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  1. 20 7月, 2007 4 次提交
    • N
      mm: fault feedback #1 · d0217ac0
      由 Nick Piggin 提交于 
      Change ->fault prototype.  We now return an int, which contains
VM_FAULT_xxx code in the low byte, and FAULT_RET_xxx code in the next byte.
 FAULT_RET_ code tells the VM whether a page was found, whether it has been
locked, and potentially other things.  This is not quite the way he wanted
it yet, but that's changed in the next patch (which requires changes to
arch code).

This means we no longer set VM_CAN_INVALIDATE in the vma in order to say
that a page is locked which requires filemap_nopage to go away (because we
can no longer remain backward compatible without that flag), but we were
going to do that anyway.

struct fault_data is renamed to struct vm_fault as Linus asked. address
is now a void __user * that we should firmly encourage drivers not to use
without really good reason.

The page is now returned via a page pointer in the vm_fault struct.
Signed-off-by: NNick Piggin <npiggin@suse.de>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      d0217ac0
    • M
      ocfs2: release page lock before calling ->page_mkwrite · 69676147
      由 Mark Fasheh 提交于 
      __do_fault() was calling ->page_mkwrite() with the page lock held, which
violates the locking rules for that callback.  Release and retake the page
lock around the callback to avoid deadlocking file systems which manually
take it.
Signed-off-by: NMark Fasheh <mark.fasheh@oracle.com>
Cc: Nick Piggin <nickpiggin@yahoo.com.au>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      69676147
    • N
      mm: merge populate and nopage into fault (fixes nonlinear) · 54cb8821
      由 Nick Piggin 提交于 
      Nonlinear mappings are (AFAIKS) simply a virtual memory concept that encodes
the virtual address -> file offset differently from linear mappings.

->populate is a layering violation because the filesystem/pagecache code
should need to know anything about the virtual memory mapping.  The hitch here
is that the ->nopage handler didn't pass down enough information (ie.  pgoff).
 But it is more logical to pass pgoff rather than have the ->nopage function
calculate it itself anyway (because that's a similar layering violation).

Having the populate handler install the pte itself is likewise a nasty thing
to be doing.

This patch introduces a new fault handler that replaces ->nopage and
->populate and (later) ->nopfn.  Most of the old mechanism is still in place
so there is a lot of duplication and nice cleanups that can be removed if
everyone switches over.

The rationale for doing this in the first place is that nonlinear mappings are
subject to the pagefault vs invalidate/truncate race too, and it seemed stupid
to duplicate the synchronisation logic rather than just consolidate the two.

After this patch, MAP_NONBLOCK no longer sets up ptes for pages present in
pagecache.  Seems like a fringe functionality anyway.

NOPAGE_REFAULT is removed.  This should be implemented with ->fault, and no
users have hit mainline yet.

[akpm@linux-foundation.org: cleanup]
[randy.dunlap@oracle.com: doc. fixes for readahead]
[akpm@linux-foundation.org: build fix]
Signed-off-by: NNick Piggin <npiggin@suse.de>
Signed-off-by: NRandy Dunlap <randy.dunlap@oracle.com>
Cc: Mark Fasheh <mark.fasheh@oracle.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      54cb8821
    • N
      mm: fix fault vs invalidate race for linear mappings · d00806b1
      由 Nick Piggin 提交于 
      Fix the race between invalidate_inode_pages and do_no_page.

Andrea Arcangeli identified a subtle race between invalidation of pages from
pagecache with userspace mappings, and do_no_page.

The issue is that invalidation has to shoot down all mappings to the page,
before it can be discarded from the pagecache.  Between shooting down ptes to
a particular page, and actually dropping the struct page from the pagecache,
do_no_page from any process might fault on that page and establish a new
mapping to the page just before it gets discarded from the pagecache.

The most common case where such invalidation is used is in file truncation.
This case was catered for by doing a sort of open-coded seqlock between the
file's i_size, and its truncate_count.

