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Date:      Thu, 28 Aug 2014 01:30:41 -0700
From:      Adrian Chadd <adrian@freebsd.org>
To:        Alan Cox <alc@freebsd.org>
Cc:        "svn-src-head@freebsd.org" <svn-src-head@freebsd.org>, "svn-src-all@freebsd.org" <svn-src-all@freebsd.org>, "src-committers@freebsd.org" <src-committers@freebsd.org>
Subject:   Re: svn commit: r269134 - head/sys/vm
Message-ID:  <CAJ-VmokUPtJQd1_Vp5c%2B0fGvWE_iDHszNGbTnta6VGwFr8oiOQ@mail.gmail.com>
In-Reply-To: <201407261810.s6QIAIIj049439@svn.freebsd.org>
References:  <201407261810.s6QIAIIj049439@svn.freebsd.org>

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Hi Alan!

I just reverted back to the commit before this one and it fixed my MIPS32 boot.

Would you have some time to help me help you figure out why things broke? :)

Thanks!



-a


On 26 July 2014 11:10, Alan Cox <alc@freebsd.org> wrote:
> Author: alc
> Date: Sat Jul 26 18:10:18 2014
> New Revision: 269134
> URL: http://svnweb.freebsd.org/changeset/base/269134
>
> Log:
>   When unwiring a region of an address space, do not assume that the
>   underlying physical pages are mapped by the pmap.  If, for example, the
>   application has performed an mprotect(..., PROT_NONE) on any part of the
>   wired region, then those pages will no longer be mapped by the pmap.
>   So, using the pmap to lookup the wired pages in order to unwire them
>   doesn't always work, and when it doesn't work wired pages are leaked.
>
>   To avoid the leak, introduce and use a new function vm_object_unwire()
>   that locates the wired pages by traversing the object and its backing
>   objects.
>
>   At the same time, switch from using pmap_change_wiring() to the recently
>   introduced function pmap_unwire() for unwiring the region's mappings.
>   pmap_unwire() is faster, because it operates a range of virtual addresses
>   rather than a single virtual page at a time.  Moreover, by operating on
>   a range, it is superpage friendly.  It doesn't waste time performing
>   unnecessary demotions.
>
>   Reported by:  markj
>   Reviewed by:  kib
>   Tested by:    pho, jmg (arm)
>   Sponsored by: EMC / Isilon Storage Division
>
> Modified:
>   head/sys/vm/vm_extern.h
>   head/sys/vm/vm_fault.c
>   head/sys/vm/vm_map.c
>   head/sys/vm/vm_object.c
>   head/sys/vm/vm_object.h
>
> Modified: head/sys/vm/vm_extern.h
> ==============================================================================
> --- head/sys/vm/vm_extern.h     Sat Jul 26 17:59:25 2014        (r269133)
> +++ head/sys/vm/vm_extern.h     Sat Jul 26 18:10:18 2014        (r269134)
> @@ -81,7 +81,6 @@ int vm_fault_hold(vm_map_t map, vm_offse
>      int fault_flags, vm_page_t *m_hold);
>  int vm_fault_quick_hold_pages(vm_map_t map, vm_offset_t addr, vm_size_t len,
>      vm_prot_t prot, vm_page_t *ma, int max_count);
> -void vm_fault_unwire(vm_map_t, vm_offset_t, vm_offset_t, boolean_t);
>  int vm_fault_wire(vm_map_t, vm_offset_t, vm_offset_t, boolean_t);
>  int vm_forkproc(struct thread *, struct proc *, struct thread *, struct vmspace *, int);
>  void vm_waitproc(struct proc *);
>
> Modified: head/sys/vm/vm_fault.c
> ==============================================================================
> --- head/sys/vm/vm_fault.c      Sat Jul 26 17:59:25 2014        (r269133)
> +++ head/sys/vm/vm_fault.c      Sat Jul 26 18:10:18 2014        (r269134)
> @@ -106,6 +106,7 @@ __FBSDID("$FreeBSD$");
>  #define PFFOR 4
>
>  static int vm_fault_additional_pages(vm_page_t, int, int, vm_page_t *, int *);
> +static void vm_fault_unwire(vm_map_t, vm_offset_t, vm_offset_t, boolean_t);
>
>  #define        VM_FAULT_READ_BEHIND    8
>  #define        VM_FAULT_READ_MAX       (1 + VM_FAULT_READ_AHEAD_MAX)
> @@ -1186,7 +1187,7 @@ vm_fault_wire(vm_map_t map, vm_offset_t
>   *
>   *     Unwire a range of virtual addresses in a map.
>   */
> -void
> +static void
>  vm_fault_unwire(vm_map_t map, vm_offset_t start, vm_offset_t end,
>      boolean_t fictitious)
>  {
>
> Modified: head/sys/vm/vm_map.c
