Commit d101a125 authored by Miklos Szeredi's avatar Miklos Szeredi Committed by Theodore Ts'o
Browse files

fs: add file_dentry() 



This series fixes bugs in nfs and ext4 due to 4bacc9c9 ("overlayfs:
Make f_path always point to the overlay and f_inode to the underlay").

Regular files opened on overlayfs will result in the file being opened on
the underlying filesystem, while f_path points to the overlayfs
mount/dentry.

This confuses filesystems which get the dentry from struct file and assume
it's theirs.

Add a new helper, file_dentry() [*], to get the filesystem's own dentry
from the file.  This checks file->f_path.dentry->d_flags against
DCACHE_OP_REAL, and returns file->f_path.dentry if DCACHE_OP_REAL is not
set (this is the common, non-overlayfs case).

In the uncommon case it will call into overlayfs's ->d_real() to get the
underlying dentry, matching file_inode(file).

The reason we need to check against the inode is that if the file is copied
up while being open, d_real() would return the upper dentry, while the open
file comes from the lower dentry.

[*] If possible, it's better simply to use file_inode() instead.

Signed-off-by: default avatarMiklos Szeredi <mszeredi@redhat.com>
Signed-off-by: default avatarTheodore Ts'o <tytso@mit.edu>
Tested-by: default avatarGoldwyn Rodrigues <rgoldwyn@suse.com>
Reviewed-by: default avatarTrond Myklebust <trond.myklebust@primarydata.com>
Cc: <stable@vger.kernel.org> # v4.2
Cc: David Howells <dhowells@redhat.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Daniel Axtens <dja@axtens.net>
parent c9af28fd

fs/dcache.c

+4 −1
Original line number Diff line number Diff line
@@ -1667,7 +1667,8 @@ void d_set_d_op(struct dentry *dentry, const struct dentry_operations *op) 
				DCACHE_OP_REVALIDATE	|

				DCACHE_OP_WEAK_REVALIDATE	|

				DCACHE_OP_DELETE	|

				DCACHE_OP_SELECT_INODE));

				DCACHE_OP_SELECT_INODE	|

				DCACHE_OP_REAL));

	dentry->d_op = op;

	if (!op)

		return;
@@ -1685,6 +1686,8 @@ void d_set_d_op(struct dentry *dentry, const struct dentry_operations *op) 
		dentry->d_flags |= DCACHE_OP_PRUNE;

	if (op->d_select_inode)

		dentry->d_flags |= DCACHE_OP_SELECT_INODE;

	if (op->d_real)

		dentry->d_flags |= DCACHE_OP_REAL;



}

EXPORT_SYMBOL(d_set_d_op);

fs/overlayfs/super.c

+33 −0
Original line number Diff line number Diff line
@@ -295,6 +295,37 @@ static void ovl_dentry_release(struct dentry *dentry) 
	}

}



static struct dentry *ovl_d_real(struct dentry *dentry, struct inode *inode)

{

	struct dentry *real;



	if (d_is_dir(dentry)) {

		if (!inode || inode == d_inode(dentry))

			return dentry;

		goto bug;

	}



	real = ovl_dentry_upper(dentry);

	if (real && (!inode || inode == d_inode(real)))

		return real;



	real = ovl_dentry_lower(dentry);

	if (!real)

		goto bug;



	if (!inode || inode == d_inode(real))

		return real;



	/* Handle recursion */

	if (real->d_flags & DCACHE_OP_REAL)

		return real->d_op->d_real(real, inode);



bug:

	WARN(1, "ovl_d_real(%pd4, %s:%lu\n): real dentry not found\n", dentry,

	     inode ? inode->i_sb->s_id : "NULL", inode ? inode->i_ino : 0);

	return dentry;

}



static int ovl_dentry_revalidate(struct dentry *dentry, unsigned int flags)

{

	struct ovl_entry *oe = dentry->d_fsdata;
@@ -339,11 +370,13 @@ static int ovl_dentry_weak_revalidate(struct dentry *dentry, unsigned int flags) 
static const struct dentry_operations ovl_dentry_operations = {

	.d_release = ovl_dentry_release,

	.d_select_inode = ovl_d_select_inode,

	.d_real = ovl_d_real,

};



static const struct dentry_operations ovl_reval_dentry_operations = {

	.d_release = ovl_dentry_release,

	.d_select_inode = ovl_d_select_inode,

	.d_real = ovl_d_real,

	.d_revalidate = ovl_dentry_revalidate,

	.d_weak_revalidate = ovl_dentry_weak_revalidate,

};

include/linux/dcache.h

+10 −0
Original line number Diff line number Diff line
@@ -161,6 +161,7 @@ struct dentry_operations { 
	struct vfsmount *(*d_automount)(struct path *);

	int (*d_manage)(struct dentry *, bool);

	struct inode *(*d_select_inode)(struct dentry *, unsigned);

	struct dentry *(*d_real)(struct dentry *, struct inode *);

} ____cacheline_aligned;



/*
@@ -229,6 +230,7 @@ struct dentry_operations { 
#define DCACHE_OP_SELECT_INODE		0x02000000 /* Unioned entry: dcache op selects inode */



#define DCACHE_ENCRYPTED_WITH_KEY	0x04000000 /* dir is encrypted with a valid key */

#define DCACHE_OP_REAL			0x08000000



extern seqlock_t rename_lock;
@@ -555,4 +557,12 @@ static inline struct dentry *d_backing_dentry(struct dentry *upper) 
	return upper;

}



static inline struct dentry *d_real(struct dentry *dentry)

{

	if (unlikely(dentry->d_flags & DCACHE_OP_REAL))

		return dentry->d_op->d_real(dentry, NULL);

	else

		return dentry;

}



#endif	/* __LINUX_DCACHE_H */

include/linux/fs.h

+10 −0
Original line number Diff line number Diff line
@@ -1241,6 +1241,16 @@ static inline struct inode *file_inode(const struct file *f) 
	return f->f_inode;

}



static inline struct dentry *file_dentry(const struct file *file)

{

	struct dentry *dentry = file->f_path.dentry;



	if (unlikely(dentry->d_flags & DCACHE_OP_REAL))

		return dentry->d_op->d_real(dentry, file_inode(file));

	else

		return dentry;

}



static inline int locks_lock_file_wait(struct file *filp, struct file_lock *fl)

{

	return locks_lock_inode_wait(file_inode(filp), fl);

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