1. 11 Dec, 2009 5 commits
  2. 24 Sep, 2009 1 commit
  3. 22 Sep, 2009 2 commits
    • Hugh Dickins's avatar
      ksm: mremap use err from ksm_madvise · 7103ad32
      Hugh Dickins authored
      
      
      mremap move's use of ksm_madvise() was assuming -ENOMEM on failure,
      because ksm_madvise used to say -EAGAIN for that; but ksm_madvise now says
      -ENOMEM (letting madvise convert that to -EAGAIN), and can also say
      -ERESTARTSYS when signalled: so pass the error from ksm_madvise.
      Signed-off-by: default avatarHugh Dickins <hugh.dickins@tiscali.co.uk>
      Acked-by: default avatarIzik Eidus <ieidus@redhat.com>
      Cc: Andrea Arcangeli <aarcange@redhat.com>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      7103ad32
    • Hugh Dickins's avatar
      ksm: prevent mremap move poisoning · 1ff82995
      Hugh Dickins authored
      
      
      KSM's scan allows for user pages to be COWed or unmapped at any time,
      without requiring any notification.  But its stable tree does assume that
      when it finds a KSM page where it placed a KSM page, then it is the same
      KSM page that it placed there.
      
      mremap move could break that assumption: if an area containing a KSM page
      was unmapped, then an area containing a different KSM page was moved with
      mremap into the place of the original, before KSM's scan came around to
      notice.  That could then poison a node of the stable tree, so that memcmps
      would "lie" and upset the ordering of the tree.
      
      Probably noone will ever need mremap move on a VM_MERGEABLE area; except
      that prohibiting it would make trouble for schemes in which we try making
      everything VM_MERGEABLE e.g.  for testing: an mremap which normally works
      would then fail mysteriously.
      
      There's no need to go to any trouble, such as re-sorting KSM's list of
      rmap_items to match the new layout: simply unmerge the area to COW all its
      KSM pages before moving, but leave VM_MERGEABLE on so that they're
      remerged later.
      Signed-off-by: default avatarHugh Dickins <hugh.dickins@tiscali.co.uk>
      Signed-off-by: default avatarChris Wright <chrisw@redhat.com>
      Signed-off-by: default avatarIzik Eidus <ieidus@redhat.com>
      Cc: Andrea Arcangeli <aarcange@redhat.com>
      Cc: Rik van Riel <riel@redhat.com>
      Cc: Wu Fengguang <fengguang.wu@intel.com>
      Cc: Balbir Singh <balbir@in.ibm.com>
      Cc: Hugh Dickins <hugh.dickins@tiscali.co.uk>
      Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
      Cc: Lee Schermerhorn <lee.schermerhorn@hp.com>
      Cc: Avi Kivity <avi@redhat.com>
      Cc: Nick Piggin <nickpiggin@yahoo.com.au>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      1ff82995
  4. 14 Jan, 2009 2 commits
  5. 06 Jan, 2009 1 commit
  6. 20 Oct, 2008 1 commit
  7. 28 Jul, 2008 1 commit
    • Andrea Arcangeli's avatar
      mmu-notifiers: core · cddb8a5c
      Andrea Arcangeli authored
      
      
      With KVM/GFP/XPMEM there isn't just the primary CPU MMU pointing to pages.
       There are secondary MMUs (with secondary sptes and secondary tlbs) too.
      sptes in the kvm case are shadow pagetables, but when I say spte in
      mmu-notifier context, I mean "secondary pte".  In GRU case there's no
      actual secondary pte and there's only a secondary tlb because the GRU
      secondary MMU has no knowledge about sptes and every secondary tlb miss
      event in the MMU always generates a page fault that has to be resolved by
      the CPU (this is not the case of KVM where the a secondary tlb miss will
      walk sptes in hardware and it will refill the secondary tlb transparently
      to software if the corresponding spte is present).  The same way
      zap_page_range has to invalidate the pte before freeing the page, the spte
      (and secondary tlb) must also be invalidated before any page is freed and
      reused.
      
      Currently we take a page_count pin on every page mapped by sptes, but that
      means the pages can't be swapped whenever they're mapped by any spte
      because they're part of the guest working set.  Furthermore a spte unmap
      event can immediately lead to a page to be freed when the pin is released
      (so requiring the same complex and relatively slow tlb_gather smp safe
      logic we have in zap_page_range and that can be avoided completely if the
      spte unmap event doesn't require an unpin of the page previously mapped in
      the secondary MMU).
      
