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Commit dd662667 authored by Miklos Szeredi's avatar Miklos Szeredi
Browse files

ovl: add mutli-layer infrastructure 



Add multiple lower layers to 'struct ovl_fs' and 'struct ovl_entry'.

ovl_entry will have an array of paths, instead of just the dentry.  This
allows a compact array containing just the layers which exist at current
point in the tree (which is expected to be a small number for the majority
of dentries).

The number of layers is not limited by this infrastructure.

Signed-off-by: default avatarMiklos Szeredi <mszeredi@suse.cz>
parent 263b4a0f

fs/overlayfs/super.c

+64 −34
Original line number Diff line number Diff line
@@ -35,7 +35,8 @@ struct ovl_config { 
/* private information held for overlayfs's superblock */

struct ovl_fs {

	struct vfsmount *upper_mnt;

	struct vfsmount *lower_mnt;

	unsigned numlower;

	struct vfsmount **lower_mnt;

	struct dentry *workdir;

	long lower_namelen;

	/* pathnames of lower and upper dirs, for show_options */
@@ -47,7 +48,6 @@ struct ovl_dir_cache; 
/* private information held for every overlayfs dentry */

struct ovl_entry {

	struct dentry *__upperdentry;

	struct dentry *lowerdentry;

	struct ovl_dir_cache *cache;

	union {

		struct {
@@ -56,10 +56,16 @@ struct ovl_entry { 
		};

		struct rcu_head rcu;

	};

	unsigned numlower;

	struct path lowerstack[];

};



const char *ovl_opaque_xattr = "trusted.overlay.opaque";



static struct dentry *__ovl_dentry_lower(struct ovl_entry *oe)

{

	return oe->numlower ? oe->lowerstack[0].dentry : NULL;

}



enum ovl_path_type ovl_path_type(struct dentry *dentry)

{
@@ -69,7 +75,7 @@ enum ovl_path_type ovl_path_type(struct dentry *dentry) 
	if (oe->__upperdentry) {

		type = __OVL_PATH_UPPER;



		if (oe->lowerdentry) {

		if (oe->numlower) {

			if (S_ISDIR(dentry->d_inode->i_mode))

				type |= __OVL_PATH_MERGE;

		} else if (!oe->opaque) {
@@ -117,7 +123,7 @@ struct dentry *ovl_dentry_lower(struct dentry *dentry) 
{

	struct ovl_entry *oe = dentry->d_fsdata;



	return oe->lowerdentry;

	return __ovl_dentry_lower(oe);

}



struct dentry *ovl_dentry_real(struct dentry *dentry)
@@ -127,7 +133,7 @@ struct dentry *ovl_dentry_real(struct dentry *dentry) 


	realdentry = ovl_upperdentry_dereference(oe);

	if (!realdentry)

		realdentry = oe->lowerdentry;

		realdentry = __ovl_dentry_lower(oe);



	return realdentry;

}
@@ -140,7 +146,7 @@ struct dentry *ovl_entry_real(struct ovl_entry *oe, bool *is_upper) 
	if (realdentry) {

		*is_upper = true;

	} else {

		realdentry = oe->lowerdentry;

		realdentry = __ovl_dentry_lower(oe);

		*is_upper = false;

	}

	return realdentry;
@@ -162,11 +168,9 @@ void ovl_set_dir_cache(struct dentry *dentry, struct ovl_dir_cache *cache) 


void ovl_path_lower(struct dentry *dentry, struct path *path)

{

	struct ovl_fs *ofs = dentry->d_sb->s_fs_info;

	struct ovl_entry *oe = dentry->d_fsdata;



	path->mnt = ofs->lower_mnt;

	path->dentry = oe->lowerdentry;

	*path = oe->numlower ? oe->lowerstack[0] : (struct path) { NULL, NULL };

}



int ovl_want_write(struct dentry *dentry)
@@ -258,8 +262,11 @@ static void ovl_dentry_release(struct dentry *dentry) 
	struct ovl_entry *oe = dentry->d_fsdata;



	if (oe) {

		unsigned int i;



		dput(oe->__upperdentry);

		dput(oe->lowerdentry);

		for (i = 0; i < oe->numlower; i++)

			dput(oe->lowerstack[i].dentry);

		kfree_rcu(oe, rcu);

	}

}
@@ -268,9 +275,15 @@ static const struct dentry_operations ovl_dentry_operations = { 
	.d_release = ovl_dentry_release,

};



static struct ovl_entry *ovl_alloc_entry(void)

static struct ovl_entry *ovl_alloc_entry(unsigned int numlower)

{

	return kzalloc(sizeof(struct ovl_entry), GFP_KERNEL);

	size_t size = offsetof(struct ovl_entry, lowerstack[numlower]);

	struct ovl_entry *oe = kzalloc(size, GFP_KERNEL);



	if (oe)

		oe->numlower = numlower;



	return oe;

}



static inline struct dentry *ovl_lookup_real(struct dentry *dir,
@@ -297,19 +310,19 @@ struct dentry *ovl_lookup(struct inode *dir, struct dentry *dentry, 
{

	struct ovl_entry *oe;

	struct dentry *upperdir;

	struct dentry *lowerdir;

	struct path lowerdir;

	struct dentry *upperdentry = NULL;

	struct dentry *lowerdentry = NULL;

	struct inode *inode = NULL;

	int err;



	err = -ENOMEM;

	oe = ovl_alloc_entry();

	oe = ovl_alloc_entry(1);

	if (!oe)

		goto out;



	upperdir = ovl_dentry_upper(dentry->d_parent);

	lowerdir = ovl_dentry_lower(dentry->d_parent);

	ovl_path_lower(dentry->d_parent, &lowerdir);



	if (upperdir) {

		upperdentry = ovl_lookup_real(upperdir, &dentry->d_name);
@@ -317,7 +330,7 @@ struct dentry *ovl_lookup(struct inode *dir, struct dentry *dentry, 
		if (IS_ERR(upperdentry))

			goto out_put_dir;



		if (lowerdir && upperdentry) {

		if (lowerdir.dentry && upperdentry) {

			if (ovl_is_whiteout(upperdentry)) {

				dput(upperdentry);

				upperdentry = NULL;
@@ -327,8 +340,8 @@ struct dentry *ovl_lookup(struct inode *dir, struct dentry *dentry, 
			}

