On Fri, Jan 31, 2020 at 12:50:04PM +0100, Miklos Szeredi wrote:
> No reason to prevent upper layer being a remote filesystem. Do the
> revalidation in that case, just as we already do for lower layers.
>
> This lets virtiofs be used as upper layer, which appears to be a real use
> case.
Hi Miklos,
I have couple of very basic questions.
- So with this change, we will allow NFS to be upper layer also?
- What does revalidation on lower/upper mean? Does that mean that
lower/upper can now change underneath overlayfs and overlayfs will
cope with it. If we still expect underlying layers not to change, then
what's the point of calling ->revalidate().
Thanks
Vivek
>
> Signed-off-by: Miklos Szeredi <mszeredi@xxxxxxxxxx>
> ---
> fs/overlayfs/namei.c | 3 +--
> fs/overlayfs/super.c | 8 ++++++--
> fs/overlayfs/util.c | 2 ++
> 3 files changed, 9 insertions(+), 4 deletions(-)
>
> diff --git a/fs/overlayfs/namei.c b/fs/overlayfs/namei.c
> index 76e61cc27822..0db23baf98e7 100644
> --- a/fs/overlayfs/namei.c
> +++ b/fs/overlayfs/namei.c
> @@ -845,8 +845,7 @@ struct dentry *ovl_lookup(struct inode *dir, struct dentry *dentry,
> if (err)
> goto out;
>
> - if (upperdentry && (upperdentry->d_flags & DCACHE_OP_REAL ||
> - unlikely(ovl_dentry_remote(upperdentry)))) {
> + if (upperdentry && upperdentry->d_flags & DCACHE_OP_REAL) {
> dput(upperdentry);
> err = -EREMOTE;
> goto out;
> diff --git a/fs/overlayfs/super.c b/fs/overlayfs/super.c
> index 26d4153240a8..ed3a11db9039 100644
> --- a/fs/overlayfs/super.c
> +++ b/fs/overlayfs/super.c
> @@ -135,9 +135,14 @@ static int ovl_dentry_revalidate_common(struct dentry *dentry,
> unsigned int flags, bool weak)
> {
> struct ovl_entry *oe = dentry->d_fsdata;
> + struct dentry *upper;
> unsigned int i;
> int ret = 1;
>
> + upper = ovl_dentry_upper(dentry);
> + if (upper)
> + ret = ovl_revalidate_real(upper, flags, weak);
> +
> for (i = 0; ret > 0 && i < oe->numlower; i++) {
> ret = ovl_revalidate_real(oe->lowerstack[i].dentry, flags,
> weak);
> @@ -747,8 +752,7 @@ static int ovl_mount_dir(const char *name, struct path *path)
> ovl_unescape(tmp);
> err = ovl_mount_dir_noesc(tmp, path);
>
> - if (!err && (ovl_dentry_remote(path->dentry) ||
> - path->dentry->d_flags & DCACHE_OP_REAL)) {
> + if (!err && path->dentry->d_flags & DCACHE_OP_REAL) {
> pr_err("filesystem on '%s' not supported as upperdir\n",
> tmp);
> path_put_init(path);
> diff --git a/fs/overlayfs/util.c b/fs/overlayfs/util.c
> index 3ad8fb291f7d..c793722739e1 100644
> --- a/fs/overlayfs/util.c
> +++ b/fs/overlayfs/util.c
> @@ -96,6 +96,8 @@ void ovl_dentry_update_reval(struct dentry *dentry, struct dentry *upperdentry,
> struct ovl_entry *oe = OVL_E(dentry);
> unsigned int i, flags = 0;
>
> + if (upperdentry)
> + flags |= upperdentry->d_flags;
> for (i = 0; i < oe->numlower; i++)
> flags |= oe->lowerstack[i].dentry->d_flags;
>
> --
> 2.21.1
>
