The patch titled
mm: page lock use lock bitops
has been removed from the -mm tree. Its filename was
mm-page-lock-use-lock-bitops.patch
This patch was dropped because it was merged into mainline or a subsystem tree
The current -mm tree may be found at http://userweb.kernel.org/~akpm/mmotm/
------------------------------------------------------
Subject: mm: page lock use lock bitops
From: Nick Piggin <npiggin@xxxxxxx>
trylock_page, unlock_page open and close a critical section. Hence,
we can use the lock bitops to get the desired memory ordering.
Also, mark trylock as likely to succeed (and remove the annotation from
callers).
Signed-off-by: Nick Piggin <npiggin@xxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
include/linux/pagemap.h | 2 +-
mm/filemap.c | 13 +++++--------
mm/swapfile.c | 2 +-
3 files changed, 7 insertions(+), 10 deletions(-)
diff -puN include/linux/pagemap.h~mm-page-lock-use-lock-bitops include/linux/pagemap.h
--- a/include/linux/pagemap.h~mm-page-lock-use-lock-bitops
+++ a/include/linux/pagemap.h
@@ -311,7 +311,7 @@ static inline void __clear_page_locked(s
static inline int trylock_page(struct page *page)
{
- return !test_and_set_bit(PG_locked, &page->flags);
+ return (likely(!test_and_set_bit_lock(PG_locked, &page->flags)));
}
/*
diff -puN mm/filemap.c~mm-page-lock-use-lock-bitops mm/filemap.c
--- a/mm/filemap.c~mm-page-lock-use-lock-bitops
+++ a/mm/filemap.c
@@ -573,17 +573,14 @@ EXPORT_SYMBOL(wait_on_page_bit);
* mechananism between PageLocked pages and PageWriteback pages is shared.
* But that's OK - sleepers in wait_on_page_writeback() just go back to sleep.
*
- * The first mb is necessary to safely close the critical section opened by the
- * test_and_set_bit() to lock the page; the second mb is necessary to enforce
- * ordering between the clear_bit and the read of the waitqueue (to avoid SMP
- * races with a parallel wait_on_page_locked()).
+ * The mb is necessary to enforce ordering between the clear_bit and the read
+ * of the waitqueue (to avoid SMP races with a parallel wait_on_page_locked()).
*/
void unlock_page(struct page *page)
{
- smp_mb__before_clear_bit();
- if (!test_and_clear_bit(PG_locked, &page->flags))
- BUG();
- smp_mb__after_clear_bit();
+ VM_BUG_ON(!PageLocked(page));
+ clear_bit_unlock(PG_locked, &page->flags);
+ smp_mb__after_clear_bit();
wake_up_page(page, PG_locked);
}
EXPORT_SYMBOL(unlock_page);
diff -puN mm/swapfile.c~mm-page-lock-use-lock-bitops mm/swapfile.c
--- a/mm/swapfile.c~mm-page-lock-use-lock-bitops
+++ a/mm/swapfile.c
@@ -422,7 +422,7 @@ void free_swap_and_cache(swp_entry_t ent
if (p) {
if (swap_entry_free(p, swp_offset(entry)) == 1) {
page = find_get_page(&swapper_space, entry.val);
- if (page && unlikely(!trylock_page(page))) {
+ if (page && !trylock_page(page)) {
page_cache_release(page);
page = NULL;
}
_
Patches currently in -mm which might be from npiggin@xxxxxxx are
origin.patch
linux-next.patch
reiser4.patch
likeliness-accounting-change-and-cleanup.patch
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