From d101a125954eae1d397adda94ca6319485a50493 Mon Sep 17 00:00:00 2001 From: Miklos Szeredi Date: Sat, 26 Mar 2016 16:14:37 -0400 Subject: fs: add file_dentry() 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 Signed-off-by: Theodore Ts'o Tested-by: Goldwyn Rodrigues Reviewed-by: Trond Myklebust Cc: # v4.2 Cc: David Howells Cc: Al Viro Cc: Daniel Axtens --- include/linux/dcache.h | 10 ++++++++++ include/linux/fs.h | 10 ++++++++++ 2 files changed, 20 insertions(+) (limited to 'include') diff --git a/include/linux/dcache.h b/include/linux/dcache.h index 7cb043d8f4e8..4bb4de8d95ea 100644 --- a/include/linux/dcache.h +++ b/include/linux/dcache.h @@ -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 */ diff --git a/include/linux/fs.h b/include/linux/fs.h index 35d99266ca9a..b2ed2311b021 100644 --- a/include/linux/fs.h +++ b/include/linux/fs.h @@ -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); -- cgit v1.2.3-59-g8ed1b