mm: page trylock rename

PATCH In review Nick Piggin 2 participants 7 messages Nov 10, 2007 – Nov 11, 2007

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Memory management VFS SCSI MM core +12 more subsystems

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Nick Piggin

author

2007-11-10 05:12 UTC #0 lore raw

PATCH 1/2 mm: page trylock rename

Hi,

OK minus the memory barrier changes for now. Can we possibly please get these into 2.6.24?

--
mm: rename page trylock

Converting page lock to new locking bitops requires a change of page flag operation naming, so we might as well convert it to something nicer (!TestSetPageLocked => trylock_page, SetPageLocked => set_page_locked).

Signed-off-by Nick Piggin <[email protected]>

---
 drivers/scsi/sg.c           |    2 +-
 fs/afs/write.c              |    2 +-
 fs/cifs/file.c              |    2 +-
 fs/jbd/commit.c             |    2 +-
 fs/jbd2/commit.c            |    2 +-
 fs/reiserfs/journal.c       |    2 +-
 fs/splice.c                 |    2 +-
 fs/xfs/linux-2.6/xfs_aops.c |    4 ++--
 include/linux/page-flags.h  |    8 --------
 include/linux/pagemap.h     |   19 +++++++++++++++++--
 mm/filemap.c                |   12 ++++++------
 mm/memory.c                 |    2 +-
 mm/migrate.c                |    4 ++--
 mm/rmap.c                   |    2 +-
 mm/shmem.c                  |    4 ++--
 mm/swap.c                   |    2 +-
 mm/swap_state.c             |    6 +++---
 mm/swapfile.c               |    2 +-
 mm/truncate.c               |    4 ++--
 mm/vmscan.c                 |    4 ++--
 20 files changed, 47 insertions(+), 40 deletions(-)

include/linux/pagemap.h +17 -2

Index: linux-2.6/include/linux/pagemap.h
===================================================================
@@ -160,13 +160,28 @@ extern void FASTCALL(__lock_page(struct 
 extern void FASTCALL(__lock_page_nosync(struct page *page));
 extern void FASTCALL(unlock_page(struct page *page));
 
+static inline void set_page_locked(struct page *page)
+{
+	set_bit(PG_locked, &page->flags);
+}
+
+static inline void clear_page_locked(struct page *page)
+{
+	clear_bit(PG_locked, &page->flags);
+}
+
+static inline int trylock_page(struct page *page)
+{
+	return !test_and_set_bit(PG_locked, &page->flags);
+}
+
 /*
  * lock_page may only be called if we have the page's inode pinned.
  */
 static inline void lock_page(struct page *page)
 {
 	might_sleep();
-	if (TestSetPageLocked(page))
+	if (!trylock_page(page))
 		__lock_page(page);
 }

@@ -177,7 +192,7 @@ static inline void lock_page(struct page
 static inline void lock_page_nosync(struct page *page)
 {
 	might_sleep();
-	if (TestSetPageLocked(page))
+	if (!trylock_page(page))
 		__lock_page_nosync(page);
 }

drivers/scsi/sg.c +1 -1

Index: linux-2.6/drivers/scsi/sg.c
===================================================================
@@ -1714,7 +1714,7 @@ st_map_user_pages(struct scatterlist *sg
                  */
 		flush_dcache_page(pages[i]);
 		/* ?? Is locking needed? I don't think so */
-		/* if (TestSetPageLocked(pages[i]))
+		/* if (!trylock_page(pages[i]))
 		   goto out_unlock; */
         }

fs/cifs/file.c +1 -1

Index: linux-2.6/fs/cifs/file.c
===================================================================
@@ -1251,7 +1251,7 @@ retry:
 
 			if (first < 0)
 				lock_page(page);
-			else if (TestSetPageLocked(page))
+			else if (!trylock_page(page))
 				break;
 
 			if (unlikely(page->mapping != mapping)) {

fs/jbd/commit.c +1 -1

Index: linux-2.6/fs/jbd/commit.c
===================================================================
@@ -63,7 +63,7 @@ static void release_buffer_page(struct b
 		goto nope;
 