> ==============================================================================
> --- head/sys/vm/vm_map.c        Sat Jul 26 17:59:25 2014        (r269133)
> +++ head/sys/vm/vm_map.c        Sat Jul 26 18:10:18 2014        (r269134)
> @@ -132,6 +132,7 @@ static void _vm_map_init(vm_map_t map, p
>      vm_offset_t max);
>  static void vm_map_entry_deallocate(vm_map_entry_t entry, boolean_t system_map);
>  static void vm_map_entry_dispose(vm_map_t map, vm_map_entry_t entry);
> +static void vm_map_entry_unwire(vm_map_t map, vm_map_entry_t entry);
>  #ifdef INVARIANTS
>  static void vm_map_zdtor(void *mem, int size, void *arg);
>  static void vmspace_zdtor(void *mem, int size, void *arg);
> @@ -2393,16 +2394,10 @@ done:
>                     (entry->eflags & MAP_ENTRY_USER_WIRED))) {
>                         if (user_unwire)
>                                 entry->eflags &= ~MAP_ENTRY_USER_WIRED;
> -                       entry->wired_count--;
> -                       if (entry->wired_count == 0) {
> -                               /*
> -                                * Retain the map lock.
> -                                */
> -                               vm_fault_unwire(map, entry->start, entry->end,
> -                                   entry->object.vm_object != NULL &&
> -                                   (entry->object.vm_object->flags &
> -                                   OBJ_FICTITIOUS) != 0);
> -                       }
> +                       if (entry->wired_count == 1)
> +                               vm_map_entry_unwire(map, entry);
> +                       else
> +                               entry->wired_count--;
>                 }
>                 KASSERT((entry->eflags & MAP_ENTRY_IN_TRANSITION) != 0,
>                     ("vm_map_unwire: in-transition flag missing %p", entry));
> @@ -2635,19 +2630,12 @@ done:
>                          * unnecessary.
>                          */
>                         entry->wired_count = 0;
> -               } else {
> -                       if (!user_wire ||
> -                           (entry->eflags & MAP_ENTRY_USER_WIRED) == 0)
> +               } else if (!user_wire ||
> +                   (entry->eflags & MAP_ENTRY_USER_WIRED) == 0) {
> +                       if (entry->wired_count == 1)
> +                               vm_map_entry_unwire(map, entry);
> +                       else
>                                 entry->wired_count--;
> -                       if (entry->wired_count == 0) {
> -                               /*
> -                                * Retain the map lock.
> -                                */
> -                               vm_fault_unwire(map, entry->start, entry->end,
> -                                   entry->object.vm_object != NULL &&
> -                                   (entry->object.vm_object->flags &
> -                                   OBJ_FICTITIOUS) != 0);
> -                       }
>                 }
>         next_entry_done:
>                 KASSERT((entry->eflags & MAP_ENTRY_IN_TRANSITION) != 0,
> @@ -2783,9 +2771,13 @@ vm_map_sync(
>  static void
>  vm_map_entry_unwire(vm_map_t map, vm_map_entry_t entry)
>  {
> -       vm_fault_unwire(map, entry->start, entry->end,
> -           entry->object.vm_object != NULL &&
> -           (entry->object.vm_object->flags & OBJ_FICTITIOUS) != 0);
> +
> +       VM_MAP_ASSERT_LOCKED(map);
> +       KASSERT(entry->wired_count > 0,
> +           ("vm_map_entry_unwire: entry %p isn't wired", entry));
> +       pmap_unwire(map->pmap, entry->start, entry->end);
> +       vm_object_unwire(entry->object.vm_object, entry->offset, entry->end -
> +           entry->start, PQ_ACTIVE);
>         entry->wired_count = 0;
>  }
>
>
> Modified: head/sys/vm/vm_object.c
> ==============================================================================
> --- head/sys/vm/vm_object.c     Sat Jul 26 17:59:25 2014        (r269133)
> +++ head/sys/vm/vm_object.c     Sat Jul 26 18:10:18 2014        (r269134)