		}

	}

	if (lowerdir && !oe->opaque) {

		lowerdentry = ovl_lookup_real(lowerdir, &dentry->d_name);

	if (lowerdir.dentry && !oe->opaque) {

		lowerdentry = ovl_lookup_real(lowerdir.dentry, &dentry->d_name);

		err = PTR_ERR(lowerdentry);

		if (IS_ERR(lowerdentry))

			goto out_dput_upper;
@@ -355,8 +368,12 @@ struct dentry *ovl_lookup(struct inode *dir, struct dentry *dentry, 
	}



	oe->__upperdentry = upperdentry;

	oe->lowerdentry = lowerdentry;



	if (lowerdentry) {

		oe->lowerstack[0].dentry = lowerdentry;

		oe->lowerstack[0].mnt = lowerdir.mnt;

	} else {

		oe->numlower = 0;

	}

	dentry->d_fsdata = oe;

	d_add(dentry, inode);
@@ -380,10 +397,12 @@ struct file *ovl_path_open(struct path *path, int flags) 
static void ovl_put_super(struct super_block *sb)

{

	struct ovl_fs *ufs = sb->s_fs_info;

	unsigned i;



	dput(ufs->workdir);

	mntput(ufs->upper_mnt);

	mntput(ufs->lower_mnt);

	for (i = 0; i < ufs->numlower; i++)

		mntput(ufs->lower_mnt[i]);



	kfree(ufs->config.lowerdir);

	kfree(ufs->config.upperdir);
@@ -641,6 +660,8 @@ static int ovl_fill_super(struct super_block *sb, void *data, int silent) 
	struct ovl_entry *oe;

	struct ovl_fs *ufs;

	struct kstatfs statfs;

	struct vfsmount *mnt;

	unsigned int i;

	int err;



	err = -ENOMEM;
@@ -661,7 +682,7 @@ static int ovl_fill_super(struct super_block *sb, void *data, int silent) 
	}



	err = -ENOMEM;

	oe = ovl_alloc_entry();

	oe = ovl_alloc_entry(1);

	if (oe == NULL)

		goto out_free_config;
@@ -727,12 +748,24 @@ static int ovl_fill_super(struct super_block *sb, void *data, int silent) 
		goto out_put_workpath;

	}



	ufs->lower_mnt = clone_private_mount(&lowerpath);

	err = PTR_ERR(ufs->lower_mnt);

	if (IS_ERR(ufs->lower_mnt)) {

		pr_err("overlayfs: failed to clone lowerpath\n");

	ufs->lower_mnt = kcalloc(1, sizeof(struct vfsmount *), GFP_KERNEL);

	if (ufs->lower_mnt == NULL)

		goto out_put_upper_mnt;



	mnt = clone_private_mount(&lowerpath);

	err = PTR_ERR(mnt);

	if (IS_ERR(mnt)) {

		pr_err("overlayfs: failed to clone lowerpath\n");

		goto out_put_lower_mnt;

	}

	/*

	 * Make lower_mnt R/O.  That way fchmod/fchown on lower file

	 * will fail instead of modifying lower fs.

	 */

	mnt->mnt_flags |= MNT_READONLY;



	ufs->lower_mnt[0] = mnt;

	ufs->numlower = 1;



	ufs->workdir = ovl_workdir_create(ufs->upper_mnt, workpath.dentry);

	err = PTR_ERR(ufs->workdir);
@@ -742,12 +775,6 @@ static int ovl_fill_super(struct super_block *sb, void *data, int silent) 
		goto out_put_lower_mnt;

	}



	/*

	 * Make lower_mnt R/O.  That way fchmod/fchown on lower file

	 * will fail instead of modifying lower fs.

	 */

	ufs->lower_mnt->mnt_flags |= MNT_READONLY;



	/* If the upper fs is r/o, we mark overlayfs r/o too */

	if (ufs->upper_mnt->mnt_sb->s_flags & MS_RDONLY)

		sb->s_flags |= MS_RDONLY;
@@ -768,7 +795,8 @@ static int ovl_fill_super(struct super_block *sb, void *data, int silent) 
	path_put(&workpath);



	oe->__upperdentry = upperpath.dentry;

	oe->lowerdentry = lowerpath.dentry;

	oe->lowerstack[0].dentry = lowerpath.dentry;

	oe->lowerstack[0].mnt = ufs->lower_mnt[0];



	root_dentry->d_fsdata = oe;
@@ -782,7 +810,9 @@ static int ovl_fill_super(struct super_block *sb, void *data, int silent) 
out_put_workdir:

	dput(ufs->workdir);

out_put_lower_mnt:

	mntput(ufs->lower_mnt);

	for (i = 0; i < ufs->numlower; i++)

		mntput(ufs->lower_mnt[i]);

	kfree(ufs->lower_mnt);

out_put_upper_mnt:

	mntput(ufs->upper_mnt);

out_put_workpath: