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authorNick Piggin <npiggin@suse.de>2007-10-16 01:24:41 -0700
committerLinus Torvalds <torvalds@woody.linux-foundation.org>2007-10-16 09:42:53 -0700
commit45726cb43d11b288c58243a26010f397054222f0 (patch)
treeae1804a34f314be18865add063d660cf783e45be
parent001281881067a5998384c6669bc8dbbbab8456c4 (diff)
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>
-rw-r--r--mm/filemap.c9
1 files changed, 5 insertions, 4 deletions
diff --git a/mm/filemap.c b/mm/filemap.c
index b436cbb3a83..7989c44cb29 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);