 	/* OK, it's a truncated page */
-	if (TestSetPageLocked(page))
+	if (!trylock_page(page))
 		goto nope;
 
 	page_cache_get(page);

fs/jbd2/commit.c +1 -1

Index: linux-2.6/fs/jbd2/commit.c
===================================================================
@@ -63,7 +63,7 @@ static void release_buffer_page(struct b
 		goto nope;
 
 	/* OK, it's a truncated page */
-	if (TestSetPageLocked(page))
+	if (!trylock_page(page))
 		goto nope;
 
 	page_cache_get(page);

fs/xfs/linux-2.6/xfs_aops.c +2 -2

Index: linux-2.6/fs/xfs/linux-2.6/xfs_aops.c
===================================================================
@@ -659,7 +659,7 @@ xfs_probe_cluster(
 			} else
 				pg_offset = PAGE_CACHE_SIZE;
 
-			if (page->index == tindex && !TestSetPageLocked(page)) {
+			if (page->index == tindex && trylock_page(page)) {
 				pg_len = xfs_probe_page(page, pg_offset, mapped);
 				unlock_page(page);
 			}

@@ -743,7 +743,7 @@ xfs_convert_page(
 
 	if (page->index != tindex)
 		goto fail;
-	if (TestSetPageLocked(page))
+	if (!trylock_page(page))
 		goto fail;
 	if (PageWriteback(page))
 		goto fail_unlock_page;

include/linux/page-flags.h +0 -8

Index: linux-2.6/include/linux/page-flags.h
===================================================================
@@ -113,14 +113,6 @@
  */
 #define PageLocked(page)		\
 		test_bit(PG_locked, &(page)->flags)
-#define SetPageLocked(page)		\
-		set_bit(PG_locked, &(page)->flags)
-#define TestSetPageLocked(page)		\
-		test_and_set_bit(PG_locked, &(page)->flags)
-#define ClearPageLocked(page)		\
-		clear_bit(PG_locked, &(page)->flags)
-#define TestClearPageLocked(page)	\
-		test_and_clear_bit(PG_locked, &(page)->flags)
 
 #define PageError(page)		test_bit(PG_error, &(page)->flags)
 #define SetPageError(page)	set_bit(PG_error, &(page)->flags)

mm/memory.c +1 -1

Index: linux-2.6/mm/memory.c
===================================================================
@@ -1559,7 +1559,7 @@ static int do_wp_page(struct mm_struct *
 	 * not dirty accountable.
 	 */
 	if (PageAnon(old_page)) {
-		if (!TestSetPageLocked(old_page)) {
+		if (trylock_page(old_page)) {
 			reuse = can_share_swap_page(old_page);
 			unlock_page(old_page);
 		}

mm/migrate.c +2 -2

Index: linux-2.6/mm/migrate.c
===================================================================
@@ -569,7 +569,7 @@ static int move_to_new_page(struct page 
 	 * establishing additional references. We are the only one
 	 * holding a reference to the new page at this point.
 	 */
-	if (TestSetPageLocked(newpage))
+	if (!trylock_page(newpage))
 		BUG();
 
 	/* Prepare mapping for the new page.*/

@@ -622,7 +622,7 @@ static int unmap_and_move(new_page_t get
 		goto move_newpage;
 
 	rc = -EAGAIN;
-	if (TestSetPageLocked(page)) {
+	if (!trylock_page(page)) {
 		if (!force)
 			goto move_newpage;
 		lock_page(page);

mm/rmap.c +1 -1

Index: linux-2.6/mm/rmap.c
===================================================================
@@ -401,7 +401,7 @@ int page_referenced(struct page *page, i
 			referenced += page_referenced_anon(page);
 		else if (is_locked)
 			referenced += page_referenced_file(page);
-		else if (TestSetPageLocked(page))
+		else if (!trylock_page(page))
 			referenced++;
 		else {
 			if (page->mapping)

mm/shmem.c +2 -2

Index: linux-2.6/mm/shmem.c
===================================================================
@@ -1182,7 +1182,7 @@ repeat:
 		}
 