      The mmu notifiers allow kvm/GRU/XPMEM to attach to the tsk->mm and know
      when the VM is swapping or freeing or doing anything on the primary MMU so
      that the secondary MMU code can drop sptes before the pages are freed,
      avoiding all page pinning and allowing 100% reliable swapping of guest
      physical address space.  Furthermore it avoids the code that teardown the
      mappings of the secondary MMU, to implement a logic like tlb_gather in
      zap_page_range that would require many IPI to flush other cpu tlbs, for
      each fixed number of spte unmapped.
      
      To make an example: if what happens on the primary MMU is a protection
      downgrade (from writeable to wrprotect) the secondary MMU mappings will be
      invalidated, and the next secondary-mmu-page-fault will call
      get_user_pages and trigger a do_wp_page through get_user_pages if it
      called get_user_pages with write=1, and it'll re-establishing an updated
      spte or secondary-tlb-mapping on the copied page.  Or it will setup a
      readonly spte or readonly tlb mapping if it's a guest-read, if it calls
      get_user_pages with write=0.  This is just an example.
      
      This allows to map any page pointed by any pte (and in turn visible in the
      primary CPU MMU), into a secondary MMU (be it a pure tlb like GRU, or an
      full MMU with both sptes and secondary-tlb like the shadow-pagetable layer
      with kvm), or a remote DMA in software like XPMEM (hence needing of
      schedule in XPMEM code to send the invalidate to the remote node, while no
      need to schedule in kvm/gru as it's an immediate event like invalidating
      primary-mmu pte).
      
      At least for KVM without this patch it's impossible to swap guests
      reliably.  And having this feature and removing the page pin allows
      several other optimizations that simplify life considerably.
      
      Dependencies:
      
      1) mm_take_all_locks() to register the mmu notifier when the whole VM
         isn't doing anything with "mm".  This allows mmu notifier users to keep
         track if the VM is in the middle of the invalidate_range_begin/end
         critical section with an atomic counter incraese in range_begin and
         decreased in range_end.  No secondary MMU page fault is allowed to map
         any spte or secondary tlb reference, while the VM is in the middle of
         range_begin/end as any page returned by get_user_pages in that critical
         section could later immediately be freed without any further
         ->invalidate_page notification (invalidate_range_begin/end works on
         ranges and ->invalidate_page isn't called immediately before freeing
         the page).  To stop all page freeing and pagetable overwrites the
         mmap_sem must be taken in write mode and all other anon_vma/i_mmap
         locks must be taken too.
      
      2) It'd be a waste to add branches in the VM if nobody could possibly
         run KVM/GRU/XPMEM on the kernel, so mmu notifiers will only enabled if
         CONFIG_KVM=m/y.  In the current kernel kvm won't yet take advantage of
         mmu notifiers, but this already allows to compile a KVM external module
         against a kernel with mmu notifiers enabled and from the next pull from
         kvm.git we'll start using them.  And GRU/XPMEM will also be able to
         continue the development by enabling KVM=m in their config, until they
         submit all GRU/XPMEM GPLv2 code to the mainline kernel.  Then they can
         also enable MMU_NOTIFIERS in the same way KVM does it (even if KVM=n).
         This guarantees nobody selects MMU_NOTIFIER=y if KVM and GRU and XPMEM
         are all =n.
      
      The mmu_notifier_register call can fail because mm_take_all_locks may be
      interrupted by a signal and return -EINTR.  Because mmu_notifier_reigster
      is used when a driver startup, a failure can be gracefully handled.  Here
      an example of the change applied to kvm to register the mmu notifiers.
      Usually when a driver startups other allocations are required anyway and
      -ENOMEM failure paths exists already.
      
       struct  kvm *kvm_arch_create_vm(void)
       {
              struct kvm *kvm = kzalloc(sizeof(struct kvm), GFP_KERNEL);
      +       int err;
      
              if (!kvm)
                      return ERR_PTR(-ENOMEM);
      
              INIT_LIST_HEAD(&kvm->arch.active_mmu_pages);
      
      +       kvm->arch.mmu_notifier.ops = &kvm_mmu_notifier_ops;
      +       err = mmu_notifier_register(&kvm->arch.mmu_notifier, current->mm);
      +       if (err) {
      +               kfree(kvm);
      +               return ERR_PTR(err);
      +       }
      +
              return kvm;
       }
      
      mmu_notifier_unregister returns void and it's reliable.
      
