[PATCH 3.12 041/122] nfs: fix dio deadlock when O_DIRECT flag is flipped

From: Jiri Slaby
Date: Tue Feb 17 2015 - 07:08:26 EST

From: Peng Tao <tao.peng@xxxxxxxxxxxxxxx>

3.12-stable review patch. If anyone has any objections, please let me know.


commit ee8a1a8b160a87dc3a9c81a86796aa4db85ea815 upstream.

We only support swap file calling nfs_direct_IO. However, application
might be able to get to nfs_direct_IO if it toggles O_DIRECT flag
during IO and it can deadlock because we grab inode->i_mutex in
nfs_file_direct_write(). So return 0 for such case. Then the generic
layer will fall back to buffer IO.

Signed-off-by: Peng Tao <tao.peng@xxxxxxxxxxxxxxx>
Signed-off-by: Trond Myklebust <trond.myklebust@xxxxxxxxxxxxxxx>
Signed-off-by: Jiri Slaby <jslaby@xxxxxxx>
fs/nfs/direct.c | 6 ++++++
1 file changed, 6 insertions(+)

diff --git a/fs/nfs/direct.c b/fs/nfs/direct.c
index d751a2383c24..db6245c1cd33 100644
--- a/fs/nfs/direct.c
+++ b/fs/nfs/direct.c
@@ -123,6 +123,12 @@ static inline int put_dreq(struct nfs_direct_req *dreq)
ssize_t nfs_direct_IO(int rw, struct kiocb *iocb, const struct iovec *iov, loff_t pos, unsigned long nr_segs)
+ struct inode *inode = iocb->ki_filp->f_mapping->host;
+ /* we only support swap file calling nfs_direct_IO */
+ if (!IS_SWAPFILE(inode))
+ return 0;
dprintk("NFS: nfs_direct_IO (%s) off/no(%Ld/%lu) EINVAL\n",

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