Truncation will decrease i_size, then increment truncate_count before
unmapping userspace pages; do_no_page will read truncate_count, then find the
page if it is within i_size, and then check truncate_count under the page
table lock and back out and retry if it had subsequently been changed (ptl
will serialise against unmapping, and ensure a potentially updated
truncate_count is actually visible).

Complexity and documentation issues aside, the locking protocol fails in the
case where we would like to invalidate pagecache inside i_size.  do_no_page
can come in anytime and filemap_nopage is not aware of the invalidation in
progress (as it is when it is outside i_size).  The end result is that
dangling (->mapping == NULL) pages that appear to be from a particular file
may be mapped into userspace with nonsense data.  Valid mappings to the same
place will see a different page.

Andrea implemented two working fixes, one using a real seqlock, another using
a page->flags bit.  He also proposed using the page lock in do_no_page, but
that was initially considered too heavyweight.  However, it is not a global or
per-file lock, and the page cacheline is modified in do_no_page to increment
_count and _mapcount anyway, so a further modification should not be a large
performance hit.  Scalability is not an issue.

This patch implements this latter approach.  ->nopage implementations return
with the page locked if it is possible for their underlying file to be
invalidated (in that case, they must set a special vm_flags bit to indicate
so).  do_no_page only unlocks the page after setting up the mapping
completely.  invalidation is excluded because it holds the page lock during
invalidation of each page (and ensures that the page is not mapped while
holding the lock).

This also allows significant simplifications in do_no_page, because we have
the page locked in the right place in the pagecache from the start.
Signed-off-by: NNick Piggin <npiggin@suse.de>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      d00806b1
  3. 18 7月, 2007 1 次提交
    • M
      Add __GFP_MOVABLE for callers to flag allocations from high memory that may be migrated · 769848c0
      由 Mel Gorman 提交于 
      It is often known at allocation time whether a page may be migrated or not.
This patch adds a flag called __GFP_MOVABLE and a new mask called
GFP_HIGH_MOVABLE.  Allocations using the __GFP_MOVABLE can be either migrated
using the page migration mechanism or reclaimed by syncing with backing
storage and discarding.

An API function very similar to alloc_zeroed_user_highpage() is added for
__GFP_MOVABLE allocations called alloc_zeroed_user_highpage_movable().  The
flags used by alloc_zeroed_user_highpage() are not changed because it would
change the semantics of an existing API.  After this patch is applied there
are no in-kernel users of alloc_zeroed_user_highpage() so it probably should
be marked deprecated if this patch is merged.

Note that this patch includes a minor cleanup to the use of __GFP_ZERO in
shmem.c to keep all flag modifications to inode->mapping in the
shmem_dir_alloc() helper function.  This clean-up suggestion is courtesy of
Hugh Dickens.

Additional credit goes to Christoph Lameter and Linus Torvalds for shaping the
concept.  Credit to Hugh Dickens for catching issues with shmem swap vector
and ramfs allocations.

[akpm@linux-foundation.org: build fix]
[hugh@veritas.com: __GFP_ZERO cleanup]
Signed-off-by: NMel Gorman <mel@csn.ul.ie>
Cc: Andy Whitcroft <apw@shadowen.org>
Cc: Christoph Lameter <clameter@sgi.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      769848c0
  5. 17 7月, 2007 3 次提交
  7. 17 6月, 2007 1 次提交
  9. 17 5月, 2007 1 次提交
  11. 08 5月, 2007 3 次提交
  13. 13 2月, 2007 2 次提交
  15. 12 2月, 2007 3 次提交
  17. 27 1月, 2007 2 次提交
    • R
      [PATCH] i386 vDSO: use VM_ALWAYSDUMP · f47aef55
      由 Roland McGrath 提交于 
      This patch fixes core dumps to include the vDSO vma, which is left out now.
It removes the special-case core writing macros, which were not doing the
right thing for the vDSO vma anyway.  Instead, it uses VM_ALWAYSDUMP in the
vma; there is no need for the fixmap page to be installed.  It handles the
CONFIG_COMPAT_VDSO case by making elf_core_dump use the fake vma from
get_gate_vma after real vmas in the same way the /proc/PID/maps code does.

