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mm: convert i_mmap_mutex to rwsem

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The i_mmap_mutex is a close cousin of the anon vma lock, both protecting
similar data, one for file backed pages and the other for anon memory.  To
this end, this lock can also be a rwsem.  In addition, there are some
important opportunities to share the lock when there are no tree
modifications.

This conversion is straightforward.  For now, all users take the write
lock.

[[email protected]: update fremap.c]
Signed-off-by: Davidlohr Bueso <[email protected]>
Reviewed-by: Rik van Riel <[email protected]>
Acked-by: "Kirill A. Shutemov" <[email protected]>
Acked-by: Hugh Dickins <[email protected]>
Cc: Oleg Nesterov <[email protected]>
Acked-by: Peter Zijlstra (Intel) <[email protected]>
Cc: Srikar Dronamraju <[email protected]>
Acked-by: Mel Gorman <[email protected]>
Signed-off-by: Stephen Rothwell <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
This commit is contained in:
Davidlohr Bueso 2014-12-12 16:54:24 -08:00 • committed by Linus Torvalds
commit c8c06efa8b
10 changed files with 30 additions and 29 deletions
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6
mm/rmap.c
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@ -23,7 +23,7 @@
* inode->i_mutex (while writing or truncating, not reading or faulting)
* mm->mmap_sem
* page->flags PG_locked (lock_page)
* mapping->i_mmap_mutex
* mapping->i_mmap_rwsem
* anon_vma->rwsem
* mm->page_table_lock or pte_lock
* zone->lru_lock (in mark_page_accessed, isolate_lru_page)
@ -1260,7 +1260,7 @@ out_mlock:
/*
* 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->rwsem or mapping->i_mmap_mutex.
* we now hold anon_vma->rwsem or mapping->i_mmap_rwsem.
* 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.
@ -1684,7 +1684,7 @@ static int rmap_walk_file(struct page *page, struct rmap_walk_control *rwc)
* The page lock not only makes sure that page->mapping cannot
* suddenly be NULLified by truncation, it makes sure that the
* structure at mapping cannot be freed and reused yet,
* so we can safely take mapping->i_mmap_mutex.
* so we can safely take mapping->i_mmap_rwsem.
*/
VM_BUG_ON_PAGE(!PageLocked(page), page);