On Mon, Feb 22, 2016 at 09:28:34AM -0500, Vivek Goyal wrote:
> During mount, make sure upper fs supports d_type otherwise error out.
>
> In some instances xfs has been created with ftype=0 and there if a file
> on lower fs is removed, overlay leaves a whiteout in upper fs but that
> whiteout does not get filtered out and is visible to overlayfs users.
>
> And reason it does not get filtered out because upper filesystem does
> not report file type of whiteout as DT_CHR during iterate_dir().
>
> So it seems to be a requirement that upper filesystem support d_type for
> overlayfs to work properly. Do this check during mount and fail if d_type
> is not supported.
>
> Suggested-by: Dave Chinner <dchinner@xxxxxxxxxx>
> Signed-off-by: Vivek Goyal <vgoyal@xxxxxxxxxx>
Queued. Thanks.
Miklos
> ---
> fs/overlayfs/overlayfs.h | 1 +
> fs/overlayfs/readdir.c | 37 +++++++++++++++++++++++++++++++++++++
> fs/overlayfs/super.c | 15 +++++++++++++++
> 3 files changed, 53 insertions(+)
>
> Index: rhvgoyal-linux/fs/overlayfs/readdir.c
> ===================================================================
> --- rhvgoyal-linux.orig/fs/overlayfs/readdir.c 2016-02-19 16:10:09.440000000 +0000
> +++ rhvgoyal-linux/fs/overlayfs/readdir.c 2016-02-22 14:09:30.745000000 +0000
> @@ -43,6 +43,7 @@ struct ovl_readdir_data {
> struct ovl_cache_entry *first_maybe_whiteout;
> int count;
> int err;
> + bool d_type_supported;
> };
>
> struct ovl_dir_file {
> @@ -577,3 +578,39 @@ void ovl_cleanup_whiteouts(struct dentry
> }
> inode_unlock(upper->d_inode);
> }
> +
> +static int ovl_check_d_type(struct dir_context *ctx, const char *name,
> + int namelen, loff_t offset, u64 ino,
> + unsigned int d_type)
> +{
> + struct ovl_readdir_data *rdd =
> + container_of(ctx, struct ovl_readdir_data, ctx);
> +
> + /* Even if d_type is not supported, DT_DIR is returned for . and .. */
> + if (!strncmp(name, ".", namelen) || !strncmp(name, "..", namelen))
> + return 0;
> +
> + if (d_type != DT_UNKNOWN)
> + rdd->d_type_supported = true;
> +
> + return 0;
> +}
> +
> +/*
> + * Returns 1 if d_type is supported, 0 not supported/unknown. Negative values
> + * if error is encountered.
> + */
> +int ovl_check_d_type_supported(struct path *realpath)
> +{
> + int err;
> + struct ovl_readdir_data rdd = {
> + .ctx.actor = ovl_check_d_type,
> + .d_type_supported = false,
> + };
> +
> + err = ovl_dir_read(realpath, &rdd);
> + if (err)
> + return err;
> +
> + return rdd.d_type_supported;
> +}
> Index: rhvgoyal-linux/fs/overlayfs/overlayfs.h
> ===================================================================
> --- rhvgoyal-linux.orig/fs/overlayfs/overlayfs.h 2016-02-19 16:10:09.440000000 +0000
> +++ rhvgoyal-linux/fs/overlayfs/overlayfs.h 2016-02-22 14:09:30.746000000 +0000
> @@ -166,6 +166,7 @@ extern const struct file_operations ovl_
> int ovl_check_empty_dir(struct dentry *dentry, struct list_head *list);
> void ovl_cleanup_whiteouts(struct dentry *upper, struct list_head *list);
> void ovl_cache_free(struct list_head *list);
> +int ovl_check_d_type_supported(struct path *realpath);
>
> /* inode.c */
> int ovl_setattr(struct dentry *dentry, struct iattr *attr);
> Index: rhvgoyal-linux/fs/overlayfs/super.c
> ===================================================================
> --- rhvgoyal-linux.orig/fs/overlayfs/super.c 2016-02-19 16:10:09.440000000 +0000
> +++ rhvgoyal-linux/fs/overlayfs/super.c 2016-02-22 14:09:30.746000000 +0000
> @@ -1025,6 +1025,21 @@ static int ovl_fill_super(struct super_b
> sb->s_flags |= MS_RDONLY;
> ufs->workdir = NULL;
> }
> +
> + /*
> + * Upper should support d_type, else whiteouts are visible.
> + * Given workdir and upper are on same fs, we can do
> + * iterate_dir() on workdir.
> + */
> + err = ovl_check_d_type_supported(&workpath);
> + if (err < 0)
> + goto out_put_workdir;
> +
> + if (!err) {
> + pr_err("overlayfs: upper fs needs to support d_type.\n");
> + err = -EINVAL;
> + goto out_put_workdir;
> + }
> }
>
> err = -ENOMEM;
--
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