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authorMiklos Szeredi <miklos@szeredi.hu>2016-03-26 23:14:37 +0300
committerTheodore Ts'o <tytso@mit.edu>2016-03-26 23:14:37 +0300
commitd101a125954eae1d397adda94ca6319485a50493 (patch)
tree0f5853af51446f389c60f1a25f3875ef8a75ba41 /include/linux/dcache.h
parentc9af28fdd44922a6c10c9f8315718408af98e315 (diff)
downloadlinux-d101a125954eae1d397adda94ca6319485a50493.tar.xz
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 <mszeredi@redhat.com> Signed-off-by: Theodore Ts'o <tytso@mit.edu> Tested-by: Goldwyn Rodrigues <rgoldwyn@suse.com> Reviewed-by: Trond 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>
Diffstat (limited to 'include/linux/dcache.h')
-rw-r--r--include/linux/dcache.h10
1 files changed, 10 insertions, 0 deletions
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 */