 		/* We have to do this with page locked to prevent races */
-		if (TestSetPageLocked(swappage)) {
+		if (!trylock_page(swappage)) {
 			shmem_swp_unmap(entry);
 			spin_unlock(&info->lock);
 			wait_on_page_locked(swappage);

@@ -1241,7 +1241,7 @@ repeat:
 		shmem_swp_unmap(entry);
 		filepage = find_get_page(mapping, idx);
 		if (filepage &&
-		    (!PageUptodate(filepage) || TestSetPageLocked(filepage))) {
+		    (!PageUptodate(filepage) || !trylock_page(filepage))) {
 			spin_unlock(&info->lock);
 			wait_on_page_locked(filepage);
 			page_cache_release(filepage);

mm/swap.c +1 -1

Index: linux-2.6/mm/swap.c
===================================================================
@@ -455,7 +455,7 @@ void pagevec_strip(struct pagevec *pvec)
 	for (i = 0; i < pagevec_count(pvec); i++) {
 		struct page *page = pvec->pages[i];
 
-		if (PagePrivate(page) && !TestSetPageLocked(page)) {
+		if (PagePrivate(page) && trylock_page(page)) {
 			if (PagePrivate(page))
 				try_to_release_page(page, 0);
 			unlock_page(page);

mm/swap_state.c +3 -3

Index: linux-2.6/mm/swap_state.c
===================================================================
@@ -104,13 +104,13 @@ static int add_to_swap_cache(struct page
 		INC_CACHE_INFO(noent_race);
 		return -ENOENT;
 	}
-	SetPageLocked(page);
+	set_page_locked(page);
 	error = __add_to_swap_cache(page, entry, GFP_KERNEL);
 	/*
 	 * Anon pages are already on the LRU, we don't run lru_cache_add here.
 	 */
 	if (error) {
-		ClearPageLocked(page);
+		clear_page_locked(page);
 		swap_free(entry);
 		if (error == -EEXIST)
 			INC_CACHE_INFO(exist_race);

@@ -255,7 +255,7 @@ int move_from_swap_cache(struct page *pa
  */
 static inline void free_swap_cache(struct page *page)
 {
-	if (PageSwapCache(page) && !TestSetPageLocked(page)) {
+	if (PageSwapCache(page) && trylock_page(page)) {
 		remove_exclusive_swap_page(page);
 		unlock_page(page);
 	}

mm/swapfile.c +1 -1

Index: linux-2.6/mm/swapfile.c
===================================================================
@@ -401,7 +401,7 @@ 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(TestSetPageLocked(page))) {
+			if (page && unlikely(!trylock_page(page))) {
 				page_cache_release(page);
 				page = NULL;
 			}

mm/truncate.c +2 -2

Index: linux-2.6/mm/truncate.c
===================================================================
@@ -189,7 +189,7 @@ void truncate_inode_pages_range(struct a
 			if (page_index > next)
 				next = page_index;
 			next++;
-			if (TestSetPageLocked(page))
+			if (!trylock_page(page))
 				continue;
 			if (PageWriteback(page)) {
 				unlock_page(page);

@@ -282,7 +282,7 @@ unsigned long __invalidate_mapping_pages
 			pgoff_t index;
 			int lock_failed;
 
-			lock_failed = TestSetPageLocked(page);
+			lock_failed = !trylock_page(page);
 
 			/*
 			 * We really shouldn't be looking at the ->index of an

mm/vmscan.c +2 -2

Index: linux-2.6/mm/vmscan.c
===================================================================
@@ -461,7 +461,7 @@ static unsigned long shrink_page_list(st
 		page = lru_to_page(page_list);
 		list_del(&page->lru);
 
-		if (TestSetPageLocked(page))
+		if (!trylock_page(page))
 			goto keep;
 
 		VM_BUG_ON(PageActive(page));