      The patch also adds a few needed but missing includes that would prevent
      kernel to compile after these changes on non-x86 archs (x86 didn't need
      them by luck).
      
      [akpm@linux-foundation.org: coding-style fixes]
      [akpm@linux-foundation.org: fix mm/filemap_xip.c build]
      [akpm@linux-foundation.org: fix mm/mmu_notifier.c build]
      Signed-off-by: default avatarAndrea Arcangeli <andrea@qumranet.com>
      Signed-off-by: default avatarNick Piggin <npiggin@suse.de>
      Signed-off-by: default avatarChristoph Lameter <cl@linux-foundation.org>
      Cc: Jack Steiner <steiner@sgi.com>
      Cc: Robin Holt <holt@sgi.com>
      Cc: Nick Piggin <npiggin@suse.de>
      Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
      Cc: Kanoj Sarcar <kanojsarcar@yahoo.com>
      Cc: Roland Dreier <rdreier@cisco.com>
      Cc: Steve Wise <swise@opengridcomputing.com>
      Cc: Avi Kivity <avi@qumranet.com>
      Cc: Hugh Dickins <hugh@veritas.com>
      Cc: Rusty Russell <rusty@rustcorp.com.au>
      Cc: Anthony Liguori <aliguori@us.ibm.com>
      Cc: Chris Wright <chrisw@redhat.com>
      Cc: Marcelo Tosatti <marcelo@kvack.org>
      Cc: Eric Dumazet <dada1@cosmosbay.com>
      Cc: "Paul E. McKenney" <paulmck@us.ibm.com>
      Cc: Izik Eidus <izike@qumranet.com>
      Cc: Anthony Liguori <aliguori@us.ibm.com>
      Cc: Rik van Riel <riel@redhat.com>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      cddb8a5c
  8. 18 Oct, 2007 1 commit
  9. 19 Jul, 2007 1 commit
  10. 12 Jul, 2007 1 commit
    • Eric Paris's avatar
      security: Protection for exploiting null dereference using mmap · ed032189
      Eric Paris authored
      
      
      Add a new security check on mmap operations to see if the user is attempting
      to mmap to low area of the address space.  The amount of space protected is
      indicated by the new proc tunable /proc/sys/vm/mmap_min_addr and defaults to
      0, preserving existing behavior.
      
      This patch uses a new SELinux security class "memprotect."  Policy already
      contains a number of allow rules like a_t self:process * (unconfined_t being
      one of them) which mean that putting this check in the process class (its
      best current fit) would make it useless as all user processes, which we also
      want to protect against, would be allowed. By taking the memprotect name of
      the new class it will also make it possible for us to move some of the other
      memory protect permissions out of 'process' and into the new class next time
      we bump the policy version number (which I also think is a good future idea)
      Acked-by: default avatarStephen Smalley <sds@tycho.nsa.gov>
      Acked-by: default avatarChris Wright <chrisw@sous-sol.org>
      Signed-off-by: default avatarEric Paris <eparis@redhat.com>
      Signed-off-by: default avatarJames Morris <jmorris@namei.org>
      ed032189
  11. 30 Jan, 2007 1 commit
    • Hugh Dickins's avatar
      [PATCH] mm: mremap correct rmap accounting · 701dfbc1
      Hugh Dickins authored
      
      
      Nick Piggin points out that page accounting on MIPS multiple ZERO_PAGEs
      is not maintained by its move_pte, and could lead to freeing a ZERO_PAGE.
      
      Instead of complicating that move_pte, just forget the minor optimization
      when mremapping, and change the one thing which needed it for correctness
      - filemap_xip use ZERO_PAGE(0) throughout instead of according to address.
      
