2; > + > + __u32 aio_flags; > + __u32 aio_resfd; > +}; > + > +.fi > +.in > +The fields of this structure are as follows: > +.TP > +.I aio_data > +This is a internal field used by the kernel. Do not modify this field after an > +.B io_submit (2) > +call. > +.TP > +.I aio_key > +This is a internal field used by the kernel. Do not modify this field after an > +.B io_submit (2) > +call. > +.TP > +.I aio_rw_flags > +This defines the R/W flags passed with structure. The valid values are: > +.RS > +.TP > +.I RWF_HIPRI > +High priority request, poll if possible > +.TP > +.I RWF_DSYNC > +Write operation complete according to requirement of synchronized I/O data integrity. Similar to a file passed > +.B O_DSYNC > +parameter to > +.B open(2) > +.TP > +.I RWF_SYNC > +Write operation complete according to requirement of synchronized I/O file integrity. Similar to a file passed > +.B .O_SYNC > +parameter to > +.B open(2) > +.TP > +.I RWF_NOWAIT > +Don't wait if the I/O will block for operations such as file block allocations, > +dirty page flush, mutex locks, or a congested block device inside the kernel. > +If any of these conditions are met, the control block is returned immediately > +with a return value of > +.B -EAGAIN > +in the res field of the io_event structure. > +.RE > +.TP > +.I aio_lio_opcode > +This defines the type of I/O to be performed by the iocb structure. The > +valid values are defined by the enum defined in linux/aio_abi.h: > +.in +4 > +.nf > +enum { > + IOCB_CMD_PREAD = 0, > + IOCB_CMD_PWRITE = 1, > + IOCB_CMD_FSYNC = 2, > + IOCB_CMD_FDSYNC = 3, > + IOCB_CMD_NOOP = 6, > + IOCB_CMD_PREADV = 7, > + IOCB_CMD_PWRITEV = 8, > +}; > +.fi > +.in > +.TP > +.I aio_reqprio > +This defines the requests priority. > +.TP > +.I aio_filedes > +The file descriptor on which the I/O operation is to be performed. > +.TP > +.I aio_buf > +This is the buffer used to transfer data for a read or write operation. > +.TP > +.I aio_nbytes > +This is the size of the buffer pointed to by > +.IR aio_buf . > +.TP > +.I aio_offset > +This is the file offset at which the I/O operation is to be performed. > +.TP > +.I aio_flags > +This is the flag to be passed iocb structure. The only valid value is > +.I IOCB_FLAG_RESFD > +, which indicates that the asynchronous I/O control must signal the file > +descriptor mentioned in > +.I aio_resfd > +upon completion. > +.TP > +.I aio_resfd > +The file descriptor to signal in the event of asynchronous I/O completion. > + > .SH RETURN VALUE > On success, > .BR io_submit () > -- Michael Kerrisk Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/ Linux/UNIX System Programming Training: http://man7.org/training/ -- To unsubscribe from this list: send the line "unsubscribe linux-man" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
