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Commit 39b681f8 authored by Miklos Szeredi's avatar Miklos Szeredi
Browse files

ovl: store real inode pointer in ->i_private 



To get from overlay inode to real inode we currently use 'struct
ovl_entry', which has lifetime connected to overlay dentry.  This is okay,
since each overlay dentry had a new overlay inode allocated.

Following patch will break that assumption, so need to leave out ovl_entry.
This patch stores the real inode directly in i_private, with the lowest bit
used to indicate whether the inode is upper or lower.

Lifetime rules remain, using ovl_inode_real() must only be done while
caller holds ref on overlay dentry (and hence on real dentry), or within
RCU protected regions.

Signed-off-by: default avatarMiklos Szeredi <mszeredi@redhat.com>
parent a999d7e1

fs/overlayfs/copy_up.c

+1 −0
Original line number Diff line number Diff line
@@ -292,6 +292,7 @@ static int ovl_copy_up_locked(struct dentry *workdir, struct dentry *upperdir, 
		goto out_cleanup;



	ovl_dentry_update(dentry, newdentry);

	ovl_inode_update(d_inode(dentry), d_inode(newdentry));

	newdentry = NULL;



	/*

fs/overlayfs/dir.c

+2 −1
Original line number Diff line number Diff line
@@ -167,6 +167,7 @@ static void ovl_instantiate(struct dentry *dentry, struct inode *inode, 
{

	ovl_dentry_version_inc(dentry->d_parent);

	ovl_dentry_update(dentry, newdentry);

	ovl_inode_update(inode, d_inode(newdentry));

	ovl_copyattr(newdentry->d_inode, inode);

	d_instantiate(dentry, inode);

}
@@ -416,7 +417,7 @@ static int ovl_create_or_link(struct dentry *dentry, int mode, dev_t rdev, 
	};



	err = -ENOMEM;

	inode = ovl_new_inode(dentry->d_sb, mode, dentry->d_fsdata);

	inode = ovl_new_inode(dentry->d_sb, mode);

	if (!inode)

		goto out;

fs/overlayfs/inode.c

+3 −8
Original line number Diff line number Diff line
@@ -117,15 +117,12 @@ static int ovl_getattr(struct vfsmount *mnt, struct dentry *dentry, 


int ovl_permission(struct inode *inode, int mask)

{

	struct ovl_entry *oe = inode->i_private;

	bool is_upper;

	struct dentry *realdentry = ovl_entry_real(oe, &is_upper);

	struct inode *realinode;

	struct inode *realinode = ovl_inode_real(inode, &is_upper);

	const struct cred *old_cred;

	int err;



	/* Careful in RCU walk mode */

	realinode = d_inode_rcu(realdentry);

	if (!realinode) {

		WARN_ON(!(mask & MAY_NOT_BLOCK));

		return -ECHILD;
@@ -312,7 +309,7 @@ int ovl_removexattr(struct dentry *dentry, const char *name) 


struct posix_acl *ovl_get_acl(struct inode *inode, int type)

{

	struct inode *realinode = ovl_inode_real(inode);

	struct inode *realinode = ovl_inode_real(inode, NULL);

	const struct cred *old_cred;

	struct posix_acl *acl;
@@ -412,8 +409,7 @@ static const struct inode_operations ovl_symlink_inode_operations = { 
	.update_time	= ovl_update_time,

};



struct inode *ovl_new_inode(struct super_block *sb, umode_t mode,

			    struct ovl_entry *oe)

struct inode *ovl_new_inode(struct super_block *sb, umode_t mode)

{

	struct inode *inode;
@@ -424,7 +420,6 @@ struct inode *ovl_new_inode(struct super_block *sb, umode_t mode, 
	inode->i_ino = get_next_ino();

	inode->i_mode = mode;

	inode->i_flags |= S_NOCMTIME;

	inode->i_private = oe;



	mode &= S_IFMT;

	switch (mode) {

fs/overlayfs/overlayfs.h

+14 −4
Original line number Diff line number Diff line
@@ -27,6 +27,8 @@ enum ovl_path_type { 
#define OVL_XATTR_PRE_LEN  16

#define OVL_XATTR_OPAQUE   OVL_XATTR_PRE_NAME"opaque"



#define OVL_ISUPPER_MASK 1UL



static inline int ovl_do_rmdir(struct inode *dir, struct dentry *dentry)

{

	int err = vfs_rmdir(dir, dentry);
@@ -131,6 +133,16 @@ static inline int ovl_do_whiteout(struct inode *dir, struct dentry *dentry) 
	return err;

}



static inline struct inode *ovl_inode_real(struct inode *inode, bool *is_upper)

{

	unsigned long x = (unsigned long) READ_ONCE(inode->i_private);



	if (is_upper)

		*is_upper = x & OVL_ISUPPER_MASK;



	return (struct inode *) (x & ~OVL_ISUPPER_MASK);

