1. 26 May, 2004 1 commit
  2. 24 May, 2004 3 commits
  3. 23 May, 2004 16 commits
  4. 22 May, 2004 20 commits
    • Linus Torvalds's avatar
      Linux 2.6.7-rc1 · 86042707
      Linus Torvalds authored
      86042707
    • Roland McGrath's avatar
      [PATCH] bogus sigaltstack calls by rt_sigreturn · ce34221e
      Roland McGrath authored
      There is a longstanding bug in the rt_sigreturn system call.
      This exists in both 2.4 and 2.6, and for almost every platform.
      
      I am referring to this code in sys_rt_sigreturn (arch/i386/kernel/signal.c):
      
      	if (__copy_from_user(&st, &frame->uc.uc_stack, sizeof(st)))
      		goto badframe;
      	/* It is more difficult to avoid calling this function than to
      	   call it and ignore errors.  */
      	/*
      	 * THIS CANNOT WORK! "&st" is a kernel address, and "do_sigaltstack()"
      	 * takes a user address (and verifies that it is a user address). End
      	 * result: it does exactly _nothing_.
      	 */
      	do_sigaltstack(&st, NULL, regs->esp);
      
      As the comment says, this is bogus.  On vanilla i386 kernels, this is just
      harmlessly stupid--do_sigaltstack always does nothing and returns -EFAULT.
      
      However this code actually bites users on kernels using Ingo Molnar's 4G/4G
      address space layout changes.  There some kernel stack address might very
      well be a lovely and readable user address as well.  When that happens, we
      make a sigaltstack call with some random buffer, and then the fun begins.
      
      To my knowledge, this has produced trouble in the real world only for 4G
      i386 kernels (RHEL and Fedora "hugemem" kernels) on machines that actually
      have several GB of physical memory (and in programs that are actually using
      sigaltstack and handling a lot of signals).  However, the same clearly
      broken code has been blindly copied to most other architecture ports, and
      off hand I don't know the address space details of any other well enough to
      know if real kernel stack addresses and real user addresses are in fact
      disjoint as they are on i386 when not using the nonstandard 4GB address
      space layout.
      
      The obvious intent of the call being there in the first place is to permit
      a signal handler to diddle its ucontext_t.uc_stack before returning, and
      have this effect a sigaltstack call on the signal handler return.  This is
      not only an optimization vs doing the extra system call, but makes it
      possible to make a sigaltstack change when that handler itself was running
      on the signal stack.  AFAICT this has never actually worked before, so
      certainly noone depends on it.  But the code certainly suggests that
      someone intended at one time for that to be the behavior.  Thus I am
      inclined to fix it so it works in that way, though it has not done so before.
      It would also be reasonable enough to simply rip out the bogus call and not
      have this functionality.
      
      From the current state of code in both 2.4 and 2.6, there is no fathoming
      how this broken code came about.  It's actually much simpler to just make
      it work!  I can only presume that at some point in the past the sigaltstack
      implementation functions were different such that this made sense.  Of the
      few ports I've looked at briefly, only the ppc/pc64 porters (go paulus!)
      actually tried to understand what the i386 code was doing and implemented
      it correctly rather than just carefully transliterating the bug.
      
      The patch below fixes only the i386 and x86_64 versions.  The x86_64
      patches I have not actually tested.  I think each and every arch (except
      ppc and ppc64) need to make the corresponding fixes as well.  Note that
      there is a function to fix for each native arch, and then one for each
      emulation flavor.  The details differ minutely for getting the calls right
      in each emulation flavor, but I think that most or all of the arch's with
      biarch/emulation support have similar enough code that each emulation
      flavor's fix will look very much like the arch/x86_64/ia32/ia32_signal.c
      patch here.
      ce34221e
    • Andrew Morton's avatar
      [PATCH] partial prefetch for vma_prio_tree_next · ad9beb31
      Andrew Morton authored
      From: Rajesh Venkatasubramanian <vrajesh@umich.edu>
      
      This patch adds prefetches for walking a vm_set.list.  Adding prefetches
      for prio tree traversals is tricky and may lead to cache trashing.  So this
      patch just adds prefetches only when walking a vm_set.list.
      