      [ "There is no block device driver one could use for XIP on mips
         platforms" - Carsten Otte ]
      Signed-off-by: default avatarHugh Dickins <hugh@veritas.com>
      Cc: Nick Piggin <nickpiggin@yahoo.com.au>
      Cc: Andrew Morton <akpm@osdl.org>
      Cc: Ralf Baechle <ralf@linux-mips.org>
      Cc: Carsten Otte <cotte@de.ibm.com>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      701dfbc1
  12. 01 Oct, 2006 1 commit
    • Zachary Amsden's avatar
      [PATCH] paravirt: lazy mmu mode hooks.patch · 6606c3e0
      Zachary Amsden authored
      
      
      Implement lazy MMU update hooks which are SMP safe for both direct and shadow
      page tables.  The idea is that PTE updates and page invalidations while in
      lazy mode can be batched into a single hypercall.  We use this in VMI for
      shadow page table synchronization, and it is a win.  It also can be used by
      PPC and for direct page tables on Xen.
      
      For SMP, the enter / leave must happen under protection of the page table
      locks for page tables which are being modified.  This is because otherwise,
      you end up with stale state in the batched hypercall, which other CPUs can
      race ahead of.  Doing this under the protection of the locks guarantees the
      synchronization is correct, and also means that spurious faults which are
      generated during this window by remote CPUs are properly handled, as the page
      fault handler must re-check the PTE under protection of the same lock.
      Signed-off-by: default avatarZachary Amsden <zach@vmware.com>
      Signed-off-by: default avatarJeremy Fitzhardinge <jeremy@xensource.com>
      Cc: Rusty Russell <rusty@rustcorp.com.au>
      Cc: Andi Kleen <ak@suse.de>
      Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
      6606c3e0
  13. 03 Jul, 2006 1 commit
  14. 12 Jan, 2006 1 commit
  15. 16 Dec, 2005 1 commit
  16. 30 Oct, 2005 7 commits
    • Hugh Dickins's avatar
      [PATCH] mm: split page table lock · 4c21e2f2
      Hugh Dickins authored
      
      
      Christoph Lameter demonstrated very poor scalability on the SGI 512-way, with
      a many-threaded application which concurrently initializes different parts of
      a large anonymous area.
      
      This patch corrects that, by using a separate spinlock per page table page, to
      guard the page table entries in that page, instead of using the mm's single
      page_table_lock.  (But even then, page_table_lock is still used to guard page
      table allocation, and anon_vma allocation.)
      
      In this implementation, the spinlock is tucked inside the struct page of the
      page table page: with a BUILD_BUG_ON in case it overflows - which it would in
      the case of 32-bit PA-RISC with spinlock debugging enabled.
      
      Splitting the lock is not quite for free: another cacheline access.  Ideally,
      I suppose we would use split ptlock only for multi-threaded processes on
      multi-cpu machines; but deciding that dynamically would have its own costs.
      So for now enable it by config, at some number of cpus - since the Kconfig
      language doesn't support inequalities, let preprocessor compare that with
      NR_CPUS.  But I don't think it's worth being user-configurable: for good
      testing of both split and unsplit configs, split now at 4 cpus, and perhaps
      change that to 8 later.
      
      There is a benefit even for singly threaded processes: kswapd can be attacking
      one part of the mm while another part is busy faulting.
      Signed-off-by: default avatarHugh Dickins <hugh@veritas.com>
      Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
      4c21e2f2
    • Hugh Dickins's avatar
      [PATCH] mm: ptd_alloc take ptlock · c74df32c
      Hugh Dickins authored
      
      
      Second step in pushing down the page_table_lock.  Remove the temporary
      bridging hack from __pud_alloc, __pmd_alloc, __pte_alloc: expect callers not
      to hold page_table_lock, whether it's on init_mm or a user mm; take
      page_table_lock internally to check if a racing task already allocated.
      
      Convert their callers from common code.  But avoid coming back to change them
      again later: instead of moving the spin_lock(&mm->page_table_lock) down,
      switch over to new macros pte_alloc_map_lock and pte_unmap_unlock, which
      encapsulate the mapping+locking and unlocking+unmapping together, and in the
      end may use alternatives to the mm page_table_lock itself.
      