This changes core dumps so they no longer include the non-PT_LOAD phdrs from
the vDSO.  I made the change to add them in the first place, but in turned out
that nothing ever wanted them there since the advent of NT_AUXV.  It's cleaner
to leave them out, and just let the phdrs inside the vDSO image speak for
themselves.
Signed-off-by: NRoland McGrath <roland@redhat.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Andi Kleen <ak@suse.de>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      f47aef55
    • R
      [PATCH] Fix gate_vma.vm_flags · b6558c4a
      由 Roland McGrath 提交于 
      This patch fixes the initialization of gate_vma.vm_flags and
gate_vma.vm_page_prot to reflect reality.  This makes the "[vdso]" line in
/proc/PID/maps correctly show r-xp instead of ---p, when gate_vma is used
(CONFIG_COMPAT_VDSO on i386).
Signed-off-by: NRoland McGrath <roland@redhat.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Andi Kleen <ak@suse.de>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      b6558c4a
  19. 09 1月, 2007 1 次提交
    • R
      [ARM] pass vma for flush_anon_page() · a6f36be3
      由 Russell King 提交于 
      Since get_user_pages() may be used with processes other than the
current process and calls flush_anon_page(), flush_anon_page() has to
cope in some way with non-current processes.

It may not be appropriate, or even desirable to flush a region of
virtual memory cache in the current process when that is different to
the process that we want the flush to occur for.

Therefore, pass the vma into flush_anon_page() so that the architecture
can work out whether the 'vmaddr' is for the current process or not.
Signed-off-by: NRussell King <rmk+kernel@arm.linux.org.uk>
      a6f36be3
  21. 23 12月, 2006 1 次提交
  23. 14 12月, 2006 1 次提交
  25. 11 12月, 2006 1 次提交
    • H
      [PATCH] read_zero_pagealigned() locking fix · 5fcf7bb7
      由 Hugh Dickins 提交于 
      Ramiro Voicu hits the BUG_ON(!pte_none(*pte)) in zeromap_pte_range: kernel
bugzilla 7645.  Right: read_zero_pagealigned uses down_read of mmap_sem,
but another thread's racing read of /dev/zero, or a normal fault, can
easily set that pte again, in between zap_page_range and zeromap_page_range
getting there.  It's been wrong ever since 2.4.3.

The simple fix is to use down_write instead, but that would serialize reads
of /dev/zero more than at present: perhaps some app would be badly
affected.  So instead let zeromap_page_range return the error instead of
BUG_ON, and read_zero_pagealigned break to the slower clear_user loop in
that case - there's no need to optimize for it.

Use -EEXIST for when a pte is found: BUG_ON in mmap_zero (the other user of
zeromap_page_range), though it really isn't interesting there.  And since
mmap_zero wants -EAGAIN for out-of-memory, the zeromaps better return that
than -ENOMEM.
Signed-off-by: NHugh Dickins <hugh@veritas.com>
Cc: Ramiro Voicu: <Ramiro.Voicu@cern.ch>
Cc: <stable@kernel.org>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>
      5fcf7bb7
  27. 08 12月, 2006 2 次提交
  29. 21 10月, 2006 1 次提交
    • D
      [PATCH] mm: D-cache aliasing issue in cow_user_page · c4ec7b0d
      由 Dmitriy Monakhov 提交于 
      --=-=-=

