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Subject[patch 04/30] nilfs2: fix missing zero-fill initialization of btree node cache
2.6.30-stable review patch.  If anyone has any objections, please let us know.

------------------
From: Ryusuke Konishi <konishi.ryusuke@lab.ntt.co.jp>
commit 1f28fcd925b2b3157411bbd08f0024b55b70d8dd upstream.

This will fix file system corruption which infrequently happens after
mount. The problem was reported from users with the title "[NILFS
users] Fail to mount NILFS." (Message-ID:
<200908211918.34720.yuri@itinteg.net>), and so forth. I've also
experienced the corruption multiple times on kernel 2.6.30 and 2.6.31.

The problem turned out to be caused due to discordance between
mapping->nrpages of a btree node cache and the actual number of pages
hung on the cache; if the mapping->nrpages becomes zero even as it has
pages, truncate_inode_pages() returns without doing anything. Usually
this is harmless except it may cause page leak, but garbage collection
fairly infrequently sees a stale page remained in the btree node cache
of DAT (i.e. disk address translation file of nilfs), and induces the
corruption.

I identified a missing initialization in btree node caches was the
root cause. This corrects the bug.

I've tested this for kernel 2.6.30 and 2.6.31.

Reported-by: Yuri Chislov <yuri@itinteg.net>
Signed-off-by: Ryusuke Konishi <konishi.ryusuke@lab.ntt.co.jp>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

---
fs/nilfs2/btnode.c | 1 +
1 file changed, 1 insertion(+)
--- a/fs/nilfs2/btnode.c
+++ b/fs/nilfs2/btnode.c
@@ -36,6 +36,7 @@

void nilfs_btnode_cache_init_once(struct address_space *btnc)
{
+ memset(btnc, 0, sizeof(*btnc));
INIT_RADIX_TREE(&btnc->page_tree, GFP_ATOMIC);
spin_lock_init(&btnc->tree_lock);
INIT_LIST_HEAD(&btnc->private_list);



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