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authorMichel Lespinasse <walken@google.com>2011-01-13 18:46:09 -0500
committerLinus Torvalds <torvalds@linux-foundation.org>2011-01-13 20:32:35 -0500
commit5ecfda041e4b4bd858d25bbf5a16c2a6c06d7272 (patch)
treee6c3e7dac64a5e45b48ab7836318752202579a17 /mm/memory.c
parent72ddc8f72270758951ccefb7d190f364d20215ab (diff)
mlock: avoid dirtying pages and triggering writeback
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 <walken@google.com> Cc: Hugh Dickins <hughd@google.com> Cc: Rik van Riel <riel@redhat.com> Cc: Kosaki Motohiro <kosaki.motohiro@jp.fujitsu.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Nick Piggin <npiggin@kernel.dk> Cc: Theodore Tso <tytso@google.com> Cc: Michael Rubin <mrubin@google.com> Cc: Suleiman Souhlal <suleiman@google.com> Cc: Dave Chinner <david@fromorbit.com> Cc: Christoph Hellwig <hch@infradead.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm/memory.c')
-rw-r--r--mm/memory.c7
1 files changed, 6 insertions, 1 deletions
diff --git a/mm/memory.c b/mm/memory.c
index 9144fae9a68b..b8f97b8575b7 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -3299,7 +3299,12 @@ int make_pages_present(unsigned long addr, unsigned long end)
3299 vma = find_vma(current->mm, addr); 3299 vma = find_vma(current->mm, addr);
3300 if (!vma) 3300 if (!vma)
3301 return -ENOMEM; 3301 return -ENOMEM;
3302 write = (vma->vm_flags & VM_WRITE) != 0; 3302 /*
3303 * We want to touch writable mappings with a write fault in order
3304 * to break COW, except for shared mappings because these don't COW
3305 * and we would not want to dirty them for nothing.
3306 */
3307 write = (vma->vm_flags & (VM_WRITE | VM_SHARED)) == VM_WRITE;
3303 BUG_ON(addr >= end); 3308 BUG_ON(addr >= end);
3304 BUG_ON(end > vma->vm_end); 3309 BUG_ON(end > vma->vm_end);
3305 len = DIV_ROUND_UP(end, PAGE_SIZE) - addr/PAGE_SIZE; 3310 len = DIV_ROUND_UP(end, PAGE_SIZE) - addr/PAGE_SIZE;