 from mm/memory.c:
  1434  static inline void cow_user_page(struct page *dst, struct page *src, unsigned long va)
  1435  {
  1436          /*
  1437           * If the source page was a PFN mapping, we don't have
  1438           * a "struct page" for it. We do a best-effort copy by
  1439           * just copying from the original user address. If that
  1440           * fails, we just zero-fill it. Live with it.
  1441           */
  1442          if (unlikely(!src)) {
  1443                  void *kaddr = kmap_atomic(dst, KM_USER0);
  1444                  void __user *uaddr = (void __user *)(va & PAGE_MASK);
  1445
  1446                  /*
  1447                   * This really shouldn't fail, because the page is there
  1448                   * in the page tables. But it might just be unreadable,
  1449                   * in which case we just give up and fill the result with
  1450                   * zeroes.
  1451                   */
  1452                  if (__copy_from_user_inatomic(kaddr, uaddr, PAGE_SIZE))
  1453                          memset(kaddr, 0, PAGE_SIZE);
  1454                  kunmap_atomic(kaddr, KM_USER0);
  #### D-cache have to be flushed here.
  #### It seems it is just forgotten.

  1455                  return;
  1456
  1457          }
  1458          copy_user_highpage(dst, src, va);
  #### Ok here. flush_dcache_page() called from this func if arch need it
  1459  }

Following is the patch  fix this issue:
Signed-off-by: NDmitriy Monakhov <dmonakhov@openvz.org>
Cc: "David S. Miller" <davem@davemloft.net>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>
      c4ec7b0d
  31. 06 10月, 2006 1 次提交
    • B
      [PATCH] page fault retry with NOPAGE_REFAULT · 7f7bbbe5
      由 Benjamin Herrenschmidt 提交于 
      Add a way for a no_page() handler to request a retry of the faulting
instruction.  It goes back to userland on page faults and just tries again
in get_user_pages().  I added a cond_resched() in the loop in that later
case.

The problem I have with signal and spufs is an actual bug affecting apps and I
don't see other ways of fixing it.

In addition, we are having issues with infiniband and 64k pages (related to
the way the hypervisor deals with some HV cards) that will require us to muck
around with the MMU from within the IB driver's no_page() (it's a pSeries
specific driver) and return to the caller the same way using NOPAGE_REFAULT.

And to add to this, the graphics folks have been following a new approach of
memory management that involves transparently swapping objects between video
ram and main meory.  To do that, they need installing PTEs from a no_page()
handler as well and that also requires returning with NOPAGE_REFAULT.

(For the later, they are currently using io_remap_pfn_range to install one PTE
from no_page() which is a bit racy, we need to add a check for the PTE having
already been installed afer taking the lock, but that's ok, they are only at
the proof-of-concept stage.  I'll send a patch adding a "clean" function to do
that, we can use that from spufs too and get rid of the sparsemem hacks we do
to create struct page for SPEs.  Basically, that provides a generic solution
for being able to have no_page() map hardware devices, which is something that
I think sound driver folks have been asking for some time too).

All of these things depend on having the NOPAGE_REFAULT exit path from
no_page() handlers.
Signed-off-by: NBenjamin Herrenchmidt <benh@kernel.crashing.org>
Cc: Hugh Dickins <hugh@veritas.com>
Cc: Nick Piggin <nickpiggin@yahoo.com.au>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>
      7f7bbbe5
  33. 01 10月, 2006 3 次提交
  35. 30 9月, 2006 1 次提交
    • S
      [PATCH] mm: fix a race condition under SMC + COW · 4ce072f1
      由 Siddha, Suresh B 提交于 
      Failing context is a multi threaded process context and the failing
sequence is as follows.

One thread T0 doing self modifying code on page X on processor P0 and
another thread T1 doing COW (breaking the COW setup as part of just
happened fork() in another thread T2) on the same page X on processor P1.
T0 doing SMC can endup modifying the new page Y (allocated by the T1 doing
COW on P1) but because of different I/D TLB's, P0 ITLB will not see the new
mapping till the flush TLB IPI from P1 is received.  During this interval,
if T0 executes the code created by SMC it can result in an app error (as
ITLB still points to old page X and endup executing the content in page X
rather than using the content in page Y).

Fix this issue by first clearing the PTE and flushing it, before updating
it with new entry.

Hugh sayeth:

  I was a bit sceptical, in the habit of thinking that Self Modifying Code
  must look such issues itself: but I guess there's nothing it can do to avoid
  this one.

