diff options
| author | Nick Piggin <npiggin@suse.de> | 2007-10-16 01:24:41 -0700 |
|---|---|---|
| committer | Linus Torvalds <torvalds@woody.linux-foundation.org> | 2007-10-16 09:42:53 -0700 |
| commit | 45726cb43d11b288c58243a26010f397054222f0 (patch) | |
| tree | ae1804a34f314be18865add063d660cf783e45be /mm/filemap.c | |
| parent | 001281881067a5998384c6669bc8dbbbab8456c4 (diff) | |
| download | lwn-45726cb43d11b288c58243a26010f397054222f0.tar.gz lwn-45726cb43d11b288c58243a26010f397054222f0.zip | |
mm: improve find_lock_page
find_lock_page does not need to recheck ->index because if the page is in the
right mapping then the index must be the same. Also, tree_lock does not need
to be retaken after the page is locked in order to test that ->mapping has not
changed, because holding the page lock pins its mapping.
Signed-off-by: Nick Piggin <npiggin@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm/filemap.c')
| -rw-r--r-- | mm/filemap.c | 9 |
1 files changed, 5 insertions, 4 deletions
diff --git a/mm/filemap.c b/mm/filemap.c index b436cbb3a834..7989c44cb293 100644 --- a/mm/filemap.c +++ b/mm/filemap.c @@ -621,26 +621,27 @@ struct page *find_lock_page(struct address_space *mapping, { struct page *page; - read_lock_irq(&mapping->tree_lock); repeat: + read_lock_irq(&mapping->tree_lock); page = radix_tree_lookup(&mapping->page_tree, offset); if (page) { page_cache_get(page); if (TestSetPageLocked(page)) { read_unlock_irq(&mapping->tree_lock); __lock_page(page); - read_lock_irq(&mapping->tree_lock); /* Has the page been truncated while we slept? */ - if (unlikely(page->mapping != mapping || - page->index != offset)) { + if (unlikely(page->mapping != mapping)) { unlock_page(page); page_cache_release(page); goto repeat; } + VM_BUG_ON(page->index != offset); + goto out; } } read_unlock_irq(&mapping->tree_lock); +out: return page; } EXPORT_SYMBOL(find_lock_page); |