just skip that page. this situation can arise legitimately when a file
with a wired mapping is truncated so that a wired page is no longer
part of the file.
from VM_FAULT_WIRE in that when the pages being wired are faulted in,
the simulated fault is at the maximum protection allowed for the mapping
instead of the current protection. use this in uvm_map_pageable{,_all}()
to fix the problem where writing via ptrace() to shared libraries that
are also mapped with wired mappings in another process causes a
diagnostic panic when the wired mapping is removed.
this is a really obscure problem so it deserves some more explanation.
ptrace() writing to another process ends up down in uvm_map_extract(),
which for MAP_PRIVATE mappings (such as shared libraries) will cause
the amap to be copied or created. then the amap is made shared
(ie. the AMAP_SHARED flag is set) between the kernel and the ptrace()d
process so that the kernel can modify pages in the amap and have the
ptrace()d process see the changes. then when the page being modified
is actually faulted on, the object pages (from the shared library vnode)
is copied to a new anon page and inserted into the shared amap.
to make all the processes sharing the amap actually see the new anon
page instead of the vnode page that was there before, we need to
invalidate all the pmap-level mappings of the vnode page in the pmaps
of the processes sharing the amap, but we don't have a good way of
doing this. the amap doesn't keep track of the vm_maps which map it.
so all we can do at this point is to remove all the mappings of the
page with pmap_page_protect(), but this has the unfortunate side-effect
of removing wired mappings as well. removing wired mappings with
pmap_page_protect() is a legitimate operation, it can happen when a file
with a wired mapping is truncated. so the pmap has no way of knowing
whether a request to remove a wired mapping is normal or when it's due to
this weird situation. so the pmap has to remove the weird mapping.
the process being ptrace()d goes away and life continues. then,
much later when we go to unwire or remove the wired vm_map mapping,
we discover that the pmap mapping has been removed when it should
still be there, and we panic.
so where did we go wrong? the problem is that we don't have any way
to update just the pmap mappings that need to be updated in this
scenario. we could invent a mechanism to do this, but that is much
more complicated than this change and it doesn't seem like the right
way to go in the long run either.
the real underlying problem here is that wired pmap mappings just
aren't a good concept. one of the original properties of the pmap
design was supposed to be that all the information in the pmap could
be thrown away at any time and the VM system could regenerate it all
through fault processing, but wired pmap mappings don't allow that.
a better design for UVM would not require wired pmap mappings,
and Chuck C. and I are talking about this, but it won't be done
anytime soon, so this change will do for now.
this change has the effect of causing MAP_PRIVATE mappings to be
copied to anonymous memory when they are mlock()d, so that uvm_fault()
doesn't need to copy these pages later when called from ptrace(), thus
avoiding the call to pmap_page_protect() and the panic that results
from this when the mlock()d region is unlocked or freed. note that
this change doesn't help the case where the wired mapping is MAP_SHARED.
discussed at great length with Chuck Cranor.
fixes PRs 10363, 12554, 12604, 13041, 13487, 14580 and 14853.
we need to make sure that vnode pages are written to disk at least once,
otherwise processes could gain access to whatever data was previously stored
in disk blocks which are freshly allocated to a file.
uobject and uanon pointers rather than at the PQ_ANON flag to determine
which lock to hold, since PQ_ANON can be clear even when the anon's lock
is the one which we should hold (if the page was loaned from an object
and then freed by the object).
if the vec pointer is valid rather than using uvm_useracc().
uvm_useracc() just tells you if the permissions of a user mapping allow
the desired access, not whether faulting on that mapping will succeed.
will be allocated for the respective usage types when there is contention
for memory.
replace "vnode" and "vtext" with "file" and "exec" in uvmexp field names
and sysctl names.
- fix the loaned case in uvm_pagefree().
- redo uvmexp.swpgonly accounting to work with page loaning.
add an assertion before each place we adjust uvmexp.swpgonly.