  Fair enough, what you're changing it to is pretty much what powerpc and
  s390 were already doing, and is a more robust way of proceeding, consistent
  with how ptes are set everywhere else.

  The ptep_clear_flush is a bit heavy-handed (it's anxious to return the pte
  that was atomically cleared), but we'd have to wander through lots of arches
  to get the right minimal behaviour.  It'd also be nice to eliminate
  ptep_establish completely, now only used to define other macros/inlines: it
  always seemed obfuscation to me, what you've got there now is clearer.
  Let's put those cleanups on a TODO list.
Signed-off-by: NSuresh Siddha <suresh.b.siddha@intel.com>
Acked-by: N"David S. Miller" <davem@davemloft.net>
Acked-by: NHugh Dickins <hugh@veritas.com>
Cc: Nick Piggin <nickpiggin@yahoo.com.au>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>
      4ce072f1
  37. 27 9月, 2006 2 次提交
    • D
      [PATCH] NOMMU: Check that access_process_vm() has a valid target · 0ec76a11
      由 David Howells 提交于 
      Check that access_process_vm() is accessing a valid mapping in the target
process.

This limits ptrace() accesses and accesses through /proc/<pid>/maps to only
those regions actually mapped by a program.
Signed-off-by: NDavid Howells <dhowells@redhat.com>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>
      0ec76a11
    • J
      [PATCH] do_no_pfn() · f4b81804
      由 Jes Sorensen 提交于 
      Implement do_no_pfn() for handling mapping of memory without a struct page
backing it.  This avoids creating fake page table entries for regions which
are not backed by real memory.

This feature is used by the MSPEC driver and other users, where it is
highly undesirable to have a struct page sitting behind the page (for
instance if the page is accessed in cached mode via the struct page in
parallel to the the driver accessing it uncached, which can result in data
corruption on some architectures, such as ia64).

This version uses specific NOPFN_{SIGBUS,OOM} return values, rather than
expect all negative pfn values would be an error.  It also bugs on cow
mappings as this would not work with the VM.

[akpm@osdl.org: micro-optimise]
Signed-off-by: NJes Sorensen <jes@sgi.com>
Cc: Hugh Dickins <hugh@veritas.com>
Cc: Nick Piggin <nickpiggin@yahoo.com.au>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>
      f4b81804
  39. 26 9月, 2006 4 次提交
    • R
      [PATCH] Add kerneldocs for some functions in mm/memory.c · bfa5bf6d
      由 Rolf Eike Beer 提交于 
      These functions are already documented quite well with long comments.  Now
add kerneldoc style header to make this turn up in everyones favorite doc
format.
Signed-off-by: NRolf Eike Beer <eike-kernel@sf-tec.de>
Cc: "Randy.Dunlap" <rdunlap@xenotime.net>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>
      bfa5bf6d
    • P
      [PATCH] mm: fixup do_wp_page() · ee6a6457
      由 Peter Zijlstra 提交于 
      Wrt. the recent modifications in do_wp_page() Hugh Dickins pointed out:

  "I now realize it's right to the first order (normal case) and to the
   second order (ptrace poke), but not to the third order (ptrace poke
   anon page here to be COWed - perhaps can't occur without intervening
   mprotects)."

This patch restores the old COW behaviour for anonymous pages.
Signed-off-by: NPeter Zijlstra <a.p.zijlstra@chello.nl>
Acked-by: NHugh Dickins <hugh@veritas.com>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>
      ee6a6457
    • P
      [PATCH] mm: balance dirty pages · edc79b2a
      由 Peter Zijlstra 提交于 
      Now that we can detect writers of shared mappings, throttle them.  Avoids OOM
by surprise.
Signed-off-by: NPeter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Hugh Dickins <hugh@veritas.com>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>
      edc79b2a
    • P
      [PATCH] mm: tracking shared dirty pages · d08b3851
      由 Peter Zijlstra 提交于 
      Tracking of dirty pages in shared writeable mmap()s.

The idea is simple: write protect clean shared writeable pages, catch the
write-fault, make writeable and set dirty.  On page write-back clean all the
PTE dirty bits and write protect them once again.