@@ -547,7 +547,7 @@ static unsigned long shrink_page_list(st
 				 * A synchronous write - probably a ramdisk.  Go
 				 * ahead and try to reclaim the page.
 				 */
-				if (TestSetPageLocked(page))
+				if (!trylock_page(page))
 					goto keep;
 				if (PageDirty(page) || PageWriteback(page))
 					goto keep_locked;

mm/filemap.c +6 -6

Index: linux-2.6/mm/filemap.c
===================================================================
@@ -433,7 +433,7 @@ int filemap_write_and_wait_range(struct 
  * @gfp_mask:	page allocation mode
  *
  * This function is used to add newly allocated pagecache pages;
- * the page is new, so we can just run SetPageLocked() against it.
+ * the page is new, so we can just run set_page_locked() against it.
  * The other page state flags were set by rmqueue().
  *
  * This function does not add the page to the LRU.  The caller must do that.

@@ -448,7 +448,7 @@ int add_to_page_cache(struct page *page,
 		error = radix_tree_insert(&mapping->page_tree, offset, page);
 		if (!error) {
 			page_cache_get(page);
-			SetPageLocked(page);
+			set_page_locked(page);
 			page->mapping = mapping;
 			page->index = offset;
 			mapping->nrpages++;

@@ -530,14 +530,14 @@ EXPORT_SYMBOL(wait_on_page_bit);
  * 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
- * TestSetPageLocked(), the second mb is necessary to enforce ordering between
+ * trylock_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()).
  */
 void fastcall unlock_page(struct page *page)
 {
 	smp_mb__before_clear_bit();
-	if (!TestClearPageLocked(page))
+	if (!test_and_clear_bit(PG_locked, &page->flags))
 		BUG();
 	smp_mb__after_clear_bit(); 
 	wake_up_page(page, PG_locked);

@@ -629,7 +629,7 @@ repeat:
 	page = radix_tree_lookup(&mapping->page_tree, offset);
 	if (page) {
 		page_cache_get(page);
-		if (TestSetPageLocked(page)) {
+		if (!trylock_page(page)) {
 			read_unlock_irq(&mapping->tree_lock);
 			__lock_page(page);

@@ -801,7 +801,7 @@ grab_cache_page_nowait(struct address_sp
 	struct page *page = find_get_page(mapping, index);
 
 	if (page) {
-		if (!TestSetPageLocked(page))
+		if (trylock_page(page))
 			return page;
 		page_cache_release(page);
 		return NULL;

fs/splice.c +1 -1

Index: linux-2.6/fs/splice.c
===================================================================
@@ -364,7 +364,7 @@ __generic_file_splice_read(struct file *
 			 * for an in-flight io page
 			 */
 			if (flags & SPLICE_F_NONBLOCK) {
-				if (TestSetPageLocked(page))
+				if (!trylock_page(page))
 					break;
 			} else
 				lock_page(page);

fs/afs/write.c +1 -1

Index: linux-2.6/fs/afs/write.c
===================================================================
@@ -404,7 +404,7 @@ static int afs_write_back_from_locked_pa
 			page = pages[loop];
 			if (page->index > wb->last)
 				break;
-			if (TestSetPageLocked(page))
+			if (!trylock_page(page))
 				break;
 			if (!PageDirty(page) ||
 			    page_private(page) != (unsigned long) wb) {

fs/reiserfs/journal.c +1 -1

Index: linux-2.6/fs/reiserfs/journal.c
===================================================================
@@ -629,7 +629,7 @@ static int journal_list_still_alive(stru
 static void release_buffer_page(struct buffer_head *bh)
 {
 	struct page *page = bh->b_page;
-	if (!page->mapping && !TestSetPageLocked(page)) {
+	if (!page->mapping && trylock_page(page)) {
 		page_cache_get(page);
 		put_bh(bh);
 		if (!page->mapping)

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Nick Piggin

author

2007-11-10 05:15 UTC #1 lore raw

PATCH 2/2 fs: buffer trylock rename

fs: rename buffer trylock

Converting the buffer lock to new bitops also requires name change, so convert the raw test_and_set bitop to a trylock.