      I haven't done any benchmarks to show that this patch improves performance.
       However, this patch should help to improve performance when vm_set.lists
      are long, e.g., libc.  Since we only prefetch vmas that are guaranteed to
      be used in the near future, this patch should not result in cache trashing,
      theoretically.
      
      I didn't add any NULL checks before prefetching because prefetch.h clearly
      says prefetch(0) is okay.
      ad9beb31
    • Andrew Morton's avatar
      [PATCH] rmap 40 better anon_vma sharing · 17e8935f
      Andrew Morton authored
      From: Hugh Dickins <hugh@veritas.com>
      
      anon_vma rmap will always necessarily be more restrictive about vma merging
      than before: according to the history of the vmas in an mm, they are liable to
      be allocated different anon_vma heads, and from that point on be unmergeable.
      
      Most of the time this doesn't matter at all; but in two cases it may matter.
      One case is that mremap refuses (-EFAULT) to span more than a single vma: so
      it is conceivable that some app has relied on vma merging prior to mremap in
      the past, and will now fail with anon_vma.  Conceivable but unlikely, let's
      cross that bridge if we come to it: and the right answer would be to extend
      mremap, which should not be exporting the kernel's implementation detail of
      vma to user interface.
      
      The other case that matters is when a reasonable repetitive sequence of
      syscalls and faults ends up with a large number of separate unmergeable vmas,
      instead of the single merged vma it could have.
      
      Andrea's mprotect-vma-merging patch fixed some such instances, but left other
      plausible cases unmerged.  There is no perfect solution, and the harder you
      try to allow vmas to be merged, the less efficient anon_vma becomes, in the
      extreme there being one to span the whole address space, from which hangs
      every private vma; but anonmm rmap is clearly superior to that extreme.
      
      Andrea's principle was that neighbouring vmas which could be mprotected into
      mergeable vmas should be allowed to share anon_vma: good insight.  His
      implementation was to arrange this sharing when trying vma merge, but that
      seems to be too early.  This patch sticks to the principle, but implements it
      in anon_vma_prepare, when handling the first write fault on a private vma:
      with better results.  The drawback is that this first write fault needs an
      extra find_vma_prev (whereas prev was already to hand when implementing
      anon_vma sharing at try-to-merge time).
      17e8935f
    • Andrew Morton's avatar
      [PATCH] rmap 39 add anon_vma rmap · 8aa3448c
      Andrew Morton authored
      From: Hugh Dickins <hugh@veritas.com>
      
      Andrea Arcangeli's anon_vma object-based reverse mapping scheme for anonymous
      pages.  Instead of tracking anonymous pages by pte_chains or by mm, this
      tracks them by vma.  But because vmas are frequently split and merged
      (particularly by mprotect), a page cannot point directly to its vma(s), but
      instead to an anon_vma list of those vmas likely to contain the page - a list
      on which vmas can easily be linked and unlinked as they come and go.  The vmas
      on one list are all related, either by forking or by splitting.
      
      This has three particular advantages over anonmm: that it can cope
      effortlessly with mremap moves; and no longer needs page_table_lock to protect
      an mm's vma tree, since try_to_unmap finds vmas via page -> anon_vma -> vma
      instead of using find_vma; and should use less cpu for swapout since it can
      locate its anonymous vmas more quickly.
      
      It does have disadvantages too: a lot more change in mmap.c to deal with
      anon_vmas, though small straightforward additions now that the vma merging has
      been refactored there; more lowmem needed for each anon_vma and vma structure;
      an additional restriction on the merging of vmas (cannot be merged if already
      assigned different anon_vmas, since then their pages will be pointing to
      different heads).
      
      (There would be no need to enlarge the vma structure if anonymous pages
      belonged only to anonymous vmas; but private file mappings accumulate
      anonymous pages by copy-on-write, so need to be listed in both anon_vma and
      prio_tree at the same time.  A different implementation could avoid that by
      using anon_vmas only for purely anonymous vmas, and use the existing prio_tree
      to locate cow pages - but that would involve a long search for each single
      private copy, probably not a good idea.)
      
