being that PHYS_TO_VM_PAGE() returns the wrong vm_page for fictitious
pages but unwiring uses PHYS_TO_VM_PAGE(). The resulting panic
reported an unexpected wired count. Rather than attempting to fix
PHYS_TO_VM_PAGE(), this fix takes advantage of the properties of
fictitious pages. Specifically, fictitious pages will never be
completely unwired. Therefore, we can keep a fictitious page's wired
count forever set to one and thereby avoid the use of
PHYS_TO_VM_PAGE() when we know that we're working with a fictitious
page, just not which one.
In collaboration with: green@, tegge@
PR: kern/29915
Some of the conditions that caused vm_page_select_cache() to deactivate a
page were wrong. For example, deactivating an unmanaged or wired page is a
nop. Thus, if vm_page_select_cache() had ever encountered an unmanaged or
wired page, it would have looped forever. Now, we assert that the page is
neither unmanaged nor wired.
Previously, mlockall(2) usage would leak MAP_FUTUREWIRE of the process's
vmspace::vm_map and subsequent processes would wire all of their memory.
Coupled with a wired-page leak in vm_fault_unwire(), this would run the
system out of free pages and cause programs to randomly SIGBUS when
faulting in new pages.
(Note that this is not the fix for the latter part; pages are still
leaked when a wired area is unmapped in some cases.)
Reviewed by: alc
PR kern/62930
allocation and deallocation. This flag's principal use is shortly after
allocation. For such cases, clearing the flag is pointless. The only
unusual use of PG_ZERO is in vfs_bio_clrbuf(). However, allocbuf() never
requests a prezeroed page. So, vfs_bio_clrbuf() never sees a prezeroed
page.
Reviewed by: tegge@
caller to vm_page_grab(). Although this gives VM_ALLOC_ZERO a
different meaning for vm_page_grab() than for vm_page_alloc(), I feel
such change is necessary to accomplish other goals. Specifically, I
want to make the PG_ZERO flag immutable between the time it is
allocated by vm_page_alloc() and freed by vm_page_free() or
vm_page_free_zero() to avoid locking overheads. Once we gave up on
the ability to automatically recognize a zeroed page upon entry to
vm_page_free(), the ability to mutate the PG_ZERO flag became useless.
Instead, I would like to say that "Once a page becomes valid, its
PG_ZERO flag must be ignored."
would actually map the file with read access enabled. According to
http://www.opengroup.org/onlinepubs/007904975/functions/mmap.html this is
an error. Similarly, an madvise(..., MADV_WILLNEED) would enable read
access on a virtual address range that was PROT_NONE.
The solution implemented herein is (1) to pass a vm_prot_t to
vm_map_pmap_enter() describing the allowed access and (2) to make
vm_map_pmap_enter() responsible for understanding the limitations of
pmap_enter_quick().
Submitted by: "Mark W. Krentel" <krentel@dreamscape.com>
PR: kern/64573
move its declaration to the machine-dependent header file on those
machines that use it. In principle, only i386 should have it.
Alpha and AMD64 should use their direct virtual-to-physical mapping.
- Remove pmap_kenter_temporary() from ia64. It is unused. Approved
by: marcel@
the reduction of the pager map's size by 8M bytes. In other words, eight
megabytes of largely wasted KVA are returned to the kernel map for use
elsewhere.
vm_mmap_vnode function, where we can safely check for a special /dev/zero
case. Rev. 1.180 has reordered checks and introduced a regression.
Submitted by: alc
Was broken by: kan
to mmap it PROT_EXEC. This also depends on the architecture, as some
architextures (e.g. i386) do not distinguish between read and exec pages
Inspired by: http://linux.bkbits.net:8080/linux-2.4/cset@1.1267.1.85
Reviewed by: alc
pmap. For the kernel pmap, Giant is not required. In general, for
other pmaps, Giant is required by i386's pmap_pte() implementation.
Specifically, the use of PMAP2/PADDR2 is synchronized by Giant.
Note: In principle, updates to the kernel pmap's wired count could be
lost without Giant. However, in practice, we never use the kernel
pmap's wired count. This will be resolved when pmap locking appears.