}



enum ovl_path_type ovl_path_type(struct dentry *dentry);

u64 ovl_dentry_version_get(struct dentry *dentry);

void ovl_dentry_version_inc(struct dentry *dentry);
@@ -141,8 +153,6 @@ int ovl_path_next(int idx, struct dentry *dentry, struct path *path); 
struct dentry *ovl_dentry_upper(struct dentry *dentry);

struct dentry *ovl_dentry_lower(struct dentry *dentry);

struct dentry *ovl_dentry_real(struct dentry *dentry);

struct dentry *ovl_entry_real(struct ovl_entry *oe, bool *is_upper);

struct inode *ovl_inode_real(struct inode *inode);

struct vfsmount *ovl_entry_mnt_real(struct ovl_entry *oe, struct inode *inode,

				    bool is_upper);

struct ovl_dir_cache *ovl_dir_cache(struct dentry *dentry);
@@ -155,6 +165,7 @@ void ovl_dentry_set_opaque(struct dentry *dentry, bool opaque); 
bool ovl_is_whiteout(struct dentry *dentry);

const struct cred *ovl_override_creds(struct super_block *sb);

void ovl_dentry_update(struct dentry *dentry, struct dentry *upperdentry);

void ovl_inode_update(struct inode *inode, struct inode *upperinode);

struct dentry *ovl_lookup(struct inode *dir, struct dentry *dentry,

			  unsigned int flags);

struct file *ovl_path_open(struct path *path, int flags);
@@ -183,8 +194,7 @@ struct posix_acl *ovl_get_acl(struct inode *inode, int type); 
int ovl_open_maybe_copy_up(struct dentry *dentry, unsigned int file_flags);

int ovl_update_time(struct inode *inode, struct timespec *ts, int flags);



struct inode *ovl_new_inode(struct super_block *sb, umode_t mode,

			    struct ovl_entry *oe);

struct inode *ovl_new_inode(struct super_block *sb, umode_t mode);

static inline void ovl_copyattr(struct inode *from, struct inode *to)

{

	to->i_uid = from->i_uid;

fs/overlayfs/super.c

+20 −24
Original line number Diff line number Diff line
@@ -145,25 +145,11 @@ struct dentry *ovl_dentry_real(struct dentry *dentry) 
	return realdentry;

}



struct dentry *ovl_entry_real(struct ovl_entry *oe, bool *is_upper)

{

	struct dentry *realdentry;



	realdentry = ovl_upperdentry_dereference(oe);

	if (realdentry) {

		*is_upper = true;

	} else {

		realdentry = __ovl_dentry_lower(oe);

		*is_upper = false;

	}

	return realdentry;

}



struct inode *ovl_inode_real(struct inode *inode)

static void ovl_inode_init(struct inode *inode, struct inode *realinode,

			   bool is_upper)

{

	bool tmp;



	return d_inode(ovl_entry_real(inode->i_private, &tmp));

	WRITE_ONCE(inode->i_private, (unsigned long) realinode |

		   (is_upper ? OVL_ISUPPER_MASK : 0));

}



struct vfsmount *ovl_entry_mnt_real(struct ovl_entry *oe, struct inode *inode,
@@ -235,7 +221,6 @@ void ovl_dentry_update(struct dentry *dentry, struct dentry *upperdentry) 


	WARN_ON(!inode_is_locked(upperdentry->d_parent->d_inode));

	WARN_ON(oe->__upperdentry);

	BUG_ON(!upperdentry->d_inode);

	/*

	 * Make sure upperdentry is consistent before making it visible to

	 * ovl_upperdentry_dereference().
@@ -244,6 +229,13 @@ void ovl_dentry_update(struct dentry *dentry, struct dentry *upperdentry) 
	oe->__upperdentry = upperdentry;

}



void ovl_inode_update(struct inode *inode, struct inode *upperinode)

{

	WARN_ON(!upperinode);

	WRITE_ONCE(inode->i_private,

		   (unsigned long) upperinode | OVL_ISUPPER_MASK);

}



void ovl_dentry_version_inc(struct dentry *dentry)

{

	struct ovl_entry *oe = dentry->d_fsdata;
@@ -574,14 +566,16 @@ struct dentry *ovl_lookup(struct inode *dir, struct dentry *dentry, 


	if (upperdentry || ctr) {

		struct dentry *realdentry;

		struct inode *realinode;



		realdentry = upperdentry ? upperdentry : stack[0].dentry;

		realinode = d_inode(realdentry);



		err = -ENOMEM;

		inode = ovl_new_inode(dentry->d_sb, realdentry->d_inode->i_mode,

				      oe);

		inode = ovl_new_inode(dentry->d_sb, realinode->i_mode);

		if (!inode)

			goto out_free_oe;

		ovl_inode_init(inode, realinode, !!upperdentry);

		ovl_copyattr(realdentry->d_inode, inode);

	}
@@ -969,6 +963,7 @@ static int ovl_fill_super(struct super_block *sb, void *data, int silent) 
	struct path upperpath = { NULL, NULL };

	struct path workpath = { NULL, NULL };

	struct dentry *root_dentry;

	struct inode *realinode;

	struct ovl_entry *oe;

	struct ovl_fs *ufs;

	struct path *stack = NULL;
@@ -1150,7 +1145,7 @@ static int ovl_fill_super(struct super_block *sb, void *data, int silent) 
	if (!oe)

		goto out_put_cred;



	root_dentry = d_make_root(ovl_new_inode(sb, S_IFDIR, oe));

	root_dentry = d_make_root(ovl_new_inode(sb, S_IFDIR));

	if (!root_dentry)

		goto out_free_oe;
@@ -1169,8 +1164,9 @@ static int ovl_fill_super(struct super_block *sb, void *data, int silent) 


	root_dentry->d_fsdata = oe;



	ovl_copyattr(ovl_dentry_real(root_dentry)->d_inode,

		     root_dentry->d_inode);

	realinode = d_inode(ovl_dentry_real(root_dentry));

	ovl_inode_init(d_inode(root_dentry), realinode, !!upperpath.dentry);

	ovl_copyattr(realinode, d_inode(root_dentry));



	sb->s_magic = OVERLAYFS_SUPER_MAGIC;

	sb->s_op = &ovl_super_operations;