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.\" $FreeBSD: head/share/man/man9/vm_page_grab.9 267936 2014-06-26 21:44:30Z bapt $
.\"
.Dd August 23, 2013
.Dt VM_PAGE_GRAB 9
.Os
.Sh NAME
.Nm vm_page_grab
.Nd "returns a page from an object"
.Sh SYNOPSIS
.In sys/param.h
.In vm/vm.h
.In vm/vm_page.h
.Ft vm_page_t
.Fn vm_page_grab "vm_object_t object" "vm_pindex_t pindex" "int allocflags"
.Sh DESCRIPTION
The
.Fn vm_page_grab
function returns the page at
.Fa pindex
from the given object.
If the page exists and is busy,
.Fn vm_page_grab
will sleep while waiting for it.
If the page does not exist, it is allocated.
The function sleeps until the allocation request can be satisfied.
.Pp
The function requires the
.Fa object
to be locked on entry, and returns with the object locked.
If the
.Fn vm_page_grab
function sleeps for any reason, the object lock is temporary dropped.
.Pp
The
.Fn vm_page_grab
supports all of the flags supported by
.Xr vm_page_alloc 9 .
In addition,
.Fn vm_page_grab
supports the following flags:
.Bl -tag -width ".Dv VM_ALLOC_IGN_SBUSY"
.It Dv VM_ALLOC_IGN_SBUSY
When waiting for the busy state of the existing page to drain,
only test for exclusive busy; ignore the shared busy counter.
.El
.Sh RETURN VALUES
The
.Fn vm_page_grab
always returns the page.
.Sh SEE ALSO
.Xr vm_page_alloc 9
.Sh AUTHORS
This manual page was written by
.An Chad David Aq Mt davidc@acns.ab.ca .