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mm: always lock the root (oldest) anon_vma

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Always (and only) lock the root (oldest) anon_vma whenever we do something
in an anon_vma.  The recently introduced anon_vma scalability is due to
the rmap code scanning only the VMAs that need to be scanned.  Many common
operations still took the anon_vma lock on the root anon_vma, so always
taking that lock is not expected to introduce any scalability issues.

However, always taking the same lock does mean we only need to take one
lock, which means rmap_walk on pages from any anon_vma in the vma is
excluded from occurring during an munmap, expand_stack or other operation
that needs to exclude rmap_walk and similar functions.

Also add the proper locking to vma_adjust.

Signed-off-by: Rik van Riel <riel@redhat.com>
Tested-by: Larry Woodman <lwoodman@redhat.com>
Acked-by: Larry Woodman <lwoodman@redhat.com>
Reviewed-by: Minchan Kim <minchan.kim@gmail.com>
Reviewed-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Acked-by: Mel Gorman <mel@csn.ul.ie>
Acked-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Rik van Riel 2010-08-09 17:18:40 -07:00 • committed by Linus Torvalds
parent 5c341ee1df
commit 012f18004d
4 changed files with 28 additions and 14 deletions
Download patch file Download diff file Expand all files Collapse all files

8
include/linux/rmap.h
View file

@ -104,24 +104,24 @@ static inline void vma_lock_anon_vma(struct vm_area_struct *vma)
{
struct anon_vma *anon_vma = vma->anon_vma;
if (anon_vma)
spin_lock(&anon_vma->lock);
spin_lock(&anon_vma->root->lock);
}
static inline void vma_unlock_anon_vma(struct vm_area_struct *vma)
{
struct anon_vma *anon_vma = vma->anon_vma;
if (anon_vma)
spin_unlock(&anon_vma->lock);
spin_unlock(&anon_vma->root->lock);
}
static inline void anon_vma_lock(struct anon_vma *anon_vma)
{
spin_lock(&anon_vma->lock);
spin_lock(&anon_vma->root->lock);
}
static inline void anon_vma_unlock(struct anon_vma *anon_vma)
{
spin_unlock(&anon_vma->lock);
spin_unlock(&anon_vma->root->lock);
}
/*