- fix uvm_km_pgremove() to always free any swap space associated with
the range being removed.
- get rid of UVM_LOAN_WIRED flag. instead, we just make sure that
pages loaned to the kernel are never on the page queues.
this allows us to assert that pages are not loaned and wired
at the same time.
- add yet more assertions.
(either the current protection or the max protection) that reference
vnodes associated with a file system mounted with the NOEXEC option.
uvm_mmap(): Don't allow PROT_EXEC mappings to be established of vnodes
which are associated with a file system mounted with the NOEXEC option.
executable mappings. Stop overloading VTEXT for this purpose (VTEXT
also has another meaning).
- Rename vn_marktext() to vn_markexec(), and use it when executable
mappings of a vnode are established.
- In places where we want to set VTEXT, set it in v_flag directly, rather
than making a function call to do this (it no longer makes sense to
use a function call, since we no longer overload VTEXT with VEXECMAP's
meaning).
VEXECMAP suggested by Chuq Silvers.
are only wired if this flag is present (i.e. they are not wired by default now)
loaned pages are unloaned via new uvm_unloan(), uvm_unloananon() and
uvm_unloanpage() are no longer exported
adjust uvm_unloanpage() to unwire the pages if UVM_LOAN_WIRED is specified
mark uvm_loanuobj() and uvm_loanzero() static also in function implementation
kern/sys_pipe.c: uvm_unloanpage() --> uvm_unloan()
- remove special treatment of pager_map mappings in pmaps. this is
required now, since I've removed the globals that expose the address range.
pager_map now uses pmap_kenter_pa() instead of pmap_enter(), so there's
no longer any need to special-case it.
- eliminate struct uvm_vnode by moving its fields into struct vnode.
- rewrite the pageout path. the pager is now responsible for handling the
high-level requests instead of only getting control after a bunch of work
has already been done on its behalf. this will allow us to UBCify LFS,
which needs tighter control over its pages than other filesystems do.
writing a page to disk no longer requires making it read-only, which
allows us to write wired pages without causing all kinds of havoc.
- use a new PG_PAGEOUT flag to indicate that a page should be freed
on behalf of the pagedaemon when it's unlocked. this flag is very similar
to PG_RELEASED, but unlike PG_RELEASED, PG_PAGEOUT can be cleared if the
pageout fails due to eg. an indirect-block buffer being locked.
this allows us to remove the "version" field from struct vm_page,
and together with shrinking "loan_count" from 32 bits to 16,
struct vm_page is now 4 bytes smaller.
- no longer use PG_RELEASED for swap-backed pages. if the page is busy
because it's being paged out, we can't release the swap slot to be
reallocated until that write is complete, but unlike with vnodes we
don't keep a count of in-progress writes so there's no good way to
know when the write is done. instead, when we need to free a busy
swap-backed page, just sleep until we can get it busy ourselves.
- implement a fast-path for extending writes which allows us to avoid
zeroing new pages. this substantially reduces cpu usage.
- encapsulate the data used by the genfs code in a struct genfs_node,
which must be the first element of the filesystem-specific vnode data
for filesystems which use genfs_{get,put}pages().
- eliminate many of the UVM pagerops, since they aren't needed anymore
now that the pager "put" operation is a higher-level operation.
- enhance the genfs code to allow NFS to use the genfs_{get,put}pages
instead of a modified copy.
- clean up struct vnode by removing all the fields that used to be used by
the vfs_cluster.c code (which we don't use anymore with UBC).
- remove kmem_object and mb_object since they were useless.
instead of allocating pages to these objects, we now just allocate
pages with no object. such pages are mapped in the kernel until they
are freed, so we can use the mapping to find the page to free it.
this allows us to remove splvm() protection in several places.
The sum of all these changes improves write throughput on my
decstation 5000/200 to within 1% of the rate of NetBSD 1.5
and reduces the elapsed time for "make release" of a NetBSD 1.5
source tree on my 128MB pc to 10% less than a 1.5 kernel took.
