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
2010-11-11T22:11:38Z

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)