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Diffstat (limited to 'upstream/opensuse-leap-15-6/man2/msync.2')
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diff --git a/upstream/opensuse-leap-15-6/man2/msync.2 b/upstream/opensuse-leap-15-6/man2/msync.2 new file mode 100644 index 00000000..e7bc7310 --- /dev/null +++ b/upstream/opensuse-leap-15-6/man2/msync.2 @@ -0,0 +1,140 @@ +.\" Copyright (C) 1996 Andries Brouwer (aeb@cwi.nl) +.\" +.\" SPDX-License-Identifier: Linux-man-pages-copyleft +.\" +.TH msync 2 2023-03-30 "Linux man-pages 6.04" +.SH NAME +msync \- synchronize a file with a memory map +.SH LIBRARY +Standard C library +.RI ( libc ", " \-lc ) +.SH SYNOPSIS +.nf +.B #include <sys/mman.h> +.PP +.BI "int msync(void " addr [. length "], size_t " length ", int " flags ); +.fi +.SH DESCRIPTION +.BR msync () +flushes changes made to the in-core copy of a file that was mapped +into memory using +.BR mmap (2) +back to the filesystem. +Without use of this call, +there is no guarantee that changes are written back before +.BR munmap (2) +is called. +To be more precise, the part of the file that +corresponds to the memory area starting at +.I addr +and having length +.I length +is updated. +.PP +The +.I flags +argument should specify exactly one of +.B MS_ASYNC +and +.BR MS_SYNC , +and may additionally include the +.B MS_INVALIDATE +bit. +These bits have the following meanings: +.TP +.B MS_ASYNC +Specifies that an update be scheduled, but the call returns immediately. +.TP +.B MS_SYNC +Requests an update and waits for it to complete. +.TP +.B MS_INVALIDATE +.\" Since Linux 2.4, this seems to be a no-op (other than the +.\" EBUSY check for VM_LOCKED). +Asks to invalidate other mappings of the same file +(so that they can be updated with the fresh values just written). +.SH RETURN VALUE +On success, zero is returned. +On error, \-1 is returned, and +.I errno +is set to indicate the error. +.SH ERRORS +.TP +.B EBUSY +.B MS_INVALIDATE +was specified in +.IR flags , +and a memory lock exists for the specified address range. +.TP +.B EINVAL +.I addr +is not a multiple of PAGESIZE; or any bit other than +.BR MS_ASYNC " | " MS_INVALIDATE " | " MS_SYNC +is set in +.IR flags ; +or both +.B MS_SYNC +and +.B MS_ASYNC +are set in +.IR flags . +.TP +.B ENOMEM +The indicated memory (or part of it) was not mapped. +.SH VERSIONS +According to POSIX, either +.B MS_SYNC +or +.B MS_ASYNC +must be specified in +.IR flags , +and indeed failure to include one of these flags will cause +.BR msync () +to fail on some systems. +However, Linux permits a call to +.BR msync () +that specifies neither of these flags, +with semantics that are (currently) equivalent to specifying +.BR MS_ASYNC . +(Since Linux 2.6.19, +.\" commit 204ec841fbea3e5138168edbc3a76d46747cc987 +.B MS_ASYNC +is in fact a no-op, since the kernel properly tracks dirty +pages and flushes them to storage as necessary.) +Notwithstanding the Linux behavior, +portable, future-proof applications should ensure that they specify either +.B MS_SYNC +or +.B MS_ASYNC +in +.IR flags . +.SH STANDARDS +POSIX.1-2008. +.SH HISTORY +POSIX.1-2001. +.PP +This call was introduced in Linux 1.3.21, and then used +.B EFAULT +instead of +.BR ENOMEM . +In Linux 2.4.19, this was changed to the POSIX value +.BR ENOMEM . +.PP +On POSIX systems on which +.BR msync () +is available, both +.B _POSIX_MAPPED_FILES +and +.B _POSIX_SYNCHRONIZED_IO +are defined in +.I <unistd.h> +to a value greater than 0. +(See also +.BR sysconf (3).) +.\" POSIX.1-2001: It shall be defined to -1 or 0 or 200112L. +.\" -1: unavailable, 0: ask using sysconf(). +.\" glibc defines them to 1. +.SH SEE ALSO +.BR mmap (2) +.PP +B.O. Gallmeister, POSIX.4, O'Reilly, pp. 128\[en]129 and 389\[en]391. |