Re: [PATCH v2 10/15] cifs: have ->mkdir() handle race with another client sanely

[Jeff Layton <jlayton@kernel.org>]

On Sat, 2021-03-13 at 04:38 +0000, Al Viro wrote:
> if we have mkdir request reported successful *and* simulating lookup
> gets us a non-directory (which is possible if another client has
> managed to get rmdir and create in between), the sane action is not
> to mangle ->i_mode of non-directory inode to S_IFDIR | mode, it's
> "report success and return with dentry negative unhashed" - that
> way the next lookup will do the right thing.
> 
> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
> ---
>  fs/cifs/inode.c | 12 +++++++++++-
>  1 file changed, 11 insertions(+), 1 deletion(-)
> 
> diff --git a/fs/cifs/inode.c b/fs/cifs/inode.c
> index d46b36d52211..80c487fcf10e 100644
> --- a/fs/cifs/inode.c
> +++ b/fs/cifs/inode.c
> @@ -1739,6 +1739,16 @@ cifs_mkdir_qinfo(struct inode *parent, struct dentry *dentry, umode_t mode,
>  	if (rc)
>  		return rc;
>  
> 
> +	if (!S_ISDIR(inode->i_mode)) {
> +		/*
> +		 * mkdir succeeded, but another client has managed to remove the
> +		 * sucker and replace it with non-directory.  Return success,
> +		 * but don't leave the child in dcache.
> +		 */
> +		 iput(inode);
> +		 d_drop(dentry);
> +		 return 0;
> +	}
>  	/*
>  	 * setting nlink not necessary except in cases where we failed to get it
>  	 * from the server or was set bogus. Also, since this is a brand new
> @@ -1790,7 +1800,7 @@ cifs_mkdir_qinfo(struct inode *parent, struct dentry *dentry, umode_t mode,
>  		}
>  	}
>  	d_instantiate(dentry, inode);
> -	return rc;
> +	return 0;
>  }
>  
> 
>  static int

Reviewed-by: Jeff Layton <jlayton@kernel.org>