Re: [PATCH] Fix bug in FUSE where the attribute cache for a file was not cleared when a file is opened with O_TRUNC.

[Andrew Morton <akpm@linux-foundation.org>]

On Sat, 30 Oct 2010 13:31:23 +0200
Miklos Szeredi <miklos@szeredi.hu> wrote:

> Subject: fuse: fix attributes after open(O_TRUNC)
> From: Ken Sumrall <ksumrall@android.com>
> 
> The attribute cache for a file was not being cleared when a file is
> opened with O_TRUNC.
> 
> If the filesystem's open operation truncates the file
> ("atomic_o_trunc" feature flag is set) then the kernel should
> invalidate the cached st_mtime and st_ctime attributes.
> 
> Also i_size should be explicitly be set to zero as it is used
> sometimes without refreshing the cache.
> 
> Signed-off-by: Ken Sumrall <ksumrall@android.com>
> Cc: Anfei <anfei.zhou@gmail.com>
> Cc: "Anand V. Avati" <avati@gluster.com>
> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
> Signed-off-by: Miklos Szeredi <miklos@szeredi.hu>
> Cc: stable@kernel.org
> ---
> 
>  fs/fuse/file.c |   10 ++++++++++
>  1 file changed, 10 insertions(+)
> 
> Index: linux-2.6/fs/fuse/file.c
> ===================================================================
> --- linux-2.6.orig/fs/fuse/file.c	2010-10-27 14:04:02.000000000 +0200
> +++ linux-2.6/fs/fuse/file.c	2010-10-30 13:14:07.000000000 +0200
> @@ -134,6 +134,7 @@ EXPORT_SYMBOL_GPL(fuse_do_open);
>  void fuse_finish_open(struct inode *inode, struct file *file)
>  {
>  	struct fuse_file *ff = file->private_data;
> +	struct fuse_conn *fc = get_fuse_conn(inode);
>  
>  	if (ff->open_flags & FOPEN_DIRECT_IO)
>  		file->f_op = &fuse_direct_io_file_operations;
> @@ -141,6 +142,15 @@ void fuse_finish_open(struct inode *inod
>  		invalidate_inode_pages2(inode->i_mapping);
>  	if (ff->open_flags & FOPEN_NONSEEKABLE)
>  		nonseekable_open(inode, file);
> +	if (fc->atomic_o_trunc && (file->f_flags & O_TRUNC)) {
> +		struct fuse_inode *fi = get_fuse_inode(inode);
> +
> +		spin_lock(&fc->lock);
> +		fi->attr_version = ++fc->attr_version;
> +		i_size_write(inode, 0);

i_size_write() requires that i_mutex be held, as described at the
i_size_write() definition site.

Is it reliably the case that i_mutex is held here?

> +		spin_unlock(&fc->lock);
> +		fuse_invalidate_attr(inode);
> +	}
>  }
>  
>  int fuse_open_common(struct inode *inode, struct file *file, bool isdir)