> @@ -2202,6 +2202,78 @@ vm_object_set_writeable_dirty(vm_object_
>         vm_object_set_flag(object, OBJ_MIGHTBEDIRTY);
>  }
>
> +/*
> + *     vm_object_unwire:
> + *
> + *     For each page offset within the specified range of the given object,
> + *     find the highest-level page in the shadow chain and unwire it.  A page
> + *     must exist at every page offset, and the highest-level page must be
> + *     wired.
> + */
> +void
> +vm_object_unwire(vm_object_t object, vm_ooffset_t offset, vm_size_t length,
> +    uint8_t queue)
> +{
> +       vm_object_t tobject;
> +       vm_page_t m, tm;
> +       vm_pindex_t end_pindex, pindex, tpindex;
> +       int depth, locked_depth;
> +
> +       KASSERT((offset & PAGE_MASK) == 0,
> +           ("vm_object_unwire: offset is not page aligned"));
> +       KASSERT((length & PAGE_MASK) == 0,
> +           ("vm_object_unwire: length is not a multiple of PAGE_SIZE"));
> +       /* The wired count of a fictitious page never changes. */
> +       if ((object->flags & OBJ_FICTITIOUS) != 0)
> +               return;
> +       pindex = OFF_TO_IDX(offset);
> +       end_pindex = pindex + atop(length);
> +       locked_depth = 1;
> +       VM_OBJECT_RLOCK(object);
> +       m = vm_page_find_least(object, pindex);
> +       while (pindex < end_pindex) {
> +               if (m == NULL || pindex < m->pindex) {
> +                       /*
> +                        * The first object in the shadow chain doesn't
> +                        * contain a page at the current index.  Therefore,
> +                        * the page must exist in a backing object.
> +                        */
> +                       tobject = object;
> +                       tpindex = pindex;
> +                       depth = 0;
> +                       do {
> +                               tpindex +=
> +                                   OFF_TO_IDX(tobject->backing_object_offset);
> +                               tobject = tobject->backing_object;
> +                               KASSERT(tobject != NULL,
> +                                   ("vm_object_unwire: missing page"));
> +                               if ((tobject->flags & OBJ_FICTITIOUS) != 0)
> +                                       goto next_page;
> +                               depth++;
> +                               if (depth == locked_depth) {
> +                                       locked_depth++;
> +                                       VM_OBJECT_RLOCK(tobject);
> +                               }
> +                       } while ((tm = vm_page_lookup(tobject, tpindex)) ==
> +                           NULL);
> +               } else {
> +                       tm = m;
> +                       m = TAILQ_NEXT(m, listq);
> +               }
> +               vm_page_lock(tm);
> +               vm_page_unwire(tm, queue);
> +               vm_page_unlock(tm);
> +next_page:
> +               pindex++;
> +       }
> +       /* Release the accumulated object locks. */
> +       for (depth = 0; depth < locked_depth; depth++) {
> +               tobject = object->backing_object;
> +               VM_OBJECT_RUNLOCK(object);
> +               object = tobject;
> +       }
> +}
> +
>  #include "opt_ddb.h"
>  #ifdef DDB
>  #include <sys/kernel.h>
>
> Modified: head/sys/vm/vm_object.h
> ==============================================================================
> --- head/sys/vm/vm_object.h     Sat Jul 26 17:59:25 2014        (r269133)
> +++ head/sys/vm/vm_object.h     Sat Jul 26 18:10:18 2014        (r269134)
> @@ -291,6 +291,8 @@ void vm_object_shadow (vm_object_t *, vm
>  void vm_object_split(vm_map_entry_t);
>  boolean_t vm_object_sync(vm_object_t, vm_ooffset_t, vm_size_t, boolean_t,
>      boolean_t);
> +void vm_object_unwire(vm_object_t object, vm_ooffset_t offset,
> +    vm_size_t length, uint8_t queue);
>  #endif                         /* _KERNEL */
>
>  #endif                         /* _VM_OBJECT_ */
>



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