      Where before the vm_pgoff of a purely anonymous (not file-backed) vma was
      meaningless, now it represents the virtual start address at which that vma is
      mapped - which the standard file pgoff manipulations treat linearly as vmas
      are split and merged.  But if mremap moves the vma, then it generally carries
      its original vm_pgoff to the new location, so pages shared with the old
      location can still be found.  Magic.
      
      Hugh has massaged it somewhat: building on the earlier rmap patches, this
      patch is a fifth of the size of Andrea's original anon_vma patch.  Please note
      that this posting will be his first sight of this patch, which he may or may
      not approve.
      8aa3448c
    • Andrew Morton's avatar
      [PATCH] rmap 38 remove anonmm rmap · a89cd0f0
      Andrew Morton authored
      From: Hugh Dickins <hugh@veritas.com>
      
      Before moving on to anon_vma rmap, remove now what's peculiar to anonmm rmap:
      the anonmm handling and the mremap move cows.  Temporarily reduce
      page_referenced_anon and try_to_unmap_anon to stubs, so a kernel built with
      this patch will not swap anonymous at all.
      a89cd0f0
    • Andrew Morton's avatar
      [PATCH] rmap 37 page_add_anon_rmap vma · e1fd9cc9
      Andrew Morton authored
      From: Hugh Dickins <hugh@veritas.com>
      
      Silly final patch for anonmm rmap: change page_add_anon_rmap's mm arg to vma
      arg like anon_vma rmap, to smooth the transition between them.
      e1fd9cc9
    • Andrew Morton's avatar
      [PATCH] rmap 36 mprotect use vma_merge · 2b2e2a36
      Andrew Morton authored
      From: Hugh Dickins <hugh@veritas.com>
      
      Earlier on, in 2.6.6, we took the vma merging code out of mremap.c and let it
      rely on vma_merge instead (via copy_vma).  Now take the vma merging code out
      of mprotect.c and let it rely on vma_merge too: so vma_merge becomes the sole
      vma merging engine.  The fruit of this consolidation is that mprotect now
      merges file-backed vmas naturally.  Make this change now because anon_vma will
      complicate the vma merging rules, let's keep them all in one place.
      
      vma_merge remains where the decisions are made, whether to merge with prev
      and/or next; but now [addr,end) may be the latter part of prev, or first part
      or whole of next, whereas before it was always a new area.
      
      vma_adjust carries out vma_merge's decision, but when sliding the boundary
      between vma and next, must temporarily remove next from the prio_tree too. 
      And it turned out (by oops) to have a surer idea of whether next needs to be
      removed than vma_merge, so the fput and freeing moves into vma_adjust.
      
      Too much decipherment of what's going on at the start of vma_adjust?  Yes, and
      there's a delicate assumption that you may use vma_adjust in sliding a
      boundary, or splitting in two, or growing a vma (mremap uses it in that way),
      but not for simply shrinking a vma.  Which is so, and must be so (how could
      pages mapped in the part to go, be zapped without first splitting?), but would
      feel better with some protection.
      
      __vma_unlink can then be moved from mm.h to mmap.c, and mm.h's more misleading
      than helpful can_vma_merge is deleted.
      2b2e2a36
    • Andrew Morton's avatar
      [PATCH] rmap 35 mmap.c cleanups · 06ecc0db
      Andrew Morton authored
      From: Hugh Dickins <hugh@veritas.com>
      
      Before some real vma_merge work in mmap.c in the next patch, a patch of
      miscellaneous cleanups to cut down the noise:
      
      - remove rb_parent arg from vma_merge: mm->mmap can do that case
      - scatter pgoff_t around to ingratiate myself with the boss
      - reorder is_mergeable_vma tests, vm_ops->close is least likely
      - can_vma_merge_before take combined pgoff+pglen arg (from Andrea)
      - rearrange do_mmap_pgoff's ever-confusing anonymous flags switch
      - comment do_mmap_pgoff's mysterious (vm_flags & VM_SHARED) test
      - fix ISO C90 warning on browse_rb if building with DEBUG_MM_RB
      - stop that long MNT_NOEXEC line wrapping
      
