linux-toradex.git/mm/memory.c, branch v2.6.23.5

mm: set_page_dirty_balance() vs ->page_mkwrite()

2007-10-08T19:58:14+00:00

All the current page_mkwrite() implementations also set the page dirty. Which
results in the set_page_dirty_balance() call to _not_ call balance, because the
page is already found dirty.

This allows us to dirty a _lot_ of pages without ever hitting
balance_dirty_pages().  Not good (tm).

Force a balance call if ->page_mkwrite() was successful.

Signed-off-by: Peter Zijlstra 
Signed-off-by: Linus Torvalds

Fix sys_remap_file_pages BUG at highmem.c:15!

2007-10-04T17:13:09+00:00

Gurudas Pai reports kernel BUG at arch/i386/mm/highmem.c:15! below
sys_remap_file_pages, while running Oracle database test on x86 in 6GB
RAM: kunmap thinks we're in_interrupt because the preempt count has
wrapped.

That's because __do_fault expected to unmap page_table, but one of its
two callers do_nonlinear_fault already unmapped it: let do_linear_fault
unmap it first too, and then there's no need to pass the page_table arg
down.

Why have we been so slow to notice this? Probably through forgetting
that the mapping_cap_account_dirty test means that sys_remap_file_pages
nowadays only goes the full nonlinear vma route on a few memory-backed
filesystems like ramfs, tmpfs and hugetlbfs.

[ It also depends on CONFIG_HIGHPTE, so it becomes even harder to
  trigger in practice. Many who have need of large memory have probably
  migrated to x86-64..

  Problem introduced by commit d0217ac04ca6591841e5665f518e38064f4e65bd
  ("mm: fault feedback #1")                -- Linus ]

Signed-off-by: Hugh Dickins 
Cc: gurudas pai 
Cc: Nick Piggin 
Cc: Andrew Morton 
Signed-off-by: Linus Torvalds

remove handle_mm_fault export

2007-07-22T00:49:16+00:00

Now that arch/powerpc/platforms/cell/spufs/fault.c is always built in
the kernel there is no need to export handle_mm_fault anymore.

Signed-off-by: Christoph Hellwig 
Cc: Nick Piggin 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

lguest: export symbols for lguest as a module

2007-07-19T17:04:52+00:00

lguest does some fairly lowlevel things to support a host, which
normal modules don't need:

math_state_restore:
	When the guest triggers a Device Not Available fault, we need
	to be able to restore the FPU

__put_task_struct:
	We need to hold a reference to another task for inter-guest
	I/O, and put_task_struct() is an inline function which calls
	__put_task_struct.

access_process_vm:
	We need to access another task for inter-guest I/O.

map_vm_area & __get_vm_area:
	We need to map the switcher shim (ie. monitor) at 0xFFC01000.

Signed-off-by: Rusty Russell 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

mm: fix clear_page_dirty_for_io vs fault race

2007-07-19T17:04:41+00:00

Fix msync data loss and (less importantly) dirty page accounting
inaccuracies due to the race remaining in clear_page_dirty_for_io().

The deleted comment explains what the race was, and the added comments
explain how it is fixed.

Signed-off-by: Nick Piggin 
Acked-by: Linus Torvalds 
Cc: Miklos Szeredi 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

mm: fault feedback #2

2007-07-19T17:04:41+00:00

This patch completes Linus's wish that the fault return codes be made into
bit flags, which I agree makes everything nicer.  This requires requires
all handle_mm_fault callers to be modified (possibly the modifications
should go further and do things like fault accounting in handle_mm_fault --
however that would be for another patch).

[akpm@linux-foundation.org: fix alpha build]
[akpm@linux-foundation.org: fix s390 build]
[akpm@linux-foundation.org: fix sparc build]
[akpm@linux-foundation.org: fix sparc64 build]
[akpm@linux-foundation.org: fix ia64 build]
Signed-off-by: Nick Piggin 
Cc: Richard Henderson 
Cc: Ivan Kokshaysky 
Cc: Russell King 
Cc: Ian Molton 
Cc: Bryan Wu 
Cc: Mikael Starvik 
Cc: David Howells 
Cc: Yoshinori Sato 
Cc: "Luck, Tony" 
Cc: Hirokazu Takata 
Cc: Geert Uytterhoeven 
Cc: Roman Zippel 
Cc: Greg Ungerer 
Cc: Matthew Wilcox 
Cc: Paul Mackerras 
Cc: Benjamin Herrenschmidt 
Cc: Heiko Carstens 
Cc: Martin Schwidefsky 
Cc: Paul Mundt 
Cc: Kazumoto Kojima 
Cc: Richard Curnow 
Cc: William Lee Irwin III 
Cc: "David S. Miller" 
Cc: Jeff Dike 
Cc: Paolo 'Blaisorblade' Giarrusso 
Cc: Miles Bader 
Cc: Chris Zankel 
Acked-by: Kyle McMartin 
Acked-by: Haavard Skinnemoen 
Acked-by: Ralf Baechle 
Acked-by: Andi Kleen 
Signed-off-by: Andrew Morton 
[ Still apparently needs some ARM and PPC loving - Linus ]
Signed-off-by: Linus Torvalds

mm: fault feedback #1

2007-07-19T17:04:41+00:00

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: Nick Piggin 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

ocfs2: release page lock before calling ->page_mkwrite

2007-07-19T17:04:41+00:00

__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: Mark Fasheh 
Cc: Nick Piggin 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

mm: merge populate and nopage into fault (fixes nonlinear)

2007-07-19T17:04:41+00:00

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: Nick Piggin 
Signed-off-by: Randy Dunlap 
Cc: Mark Fasheh 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

mm: fix fault vs invalidate race for linear mappings

2007-07-19T17:04:41+00:00

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: Nick Piggin 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds