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nfs: fix dio deadlock when O_DIRECT flag is flipped 

commit ee8a1a8b16 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: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Peng Tao 2015-01-20 07:44:29 +08:00 committed by Greg Kroah-Hartman
parent 907fe767f3
commit 1066a175c7
1 changed files with 6 additions and 0 deletions
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6
fs/nfs/direct.c
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@ -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 (%pD) off/no(%Ld/%lu) EINVAL\n",
iocb->ki_filp, (long long) pos, nr_segs);