On Thu, Jan 4, 2018 at 6:20 PM, Amir Goldstein <amir73il@xxxxxxxxx> wrote:
> Decoding an indexed non-dir file handle is similar to decoding a lower
> non-dir file handle, but additionally, we lookup the file handle in index
> dir by name to find the real upper inode.
>
> Signed-off-by: Amir Goldstein <amir73il@xxxxxxxxx>
> ---
> fs/overlayfs/export.c | 72 +++++++++++++++++++++++++++++++++------------------
> 1 file changed, 47 insertions(+), 25 deletions(-)
>
> diff --git a/fs/overlayfs/export.c b/fs/overlayfs/export.c
> index 6b359f968c01..602bada474ba 100644
> --- a/fs/overlayfs/export.c
> +++ b/fs/overlayfs/export.c
> @@ -168,22 +168,24 @@ static int ovl_encode_inode_fh(struct inode *inode, u32 *fid, int *max_len,
> }
>
> /*
> - * Find or instantiate an overlay dentry from real dentries.
> + * Find or instantiate an overlay dentry from real dentries and index.
> */
> static struct dentry *ovl_obtain_alias(struct super_block *sb,
> - struct dentry *upper,
> - struct ovl_path *lowerpath)
> + struct dentry *upper_alias,
> + struct ovl_path *lowerpath,
> + struct dentry *index)
> {
> struct dentry *lower = lowerpath ? lowerpath->dentry : NULL;
> + struct dentry *upper = upper_alias ?: index;
> struct dentry *dentry;
> struct inode *inode;
> struct ovl_entry *oe;
>
> - /* TODO: obtain an indexed non-dir upper with origin */
> - if (lower && (upper || d_is_dir(lower)))
> + /* We get overlay directory dentries with ovl_lookup_real() */
> + if (d_is_dir(upper ?: lower))
> return ERR_PTR(-EIO);
>
> - inode = ovl_get_inode(sb, dget(upper), lower, NULL, !!lower);
> + inode = ovl_get_inode(sb, dget(upper), lower, index, !!lower);
> if (IS_ERR(inode)) {
> dput(upper);
> return ERR_CAST(inode);
> @@ -200,13 +202,16 @@ static struct dentry *ovl_obtain_alias(struct super_block *sb,
> }
>
> dentry->d_fsdata = oe;
> - if (upper)
> + if (upper_alias)
> ovl_dentry_set_upper_alias(dentry);
> if (lower) {
> oe->lowerstack->dentry = dget(lower);
> oe->lowerstack->layer = lowerpath->layer;
> }
>
> + if (index)
> + ovl_set_flag(OVL_INDEX, inode);
> +
> return dentry;
> }
>
> @@ -321,30 +326,26 @@ static struct dentry *ovl_lookup_real(struct super_block *sb,
> }
>
> /*
> - * Get an overlay dentry from upper/lower real dentries.
> + * Get an overlay dentry from upper/lower real dentries and index.
> */
> static struct dentry *ovl_get_dentry(struct super_block *sb,
> struct dentry *upper,
> - struct ovl_path *lowerpath)
> + struct ovl_path *lowerpath,
> + struct dentry *index)
> {
> + struct dentry *real = upper ?: (index ?: lowerpath->dentry);
> +
> /*
> - * Obtain a disconnected overlay dentry from a disconnected non-dir
> - * real lower dentry.
> + * Obtain a disconnected overlay dentry from a non-dir real dentry
> + * and index.
> */
> - if (!upper && !d_is_dir(lowerpath->dentry))
> - return ovl_obtain_alias(sb, NULL, lowerpath);
> + if (!d_is_dir(real))
> + return ovl_obtain_alias(sb, upper, lowerpath, index);
>
> /* TODO: lookup connected dir from real lower dir */
> if (!upper)
> return ERR_PTR(-EACCES);
>
> - /*
> - * Obtain a disconnected overlay dentry from a non-dir real upper
> - * dentry.
> - */
> - if (!d_is_dir(upper))
> - return ovl_obtain_alias(sb, upper, NULL);
> -
> /* Removed empty directory? */
> if ((upper->d_flags & DCACHE_DISCONNECTED) || d_unhashed(upper))
> return ERR_PTR(-ENOENT);
> @@ -370,7 +371,7 @@ static struct dentry *ovl_upper_fh_to_d(struct super_block *sb,
> if (IS_ERR_OR_NULL(upper))
> return upper;
>
> - dentry = ovl_get_dentry(sb, upper, NULL);
> + dentry = ovl_get_dentry(sb, upper, NULL, NULL);
> dput(upper);
>
> return dentry;
> @@ -383,17 +384,38 @@ static struct dentry *ovl_lower_fh_to_d(struct super_block *sb,
> struct ovl_path origin = { };
> struct ovl_path *stack = &origin;
> struct dentry *dentry = NULL;
> + struct dentry *index = NULL;
> int err;
>
> + /* First lookup indexed upper by fh */
> + index = ovl_get_index_fh(ofs, fh);
> + err = PTR_ERR(index);
> + if (IS_ERR(index))
> + return ERR_PTR(err);
> +
> + /* Then lookup origin by fh */
> err = ovl_check_origin_fh(fh, NULL, ofs->lower_layers, ofs->numlower,
> &stack);
> - if (err)
> - return ERR_PTR(err);
> + if (err) {
> + goto out_err;
> + } else if (!index && !origin.dentry) {
origin.dentry is not going to be NULL if ovl_check_origin_fh()
returns. So checking for non-NULL is not needed here
> + return NULL;
> + } else if (index && origin.dentry) {
here, and following patch.
> + err = ovl_verify_origin(index, origin.dentry, false, false);
> + if (err)
> + goto out_err;
> + }
>
> - dentry = ovl_get_dentry(sb, NULL, &origin);
> - dput(origin.dentry);
> + dentry = ovl_get_dentry(sb, NULL, &origin, index);
>
> +out:
> + dput(origin.dentry);
> + dput(index);
> return dentry;
> +
> +out_err:
> + dentry = ERR_PTR(err);
> + goto out;
> }
>
> static struct dentry *ovl_fh_to_dentry(struct super_block *sb, struct fid *fid,
> --
> 2.7.4
>
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