linux.git/mm/mlock.c, branch v2.6.38

mlock: operate on any regions with protection != PROT_NONE

2011-02-01T23:20:50+00:00

As Tao Ma noticed, change 5ecfda0 breaks blktrace. This is because
blktrace mmaps a file with PROT_WRITE permissions but without PROT_READ,
so my attempt to not unnecessarity break COW during mlock ended up
causing mlock to fail with a permission problem.

I am proposing to let mlock ignore vma protection in all cases except
PROT_NONE. In particular, mlock should not fail for PROT_WRITE regions
(as in the blktrace case, which broke at 5ecfda0) or for PROT_EXEC
regions (which seem to me like they were always broken).

Signed-off-by: Michel Lespinasse 
Acked-by: Rik van Riel 
Signed-off-by: Linus Torvalds

mlock: do not hold mmap_sem for extended periods of time

2011-01-14T01:32:36+00:00

__get_user_pages gets a new 'nonblocking' parameter to signal that the
caller is prepared to re-acquire mmap_sem and retry the operation if
needed.  This is used to split off long operations if they are going to
block on a disk transfer, or when we detect contention on the mmap_sem.

[akpm@linux-foundation.org: remove ref to rwsem_is_contended()]
Signed-off-by: Michel Lespinasse 
Cc: Hugh Dickins 
Cc: Rik van Riel 
Cc: Peter Zijlstra 
Cc: Nick Piggin 
Cc: KOSAKI Motohiro 
Cc: Ingo Molnar 
Cc: "H. Peter Anvin" 
Cc: Thomas Gleixner 
Cc: David Howells 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

mm: move VM_LOCKED check to __mlock_vma_pages_range()

2011-01-14T01:32:36+00:00

Use a single code path for faulting in pages during mlock.

The reason to have it in this patch series is that I did not want to
update both code paths in a later change that releases mmap_sem when
blocking on disk.

Signed-off-by: Michel Lespinasse 
Cc: Hugh Dickins 
Cc: Rik van Riel 
Cc: Peter Zijlstra 
Cc: Nick Piggin 
Cc: KOSAKI Motohiro 
Cc: Ingo Molnar 
Cc: "H. Peter Anvin" 
Cc: Thomas Gleixner 
Cc: David Howells 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

mm: add FOLL_MLOCK follow_page flag.

2011-01-14T01:32:36+00:00

Move the code to mlock pages from __mlock_vma_pages_range() to
follow_page().

This allows __mlock_vma_pages_range() to not have to break down work into
16-page batches.

An additional motivation for doing this within the present patch series is
that it'll make it easier for a later chagne to drop mmap_sem when
blocking on disk (we'd like to be able to resume at the page that was read
from disk instead of at the start of a 16-page batch).

Signed-off-by: Michel Lespinasse 
Cc: Hugh Dickins 
Cc: Rik van Riel 
Cc: Peter Zijlstra 
Cc: Nick Piggin 
Cc: KOSAKI Motohiro 
Cc: Ingo Molnar 
Cc: "H. Peter Anvin" 
Cc: Thomas Gleixner 
Cc: David Howells 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

mlock: only hold mmap_sem in shared mode when faulting in pages

2011-01-14T01:32:35+00:00

Currently mlock() holds mmap_sem in exclusive mode while the pages get
faulted in.  In the case of a large mlock, this can potentially take a
very long time, during which various commands such as 'ps auxw' will
block.  This makes sysadmins unhappy:

real    14m36.232s
user    0m0.003s
sys     0m0.015s
(output from 'time ps auxw' while a 20GB file was being mlocked without
being previously preloaded into page cache)

I propose that mlock() could release mmap_sem after the VM_LOCKED bits
have been set in all appropriate VMAs.  Then a second pass could be done
to actually mlock the pages, in small batches, releasing mmap_sem when we
block on disk access or when we detect some contention.

This patch:

Before this change, mlock() holds mmap_sem in exclusive mode while the
pages get faulted in.  In the case of a large mlock, this can potentially
take a very long time.  Various things will block while mmap_sem is held,
including 'ps auxw'.  This can make sysadmins angry.

I propose that mlock() could release mmap_sem after the VM_LOCKED bits
have been set in all appropriate VMAs.  Then a second pass could be done
to actually mlock the pages with mmap_sem held for reads only.  We need to
recheck the vma flags after we re-acquire mmap_sem, but this is easy.