Signed-off-by Nick Piggin <[email protected]>

---
 fs/buffer.c                 |    4 ++--
 fs/jbd/commit.c             |    2 +-
 fs/jbd2/commit.c            |    2 +-
 fs/ntfs/aops.c              |    2 +-
 fs/ntfs/compress.c          |    2 +-
 fs/ntfs/mft.c               |    4 ++--
 fs/reiserfs/inode.c         |    2 +-
 fs/reiserfs/journal.c       |    4 ++--
 include/linux/buffer_head.h |    8 ++++++--
 9 files changed, 17 insertions(+), 13 deletions(-)

fs/jbd/commit.c +1 -1

Index: linux-2.6/fs/jbd/commit.c
===================================================================
@@ -208,7 +208,7 @@ write_out_data:
 		 * blocking lock_buffer().
 		 */
 		if (buffer_dirty(bh)) {
-			if (test_set_buffer_locked(bh)) {
+			if (!trylock_buffer(bh)) {
 				BUFFER_TRACE(bh, "needs blocking lock");
 				spin_unlock(&journal->j_list_lock);
 				/* Write out all data to prevent deadlocks */

fs/jbd2/commit.c +1 -1

Index: linux-2.6/fs/jbd2/commit.c
===================================================================
@@ -208,7 +208,7 @@ write_out_data:
 		 * blocking lock_buffer().
 		 */
 		if (buffer_dirty(bh)) {
-			if (test_set_buffer_locked(bh)) {
+			if (!trylock_buffer(bh)) {
 				BUFFER_TRACE(bh, "needs blocking lock");
 				spin_unlock(&journal->j_list_lock);
 				/* Write out all data to prevent deadlocks */

fs/buffer.c +2 -2

Index: linux-2.6/fs/buffer.c
===================================================================
@@ -1688,7 +1688,7 @@ static int __block_write_full_page(struc
 		 */
 		if (wbc->sync_mode != WB_SYNC_NONE || !wbc->nonblocking) {
 			lock_buffer(bh);
-		} else if (test_set_buffer_locked(bh)) {
+		} else if (!trylock_buffer(bh)) {
 			redirty_page_for_writepage(wbc, page);
 			continue;
 		}

@@ -2943,7 +2943,7 @@ void ll_rw_block(int rw, int nr, struct 
 
 		if (rw == SWRITE)
 			lock_buffer(bh);
-		else if (test_set_buffer_locked(bh))
+		else if (!trylock_buffer(bh))
 			continue;
 
 		if (rw == WRITE || rw == SWRITE) {

include/linux/buffer_head.h +6 -2

Index: linux-2.6/include/linux/buffer_head.h
===================================================================
@@ -115,7 +115,6 @@ BUFFER_FNS(Uptodate, uptodate)
 BUFFER_FNS(Dirty, dirty)
 TAS_BUFFER_FNS(Dirty, dirty)
 BUFFER_FNS(Lock, locked)
-TAS_BUFFER_FNS(Lock, locked)
 BUFFER_FNS(Req, req)
 TAS_BUFFER_FNS(Req, req)
 BUFFER_FNS(Mapped, mapped)

@@ -318,10 +317,15 @@ static inline void wait_on_buffer(struct
 		__wait_on_buffer(bh);
 }
 
+static inline int trylock_buffer(struct buffer_head *bh)
+{
+	return likely(!test_and_set_bit(BH_Lock, &bh->b_state));
+}
+
 static inline void lock_buffer(struct buffer_head *bh)
 {
 	might_sleep();
-	if (test_set_buffer_locked(bh))
+	if (!trylock_buffer(bh))
 		__lock_buffer(bh);
 }

fs/ntfs/aops.c +1 -1

Index: linux-2.6/fs/ntfs/aops.c
===================================================================
@@ -1191,7 +1191,7 @@ lock_retry_remap:
 		tbh = bhs[i];
 		if (!tbh)
 			continue;
-		if (unlikely(test_set_buffer_locked(tbh)))
+		if (!trylock_buffer(tbh))
 			BUG();
 		/* The buffer dirty state is now irrelevant, just clean it. */
 		clear_buffer_dirty(tbh);

fs/ntfs/compress.c +1 -1

Index: linux-2.6/fs/ntfs/compress.c
===================================================================
@@ -665,7 +665,7 @@ lock_retry_remap:
 	for (i = 0; i < nr_bhs; i++) {
 		struct buffer_head *tbh = bhs[i];
 
