Patch "fs: add file_dentry()" has been added to the 4.4-stable tree

PATCH [email protected] 1 participant 1 message Apr 17, 2016

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Stable branch VFS Overlay filesystem

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2016-04-17 12:59 UTC #0 lore raw

This is a note to let you know that I've just added the patch titled

fs: add file_dentry()

to the 4.4-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
fs-add-file_dentry.patch
and it can be found in the queue-4.4 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

Quoted 1 line

From d101a125954eae1d397adda94ca6319485a50493 Mon Sep 17 00:00:00 2001

From: Miklos Szeredi <[email protected]>
Date: Sat, 26 Mar 2016 16:14:37 -0400
Subject: fs: add file_dentry()

From: Miklos Szeredi <[email protected]>

commit d101a125954eae1d397adda94ca6319485a50493 upstream.

This series fixes bugs in nfs and ext4 due to 4bacc9c9234c ("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 Miklos Szeredi <[email protected]>

Signed-off-by Theodore Ts'o <[email protected]>

Tested-by Goldwyn Rodrigues <[email protected]>

Reviewed-by Trond Myklebust <[email protected]>

Cc David Howells <[email protected]>

Cc Al Viro <[email protected]>

Cc Daniel Axtens <[email protected]>

Signed-off-by Greg Kroah-Hartman <[email protected]>

---
 fs/dcache.c            |    5 ++++-
 fs/overlayfs/super.c   |   33 +++++++++++++++++++++++++++++++++
 include/linux/dcache.h |   10 ++++++++++
 include/linux/fs.h     |   10 ++++++++++
 4 files changed, 57 insertions(+), 1 deletion(-)

fs/dcache.c +4 -1

@@ -1666,7 +1666,8 @@ void d_set_d_op(struct dentry *dentry, c
 				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;

@@ -1684,6 +1685,8 @@ void d_set_d_op(struct dentry *dentry, c
 		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

@@ -276,6 +276,37 @@ static void ovl_dentry_release(struct de
 	}
 }
 
+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;

@@ -320,11 +351,13 @@ static int ovl_dentry_weak_revalidate(st
 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

@@ -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;
 
 /*

@@ -227,6 +228,7 @@ struct dentry_operations {
 #define DCACHE_MAY_FREE			0x00800000
 #define DCACHE_FALLTHRU			0x01000000 /* Fall through to lower layer */
 #define DCACHE_OP_SELECT_INODE		0x02000000 /* Unioned entry: dcache op selects inode */
+#define DCACHE_OP_REAL			0x08000000
 
 extern seqlock_t rename_lock;

@@ -582,4 +584,12 @@ static inline struct dentry *d_backing_d
 	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

@@ -1207,6 +1207,16 @@ static inline struct inode *file_inode(c
 	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);

Patches currently in stable-queue which might be from [email protected] are

queue-4.4/fs-add-file_dentry.patch