Re: Checking page_count(page) in invalidate_complete_page

Andrew Morton
2006-09-29T21:44:21Z

buggerit, let's do this. It'll fix NFS, yes?

From: Andrew Morton <akpm@osdl.org>

The recent fix to invalidate_inode_pages() (git commit 016eb4a) managed to
unfix invalidate_inode_pages2().

The problem is that various bits of code in the kernel can take transient refs
on pages: the page scanner will do this when inspecting a batch of pages, and
the lru_cache_add() batching pagevecs also hold a ref.

Net result is transient failures in invalidate_inode_pages2(). This affects
NFS directory invalidation (observed) and presumably also block-backed
direct-io (not yet reported).

Fix it by reverting invalidate_inode_pages2() back to the old version which
ignores the page refcounts.

We may come up with something more clever later, but for now we need a 2.6.18
fix for NFS.

Cc: Chuck Lever <cel@citi.umich.edu>
Cc: Nick Piggin <nickpiggin@yahoo.com.au>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: <stable@kernel.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
---

mm/truncate.c | 34 ++++++++++++++++++++++++++++++++--
1 files changed, 32 insertions(+), 2 deletions(-)

diff -puN mm/truncate.c~invalidate_inode_pages2-ignore-page-refcounts mm/truncate.c
--- a/mm/truncate.c~invalidate_inode_pages2-ignore-page-refcounts
+++ a/mm/truncate.c
@@ -261,9 +261,39 @@ unsigned long invalidate_inode_pages(str
{
return invalidate_mapping_pages(mapping, 0, ~0UL);
}
-
EXPORT_SYMBOL(invalidate_inode_pages);

+/*
+ * This is like invalidate_complete_page(), except it ignores the page's
+ * refcount. We do this because invalidate_indoe_pages2() needs stronger
+ * invalidation guarantees, and cannot afford to leave pages behind because
+ * shrink_list() has a temp ref on them, or because they're transiently sitting
+ * in the lru_cache_add() pagevecs.
+ */
+static int
+invalidate_complete_page2(struct address_space *mapping, struct page *page)
+{
+ if (page->mapping != mapping)
+ return 0;
+
+ if (PagePrivate(page) && !try_to_release_page(page, 0))
+ return 0;
+
+ write_lock_irq(&mapping->tree_lock);
+ if (PageDirty(page))
+ goto failed;
+
+ BUG_ON(PagePrivate(page));
+ __remove_from_page_cache(page);
+ write_unlock_irq(&mapping->tree_lock);
+ ClearPageUptodate(page);
+ page_cache_release(page); /* pagecache ref */
+ return 1;
+failed:
+ write_unlock_irq(&mapping->tree_lock);
+ return 0;
+}
+
/**
* invalidate_inode_pages2_range - remove range of pages from an address_space
* @mapping: the address_space
@@ -330,7 +360,7 @@ int invalidate_inode_pages2_range(struct
}
}
was_dirty = test_clear_page_dirty(page);
- if (!invalidate_complete_page(mapping, page)) {
+ if (!invalidate_complete_page2(mapping, page)) {
if (was_dirty)
set_page_dirty(page);
ret = -EIO;
_