On Wed, 2023-04-12 at 16:54 +0300, Amir Goldstein wrote:
> Make the code handle the case of numlower > 1 and missing lowerdata
> dentry gracefully.
>
> Missing lowerdata dentry is an indication for lazy lookup of
> lowerdata
> and in that case the lowerdata_redirect path is stored in ovl_inode.
>
> Following commits will defer lookup and perform the lazy lookup on
> acccess.
>
> Signed-off-by: Amir Goldstein <amir73il@xxxxxxxxx>
Reviewed-by: Alexander Larsson <alexl@xxxxxxxxxx>
> ---
> fs/overlayfs/export.c | 2 +-
> fs/overlayfs/file.c | 7 +++++++
> fs/overlayfs/inode.c | 18 ++++++++++++++----
> fs/overlayfs/super.c | 3 +++
> fs/overlayfs/util.c | 2 +-
> 5 files changed, 26 insertions(+), 6 deletions(-)
>
> diff --git a/fs/overlayfs/export.c b/fs/overlayfs/export.c
> index 9951c504fb8d..2498fa8311e3 100644
> --- a/fs/overlayfs/export.c
> +++ b/fs/overlayfs/export.c
> @@ -343,7 +343,7 @@ static struct dentry *ovl_dentry_real_at(struct
> dentry *dentry, int idx)
> if (!idx)
> return ovl_dentry_upper(dentry);
>
> - for (i = 0; i < ovl_numlower(oe); i++) {
> + for (i = 0; i < ovl_numlower(oe) && lowerstack[i].layer; i++)
> {
> if (lowerstack[i].layer->idx == idx)
> return lowerstack[i].dentry;
> }
> diff --git a/fs/overlayfs/file.c b/fs/overlayfs/file.c
> index 7c04f033aadd..951683a66ff6 100644
> --- a/fs/overlayfs/file.c
> +++ b/fs/overlayfs/file.c
> @@ -115,6 +115,9 @@ static int ovl_real_fdget_meta(const struct file
> *file, struct fd *real,
> ovl_path_real(dentry, &realpath);
> else
> ovl_path_realdata(dentry, &realpath);
> + /* TODO: lazy lookup of lowerdata */
> + if (!realpath.dentry)
> + return -EIO;
>
> /* Has it been copied up since we'd opened it? */
> if (unlikely(file_inode(real->file) !=
> d_inode(realpath.dentry))) {
> @@ -158,6 +161,10 @@ static int ovl_open(struct inode *inode, struct
> file *file)
> file->f_flags &= ~(O_CREAT | O_EXCL | O_NOCTTY | O_TRUNC);
>
> ovl_path_realdata(dentry, &realpath);
> + /* TODO: lazy lookup of lowerdata */
> + if (!realpath.dentry)
> + return -EIO;
> +
> realfile = ovl_open_realfile(file, &realpath);
> if (IS_ERR(realfile))
> return PTR_ERR(realfile);
> diff --git a/fs/overlayfs/inode.c b/fs/overlayfs/inode.c
> index 35d51a6dced7..c29cbd9db64a 100644
> --- a/fs/overlayfs/inode.c
> +++ b/fs/overlayfs/inode.c
> @@ -240,15 +240,22 @@ int ovl_getattr(struct mnt_idmap *idmap, const
> struct path *path,
> /*
> * If lower is not same as lowerdata or if
> there was
> * no origin on upper, we can end up here.
> + * With lazy lowerdata lookup, guess
> lowerdata blocks
> + * from size to avoid lowerdata lookup on
> stat(2).
> */
> struct kstat lowerdatastat;
> u32 lowermask = STATX_BLOCKS;
>
> ovl_path_lowerdata(dentry, &realpath);
> - err = vfs_getattr(&realpath, &lowerdatastat,
> - lowermask, flags);
> - if (err)
> - goto out;
> + if (realpath.dentry) {
> + err = vfs_getattr(&realpath,
> &lowerdatastat,
> + lowermask, flags);
> + if (err)
> + goto out;
> + } else {
> + lowerdatastat.blocks =
> + round_up(stat->size, stat-
> >blksize) >> 9;
> + }
> stat->blocks = lowerdatastat.blocks;
> }
> }
> @@ -710,6 +717,9 @@ static int ovl_fiemap(struct inode *inode, struct
> fiemap_extent_info *fieinfo,
> struct inode *realinode = ovl_inode_realdata(inode);
> const struct cred *old_cred;
>
> + if (!realinode)
> + return -EIO;
> +
>
> if (!realinode->i_op->fiemap)
> return -EOPNOTSUPP;
>
> diff --git a/fs/overlayfs/super.c b/fs/overlayfs/super.c
> index 3484f39a8f27..ef78abc21998 100644
> --- a/fs/overlayfs/super.c
> +++ b/fs/overlayfs/super.c
> @@ -103,6 +103,9 @@ static int ovl_revalidate_real(struct dentry *d,
> unsigned int flags, bool weak)
> {
> int ret = 1;
>
> + if (!d)
> + return 1;
> +
> if (weak) {
> if (d->d_flags & DCACHE_OP_WEAK_REVALIDATE)
> ret = d->d_op->d_weak_revalidate(d, flags);
> diff --git a/fs/overlayfs/util.c b/fs/overlayfs/util.c
> index fe2e5a8b216b..284b5ba4fcf6 100644
> --- a/fs/overlayfs/util.c
> +++ b/fs/overlayfs/util.c
> @@ -179,7 +179,7 @@ void ovl_dentry_init_flags(struct dentry *dentry,
> struct dentry *upperdentry,
>
> if (upperdentry)
> flags |= upperdentry->d_flags;
> - for (i = 0; i < ovl_numlower(oe); i++)
> + for (i = 0; i < ovl_numlower(oe) && lowerstack[i].dentry;
> i++)
> flags |= lowerstack[i].dentry->d_flags;
>
> spin_lock(&dentry->d_lock);
--
=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
=-=-=
Alexander Larsson Red Hat,
Inc
alexl@xxxxxxxxxx alexander.larsson@xxxxxxxxx
He's a time-tossed Amish vagrant who knows the secret of the alien
invasion. She's a high-kicking gypsy barmaid from a family of eight
older
brothers. They fight crime!
