On Fri, Jan 19, 2018 at 12:39 PM, Miklos Szeredi <miklos@xxxxxxxxxx> wrote:
> On Fri, Jan 19, 2018 at 02:23:35AM +0200, Amir Goldstein wrote:
>> > How is this for an option?
> [...]
>> > +struct dentry *d_obtain_alias_fsdata(struct inode *inode, void **fsdata)
>> > +{
>> > + return __d_obtain_alias(inode, 1, fsdata);
>> > }
>> > EXPORT_SYMBOL(d_obtain_alias);
>
> It would work, but I like this interface better:
>
> +extern struct dentry * d_alloc_anon(struct super_block *);
> +extern struct dentry * d_instantiate_anon(struct dentry *, struct inode *);
>
OK. Thanks for the patch!
> And full patch:
>
> diff --git a/fs/dcache.c b/fs/dcache.c
> index b5d5ea984ac4..15dc32178813 100644
> --- a/fs/dcache.c
> +++ b/fs/dcache.c
> @@ -1699,9 +1699,15 @@ struct dentry *d_alloc(struct dentry * parent, const struct qstr *name)
> }
> EXPORT_SYMBOL(d_alloc);
>
> +struct dentry *d_alloc_anon(struct super_block *sb)
> +{
> + return __d_alloc(sb, NULL);
> +}
> +EXPORT_SYMBOL(d_alloc_anon);
> +
> struct dentry *d_alloc_cursor(struct dentry * parent)
> {
> - struct dentry *dentry = __d_alloc(parent->d_sb, NULL);
> + struct dentry *dentry = d_alloc_anon(parent->d_sb);
> if (dentry) {
> dentry->d_flags |= DCACHE_RCUACCESS | DCACHE_DENTRY_CURSOR;
> dentry->d_parent = dget(parent);
> @@ -1887,7 +1893,7 @@ struct dentry *d_make_root(struct inode *root_inode)
> struct dentry *res = NULL;
>
> if (root_inode) {
> - res = __d_alloc(root_inode->i_sb, NULL);
> + res = d_alloc_anon(root_inode->i_sb);
> if (res)
> d_instantiate(res, root_inode);
> else
> @@ -1926,33 +1932,18 @@ struct dentry *d_find_any_alias(struct inode *inode)
> }
> EXPORT_SYMBOL(d_find_any_alias);
>
> -static struct dentry *__d_obtain_alias(struct inode *inode, int disconnected)
> +static struct dentry *__d_instantiate_anon(struct dentry *dentry,
> + struct inode *inode,
> + bool disconnected)
> {
> - struct dentry *tmp;
> struct dentry *res;
> - unsigned add_flags;
> -
> - if (!inode)
> - return ERR_PTR(-ESTALE);
> - if (IS_ERR(inode))
> - return ERR_CAST(inode);
> -
> - res = d_find_any_alias(inode);
> - if (res)
> - goto out_iput;
>
> - tmp = __d_alloc(inode->i_sb, NULL);
> - if (!tmp) {
> - res = ERR_PTR(-ENOMEM);
> - goto out_iput;
> - }
> -
> - security_d_instantiate(tmp, inode);
> + security_d_instantiate(dentry, inode);
> spin_lock(&inode->i_lock);
> res = __d_find_any_alias(inode);
> if (res) {
> spin_unlock(&inode->i_lock);
> - dput(tmp);
> + dput(dentry);
> goto out_iput;
> }
>
> @@ -1962,22 +1953,56 @@ static struct dentry *__d_obtain_alias(struct inode *inode, int disconnected)
> if (disconnected)
> add_flags |= DCACHE_DISCONNECTED;
>
> - spin_lock(&tmp->d_lock);
> - __d_set_inode_and_type(tmp, inode, add_flags);
> - hlist_add_head(&tmp->d_u.d_alias, &inode->i_dentry);
> - hlist_bl_lock(&tmp->d_sb->s_anon);
> - hlist_bl_add_head(&tmp->d_hash, &tmp->d_sb->s_anon);
> - hlist_bl_unlock(&tmp->d_sb->s_anon);
> - spin_unlock(&tmp->d_lock);
> + spin_lock(&dentry->d_lock);
> + __d_set_inode_and_type(dentry, inode, add_flags);
> + hlist_add_head(&dentry->d_u.d_alias, &inode->i_dentry);
> + hlist_bl_lock(&dentry->d_sb->s_anon);
> + hlist_bl_add_head(&dentry->d_hash, &dentry->d_sb->s_anon);
> + hlist_bl_unlock(&dentry->d_sb->s_anon);
> + spin_unlock(&dentry->d_lock);
> spin_unlock(&inode->i_lock);
>
> - return tmp;
> + return dentry;
>
> out_iput:
> iput(inode);
> return res;
> }
>
> +struct dentry *d_instantiate_anon(struct dentry *dentry, struct inode *inode)
> +{
> + return __d_instantiate_anon(dentry, inode, true);
> +}
> +EXPORT_SYMBOL(d_instantiate_anon);
> +
> +static struct dentry *__d_obtain_alias(struct inode *inode, bool disconnected)
