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VOP_GETPAGES.9: clarify and correct description of parameters and requirements

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In cooperation with alc and kib, who provided valuable insights and
suggestions.

Reviewed by:	alc, kib (earlier version)
MFC after:	4 days
This commit is contained in:
avg 2010-10-20 05:57:54 +00:00
parent 9f9aed22bf
commit 2e7847beec
1 changed files with 18 additions and 13 deletions
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31
share/man/man9/VOP_GETPAGES.9
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@ -41,9 +41,9 @@
.In sys/vnode.h
.In vm/vm.h
.Ft int
.Fn VOP_GETPAGES "struct vnode *vp" "vm_page_t *m" "int count" "int reqpage" "vm_ooffset_t offset"
.Fn VOP_GETPAGES "struct vnode *vp" "vm_page_t *ma" "int count" "int reqpage" "vm_ooffset_t offset"
.Ft int
.Fn VOP_PUTPAGES "struct vnode *vp" "vm_page_t *m" "int count" "int sync" "int *rtvals" "vm_ooffset_t offset"
.Fn VOP_PUTPAGES "struct vnode *vp" "vm_page_t *ma" "int count" "int sync" "int *rtvals" "vm_ooffset_t offset"
.Sh DESCRIPTION
The
.Fn VOP_GETPAGES
@ -66,11 +66,11 @@ The arguments are:
.Bl -tag -width reqpage
.It Fa vp
The file to access.
.It Fa m
Pointer to the first element of an array of contiguous pages representing a
.It Fa ma
Pointer to the first element of an array of pages representing a
contiguous region of the file to be read or written.
.It Fa count
The number of pages in the array.
The number of bytes that should be read into the pages of the array.
.It Fa sync
.Dv VM_PAGER_PUT_SYNC
if the write should be synchronous.
@ -123,22 +123,27 @@ The page was not handled by this request.
The
.Fn VOP_GETPAGES
method is expected to release any pages in
.Fa m
.Fa ma
that it does not successfully handle, by calling
.Xr vm_page_free 9 .
When it succeeds,
.Fn VOP_GETPAGES
must set the valid bits appropriately, clear the dirty bit
(using
.Xr vm_page_undirty 9 ) ,
either activate the page (if its wanted bit is set)
must set the valid bits appropriately.
.Fn VOP_GETPAGES
must keep
.Fa reqpage
busy.
It must unbusy all other successfully handled pages and put them
on appropriate page queue(s).
For example,
.Fn VOP_GETPAGES
may either activate a page (if its wanted bit is set)
or deactivate it (otherwise), and finally call
.Xr vm_page_wakeup 9
to arouse any threads currently waiting for the page to be faulted in,
for each page read.
to arouse any threads currently waiting for the page to be faulted in.
.Sh RETURN VALUES
If it successfully reads
.Fa m[reqpage] ,
.Fa ma[reqpage] ,
.Fn VOP_GETPAGES
returns
.Dv VM_PAGER_OK ;