mm/rmap: Convert the struct anon_vma::mutex to an rwsem
Convert the struct anon_vma::mutex to an rwsem, which will help
in solving a page-migration scalability problem. (Addressed in
a separate patch.)
The conversion is simple and straightforward: in every case
where we mutex_lock()ed we'll now down_write().
Suggested-by: Linus Torvalds <torvalds@linux-foundation.org>
Reviewed-by: Rik van Riel <riel@redhat.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Paul Turner <pjt@google.com>
Cc: Lee Schermerhorn <Lee.Schermerhorn@hp.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Hugh Dickins <hughd@google.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Mel Gorman <mgorman@suse.de>
diff --git a/mm/rmap.c b/mm/rmap.c
index 2ee1ef0..6e3ee3b 100644
--- a/mm/rmap.c
+++ b/mm/rmap.c
@@ -24,7 +24,7 @@
* mm->mmap_sem
* page->flags PG_locked (lock_page)
* mapping->i_mmap_mutex
- * anon_vma->mutex
+ * anon_vma->rwsem
* mm->page_table_lock or pte_lock
* zone->lru_lock (in mark_page_accessed, isolate_lru_page)
* swap_lock (in swap_duplicate, swap_info_get)
@@ -37,7 +37,7 @@
* in arch-dependent flush_dcache_mmap_lock,
* within bdi.wb->list_lock in __sync_single_inode)
*
- * anon_vma->mutex,mapping->i_mutex (memory_failure, collect_procs_anon)
+ * anon_vma->rwsem,mapping->i_mutex (memory_failure, collect_procs_anon)
* ->tasklist_lock
* pte map lock
*/
@@ -103,7 +103,7 @@
* LOCK should suffice since the actual taking of the lock must
* happen _before_ what follows.
*/
- if (mutex_is_locked(&anon_vma->root->mutex)) {
+ if (rwsem_is_locked(&anon_vma->root->rwsem)) {
anon_vma_lock(anon_vma);
anon_vma_unlock(anon_vma);
}
@@ -219,9 +219,9 @@
struct anon_vma *new_root = anon_vma->root;
if (new_root != root) {
if (WARN_ON_ONCE(root))
- mutex_unlock(&root->mutex);
+ up_write(&root->rwsem);
root = new_root;
- mutex_lock(&root->mutex);
+ down_write(&root->rwsem);
}
return root;
}
@@ -229,7 +229,7 @@
static inline void unlock_anon_vma_root(struct anon_vma *root)
{
if (root)
- mutex_unlock(&root->mutex);
+ up_write(&root->rwsem);
}
/*
@@ -349,7 +349,7 @@
/*
* Iterate the list once more, it now only contains empty and unlinked
* anon_vmas, destroy them. Could not do before due to __put_anon_vma()
- * needing to acquire the anon_vma->root->mutex.
+ * needing to write-acquire the anon_vma->root->rwsem.
*/
list_for_each_entry_safe(avc, next, &vma->anon_vma_chain, same_vma) {
struct anon_vma *anon_vma = avc->anon_vma;
@@ -365,7 +365,7 @@
{
struct anon_vma *anon_vma = data;
- mutex_init(&anon_vma->mutex);
+ init_rwsem(&anon_vma->rwsem);
atomic_set(&anon_vma->refcount, 0);
anon_vma->rb_root = RB_ROOT;
}
@@ -457,14 +457,14 @@
anon_vma = (struct anon_vma *) (anon_mapping - PAGE_MAPPING_ANON);
root_anon_vma = ACCESS_ONCE(anon_vma->root);
- if (mutex_trylock(&root_anon_vma->mutex)) {
+ if (down_write_trylock(&root_anon_vma->rwsem)) {
/*
* If the page is still mapped, then this anon_vma is still
* its anon_vma, and holding the mutex ensures that it will
* not go away, see anon_vma_free().
*/
if (!page_mapped(page)) {
- mutex_unlock(&root_anon_vma->mutex);
+ up_write(&root_anon_vma->rwsem);
anon_vma = NULL;
}
goto out;
@@ -1299,7 +1299,7 @@
/*
* We need mmap_sem locking, Otherwise VM_LOCKED check makes
* unstable result and race. Plus, We can't wait here because
- * we now hold anon_vma->mutex or mapping->i_mmap_mutex.
+ * we now hold anon_vma->rwsem or mapping->i_mmap_mutex.
* if trylock failed, the page remain in evictable lru and later
* vmscan could retry to move the page to unevictable lru if the
* page is actually mlocked.