асинхронная синхронизация файлов (asynchronous file synchronization)
Пролог (Prolog)
This manual page is part of the POSIX Programmer's Manual. The
Linux implementation of this interface may differ (consult the
corresponding Linux manual page for details of Linux behavior),
or the interface may not be implemented on Linux.
Имя (Name)
aio_fsync — asynchronous file synchronization
Синопсис (Synopsis)
#include <aio.h>
int aio_fsync(int op, struct aiocb *aiocbp);
Описание (Description)
The aio_fsync() function shall asynchronously perform a file
synchronization operation, as specified by the op argument, for
I/O operations associated with the file indicated by the file
descriptor aio_fildes member of the aiocb structure referenced by
the aiocbp argument and queued at the time of the call to
aio_fsync(). The function call shall return when the
synchronization request has been initiated or queued to the file
or device (even when the data cannot be synchronized
immediately).
If op is O_DSYNC, all currently queued I/O operations shall be
completed as if by a call to fdatasync(); that is, as defined for
synchronized I/O data integrity completion.
If op is O_SYNC, all currently queued I/O operations shall be
completed as if by a call to fsync(); that is, as defined for
synchronized I/O file integrity completion. If the aio_fsync()
function fails, or if the operation queued by aio_fsync() fails,
then outstanding I/O operations are not guaranteed to have been
completed.
If aio_fsync() succeeds, then it is only the I/O that was queued
at the time of the call to aio_fsync() that is guaranteed to be
forced to the relevant completion state. The completion of
subsequent I/O on the file descriptor is not guaranteed to be
completed in a synchronized fashion.
The aiocbp argument refers to an asynchronous I/O control block.
The aiocbp value may be used as an argument to aio_error() and
aio_return() in order to determine the error status and return
status, respectively, of the asynchronous operation while it is
proceeding. When the request is queued, the error status for the
operation is [EINPROGRESS]. When all data has been successfully
transferred, the error status shall be reset to reflect the
success or failure of the operation. If the operation does not
complete successfully, the error status for the operation shall
be set to indicate the error. The aio_sigevent member determines
the asynchronous notification to occur as specified in Section
2.4.1, Signal Generation and Delivery when all operations have
achieved synchronized I/O completion. All other members of the
structure referenced by aiocbp are ignored. If the control block
referenced by aiocbp becomes an illegal address prior to
asynchronous I/O completion, then the behavior is undefined.
If the aio_fsync() function fails or aiocbp indicates an error
condition, data is not guaranteed to have been successfully
transferred.
Возвращаемое значение (Return value)
The aio_fsync() function shall return the value 0 if the I/O
operation is successfully queued; otherwise, the function shall
return the value -1 and set errno to indicate the error.
Ошибки (Error)
The aio_fsync() function shall fail if:
EAGAIN The requested asynchronous operation was not queued due to
temporary resource limitations.
EBADF The aio_fildes member of the aiocb structure referenced by
the aiocbp argument is not a valid file descriptor.
EINVAL This implementation does not support synchronized I/O for
this file.
EINVAL The aio_fildes member of the aiocb structure refers to a
file on which an fsync() operation is not possible.
EINVAL A value of op other than O_DSYNC or O_SYNC was specified,
or O_DSYNC was specified and the implementation does not
provide runtime support for the Synchronized Input and
Output option, or O_SYNC was specified and the
implementation does not provide runtime support for the
File Synchronization option.
In the event that any of the queued I/O operations fail,
aio_fsync() shall return the error condition defined for read()
and write(). The error is returned in the error status for the
asynchronous operation, which can be retrieved using aio_error().
The following sections are informative.
Примеры (Examples)
None.
Использование в приложениях (Application usage)
Note that even if the file descriptor is not open for writing, if
there are any pending write requests on the underlying file, then
that I/O will be completed prior to the return of a call to
aio_error() or aio_return() indicating that the operation has
completed.
Обоснование (Rationale)
None.
Будущие направления (Future directions)
None.
Смотри также (See also)
aio_error(3p), aio_return(3p), fcntl(3p), fdatasync(3p),
fsync(3p), open(3p), read(3p), write(3p)
The Base Definitions volume of POSIX.1‐2017, aio.h(0p)
