linux-kernel - Re: [fuse-devel] [PATCH] fuse: Fix fuse_get_user

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Date:	Tue, 19 Apr 2016 15:57:52 -0700
From:	Ashish Samant <ashish.samant@...cle.com>
To:	Seth Forshee <seth.forshee@...onical.com>,
	Miklos Szeredi <miklos@...redi.hu>
Cc:	fuse-devel@...ts.sourceforge.net, linux-kernel@...r.kernel.org
Subject: Re: [fuse-devel] [PATCH] fuse: Fix fuse_get_user_pages() return value

Hi Seth,
On 04/19/2016 03:43 PM, Seth Forshee wrote:
> fuse_direct_io() expects this to return either 0 or a negative
> error code, but on success it may return a positive value.
> fuse_direct_io() may return this same value when the subsequent
> I/O operation doesn't transfer any data, which means that it will
> return a positive value when no bytes were transferred. This is
> obviously problematic.
>
> Fix fuse_get_user_pages() to return 0 on success. This will in
> turn make it so that fuse_direct_io() returns 0 if no bytes are
> transferred.
>
> Fixes: 742f992708df ("fuse: return patrial success from fuse_direct_io()")
> Signed-off-by: Seth Forshee <seth.forshee@...onical.com>
> ---
>   fs/fuse/file.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/fs/fuse/file.c b/fs/fuse/file.c
> index b5c616c5ec98..78af5c0996b8 100644
> --- a/fs/fuse/file.c
> +++ b/fs/fuse/file.c
> @@ -1295,7 +1295,7 @@ static int fuse_get_user_pages(struct fuse_req *req, struct iov_iter *ii,
>   
>   	*nbytesp = nbytes;
>   
> -	return ret;
> +	return ret < 0 ? ret : 0;
>   }
>   
>   static inline int fuse_iter_npages(const struct iov_iter *ii_p)


I have already sent a patch to the list that does exactly the same thing :)

https://sourceforge.net/p/fuse/mailman/message/34966327/

Thanks,
Ashish