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author | Rik van Riel <riel@redhat.com> | 2010-08-09 17:18:40 -0700 |
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committer | Linus Torvalds <torvalds@linux-foundation.org> | 2010-08-09 20:44:55 -0700 |
commit | 012f18004da33ba672e3c60838cc4898126174d3 (patch) | |
tree | 990382f9f8c0d885463ac9195b8e9a18043f716d /mm/mmap.c | |
parent | 5c341ee1dfc8fe69d66b1c8b19e463c6d7201ae1 (diff) | |
download | kernel_samsung_crespo-012f18004da33ba672e3c60838cc4898126174d3.zip kernel_samsung_crespo-012f18004da33ba672e3c60838cc4898126174d3.tar.gz kernel_samsung_crespo-012f18004da33ba672e3c60838cc4898126174d3.tar.bz2 |
mm: always lock the root (oldest) anon_vma
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>
Diffstat (limited to 'mm/mmap.c')
-rw-r--r-- | mm/mmap.c | 30 |
1 files changed, 22 insertions, 8 deletions
@@ -506,6 +506,7 @@ int vma_adjust(struct vm_area_struct *vma, unsigned long start, struct vm_area_struct *importer = NULL; struct address_space *mapping = NULL; struct prio_tree_root *root = NULL; + struct anon_vma *anon_vma = NULL; struct file *file = vma->vm_file; long adjust_next = 0; int remove_next = 0; @@ -578,6 +579,17 @@ again: remove_next = 1 + (end > next->vm_end); } } + /* + * When changing only vma->vm_end, we don't really need anon_vma + * lock. This is a fairly rare case by itself, but the anon_vma + * lock may be shared between many sibling processes. Skipping + * the lock for brk adjustments makes a difference sometimes. + */ + if (vma->anon_vma && (insert || importer || start != vma->vm_start)) { + anon_vma = vma->anon_vma; + anon_vma_lock(anon_vma); + } + if (root) { flush_dcache_mmap_lock(mapping); vma_prio_tree_remove(vma, root); @@ -617,6 +629,8 @@ again: remove_next = 1 + (end > next->vm_end); __insert_vm_struct(mm, insert); } + if (anon_vma) + anon_vma_unlock(anon_vma); if (mapping) spin_unlock(&mapping->i_mmap_lock); @@ -2470,23 +2484,23 @@ static DEFINE_MUTEX(mm_all_locks_mutex); static void vm_lock_anon_vma(struct mm_struct *mm, struct anon_vma *anon_vma) { - if (!test_bit(0, (unsigned long *) &anon_vma->head.next)) { + if (!test_bit(0, (unsigned long *) &anon_vma->root->head.next)) { /* * The LSB of head.next can't change from under us * because we hold the mm_all_locks_mutex. */ - spin_lock_nest_lock(&anon_vma->lock, &mm->mmap_sem); + spin_lock_nest_lock(&anon_vma->root->lock, &mm->mmap_sem); /* * We can safely modify head.next after taking the - * anon_vma->lock. If some other vma in this mm shares + * anon_vma->root->lock. If some other vma in this mm shares * the same anon_vma we won't take it again. * * No need of atomic instructions here, head.next * can't change from under us thanks to the - * anon_vma->lock. + * anon_vma->root->lock. */ if (__test_and_set_bit(0, (unsigned long *) - &anon_vma->head.next)) + &anon_vma->root->head.next)) BUG(); } } @@ -2577,7 +2591,7 @@ out_unlock: static void vm_unlock_anon_vma(struct anon_vma *anon_vma) { - if (test_bit(0, (unsigned long *) &anon_vma->head.next)) { + if (test_bit(0, (unsigned long *) &anon_vma->root->head.next)) { /* * The LSB of head.next can't change to 0 from under * us because we hold the mm_all_locks_mutex. @@ -2588,10 +2602,10 @@ static void vm_unlock_anon_vma(struct anon_vma *anon_vma) * * No need of atomic instructions here, head.next * can't change from under us until we release the - * anon_vma->lock. + * anon_vma->root->lock. */ if (!__test_and_clear_bit(0, (unsigned long *) - &anon_vma->head.next)) + &anon_vma->root->head.next)) BUG(); anon_vma_unlock(anon_vma); } |