- With the above change, cpu_thread_clean() and uma_large_free() need
not acquire Giant. (The first case is simply the revival of
i386/i386/vm_machdep.c's revision 1.226 by peter.)
ever since alpha/alpha/pmap.c revision 1.81 introduced the list allpmaps,
there has been no reason for having this function on Alpha. Briefly,
when pmap_growkernel() relied upon the list of all processes to find and
update the various pmaps to reflect a growth in the kernel's valid
address space, pmap_init2() served to avoid a race between pmap
initialization and pmap_growkernel(). Specifically, pmap_pinit2() was
responsible for initializing the kernel portions of the pmap and
pmap_pinit2() was called after the process structure contained a pointer
to the new pmap for use by pmap_growkernel(). Thus, an update to the
kernel's address space might be applied to the new pmap unnecessarily,
but an update would never be lost.
introduction of kern_mlock() and kern_munlock() in
src/sys/kern/kern_sysctl.c 1.150
src/sys/vm/vm_extern.h 1.69
src/sys/vm/vm_glue.c 1.190
src/sys/vm/vm_mmap.c 1.179
because different resource limits are appropriate for transient and
"permanent" page wiring requests.
Retain the kern_mlock() and kern_munlock() API in the revived
vslock() and vsunlock() functions.
Combine the best parts of each of the original sets of implementations
with further code cleanup. Make the mclock() and vslock()
implementations as similar as possible.
Retain the RLIMIT_MEMLOCK check in mlock(). Move the most strigent
test, which can return EAGAIN, last so that requests that have no
hope of ever being satisfied will not be retried unnecessarily.
Disable the test that can return EAGAIN in the vslock() implementation
because it will cause the sysctl code to wedge.
Tested by: Cy Schubert <Cy.Schubert AT komquats.com>
unnecessary and wrong. While it is necessary to verify that the page is
still free after dropping and reacquiring the free page queue lock, the
physical contiguity of the page can not change, making this check
unnecessary. This check was wrong in that it could cause an out-of-bounds
array access.
Tested by: rwatson
vm_page_free() is called. The problem with holding this lock is that it is
a spin lock and vm_page_free() may attempt the acquisition of a different
default-type lock.
the syscall arguments and does the suser() permission check, and
kern_mlock(), which does the resource limit checking and calls
vm_map_wire(). Split munlock() in a similar way.
Enable the RLIMIT_MEMLOCK checking code in kern_mlock().
Replace calls to vslock() and vsunlock() in the sysctl code with
calls to kern_mlock() and kern_munlock() so that the sysctl code
will obey the wired memory limits.
Nuke the vslock() and vsunlock() implementations, which are no
longer used.
Add a member to struct sysctl_req to track the amount of memory
that is wired to handle the request.
Modify sysctl_wire_old_buffer() to return an error if its call to
kern_mlock() fails. Only wire the minimum of the length specified
in the sysctl request and the length specified in its argument list.
It is recommended that sysctl handlers that use sysctl_wire_old_buffer()
should specify reasonable estimates for the amount of data they
want to return so that only the minimum amount of memory is wired
no matter what length has been specified by the request.
Modify the callers of sysctl_wire_old_buffer() to look for the
error return.
Modify sysctl_old_user to obey the wired buffer length and clean up
its implementation.
Reviewed by: bms
swap_pager_putpages()'s buffer completion code. Note: the only
difference between swp_pager_sync_iodone() and bdone(), aside from
the locking in the latter, was the unnecessary clearing of B_ASYNC.
- Remove an unnecessary pmap_page_protect() from
swp_pager_async_iodone().
Reviewed by: tegge
result in a panic "vm_page_cache: caching a dirty page, ...": Access to the
page must be restricted or removed before calling vm_page_cache(). This
race condition is identical in nature to that which was addressed by
vm_pageout.c's revision 1.251 and vm_page.c's revision 1.275.
MFC after: 7 days
panic "vm_page_cache: caching a dirty page, ...": Access to the page must
be restricted or removed before calling vm_page_cache(). This race
condition is identical in nature to that which was addressed by
vm_pageout.c's revision 1.251 and vm_page.c's revision 1.275.
Reviewed by: tegge
MFC after: 7 days