      Yes, buried in amidst these is indeed one pgoff replaced by "next->vm_pgoff -
      pglen" (reverting a mod of mine which took pgoff supplied by user too
      seriously in the anon case), and another pgoff replaced by 0 (reverting
      anon_vma mod which crept in with NUMA API): neither of them really matters,
      except perhaps in /proc/pid/maps.
      06ecc0db
    • Andrew Morton's avatar
      [PATCH] rmap 34 vm_flags page_table_lock · 4877b14f
      Andrew Morton authored
      From: Hugh Dickins <hugh@veritas.com>
      
      First of a batch of seven rmap patches, based on 2.6.6-mm3.  Probably the
      final batch: remaining issues outstanding can have isolated patches.  The
      first half of the batch is good for anonmm or anon_vma, the second half of the
      batch replaces my anonmm rmap by Andrea's anon_vma rmap.
      
      Judge for yourselves which you prefer.  I do think I was wrong to call
      anon_vma more complex than anonmm (its lists are easier to understand than my
      refcounting), and I'm happy with its vma merging after the last patch.  It
      just comes down to whether we can spare the extra 24 bytes (maximum, on
      32-bit) per vma for its advantages in swapout and mremap.
      
      rmap 34 vm_flags page_table_lock
      
      Why do we guard vm_flags mods with page_table_lock when it's already
      down_write guarded by mmap_sem?  There's probably a historical reason, but no
      sign of any need for it now.  Andrea added a comment and removed the instance
      from mprotect.c, Hugh plagiarized his comment and removed the instances from
      madvise.c and mlock.c.  Huge leap in scalability...  not expected; but this
      should stop people asking why those spinlocks.
      4877b14f
    • Andrew Morton's avatar
      [PATCH] rmap 33 install_arg_page vma · 114c71ee
      Andrew Morton authored
      From: Hugh Dickins <hugh@veritas.com>
      
      anon_vma will need to pass vma to put_dirty_page, so change it and its
      various callers (setup_arg_pages and its 32-on-64-bit arch variants); and
      please, let's rename it to install_arg_page.
      
      Earlier attempt to do this (rmap 26 __setup_arg_pages) tried to clean up
      those callers instead, but failed to boot: so now apply rmap 27's memset
      initialization of vmas to these callers too; which relieves them from
      needing the recently included linux/mempolicy.h.
      
      While there, moved install_arg_page's flush_dcache_page up before
      page_table_lock - doesn't in fact matter at all, just saves one worry when
      researching flush_dcache_page locking constraints.
      114c71ee
    • Andrew Morton's avatar
      [PATCH] rmap 32 zap_pmd_range wrap · 5911438d
      Andrew Morton authored
      From: Hugh Dickins <hugh@veritas.com>
      
      From: Andrea Arcangeli <andrea@suse.de>
      
      zap_pmd_range, alone of all those page_range loops, lacks the check for
      whether address wrapped.  Hugh is in doubt as to whether this makes any
      difference to any config on any arch, but eager to fix the odd one out.
      5911438d
    • Andrew Morton's avatar
      [PATCH] rmap 31 unlikely bad memory · 68c45e43
      Andrew Morton authored
      From: Hugh Dickins <hugh@veritas.com>
      
      From: Andrea Arcangeli <andrea@suse.de>
      
      Sprinkle unlikelys throughout mm/memory.c, wherever we see a pgd_bad or a
      pmd_bad; likely or unlikely on pte_same or !pte_same.  Put the jump in the
      error return from do_no_page, not in the fast path.
      68c45e43
    • Andrew Morton's avatar
      [PATCH] rmap 30 fix bad mapcount · d321a42d
      Andrew Morton authored
      From: Hugh Dickins <hugh@veritas.com>
      