> +{
> + struct dentry *tmp;
> + struct dentry *res;
> + unsigned add_flags;
> +
> + if (!inode)
> + return ERR_PTR(-ESTALE);
> + if (IS_ERR(inode))
> + return ERR_CAST(inode);
> +
> + res = d_find_any_alias(inode);
> + if (res)
> + goto out_iput;
> +
> + tmp = d_alloc_anon(inode->i_sb);
> + if (!tmp) {
> + res = ERR_PTR(-ENOMEM);
> + goto out_iput;
> + }
> +
> + return __d_instantiate_anon(tmp, inode, disconnected);
> +
> +out_iput:
> + iput(inode);
> + return res;
> +}
> +
> /**
> * d_obtain_alias - find or allocate a DISCONNECTED dentry for a given inode
> * @inode: inode to allocate the dentry for
> @@ -1998,7 +2023,7 @@ static struct dentry *__d_obtain_alias(struct inode *inode, int disconnected)
> */
> struct dentry *d_obtain_alias(struct inode *inode)
> {
> - return __d_obtain_alias(inode, 1);
> + return __d_obtain_alias(inode, true);
> }
> EXPORT_SYMBOL(d_obtain_alias);
>
> @@ -2019,7 +2044,7 @@ EXPORT_SYMBOL(d_obtain_alias);
> */
> struct dentry *d_obtain_root(struct inode *inode)
> {
> - return __d_obtain_alias(inode, 0);
> + return __d_obtain_alias(inode, false);
> }
> EXPORT_SYMBOL(d_obtain_root);
>
> diff --git a/fs/overlayfs/export.c b/fs/overlayfs/export.c
> index 25461781c103..7477f28cb99b 100644
> --- a/fs/overlayfs/export.c
> +++ b/fs/overlayfs/export.c
> @@ -184,28 +184,32 @@ static struct dentry *ovl_obtain_alias(struct super_block *sb,
> return ERR_CAST(inode);
> }
>
> - dentry = d_obtain_alias(inode);
> - if (IS_ERR(dentry) || dentry->d_fsdata)
> - return dentry;
> -
> - oe = ovl_alloc_entry(!!lower);
> - if (!oe) {
> - dput(dentry);
> - return ERR_PTR(-ENOMEM);
> - }
> + if (index)
> + ovl_set_flag(OVL_INDEX, inode);
>
> - dentry->d_fsdata = oe;
> - if (upper_alias)
> - ovl_dentry_set_upper_alias(dentry);
> - if (lower) {
> - oe->lowerstack->dentry = dget(lower);
> - oe->lowerstack->layer = lowerpath->layer;
> + dentry = d_find_any_alias(inode);
> + if (!dentry) {
> + dentry = d_alloc_anon(inode->i_sb);
> + if (!dentry)
> + goto nomem;
> + oe = ovl_alloc_entry(lower ? 1 : 0);
> + if (!oe)
> + goto nomem;
> + if (lower) {
> + oe->lowerstack->dentry = dget(lower);
> + oe->lowerstack->layer = lowerpath->layer;
> + }
> + dentry->d_fsdata = oe;
> + if (upper_alias)
> + ovl_dentry_set_upper_alias(dentry);
> }
>
> - if (index)
> - ovl_set_flag(OVL_INDEX, inode);
> + return d_instantiate_anon(dentry, inode);
>
> - return dentry;
> +nomem:
> + iput(inode);
> + dput(dentry);
> + return ERR_PTR(-ENOMEM);
> }
>
> /* Get the upper or lower dentry in stach whose on layer @idx */
> diff --git a/include/linux/dcache.h b/include/linux/dcache.h
> index 65cd8ab60b7a..82a99d366aec 100644
> --- a/include/linux/dcache.h
> +++ b/include/linux/dcache.h
> @@ -227,6 +227,7 @@ extern seqlock_t rename_lock;
> */
> extern void d_instantiate(struct dentry *, struct inode *);
> extern struct dentry * d_instantiate_unique(struct dentry *, struct inode *);
> +extern struct dentry * d_instantiate_anon(struct dentry *, struct inode *);
> extern int d_instantiate_no_diralias(struct dentry *, struct inode *);
> extern void __d_drop(struct dentry *dentry);
> extern void d_drop(struct dentry *dentry);
> @@ -235,6 +236,7 @@ extern void d_set_d_op(struct dentry *dentry, const struct dentry_operations *op
>
> /* allocate/de-allocate */
> extern struct dentry * d_alloc(struct dentry *, const struct qstr *);
> +extern struct dentry * d_alloc_anon(struct super_block *);
> extern struct dentry * d_alloc_pseudo(struct super_block *, const struct qstr *);
> extern struct dentry * d_alloc_parallel(struct dentry *, const struct qstr *,
> wait_queue_head_t *);
>