-		if (unlikely(test_set_buffer_locked(tbh)))
+		if (!trylock_buffer(tbh))
 			continue;
 		if (unlikely(buffer_uptodate(tbh))) {
 			unlock_buffer(tbh);

fs/ntfs/mft.c +2 -2

Index: linux-2.6/fs/ntfs/mft.c
===================================================================
@@ -586,7 +586,7 @@ int ntfs_sync_mft_mirror(ntfs_volume *vo
 		for (i_bhs = 0; i_bhs < nr_bhs; i_bhs++) {
 			struct buffer_head *tbh = bhs[i_bhs];
 
-			if (unlikely(test_set_buffer_locked(tbh)))
+			if (!trylock_buffer(tbh))
 				BUG();
 			BUG_ON(!buffer_uptodate(tbh));
 			clear_buffer_dirty(tbh);

@@ -779,7 +779,7 @@ int write_mft_record_nolock(ntfs_inode *
 	for (i_bhs = 0; i_bhs < nr_bhs; i_bhs++) {
 		struct buffer_head *tbh = bhs[i_bhs];
 
-		if (unlikely(test_set_buffer_locked(tbh)))
+		if (!trylock_buffer(tbh))
 			BUG();
 		BUG_ON(!buffer_uptodate(tbh));
 		clear_buffer_dirty(tbh);

fs/reiserfs/inode.c +1 -1

Index: linux-2.6/fs/reiserfs/inode.c
===================================================================
@@ -2433,7 +2433,7 @@ static int reiserfs_write_full_page(stru
 		if (wbc->sync_mode != WB_SYNC_NONE || !wbc->nonblocking) {
 			lock_buffer(bh);
 		} else {
-			if (test_set_buffer_locked(bh)) {
+			if (!trylock_buffer(bh)) {
 				redirty_page_for_writepage(wbc, page);
 				continue;
 			}

fs/reiserfs/journal.c +2 -2

Index: linux-2.6/fs/reiserfs/journal.c
===================================================================
@@ -857,7 +857,7 @@ static int write_ordered_buffers(spinloc
 		jh = JH_ENTRY(list->next);
 		bh = jh->bh;
 		get_bh(bh);
-		if (test_set_buffer_locked(bh)) {
+		if (!trylock_buffer(bh)) {
 			if (!buffer_dirty(bh)) {
 				list_move(&jh->list, &tmp);
 				goto loop_next;

@@ -3877,7 +3877,7 @@ int reiserfs_prepare_for_journal(struct 
 {
 	PROC_INFO_INC(p_s_sb, journal.prepare);
 
-	if (test_set_buffer_locked(bh)) {
+	if (!trylock_buffer(bh)) {
 		if (!wait)
 			return 0;
 		lock_buffer(bh);

Peter Zijlstra

Acked-by on v1 2/2

2007-11-10 11:44 UTC #2 lore raw

Re: [patch 2/2] fs: buffer trylock rename

Quoted 6 lines · Nick Piggin

fs: rename buffer trylock
Converting the buffer lock to new bitops also requires name change, so convert the raw test_and_set bitop to a trylock.
Signed-off-by Nick Piggin <[email protected]>

Looks simple enough, I'll look into doing a lockdep annotation for it some time.

Acked-by Peter Zijlstra <[email protected]>

Nick Piggin

author

2007-11-10 05:43 UTC #3 lore raw

In reply to Nick Piggin

Here's a little something to make up for the occasional extra cacheline write in add_to_page_cache. Saves an atomic operation and 2 memory barriers for every add_to_page_cache().