In the case where a vma has been munlocked before mlock completes, pages
that were already marked as PageMlocked() are handled by the munlock()
call, and mlock() is careful to not mark new page batches as PageMlocked()
after the munlock() call has cleared the VM_LOCKED vma flags.  So, the end
result will be identical to what'd happen if munlock() had executed after
the mlock() call.

In a later change, I will allow the second pass to release mmap_sem when
blocking on disk accesses or when it is otherwise contended, so that it
won't be held for long periods of time even in shared mode.

Signed-off-by: Michel Lespinasse 
Tested-by: Valdis Kletnieks 
Cc: Hugh Dickins 
Cc: Rik van Riel 
Cc: Peter Zijlstra 
Cc: Nick Piggin 
Cc: KOSAKI Motohiro 
Cc: Ingo Molnar 
Cc: "H. Peter Anvin" 
Cc: Thomas Gleixner 
Cc: David Howells 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

mlock: avoid dirtying pages and triggering writeback

2011-01-14T01:32:35+00:00

When faulting in pages for mlock(), we want to break COW for anonymous or
file pages within VM_WRITABLE, non-VM_SHARED vmas.  However, there is no
need to write-fault into VM_SHARED vmas since shared file pages can be
mlocked first and dirtied later, when/if they actually get written to.
Skipping the write fault is desirable, as we don't want to unnecessarily
cause these pages to be dirtied and queued for writeback.

Signed-off-by: Michel Lespinasse 
Cc: Hugh Dickins 
Cc: Rik van Riel 
Cc: Kosaki Motohiro 
Cc: Peter Zijlstra 
Cc: Nick Piggin 
Cc: Theodore Tso 
Cc: Michael Rubin 
Cc: Suleiman Souhlal 
Cc: Dave Chinner 
Cc: Christoph Hellwig 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

mm: Move vma_stack_continue into mm.h

2010-09-09T16:05:06+00:00

So it can be used by all that need to check for that.

Signed-off-by: Stefan Bader 
Signed-off-by: Linus Torvalds

mm: make the mlock() stack guard page checks stricter

2010-08-21T15:49:50+00:00

If we've split the stack vma, only the lowest one has the guard page.
Now that we have a doubly linked list of vma's, checking this is trivial.

Tested-by: Ian Campbell 
Signed-off-by: Linus Torvalds

mm: fix up some user-visible effects of the stack guard page

2010-08-15T18:35:52+00:00

This commit makes the stack guard page somewhat less visible to user
space. It does this by:

 - not showing the guard page in /proc//maps

   It looks like lvm-tools will actually read /proc/self/maps to figure
   out where all its mappings are, and effectively do a specialized
   "mlockall()" in user space.  By not showing the guard page as part of
   the mapping (by just adding PAGE_SIZE to the start for grows-up
   pages), lvm-tools ends up not being aware of it.

 - by also teaching the _real_ mlock() functionality not to try to lock
   the guard page.

   That would just expand the mapping down to create a new guard page,
   so there really is no point in trying to lock it in place.

It would perhaps be nice to show the guard page specially in
/proc//maps (or at least mark grow-down segments some way), but
let's not open ourselves up to more breakage by user space from programs
that depends on the exact deails of the 'maps' file.

Special thanks to Henrique de Moraes Holschuh for diving into lvm-tools
source code to see what was going on with the whole new warning.

Reported-and-tested-by: François Valenduc 
Cc: stable@kernel.org
Signed-off-by: Linus Torvalds

x86, perf, bts, mm: Delete the never used BTS-ptrace code

2010-03-26T10:33:55+00:00

Support for the PMU's BTS features has been upstreamed in
v2.6.32, but we still have the old and disabled ptrace-BTS,
as Linus noticed it not so long ago.

It's buggy: TIF_DEBUGCTLMSR is trampling all over that MSR without
regard for other uses (perf) and doesn't provide the flexibility
needed for perf either.

Its users are ptrace-block-step and ptrace-bts, since ptrace-bts
was never used and ptrace-block-step can be implemented using a
much simpler approach.

So axe all 3000 lines of it. That includes the *locked_memory*()
APIs in mm/mlock.c as well.

Reported-by: Linus Torvalds 
Signed-off-by: Peter Zijlstra 
Cc: Roland McGrath 
Cc: Oleg Nesterov 
Cc: Markus Metzger 
Cc: Steven Rostedt 
Cc: Andrew Morton 
LKML-Reference: <20100325135413.938004390@chello.nl>
Signed-off-by: Ingo Molnar