This will allow improvements to the pmaps so that they can more easily defer expensive operations, eg tlb/cache flush, til the last possible moment.
Currently this is a no-op on most platforms, so they should see no difference.
Reviewed by Jason.
kernel_map. use this instead of the static map entries when allocating
map entries for kernel_map. this greatly reduces the number of static
map entries used and should eliminate the problems with running out.
loop returns 0. loanentry was returning >0, but was unlocking the maps
(because of the zero). reworked to avoid this. problem reported by
chuck silvers. also clarify a comment that jdolecek asked about.
provides us more flexibility with pageq-locked fields, and clarifies the
locking semantics for platforms which cannot address shorts.
From Ross Harvey.
an spl-protected "interrupt safe map" list, simply require that callers
of uvm_fault() never call us in interrupt context (MD code must make
the assertion), and check for interrupt-safe maps in uvmfault_lookup()
before we lock the map.
between creation of a file descriptor and close(2) when using kernel
assisted threads. What we do is stick descriptors in the table, but
mark them as "larval". This causes essentially everything to treat
it as a non-existent descriptor, except for fdalloc(), which sees a
filled slot so that it won't (incorrectly) allocate it again. When
a descriptor is fully constructed, the code that has constructed it
marks it as "mature" (which actually clears the "larval" flag), and
things continue to work as normal.
While here, gather all the code that gets a descriptor from the table
into a fd_getfile() function, and call it, rather than having the
same (sometimes incorrect) code copied all over the place.
some time ago. The mistake was to check that the page was not
referenced since the last active scan before moving it to inactive.
Now we just clear reference and move it to inacive (which is where
the second clock hand sweep occurs).
dynamically re-coloring pages; as machine-dependent code discovers
the size of the system's caches, it may call uvm_page_recolor() with
the new number of colors to use. If the new mumber of colors is
smaller (or equal to) the current number of colors, then uvm_page_recolor()
is a no-op.
The system defaults to one bucket if machine-dependent code does not
initialize uvmexp.ncolors before uvm_page_init() is called.
Note that the number of color bins should be initialized to something
reasonable as early as possible -- for many early memory allocations,
we live with the consequences of the page choice for the lifetime of
the boot.
each vm_page structure. Add a VM_MDPAGE_INIT() macro to init this
data when pages are initialized by UVM. These macros are mandatory,
but ports may #define them to nothing if they are not needed/used.
This deprecates struct pmap_physseg. As a transitional measure,
allow a port to #define PMAP_PHYSSEG so that it can continue to
use it until its pmap is converted to use VM_MDPAGE_MEMBERS.
Use all this stuff to eliminate a lot of extra work in the Alpha
pmap module (it's smaller and faster now). Changes to other pmap
modules will follow.
algorithm (Solaris calls this "Bin Hopping").
This implementation currently relies on MD code to define a
constant defining the number of buckets. This will change
reasonably soon (MD code will be able to dynamically size
the bucket array).
- pmap_enter()
- pmap_remove()
- pmap_protect()
- pmap_kenter_pa()
- pmap_kremove()
as described in pmap(9).
These calls are relatively conservative. It may be possible to
optimize these a little more.
which have pmap_steal_memory(). This is to reduce the API differences
between pmaps that implement pmap_steal_memory() and pmaps which do
not.
Note that pmap_steal_memory() needs to adjust *vstartp and/or
*vendp only if it used addresses within the range provided to UVM
via the pmap_virtual_space() call. I.e. it is not necessary to do
so in any current pmap_steal_memory() implementation.
on locking rules to make code easier to understand. locking in
uvm_loananon still needs some work on fringe cases where anon's page
is actually on loan from a uobj.
if uvm_loanentry() returned 0; otherwise, the unlocking would already
have been done by uvmfault_unlockall() call in uvm_loanentry().
