On Wed, Aug 26, 2015 at 04:16:46PM +0800, Peng Tao wrote:
> Signed-off-by: Peng Tao <tao.peng@xxxxxxxxxxxxxxx>
> ---
> fs/nfs/nfs4file.c | 50 ++++++++++++++++++++++++++++++++++++++++++++++++++
> 1 file changed, 50 insertions(+)
>
> diff --git a/fs/nfs/nfs4file.c b/fs/nfs/nfs4file.c
> index dcd39d4..c335cb0 100644
> --- a/fs/nfs/nfs4file.c
> +++ b/fs/nfs/nfs4file.c
> @@ -4,6 +4,7 @@
> * Copyright (C) 1992 Rick Sladkey
> */
> #include <linux/fs.h>
> +#include <linux/file.h>
> #include <linux/falloc.h>
> #include <linux/nfs_fs.h>
> #include "internal.h"
> @@ -166,6 +167,54 @@ static long nfs42_fallocate(struct file *filep, int mode, loff_t offset, loff_t
> return nfs42_proc_deallocate(filep, offset, len);
> return nfs42_proc_allocate(filep, offset, len);
> }
> +
> +static noinline int
> +nfs42_file_clone_range(struct file *src_file, struct file *dst_file,
> + loff_t src_off, size_t dst_off, loff_t count)
> +{
> + struct inode *dst_inode = file_inode(dst_file);
> + struct inode *src_inode = file_inode(src_file);
> + int ret;
> +
> + /* src and dst must be different files */
> + if (src_inode == dst_inode)
> + return -EINVAL;
> +
> + /* XXX: do we lock at all? what if server needs CB_RECALL_LAYOUT? */
> + if (dst_inode < src_inode) {
> + mutex_lock_nested(&dst_inode->i_mutex, I_MUTEX_PARENT);
> + mutex_lock_nested(&src_inode->i_mutex, I_MUTEX_CHILD);
> + } else {
> + mutex_lock_nested(&src_inode->i_mutex, I_MUTEX_PARENT);
> + mutex_lock_nested(&dst_inode->i_mutex, I_MUTEX_CHILD);
> + }
Is that safe? Between two operations, the inode code be reclaimed
and re-instantiated, resulting in the second operation having a
different locking order for the same files compared to the
first operation...
> +out_unlock:
> + if (dst_inode < src_inode) {
> + mutex_unlock(&src_inode->i_mutex);
> + mutex_unlock(&dst_inode->i_mutex);
> + } else {
> + mutex_unlock(&dst_inode->i_mutex);
> + mutex_unlock(&src_inode->i_mutex);
> + }
You don't have to care about lock order on unlock.
Cheers,
Dave.
--
Dave Chinner
david@xxxxxxxxxxxxx
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