Commit 00675017 authored by Christian Brauner's avatar Christian Brauner Committed by Miklos Szeredi
Browse files

fs: add two trivial lookup helpers 



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: <linux-fsdevel@vger.kernel.org>
Tested-by: default avatarGiuseppe Scrivano <gscrivan@redhat.com>
Reviewed-by: default avatarAmir Goldstein <amir73il@gmail.com>
Reviewed-by: default avatarChristoph Hellwig <hch@lst.de>
Signed-off-by: default avatarChristian Brauner (Microsoft) <brauner@kernel.org>
Signed-off-by: default avatarMiklos Szeredi <mszeredi@redhat.com>
parent 31231092

fs/namei.c

+60 −10
Original line number Diff line number Diff line
@@ -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 +2797,59 @@ struct dentry *lookup_one_len_unlocked(const char *name, 
		ret = lookup_slow(&this, base, 0);

	return ret;

}

EXPORT_SYMBOL(lookup_one_unlocked);



/**

 * lookup_one_positive_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

 *

 * This helper will yield ERR_PTR(-ENOENT) on negatives. The helper returns

 * known positive or ERR_PTR(). This is what most of the users want.

 *

 * Note that pinned negative with unlocked parent _can_ become positive at any

 * time, so callers of lookup_one_unlocked() need to be very careful; pinned

 * positives have >d_inode stable, so this one avoids such problems.

 *

 * Note that this routine is purely a helper for filesystem usage and should

 * not be called by generic code.

 *

 * The helper should be called without i_mutex held.

 */

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 +2863,7 @@ 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);

include/linux/namei.h

+6 −0
Original line number Diff line number Diff line
@@ -69,6 +69,12 @@ 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 *mnt_userns,

				   const char *name, struct dentry *base,

				   int len);

struct dentry *lookup_one_positive_unlocked(struct user_namespace *mnt_userns,

					    const char *name,

					    struct dentry *base, int len);



extern int follow_down_one(struct path *);

extern int follow_down(struct path *);