Okay'ed by Chuck Silvers
the process dsize for both positive and negative changes. Since atop()
casts its result to a paddr_t (which is unsigned), negative changes in
process data size resulted in unrealistic dsizes being set. Use
"dsize -= atop(-diff)" for a negative diffs. Fixes the "Impossible
process sizes" mentioned on current-users.
Unsigned cast catch and much debugging help from Martin Laubach.
the mapping is:
VM_PAGER_OK 0
VM_PAGER_BAD <unused>
VM_PAGER_FAIL <unused>
VM_PAGER_PEND 0 (see below)
VM_PAGER_ERROR EIO
VM_PAGER_AGAIN EAGAIN
VM_PAGER_UNLOCK EBUSY
VM_PAGER_REFAULT ERESTART
for async i/o requests, it used to be possible for the request to
be convert to sync, and the pager would return VM_PAGER_OK or VM_PAGER_PEND
to indicate whether the caller should perform post-i/o cleanup.
this is no longer allowed; pagers must now return 0 to indicate that
the async i/o was successfully started, and the caller never needs to
worry about doing the post-i/o cleanup.
each of the basic types (anonymous data, executable image, cached files)
and prevent the pagedaemon from reusing a given page if that would reduce
the count of that type of page below a sysctl-setable minimum threshold.
the thresholds are controlled via three new sysctl tunables:
vm.anonmin, vm.vnodemin, and vm.vtextmin. these tunables are the
percentages of pageable memory reserved for each usage, and we do not allow
the sum of the minimums to be more than 95% so that there's always some
memory that can be reused.
failed because we failed to acquire some resource needed to initiate
the pageout (such as failing to lock an indirect buffer) rather than
a hard i/o error. in this case we just want to reactivate the page(s)
so that we'll try to write them again later.
while I'm here, clean up some DIAGNOSTIC code.
space is already torn down in uvmspace_free() when the vmspace
refrence count reaches 0. Move the shmexit() call into uvmspace_free().
Note that there is a beneficial side-effect of deferring the unmap
to uvmspace_free() -- on systems where TLB invalidations are
particularly expensive, the unmapping of the address space won't
have to cause TLB invalidations; uvmspace_free() is going to be
run in a context other than the exiting process's, so the "pmap is
active" test will evaluate to FALSE in the pmap module.
entry in the map. the old code would walk around the end of the linked list,
through the header entry, and keep going from the first map entry until it
found a gap in the map, at which point it would return an error. if the map
had no gaps then it would loop forever. reported by k-abe@cs.utah.edu.
while I'm here, clean up this function a bit.
also, use MIN() instead of min(), since the latter takes arguments of
type "int" but we're passing it values of type "vaddr_t", which can be
a larger size.
Mach VM's now. Specific changes:
- Pages now need not have all of their mappings removed before being
put on the inactive list. They only need to have the "referenced"
attribute cleared. This makes putting pages onto the inactive list
much more efficient. In order to eliminate redundant clearings of
"refrenced", callers of uvm_pagedeactivate() must now do this
themselves.
- When checking the "modified" attribute for a page (for clearing
PG_CLEAN), make sure to only do it if PG_CLEAN is currently set on
the page (saves a potentially expensive pmap operation).
- When scanning the inactive list, if a page is referenced, reactivate
it (this part was actually added in uvm_pdaemon.c,v 1.27). This
now works properly now that pages on the inactive list are allowed to
have mappings.
- When scanning the inactive list and considering a page for freeing,
remove all mappings, and then check the "modified" attribute if the
page is marked PG_CLEAN.
- When scanning the active list, if the page was referenced since its
last sweep by the scanner, don't deactivate it. (This part was
actually added in uvm_pdaemon.c,v 1.28.)
