path: root/fs/nfs
diff options
authorJeff Layton <jlayton@redhat.com>2012-12-10 09:25:48 -0500
committerTrond Myklebust <Trond.Myklebust@netapp.com>2012-12-11 09:14:51 -0500
commit81d9bce5309288086b58b4d97a644e495fef75f2 (patch)
tree336223a2fd5312fb80d93fd7cdc1cf4fba41d103 /fs/nfs
parent7d3e91a89b7adbc2831334def9e494dd9892f9af (diff)
nfs: don't extend writes to cover entire page if pagecache is invalid
Jian reported that the following sequence would leave "testfile" with corrupt data: # mount localhost:/export /mnt/nfs/ -o vers=3 # echo abc > /mnt/nfs/testfile; echo def >> /export/testfile; echo ghi >> /mnt/nfs/testfile # cat -v /export/testfile abc ^@^@^@^@ghi While there's no locking involved here, the operations are serialized, so CTO should prevent corruption. The first write to the file is fine and writes 4 bytes. The file is then extended on the server. When it's reopened a GETATTR is issued and the size change is noticed. This causes NFS_INO_INVALID_DATA to be set on the file. Because the file is opened for write only, nfs_want_read_modify_write() returns 0 to nfs_write_begin(). nfs_updatepage then calls nfs_write_pageuptodate() to see if it should extend the nfs_page to cover the whole page. NFS_INO_INVALID_DATA is still set on the file at that point, but that flag is ignored and nfs_pageuptodate erroneously extends the write to cover the whole page, with the write done on the server side filled in with zeroes. This patch just has that function check for NFS_INO_INVALID_DATA in addition to NFS_INO_REVAL_PAGECACHE. This fixes the bug, but looking over the code, I wonder if we might have a similar bug in nfs_revalidate_size(). The difference between those two flags is very subtle, so it seems like we ought to be checking for NFS_INO_INVALID_DATA in most of the places that we look for NFS_INO_REVAL_PAGECACHE. I believe this is regression introduced by commit 8d197a568. The code did check for NFS_INO_INVALID_DATA prior to that patch. Original bug report is here: https://bugzilla.redhat.com/show_bug.cgi?id=885743 Cc: <stable@vger.kernel.org> # 3.5+ Reported-by: Jian Li <jiali@redhat.com> Signed-off-by: Jeff Layton <jlayton@redhat.com> Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
Diffstat (limited to 'fs/nfs')
1 files changed, 1 insertions, 1 deletions
diff --git a/fs/nfs/write.c b/fs/nfs/write.c
index f710e39f6ba..eecd8b879af 100644
--- a/fs/nfs/write.c
+++ b/fs/nfs/write.c
@@ -884,7 +884,7 @@ static bool nfs_write_pageuptodate(struct page *page, struct inode *inode)
if (nfs_have_delegated_attributes(inode))
goto out;
- if (NFS_I(inode)->cache_validity & NFS_INO_REVAL_PAGECACHE)
+ if (NFS_I(inode)->cache_validity & (NFS_INO_INVALID_DATA|NFS_INO_REVAL_PAGECACHE))
return false;
return PageUptodate(page) != 0;