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 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 () -- 2.12.3 -- 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