      These callers all hold mmap_sem (some exclusively, some not), so at no level
      can a page table be whipped away from beneath them; and pte_alloc uses the
      "atomic" pmd_present to test whether it needs to allocate.  It appears that on
      all arches we can safely descend without page_table_lock.
      Signed-off-by: default avatarHugh Dickins <hugh@veritas.com>
      Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
      c74df32c
    • Hugh Dickins's avatar
      [PATCH] mm: ptd_alloc inline and out · 1bb3630e
      Hugh Dickins authored
      
      
      It seems odd to me that, whereas pud_alloc and pmd_alloc test inline, only
      calling out-of-line __pud_alloc __pmd_alloc if allocation needed,
      pte_alloc_map and pte_alloc_kernel are entirely out-of-line.  Though it does
      add a little to kernel size, change them to macros testing inline, calling
      __pte_alloc or __pte_alloc_kernel to allocate out-of-line.  Mark none of them
      as fastcalls, leave that to CONFIG_REGPARM or not.
      
      It also seems more natural for the out-of-line functions to leave the offset
      calculation and map to the inline, which has to do it anyway for the common
      case.  At least mremap move wants __pte_alloc without _map.
      
      Macros rather than inline functions, certainly to avoid the header file issues
      which arise from CONFIG_HIGHPTE needing kmap_types.h, but also in case any
      architectures I haven't built would have other such problems.
      Signed-off-by: default avatarHugh Dickins <hugh@veritas.com>
      Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
      1bb3630e
    • Hugh Dickins's avatar
      [PATCH] mm: update_hiwaters just in time · 365e9c87
      Hugh Dickins authored
      
      
      update_mem_hiwater has attracted various criticisms, in particular from those
      concerned with mm scalability.  Originally it was called whenever rss or
      total_vm got raised.  Then many of those callsites were replaced by a timer
      tick call from account_system_time.  Now Frank van Maarseveen reports that to
      be found inadequate.  How about this?  Works for Frank.
      
      Replace update_mem_hiwater, a poor combination of two unrelated ops, by macros
      update_hiwater_rss and update_hiwater_vm.  Don't attempt to keep
      mm->hiwater_rss up to date at timer tick, nor every time we raise rss (usually
      by 1): those are hot paths.  Do the opposite, update only when about to lower
      rss (usually by many), or just before final accounting in do_exit.  Handle
      mm->hiwater_vm in the same way, though it's much less of an issue.  Demand
      that whoever collects these hiwater statistics do the work of taking the
      maximum with rss or total_vm.
      
      And there has been no collector of these hiwater statistics in the tree.  The
      new convention needs an example, so match Frank's usage by adding a VmPeak
      line above VmSize to /proc/<pid>/status, and also a VmHWM line above VmRSS
      (High-Water-Mark or High-Water-Memory).
      
      There was a particular anomaly during mremap move, that hiwater_vm might be
      captured too high.  A fleeting such anomaly remains, but it's quickly
      corrected now, whereas before it would stick.
      
      What locking?  None: if the app is racy then these statistics will be racy,
      it's not worth any overhead to make them exact.  But whenever it suits,
      hiwater_vm is updated under exclusive mmap_sem, and hiwater_rss under
      page_table_lock (for now) or with preemption disabled (later on): without
      going to any trouble, minimize the time between reading current values and
      updating, to minimize those occasions when a racing thread bumps a count up
      and back down in between.
      Signed-off-by: default avatarHugh Dickins <hugh@veritas.com>
      Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
      365e9c87
    • Hugh Dickins's avatar
      [PATCH] mm: do_mremap current mm · d0de32d9
      Hugh Dickins authored
      
      
      Cleanup: relieve do_mremap from its surfeit of current->mms.
      Signed-off-by: default avatarHugh Dickins <hugh@veritas.com>
      Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
      d0de32d9
    • Hugh Dickins's avatar
      [PATCH] mm: move_page_tables by extents · 7be7a546
      Hugh Dickins authored
      
      
      Speeding up mremap's moving of ptes has never been a priority, but the locking
      will get more complicated shortly, and is already too baroque.
      
      Scrap the current one-by-one moving, do an extent at a time: curtailed by end
      of src and dst pmds (have to use PMD_SIZE: the way pmd_addr_end gets elided
      doesn't match this usage), and by latency considerations.
      