The implementation is a tad harder, mainly because the default
backing_dev_info capabilities were too loosely maintained.  Hence it is not
enough to test the backing_dev_info for cap_account_dirty.

The current heuristic is as follows, a VMA is eligible when:
 - its shared writeable
    (vm_flags & (VM_WRITE|VM_SHARED)) == (VM_WRITE|VM_SHARED)
 - it is not a 'special' mapping
    (vm_flags & (VM_PFNMAP|VM_INSERTPAGE)) == 0
 - the backing_dev_info is cap_account_dirty
    mapping_cap_account_dirty(vma->vm_file->f_mapping)
 - f_op->mmap() didn't change the default page protection

Page from remap_pfn_range() are explicitly excluded because their COW
semantics are already horrid enough (see vm_normal_page() in do_wp_page()) and
because they don't have a backing store anyway.

mprotect() is taught about the new behaviour as well.  However it overrides
the last condition.

Cleaning the pages on write-back is done with page_mkclean() a new rmap call.
It can be called on any page, but is currently only implemented for mapped
pages, if the page is found the be of a VMA that accounts dirty pages it will
also wrprotect the PTE.

Finally, in fs/buffers.c:try_to_free_buffers(); remove clear_page_dirty() from
under ->private_lock.  This seems to be safe, since ->private_lock is used to
serialize access to the buffers, not the page itself.  This is needed because
clear_page_dirty() will call into page_mkclean() and would thereby violate
locking order.

[dhowells@redhat.com: Provide a page_mkclean() implementation for NOMMU]
Signed-off-by: NPeter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Hugh Dickins <hugh@veritas.com>
Signed-off-by: NDavid Howells <dhowells@redhat.com>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>
      d08b3851
  41. 15 7月, 2006 2 次提交
    • S
      [PATCH] per-task-delay-accounting: sync block I/O and swapin delay collection · 0ff92245
      由 Shailabh Nagar 提交于 
      Unlike earlier iterations of the delay accounting patches, now delays are only
collected for the actual I/O waits rather than try and cover the delays seen
in I/O submission paths.

Account separately for block I/O delays incurred as a result of swapin page
faults whose frequency can be affected by the task/process' rss limit.  Hence
swapin delays can act as feedback for rss limit changes independent of I/O
priority changes.
Signed-off-by: NShailabh Nagar <nagar@watson.ibm.com>
Signed-off-by: NBalbir Singh <balbir@in.ibm.com>
Cc: Jes Sorensen <jes@sgi.com>
Cc: Peter Chubb <peterc@gelato.unsw.edu.au>
Cc: Erich Focht <efocht@ess.nec.de>
Cc: Levent Serinol <lserinol@gmail.com>
Cc: Jay Lan <jlan@engr.sgi.com>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>
      0ff92245
    • A
      [PATCH] ia64: race flushing icache in COW path · c38c8db7
      由 Anil Keshavamurthy 提交于 
      There is a race condition that showed up in a threaded JIT environment.
The situation is that a process with a JIT code page forks, so the page is
marked read-only, then some threads are created in the child.  One of the
threads attempts to add a new code block to the JIT page, so a
copy-on-write fault is taken, and the kernel allocates a new page, copies
the data, installs the new pte, and then calls lazy_mmu_prot_update() to
flush caches to make sure that the icache and dcache are in sync.
Unfortunately, the other thread runs right after the new pte is installed,
but before the caches have been flushed.  It tries to execute some old JIT
code that was already in this page, but it sees some garbage in the i-cache
from the previous users of the new physical page.

Fix: we must make the caches consistent before installing the pte.  This is
an ia64 only fix because lazy_mmu_prot_update() is a no-op on all other
architectures.
Signed-off-by: NAnil Keshavamurthy <anil.s.keshavamurthy@intel.com>
Signed-off-by: NTony Luck <tony.luck@intel.com>
Cc: Hugh Dickins <hugh@veritas.com>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>
      c38c8db7