16846fb575
Document EIO from msync(2). Inspired by PR: docs/165929 [1] Reviewed by: jilles MFC after: 2 weeks
125 lines
3.4 KiB
Groff
125 lines
3.4 KiB
Groff
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.\" @(#)msync.2 8.2 (Berkeley) 6/21/94
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.\" $FreeBSD$
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.\"
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.Dd March 18, 2012
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.Dt MSYNC 2
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.Os
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.Sh NAME
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.Nm msync
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.Nd synchronize a mapped region
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.Sh LIBRARY
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.Lb libc
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.Sh SYNOPSIS
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.In sys/mman.h
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.Ft int
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.Fn msync "void *addr" "size_t len" "int flags"
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.Sh DESCRIPTION
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The
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.Fn msync
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system call
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writes any modified pages back to the file system and updates
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the file modification time.
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If
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.Fa len
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is 0, all modified pages within the region containing
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.Fa addr
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will be flushed;
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if
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.Fa len
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is non-zero, only those pages containing
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.Fa addr
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and
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.Fa len-1
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succeeding locations will be examined.
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The
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.Fa flags
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argument may be specified as follows:
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.Pp
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.Bl -tag -width ".Dv MS_INVALIDATE" -compact
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.It Dv MS_ASYNC
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Return immediately
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.It Dv MS_SYNC
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Perform synchronous writes
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.It Dv MS_INVALIDATE
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Invalidate all cached data
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.El
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.Sh RETURN VALUES
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.Rv -std msync
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.Sh ERRORS
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The
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.Fn msync
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system call
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will fail if:
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.Bl -tag -width Er
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.It Bq Er EBUSY
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Some or all of the pages in the specified region are locked and
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.Dv MS_INVALIDATE
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is specified.
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.It Bq Er EINVAL
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The
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.Fa addr
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argument
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is not a multiple of the hardware page size.
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.It Bq Er EINVAL
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The
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.Fa len
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argument
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is too large or negative.
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.It Bq Er EINVAL
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The
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.Fa flags
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argument
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was both MS_ASYNC and MS_INVALIDATE.
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Only one of these flags is allowed.
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.It Bq Er EIO
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An error occurred while writing at least one of the pages in
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the specified region.
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.El
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.Sh SEE ALSO
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.Xr madvise 2 ,
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.Xr mincore 2 ,
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.Xr mlock 2 ,
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.Xr mprotect 2 ,
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.Xr munmap 2
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.Sh HISTORY
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The
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.Fn msync
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system call first appeared in
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.Bx 4.4 .
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.Sh BUGS
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The
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.Fn msync
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system call is usually not needed since
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.Bx
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implements a coherent file system buffer cache.
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However, it may be used to associate dirty VM pages with file system
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buffers and thus cause them to be flushed to physical media sooner
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rather than later.
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