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authorDavid Howells <dhowells@redhat.com>2015-01-29 12:02:27 +0000
committerAl Viro <viro@zeniv.linux.org.uk>2015-02-22 11:38:15 -0500
commit155e35d4daa804582f75acaa2c74ec797a89c615 (patch)
tree322e9d089bd5610164aeadf164a237328cb0b19c
parentce7b9facdf43b42fb95bdff9069aefeddb7d0a69 (diff)
downloadlinux-155e35d4daa804582f75acaa2c74ec797a89c615.tar.gz
VFS: Introduce inode-getting helpers for layered/unioned fs environments
Introduce some function for getting the inode (and also the dentry) in an environment where layered/unioned filesystems are in operation. The problem is that we have places where we need *both* the union dentry and the lower source or workspace inode or dentry available, but we can only have a handle on one of them. Therefore we need to derive the handle to the other from that. The idea is to introduce an extra field in struct dentry that allows the union dentry to refer to and pin the lower dentry. Signed-off-by: David Howells <dhowells@redhat.com> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
-rw-r--r--include/linux/dcache.h57
1 files changed, 57 insertions, 0 deletions
diff --git a/include/linux/dcache.h b/include/linux/dcache.h
index 92c08cf..047c0db 100644
--- a/include/linux/dcache.h
+++ b/include/linux/dcache.h
@@ -464,4 +464,61 @@ static inline unsigned long vfs_pressure_ratio(unsigned long val)
{
return mult_frac(val, sysctl_vfs_cache_pressure, 100);
}
+
+/**
+ * d_inode - Get the actual inode of this dentry
+ * @dentry: The dentry to query
+ *
+ * This is the helper normal filesystems should use to get at their own inodes
+ * in their own dentries and ignore the layering superimposed upon them.
+ */
+static inline struct inode *d_inode(const struct dentry *dentry)
+{
+ return dentry->d_inode;
+}
+
+/**
+ * d_inode_rcu - Get the actual inode of this dentry with ACCESS_ONCE()
+ * @dentry: The dentry to query
+ *
+ * This is the helper normal filesystems should use to get at their own inodes
+ * in their own dentries and ignore the layering superimposed upon them.
+ */
+static inline struct inode *d_inode_rcu(const struct dentry *dentry)
+{
+ return ACCESS_ONCE(dentry->d_inode);
+}
+
+/**
+ * d_backing_inode - Get upper or lower inode we should be using
+ * @upper: The upper layer
+ *
+ * This is the helper that should be used to get at the inode that will be used
+ * if this dentry were to be opened as a file. The inode may be on the upper
+ * dentry or it may be on a lower dentry pinned by the upper.
+ *
+ * Normal filesystems should not use this to access their own inodes.
+ */
+static inline struct inode *d_backing_inode(const struct dentry *upper)
+{
+ struct inode *inode = upper->d_inode;
+
+ return inode;
+}
+
+/**
+ * d_backing_dentry - Get upper or lower dentry we should be using
+ * @upper: The upper layer
+ *
+ * This is the helper that should be used to get the dentry of the inode that
+ * will be used if this dentry were opened as a file. It may be the upper
+ * dentry or it may be a lower dentry pinned by the upper.
+ *
+ * Normal filesystems should not use this to access their own dentries.
+ */
+static inline struct dentry *d_backing_dentry(struct dentry *upper)
+{
+ return upper;
+}
+
#endif /* __LINUX_DCACHE_H */