[v2,01/19] fs: add two trivial lookup helpers

Commit Message

Christian Brauner March 30, 2022, 10:23 a.m. UTC

Similar to the addition of lookup_one() add a version of
lookup_one_unlocked() and lookup_one_positive_unlocked() that take
idmapped mounts into account. This is required to port overlay to
support idmapped base layers.

Cc: <[e-mail]>
Tested-by: Giuseppe Scrivano <[e-mail]>
Reviewed-by: Amir Goldstein <[e-mail]>
Signed-off-by: Christian Brauner (Microsoft) <[e-mail]>
---
/* v2 */
unchanged
---
 fs/namei.c            | 52 ++++++++++++++++++++++++++++++++++---------
 include/linux/namei.h |  2 ++
 2 files changed, 44 insertions(+), 10 deletions(-)

Comments

Christoph Hellwig March 30, 2022, 3:25 p.m. UTC | #1

> +
> +/*
> + * Like lookup_positive_unlocked() but takes a mount's idmapping into account.
> + */

Can you add a real kerneldoc comment here instead of referring to
another function that will hopefully be removed rather sooner than
later?

> +struct dentry *lookup_one_unlocked(struct user_namespace *, const char *, struct dentry *, int);
> +struct dentry *lookup_one_positive_unlocked(struct user_namespace *, const char *, struct dentry *, int);

Please spellt out the parameter names and avoid the overy long lines.

Otherwise looks good:

Reviewed-by: Christoph Hellwig <[e-mail]>

Christian Brauner March 30, 2022, 4:02 p.m. UTC | #2

On Wed, Mar 30, 2022 at 05:25:32PM +0200, Christoph Hellwig wrote:
> > +
> > +/*
> > + * Like lookup_positive_unlocked() but takes a mount's idmapping into account.
> > + */
> 
> Can you add a real kerneldoc comment here instead of referring to
> another function that will hopefully be removed rather sooner than
> later?

Done.

> 
> > +struct dentry *lookup_one_unlocked(struct user_namespace *, const char *, struct dentry *, int);
> > +struct dentry *lookup_one_positive_unlocked(struct user_namespace *, const char *, struct dentry *, int);
> 
> Please spellt out the parameter names and avoid the overy long lines.

Done.

> 
> Otherwise looks good:
> 
> Reviewed-by: Christoph Hellwig <[e-mail]>

Thanks!

Patch

diff --git a/fs/namei.c b/fs/namei.c
index 3f1829b3ab5b..ca2a490a1f6b 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -2768,7 +2768,8 @@  struct dentry *lookup_one(struct user_namespace *mnt_userns, const char *name,
 EXPORT_SYMBOL(lookup_one);
 
 /**
- * lookup_one_len_unlocked - filesystem helper to lookup single pathname component
+ * lookup_one_unlocked - filesystem helper to lookup single pathname component
+ * @mnt_userns:	idmapping of the mount the lookup is performed from
  * @name:	pathname component to lookup
  * @base:	base directory to lookup from
  * @len:	maximum length @len should be interpreted to
@@ -2779,14 +2780,15 @@  EXPORT_SYMBOL(lookup_one);
  * Unlike lookup_one_len, it should be called without the parent
  * i_mutex held, and will take the i_mutex itself if necessary.
  */
-struct dentry *lookup_one_len_unlocked(const char *name,
-				       struct dentry *base, int len)
+struct dentry *lookup_one_unlocked(struct user_namespace *mnt_userns,
+				   const char *name, struct dentry *base,
+				   int len)
 {
 	struct qstr this;
 	int err;
 	struct dentry *ret;
 
-	err = lookup_one_common(&init_user_ns, name, base, len, &this);
+	err = lookup_one_common(mnt_userns, name, base, len, &this);
 	if (err)
 		return ERR_PTR(err);
 
@@ -2795,6 +2797,41 @@  struct dentry *lookup_one_len_unlocked(const char *name,
 		ret = lookup_slow(&this, base, 0);
 	return ret;
 }
+EXPORT_SYMBOL(lookup_one_unlocked);
+
+/*
+ * Like lookup_positive_unlocked() but takes a mount's idmapping into account.
+ */
+struct dentry *lookup_one_positive_unlocked(struct user_namespace *mnt_userns,
+					    const char *name,
+					    struct dentry *base, int len)
+{
+	struct dentry *ret = lookup_one_unlocked(mnt_userns, name, base, len);
+	if (!IS_ERR(ret) && d_flags_negative(smp_load_acquire(&ret->d_flags))) {
+		dput(ret);
+		ret = ERR_PTR(-ENOENT);
+	}
+	return ret;
+}
+EXPORT_SYMBOL(lookup_one_positive_unlocked);
+
+/**
+ * lookup_one_len_unlocked - filesystem helper to lookup single pathname component
+ * @name:	pathname component to lookup
+ * @base:	base directory to lookup from
+ * @len:	maximum length @len should be interpreted to
+ *
+ * Note that this routine is purely a helper for filesystem usage and should
+ * not be called by generic code.
+ *
+ * Unlike lookup_one_len, it should be called without the parent
+ * i_mutex held, and will take the i_mutex itself if necessary.
+ */
+struct dentry *lookup_one_len_unlocked(const char *name,
+				       struct dentry *base, int len)
+{
+	return lookup_one_unlocked(&init_user_ns, name, base, len);
+}
 EXPORT_SYMBOL(lookup_one_len_unlocked);
 
 /*
@@ -2808,12 +2845,7 @@  EXPORT_SYMBOL(lookup_one_len_unlocked);
 struct dentry *lookup_positive_unlocked(const char *name,
 				       struct dentry *base, int len)
 {
-	struct dentry *ret = lookup_one_len_unlocked(name, base, len);
-	if (!IS_ERR(ret) && d_flags_negative(smp_load_acquire(&ret->d_flags))) {
-		dput(ret);
-		ret = ERR_PTR(-ENOENT);
-	}
-	return ret;
+	return lookup_one_positive_unlocked(&init_user_ns, name, base, len);
 }
 EXPORT_SYMBOL(lookup_positive_unlocked);
 
diff --git a/include/linux/namei.h b/include/linux/namei.h
index e89329bb3134..759b996b9e1a 100644
--- a/include/linux/namei.h
+++ b/include/linux/namei.h
@@ -69,6 +69,8 @@  extern struct dentry *lookup_one_len(const char *, struct dentry *, int);
 extern struct dentry *lookup_one_len_unlocked(const char *, struct dentry *, int);
 extern struct dentry *lookup_positive_unlocked(const char *, struct dentry *, int);
 struct dentry *lookup_one(struct user_namespace *, const char *, struct dentry *, int);
+struct dentry *lookup_one_unlocked(struct user_namespace *, const char *, struct dentry *, int);
+struct dentry *lookup_one_positive_unlocked(struct user_namespace *, const char *, struct dentry *, int);
 
 extern int follow_down_one(struct path *);
 extern int follow_down(struct path *);