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    Subject[PATCH 3.12 041/122] nfs: fix dio deadlock when O_DIRECT flag is flipped
    Date
    From: Peng Tao <tao.peng@primarydata.com>

    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@primarydata.com>
    Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>
    Signed-off-by: Jiri Slaby <jslaby@suse.cz>
    ---
    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;
    +
    #ifndef CONFIG_NFS_SWAP
    dprintk("NFS: nfs_direct_IO (%s) off/no(%Ld/%lu) EINVAL\n",
    iocb->ki_filp->f_path.dentry->d_name.name,
    --
    2.2.2


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