I suspect lockdepifying the page lock will also barf without this, too...

---
Setting and clearing the page locked when inserting it into swapcache / pagecache when it has no other references can use non-atomic page flags operatoins because no other CPU may be operating on it at this time.

Also, remove comments in add_to_swap_cache that suggest the contrary, and rename it to add_to_swap_cache_lru(), better matching the filemap code, and which meaks it more clear that the page has no other references yet.

Also, the comments in add_to_page_cache aren't really correct. It is not just called for new pages, but for tmpfs pages as well. They are locked when called, so it is OK for atomic bitflag access, but we can't do non-atomic access. Split this into add_to_page_cache_locked, for tmpfs.

Signed-off-by Nick Piggin <[email protected]>

---

mm/filemap.c +8 -9

Index: linux-2.6/mm/filemap.c
===================================================================
@@ -426,29 +426,28 @@ int filemap_write_and_wait_range(struct 
 }
 
 /**
- * add_to_page_cache - add newly allocated pagecache pages
+ * add_to_page_cache_locked - add a locked page to pagecache
  * @page:	page to add
  * @mapping:	the page's address_space
  * @offset:	page index
  * @gfp_mask:	page allocation mode
  *
- * This function is used to add newly allocated pagecache pages;
- * the page is new, so we can just run set_page_locked() against it.
- * The other page state flags were set by rmqueue().
- *
+ * This function is used to add a page to the pagecache. It must be locked.
  * This function does not add the page to the LRU.  The caller must do that.
  */
-int add_to_page_cache(struct page *page, struct address_space *mapping,
+int add_to_page_cache_locked(struct page *page, struct address_space *mapping,
 		pgoff_t offset, gfp_t gfp_mask)
 {
-	int error = radix_tree_preload(gfp_mask & ~__GFP_HIGHMEM);
+	int error;
+
+	VM_BUG_ON(!PageLocked(page));
 
+	error = radix_tree_preload(gfp_mask & ~__GFP_HIGHMEM);
 	if (error == 0) {
 		write_lock_irq(&mapping->tree_lock);
 		error = radix_tree_insert(&mapping->page_tree, offset, page);
 		if (!error) {
 			page_cache_get(page);
-			set_page_locked(page);
 			page->mapping = mapping;
 			page->index = offset;
 			mapping->nrpages++;

@@ -459,7 +458,7 @@ int add_to_page_cache(struct page *page,
 	}
 	return error;
 }
-EXPORT_SYMBOL(add_to_page_cache);
+EXPORT_SYMBOL(add_to_page_cache_locked);
 
 int add_to_page_cache_lru(struct page *page, struct address_space *mapping,
 				pgoff_t offset, gfp_t gfp_mask)

mm/swap_state.c +7 -9

Index: linux-2.6/mm/swap_state.c
===================================================================
@@ -95,7 +95,7 @@ static int __add_to_swap_cache(struct pa
 	return error;
 }
 
-static int add_to_swap_cache(struct page *page, swp_entry_t entry)
+static int add_to_swap_cache_lru(struct page *page, swp_entry_t entry)
 {
 	int error;

@@ -104,19 +104,18 @@ static int add_to_swap_cache(struct page
 		INC_CACHE_INFO(noent_race);
 		return -ENOENT;
 	}
-	set_page_locked(page);
+	__set_page_locked(page);
 	error = __add_to_swap_cache(page, entry, GFP_KERNEL);
-	/*
-	 * Anon pages are already on the LRU, we don't run lru_cache_add here.
-	 */
 	if (error) {
-		clear_page_locked(page);
+		__clear_page_locked(page);
 		swap_free(entry);
 		if (error == -EEXIST)
 			INC_CACHE_INFO(exist_race);
 		return error;
 	}
 	INC_CACHE_INFO(add_total);
+	lru_cache_add_active(page);
+
 	return 0;
 }