These changes greatly improve interactive performance during
moderate to high memory and I/O load.
amap_free(): Assert that the amap is locked.
amap_share_protect(): Assert that the amap is locked.
amap_wipeout(): Assert that the amap is locked.
uvm_anfree(): Assert that the anon has a reference count of 0 and is
not locked.
uvm_anon_lockloanpg(): Assert that the anon is locked.
anon_pagein(): Assert that the anon is locked.
uvmfault_anonget(): Assert that the anon is locked.
uvm_pagealloc_strat(): Assert that the uobj or the anon is locked
And fix the problems these have uncovered:
amap_cow_now(): Lock the new anon after allocating it, and unref and
unlock it (rather than lock!) before freeing it in case
of an error condition. This should fix a problem reported
by Dan Carosone using cdrecord on an i386 MP kernel.
uvm_fault(): Case1B -- Lock the new anon afer allocating it, and unlock
it later when we unlock the old anon.
Case2 -- Lock the new anon after allocating it, and unlock
it later by passing it to uvmfault_unlockall() (we set anon
to NULL if we're not doing a promote fault).
pending i/os to complete before returning even if PGO_CLEANIT is not
specified. this fixes two races:
(1) NFS write rpcs vs. setattr operations which truncate the file.
if the truncate doesn't wait for pending writes to complete then
a later write rpc completion can undo the effect of the truncate.
this problem has been reported by several people.
(2) write i/os in disk-based filesystem vs. the disk block being
freed by a truncation, allocated to a new file, and written
again with different data. if the disk driver reorders the requests
and does the second i/o first, the old data will clobber the new,
corrupting the new file. I haven't heard of anyone experiencing
this problem yet, but it's fixed now anyway.
doesn't have the exec bit set, we need to have PROT_EXEC set
in order for some expected mmap/mprotect behavior to work, so
do the last bit slightly differently: if udv_attach() fails, and
the protection (NOT maxprot) doens't include PROT_EXEC, then clear
PROT_EXEC from maxprot and try udv_attach() again.
Sigh, mmap really needs to be rototilled.
in the mmap() call. maxprot is used to create device mappings,
and always including PROT_EXEC causes the mapping to fail on the Alpha
when mapping a non-RAM offset of /dev/mem (which may be sparse, so
instruction fetch from there is disallowed).
use queue.h macros and KASSERT().
address amap offsets in pages instead of bytes.
make amap_ref() and amap_unref() take an amap, offset and length
instead of a vm_map_entry_t.
improve whitespace and comments.
devices will actually be notified if this is the last close.
this allows raidframe swap devices to be marked clean.
also, move the corresponding vref() into swap_on() for symmetry
and improve some comments.
it and free it as appropriate. Activate p2's new address space once
it references p1's.
- uvm_fork(): Make sure the child's vmspace is NULL before calling
uvmspace_share() (the child doens't have one already in this case).
These changes do not change the behavior for the current use of
uvmspace_share() (vfork(2)), but make it possible for an already
running process (such as a kernel thread) to properly attach to
another process's address space.
to the contents of the hint in the map, and the hint saved in the
map only if the two values match. When an unconditional save is
required, the "check" value passed should be map->hint (and the
compiler will optimize the test away). When deleting a map entry,
the new SAVE_HINT() will only change the hint if the entry being
deleted was the hint value (thus preserving any meaningful hint
that may have been there previously, rather than stomping on it).
- Add a missing hint update when deleting the map entry in
uvm_map_entry_unlink(). This is the fix for kern/11125, from
ITOH Yasufumi <itohy@netbsd.org>.
`struct vmspace' has a new field `vm_minsaddr' which is the user TOS.
PS_STRINGS is deprecated in favor of curproc->p_pstr which is derived
from `vm_minsaddr'.
Bump the kernel version number.
that the page being zero'd was not completed and that page zeroing
should be aborted. This may be used by machine-dependent code doing
slow page access to reduce the latency of running a process that has
become runnable while in the middle of doing a slow page zero.
routine. Works similarly fto pmap_prefer(), but allows callers
to specify a minimum power-of-two alignment of the region.
How we ever got along without this for so long is beyond me.
chs