      From: Andrea Arcangeli <andrea@suse.de>
      
      page_alloc.c's bad_page routine should reset a bad mapcount; and it's more
      revealing to show the bad mapcount than just the boolean mapped.
      d321a42d
    • Andrew Morton's avatar
      [PATCH] rmap 29 VM_RESERVED safety · c3a17613
      Andrew Morton authored
      From: Hugh Dickins <hugh@veritas.com>
      
      From: Andrea Arcangeli <andrea@suse.de>
      
      Set VM_RESERVED in videobuf_mmap_mapper, to warn do_no_page and swapout not to
      worry about its pages.  Set VM_RESERVED in ia64_elf32_init, it too provides an
      unusual nopage which might surprise higher level checks.  Future safety: they
      don't actually pose a problem in this current tree.
      c3a17613
    • Andrew Morton's avatar
      [PATCH] rmap 28 remove_vm_struct · bbdaef5f
      Andrew Morton authored
      From: Hugh Dickins <hugh@veritas.com>
      
      The callers of remove_shared_vm_struct then proceed to do several more
      identical things: gather them together in remove_vm_struct.
      bbdaef5f
    • Andrew Morton's avatar
      [PATCH] rmap 27 memset 0 vma · c8ba2065
      Andrew Morton authored
      From: Hugh Dickins <hugh@veritas.com>
      
      We're NULLifying more and more fields when initializing a vma
      (mpol_set_vma_default does that too, if configured to do anything).  Now use
      memset to avoid specifying fields, and save a little code too.
      
      (Yes, I realize anon_vma will want to set vm_pgoff non-0, but I think that
      will be better handled at the core, since anon vm_pgoff is negotiable up until
      an anon_vma is actually assigned.)
      c8ba2065
    • Andrew Morton's avatar
      [PATCH] rmap 24 no rmap fastcalls · ee7baa35
      Andrew Morton authored
      From: Hugh Dickins <hugh@veritas.com>
      
      I like CONFIG_REGPARM, even when it's forced on: because it's easy to force
      off for debugging - easier than editing out scattered fastcalls.  Plus I've
      never understood why we make function foo a fastcall, but function bar not.
      Remove fastcall directives from rmap.  And fix comment about mremap_moved
      race: it only applies to anon pages.
      ee7baa35
    • Andrew Morton's avatar
      [PATCH] rmap 23 empty flush_dcache_mmap_lock · 4a72e942
      Andrew Morton authored
      From: Hugh Dickins <hugh@veritas.com>
      
      Most architectures (like i386) do nothing in flush_dcache_page, or don't scan
      i_mmap in flush_dcache_page, so don't need flush_dcache_mmap_lock to do
      anything: define it and flush_dcache_mmap_unlock away.  Noticed arm26, cris,
      h8300 still defining flush_page_to_ram: delete it again.
      4a72e942
    • Andrew Morton's avatar
      [PATCH] rmap 22 flush_dcache_mmap_lock · 16ceff2d
      Andrew Morton authored
      From: Hugh Dickins <hugh@veritas.com>
      
      arm and parisc __flush_dcache_page have been scanning the i_mmap(_shared) list
      without locking or disabling preemption.  That may be even more unsafe now
      it's a prio tree instead of a list.
      
      It looks like we cannot use i_shared_lock for this protection: most uses of
      flush_dcache_page are okay, and only one would need lock ordering fixed
      (get_user_pages holds page_table_lock across flush_dcache_page); but there's a
      few (e.g.  in net and ntfs) which look as if they're using it in I/O
      completion - and it would be restrictive to disallow it there.
      
      So, on arm and parisc only, define flush_dcache_mmap_lock(mapping) as
      spin_lock_irq(&(mapping)->tree_lock); on i386 (and other arches left to the
      next patch) define it away to nothing; and use where needed.
      
      While updating locking hierarchy in filemap.c, remove two layers of the fossil
      record from add_to_page_cache comment: no longer used for swap.
      
      I believe all the #includes will work out, but have only built i386.  I can
      see several things about this patch which might cause revulsion: the name
      flush_dcache_mmap_lock?  the reuse of the page radix_tree's tree_lock for this
      different purpose?  spin_lock_irqsave instead?  can't we somehow get
      i_shared_lock to handle the problem?
      16ceff2d