@@ -235,7 +234,7 @@ int move_to_swap_cache(struct page *page
 int move_from_swap_cache(struct page *page, unsigned long index,
 		struct address_space *mapping)
 {
-	int err = add_to_page_cache(page, mapping, index, GFP_ATOMIC);
+	int err = add_to_page_cache_locked(page, mapping, index, GFP_ATOMIC);
 	if (!err) {
 		delete_from_swap_cache(page);
 		/* shift page from clean_pages to dirty_pages list */

@@ -353,12 +352,11 @@ struct page *read_swap_cache_async(swp_e
 		 * the just freed swap entry for an existing page.
 		 * May fail (-ENOMEM) if radix-tree node allocation failed.
 		 */
-		err = add_to_swap_cache(new_page, entry);
+		err = add_to_swap_cache_lru(new_page, entry);
 		if (!err) {
 			/*
 			 * Initiate read into locked page and return.
 			 */
-			lru_cache_add_active(new_page);
 			swap_readpage(NULL, new_page);
 			return new_page;
 		}

include/linux/pagemap.h +33 ~~-11~~

66 lines not on this page · raw message

Peter Zijlstra

Reviewed-by

2007-11-10 11:51 UTC #4 lore raw

Quoted 5 lines · Nick Piggin

Here's a little something to make up for the occasional extra cacheline write in add_to_page_cache. Saves an atomic operation and 2 memory barriers for every add_to_page_cache().
I suspect lockdepifying the page lock will also barf without this, too...

Yeah, I had a rather ugly trylock_page() in there. Was planning on doing something similar to this, never got round to actually doing it, thanks!

Quoted 9 lines

---
Setting and clearing the page locked when inserting it into swapcache / pagecache when it has no other references can use non-atomic page flags operatoins because no other CPU may be operating on it at this time.
Also, remove comments in add_to_swap_cache that suggest the contrary, and rename it to add_to_swap_cache_lru(), better matching the filemap code, and which meaks it more clear that the page has no other references yet.

Quoted 6 lines

Also, the comments in add_to_page_cache aren't really correct. It is not just called for new pages, but for tmpfs pages as well. They are locked when called, so it is OK for atomic bitflag access, but we can't do non-atomic access. Split this into add_to_page_cache_locked, for tmpfs.
Signed-off-by Nick Piggin <[email protected]>

Reviewed-by Peter Zijlstra <[email protected]>

Nick Piggin

author

2007-11-11 08:40 UTC #5 lore raw

PATCH 1/1 mm: unlockless reclaim

Combined with the previous and subsequent patches, throughput of pages through the pagecache on an Opteron system here goes up by anywhere from 50% to 500%, depending on the number of files and threads involved.
--

unlock_page is fairly expensive. It can be avoided in page reclaim.

Signed-off-by Nick Piggin <[email protected]>

---

mm/vmscan.c +8 -1

Index: linux-2.6/mm/vmscan.c
===================================================================
@@ -589,7 +589,14 @@ static unsigned long shrink_page_list(st
 			goto keep_locked;
 
 free_it:
-		unlock_page(page);
+		/*
+		 * At this point, we have no other references and there is
+		 * no way to pick any more up (removed from LRU, removed
+		 * from pagecache). Can use non-atomic bitops now (and
+		 * we obviously don't have to worry about waking up a process
+		 * waiting on the page lock, because there are no references.
+		 */
+		__clear_page_locked(page);
 		nr_reclaimed++;
 		if (!pagevec_add(&freed_pvec, page))
 			__pagevec_release_nonlru(&freed_pvec);

Peter Zijlstra

Acked-by on v1 1/2

2007-11-10 11:43 UTC #6 lore raw

In reply to Nick Piggin

Quoted 5 lines · Nick Piggin

Hi,
OK minus the memory barrier changes for now. Can we possibly please get these into 2.6.24?

Quoted 8 lines

--
mm: rename page trylock
Converting page lock to new locking bitops requires a change of page flag operation naming, so we might as well convert it to something nicer (!TestSetPageLocked => trylock_page, SetPageLocked => set_page_locked).
Signed-off-by Nick Piggin <[email protected]>

Acked-by Peter Zijlstra <[email protected]>