Attachment #122693 for bug #165929

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system call generally do not flush dirty NOSYNC VM data.
The
.Xr msync 2
system call may be used to associate dirty VM pages with file system
buffers and thus cause them to be flushed to physical media sooner
rather than later.
However, it may be
used to associate dirty VM pages with file system buffers and thus cause
them to be flushed to physical media sooner rather than later.
.It Dv MAP_PREFAULT_READ
Immediately update the calling process's lowest-level virtual address
translation structures, such as its page table, so that every memory




.Sh BUGS
The
.Fn msync
system call does not report errors if dirty pages could not be written.
This is expected to be fixed in a future release of
.Fx .
.Pp
If another process, such as
.Xr syncer 4 ,
attempts to flush dirty pages on an NFS-backed file, but lacks
permissions on the server to do so, it may fail.  If this happens,
future calls to
.Fn msync
may not have any effect.  This is not a bug in
.Fn msync ,
although it may appear to be; it is actually a bug in NFS.

Return to bug 165929

Lines 205-216 Link Here

(-)lib/libc/sys/mmap.2 (-6 / +3 lines)
205	system call generally do not flush dirty NOSYNC VM data.	205	system call generally do not flush dirty NOSYNC VM data.
206	The	206	The
207	.Xr msync 2	207	.Xr msync 2
208	system call is obsolete since	208	system call may be used to associate dirty VM pages with file system
209	.Bx	209	buffers and thus cause them to be flushed to physical media sooner
210	implements a coherent file system buffer cache.	210	rather than later.
211	However, it may be
212	used to associate dirty VM pages with file system buffers and thus cause
213	them to be flushed to physical media sooner rather than later.
214	.It Dv MAP_PREFAULT_READ	211	.It Dv MAP_PREFAULT_READ
215	Immediately update the calling process's lowest-level virtual address	212	Immediately update the calling process's lowest-level virtual address
216	translation structures, such as its page table, so that every memory	213	translation structures, such as its page table, so that every memory

Lines 113-121 Link Here

(-)lib/libc/sys/msync.2 (-6 / +13 lines)
113	.Sh BUGS	113	.Sh BUGS
114	The	114	The
115	.Fn msync	115	.Fn msync
116	system call is obsolete since	116	system call does not report errors if dirty pages could not be written.
117	.Bx	117	This is expected to be fixed in a future release of
118	implements a coherent file system buffer cache.	118	.Fx .
119	However, it may be used to associate dirty VM pages with file system	119	.Pp
120	buffers and thus cause them to be flushed to physical media sooner	120	If another process, such as
121	rather than later.	121	.Xr syncer 4 ,
		122	attempts to flush dirty pages on an NFS-backed file, but lacks
		123	permissions on the server to do so, it may fail. If this happens,
		124	future calls to
		125	.Fn msync
		126	may not have any effect. This is not a bug in
		127	.Fn msync ,
		128	although it may appear to be; it is actually a bug in NFS.