On Thu, 2017-06-15 at 12:13 -0400, Benjamin Coddington wrote:
> An interrupted rename will leave the old dentry behind if the rename
> succeeds. Fix this by forcing a lookup the next time through
> ->d_revalidate.
>
> A previous attempt at solving this problem took the approach to complete
> the work of the rename asynchronously, however that approach was wrong
> since it would allow the d_move() to occur after the directory's i_mutex
> had been dropped by the original process.
>
> Signed-off-by: Benjamin Coddington <bcodding@xxxxxxxxxx>
> ---
> fs/nfs/dir.c | 2 ++
> fs/nfs/unlink.c | 7 +++++++
> include/linux/nfs_xdr.h | 1 +
> 3 files changed, 10 insertions(+)
>
> diff --git a/fs/nfs/dir.c b/fs/nfs/dir.c
> index 1faf337b316f..bb697e5c3f6c 100644
> --- a/fs/nfs/dir.c
> +++ b/fs/nfs/dir.c
> @@ -2037,6 +2037,8 @@ int nfs_rename(struct inode *old_dir, struct dentry *old_dentry,
> error = rpc_wait_for_completion_task(task);
> if (error == 0)
> error = task->tk_status;
> + else
> + ((struct nfs_renamedata *)task->tk_calldata)->cancelled = 1;
This looks a bit racy. You could end up setting cancelled just after the
reply comes in and the completion callback checks it. I think that you
probably either want to do this with an atomic operation or under a lock
of some sort.
You could probably do it with an xchg() operation?
> rpc_put_task(task);
> nfs_mark_for_revalidate(old_inode);
> out:
> diff --git a/fs/nfs/unlink.c b/fs/nfs/unlink.c
> index 191aa577dd1f..b47158a34879 100644
> --- a/fs/nfs/unlink.c
> +++ b/fs/nfs/unlink.c
> @@ -288,6 +288,13 @@ static void nfs_async_rename_release(void *calldata)
> if (d_really_is_positive(data->old_dentry))
> nfs_mark_for_revalidate(d_inode(data->old_dentry));
>
> + /* The result of the rename is unknown. Play it safe by
> + * forcing a new lookup */
> + if (data->cancelled) {
> + nfs_force_lookup_revalidate(data->old_dir);
> + nfs_force_lookup_revalidate(data->new_dir);
> + }
> +
> dput(data->old_dentry);
> dput(data->new_dentry);
> iput(data->old_dir);
> diff --git a/include/linux/nfs_xdr.h b/include/linux/nfs_xdr.h
> index b28c83475ee8..2a8406b4b353 100644
> --- a/include/linux/nfs_xdr.h
> +++ b/include/linux/nfs_xdr.h
> @@ -1533,6 +1533,7 @@ struct nfs_renamedata {
> struct nfs_fattr new_fattr;
> void (*complete)(struct rpc_task *, struct nfs_renamedata *);
> long timeout;
> + int cancelled;
No need for a whole int for a flag and these do get allocated. Make it a
bool?
> };
>
> struct nfs_access_entry;
--
Jeff Layton <jlayton@xxxxxxxxxx>
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