      One nice property of the old method is lost: it never allocated a page table
      unless absolutely necessary, so you could free empty page tables by mremapping
      to and fro.  Whereas this way, it allocates a dst table wherever there was a
      src table.  I keep diving in to reinstate the old behaviour, then come out
      preferring not to clutter how it now is.
      Signed-off-by: default avatarHugh Dickins <hugh@veritas.com>
      Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
      7be7a546
    • Hugh Dickins's avatar
      [PATCH] mm: vm_stat_account unshackled · ab50b8ed
      Hugh Dickins authored
      
      
      The original vm_stat_account has fallen into disuse, with only one user, and
      only one user of vm_stat_unaccount.  It's easier to keep track if we convert
      them all to __vm_stat_account, then free it from its __shackles.
      Signed-off-by: default avatarHugh Dickins <hugh@veritas.com>
      Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
      ab50b8ed
  17. 28 Sep, 2005 1 commit
    • Nick Piggin's avatar
      [PATCH] mm: move_pte to remap ZERO_PAGE · 8b1f3124
      Nick Piggin authored
      
      
      Move the ZERO_PAGE remapping complexity to the move_pte macro in
      asm-generic, have it conditionally depend on
      __HAVE_ARCH_MULTIPLE_ZERO_PAGE, which gets defined for MIPS.
      
      For architectures without __HAVE_ARCH_MULTIPLE_ZERO_PAGE, move_pte becomes
      a noop.
      
      From: Hugh Dickins <hugh@veritas.com>
      
      Fix nasty little bug we've missed in Nick's mremap move ZERO_PAGE patch.
      The "pte" at that point may be a swap entry or a pte_file entry: we must
      check pte_present before perhaps corrupting such an entry.
      
      Patch below against 2.6.14-rc2-mm1, but the same bug is in 2.6.14-rc2's
      mm/mremap.c, and more dangerous there since it's affecting all arches: I
      think the safest course is to send Nick's patch and Yoichi's build fix and
      this fix (build tested) on to Linus - so only MIPS can be affected.
      Signed-off-by: default avatarNick Piggin <npiggin@suse.de>
      Signed-off-by: default avatarHugh Dickins <hugh@veritas.com>
      Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
      8b1f3124
  18. 05 Sep, 2005 1 commit
    • Nick Piggin's avatar
      [PATCH] mm: remap ZERO_PAGE mappings · 9a61c349
      Nick Piggin authored
      
      
      filemap_xip's nopage routine maps the ZERO_PAGE into readonly mappings, if it
      has no data page to map there: then if the hole in the file is later filled,
      __xip_unmap uses an rmap technique to replace the ZERO_PAGEs mapped for that
      offset by the newly allocated file page, so that established mappings will see
      the newly written data.
      
      However, on MIPS (alone) there's not one but as many as eight ZERO_PAGEs,
      chosen for coloring by user virtual address; and if mremap has meanwhile been
      used to move a mapping containing a ZERO_PAGE, it will generally not match the
      ZERO_PAGE(address) __xip_unmap is looking for.
      
      To maintain XIP's established mappings correctly on MIPS, we need Nick's fix
      to mremap's move_one_page (originally presented as an optimization), to
      replace the ZERO_PAGE appropriate to the old address by the ZERO_PAGE
      appropriate to the new address.
      
      (But when I first saw this, I was thinking the ZERO_PAGEs themselves would get
      corrupted, very bad.  Now I think it's the other way round, that the
      established mappings will fail to see the newly written data: incorrect, but
      not corrupting everything else.  Whether filemap_xip's technique is generally
      safe, I'd hesitate to say in a hurry: it's interesting, but we've never tried
      to do that in tmpfs.)
      Signed-off-by: default avatarHugh Dickins <hugh@veritas.com>
      Signed-off-by: default avatarNick Piggin <npiggin@suse.de>
      Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
      9a61c349
  19. 04 Aug, 2005 1 commit
  20. 17 May, 2005 1 commit
  21. 01 May, 2005 1 commit
  22. 16 Apr, 2005 1 commit
    • Linus Torvalds's avatar
      Linux-2.6.12-rc2 · 1da177e4
      Linus Torvalds authored
      Initial git repository build. I'm not bothering with the full history,
      even though we have it. We can create a separate "historical" git
      archive of that later if we want to, and in the meantime it's about
      3.2GB when imported into git - space that would just make the early
      git days unnecessarily complicated, when we don't have a lot of good
      infrastructure for it.
      
      Let it rip!
      1da177e4