1io_submit(2) System Calls Manual io_submit(2)
2
6 io_submit - submit asynchronous I/O blocks for processing
7
9 Standard C library (libc, -lc)
10 Alternatively, Asynchronous I/O library (libaio, -laio); see VERSIONS.
12
14 #include <linux/aio_abi.h> /* Defines needed types */
15 int io_submit(aio_context_t ctx_id, long nr, struct iocb **iocbpp);
17 Note: There is no glibc wrapper for this system call; see VERSIONS.
19
21 Note: this page describes the raw Linux system call interface. The
22 wrapper function provided by libaio uses a different type for the
23 ctx_id argument. See VERSIONS.
24 The io_submit() system call queues nr I/O request blocks for processing
26 in the AIO context ctx_id. The iocbpp argument should be an array of
27 nr AIO control blocks, which will be submitted to context ctx_id.
28 The iocb (I/O control block) structure defined in linux/aio_abi.h de‐
30 fines the parameters that control the I/O operation.
31 #include <linux/aio_abi.h>
33 struct iocb {
35 __u64 aio_data;
36 __u32 PADDED(aio_key, aio_rw_flags);
37 __u16 aio_lio_opcode;
38 __s16 aio_reqprio;
39 __u32 aio_fildes;
40 __u64 aio_buf;
41 __u64 aio_nbytes;
42 __s64 aio_offset;
43 __u64 aio_reserved2;
44 __u32 aio_flags;
45 __u32 aio_resfd;
46 };
47 The fields of this structure are as follows:
49 aio_data
51 This data is copied into the data field of the io_event struc‐
52 ture upon I/O completion (see io_getevents(2)).
53 aio_key
55 This is an internal field used by the kernel. Do not modify
56 this field after an io_submit() call.
57 aio_rw_flags
59 This defines the R/W flags passed with structure. The valid
60 values are:
61 RWF_APPEND (since Linux 4.16)
63 Append data to the end of the file. See the description
64 of the flag of the same name in pwritev2(2) as well as
65 the description of O_APPEND in open(2). The aio_offset
66 field is ignored. The file offset is not changed.
67 RWF_DSYNC (since Linux 4.13)
69 Write operation complete according to requirement of syn‐
70 chronized I/O data integrity. See the description of the
71 flag of the same name in pwritev2(2) as well the descrip‐
72 tion of O_DSYNC in open(2).
73 RWF_HIPRI (since Linux 4.13)
75 High priority request, poll if possible
76 RWF_NOWAIT (since Linux 4.14)
78 Don't wait if the I/O will block for operations such as
79 file block allocations, dirty page flush, mutex locks, or
80 a congested block device inside the kernel. If any of
81 these conditions are met, the control block is returned
82 immediately with a return value of -EAGAIN in the res
83 field of the io_event structure (see io_getevents(2)).
84 RWF_SYNC (since Linux 4.13)
86 Write operation complete according to requirement of syn‐
87 chronized I/O file integrity. See the description of the
88 flag of the same name in pwritev2(2) as well the descrip‐
89 tion of O_SYNC in open(2).
90 aio_lio_opcode
92 This defines the type of I/O to be performed by the iocb struc‐
93 ture. The valid values are defined by the enum defined in
94 linux/aio_abi.h:
95 enum {
97 IOCB_CMD_PREAD = 0,
98 IOCB_CMD_PWRITE = 1,
99 IOCB_CMD_FSYNC = 2,
100 IOCB_CMD_FDSYNC = 3,
101 IOCB_CMD_POLL = 5,
102 IOCB_CMD_NOOP = 6,
103 IOCB_CMD_PREADV = 7,
104 IOCB_CMD_PWRITEV = 8,
105 };
106 aio_reqprio
108 This defines the requests priority.
109 aio_fildes
111 The file descriptor on which the I/O operation is to be per‐
112 formed.
113 aio_buf
115 This is the buffer used to transfer data for a read or write op‐
116 eration.
117 aio_nbytes
119 This is the size of the buffer pointed to by aio_buf.
120 aio_offset
122 This is the file offset at which the I/O operation is to be per‐
123 formed.
124 aio_flags
126 This is the set of flags associated with the iocb structure.
127 The valid values are:
128 IOCB_FLAG_RESFD
130 Asynchronous I/O control must signal the file descriptor
131 mentioned in aio_resfd upon completion.
132 IOCB_FLAG_IOPRIO (since Linux 4.18)
134 Interpret the aio_reqprio field as an IOPRIO_VALUE as de‐
135 fined by linux/ioprio.h.
136 aio_resfd
138 The file descriptor to signal in the event of asynchronous I/O
139 completion.
140
142 On success, io_submit() returns the number of iocbs submitted (which
143 may be less than nr, or 0 if nr is zero). For the failure return, see
144 VERSIONS.
145
147 EAGAIN Insufficient resources are available to queue any iocbs.
148 EBADF The file descriptor specified in the first iocb is invalid.
150 EFAULT One of the data structures points to invalid data.
152 EINVAL The AIO context specified by ctx_id is invalid. nr is less than
154 0. The iocb at *iocbpp[0] is not properly initialized, the op‐
155 eration specified is invalid for the file descriptor in the
156 iocb, or the value in the aio_reqprio field is invalid.
157 ENOSYS io_submit() is not implemented on this architecture.
159 EPERM The aio_reqprio field is set with the class IOPRIO_CLASS_RT, but
161 the submitting context does not have the CAP_SYS_ADMIN capabil‐
162 ity.
163
165 glibc does not provide a wrapper for this system call. You could in‐
166 voke it using syscall(2). But instead, you probably want to use the
167 io_submit() wrapper function provided by libaio.
168 Note that the libaio wrapper function uses a different type (io_con‐
170 text_t) for the ctx_id argument. Note also that the libaio wrapper
171 does not follow the usual C library conventions for indicating errors:
172 on error it returns a negated error number (the negative of one of the
173 values listed in ERRORS). If the system call is invoked via
174 syscall(2), then the return value follows the usual conventions for in‐
175 dicating an error: -1, with errno set to a (positive) value that indi‐
176 cates the error.
177
179 Linux.
180
182 Linux 2.5.
183
185 io_cancel(2), io_destroy(2), io_getevents(2), io_setup(2), aio(7)
186Linux man-pages 6.04 2023-03-30 io_submit(2)