VFS: Add a fallthrough flag for marking virtual dentries
Add a DCACHE_FALLTHRU flag to indicate that, in a layered filesystem, this is
a virtual dentry that covers another one in a lower layer that should be used
instead. This may be recorded on medium if directory integration is stored
there.
The flag can be set with d_set_fallthru() and tested with d_is_fallthru().
Original-author: Valerie Aurora <vaurora@redhat.com>
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
diff --git a/fs/dcache.c b/fs/dcache.c
index dc400fd..e33a093 100644
--- a/fs/dcache.c
+++ b/fs/dcache.c
@@ -1659,6 +1659,22 @@
}
EXPORT_SYMBOL(d_set_d_op);
+
+/*
+ * d_set_fallthru - Mark a dentry as falling through to a lower layer
+ * @dentry - The dentry to mark
+ *
+ * Mark a dentry as falling through to the lower layer (as set with
+ * d_pin_lower()). This flag may be recorded on the medium.
+ */
+void d_set_fallthru(struct dentry *dentry)
+{
+ spin_lock(&dentry->d_lock);
+ dentry->d_flags |= DCACHE_FALLTHRU;
+ spin_unlock(&dentry->d_lock);
+}
+EXPORT_SYMBOL(d_set_fallthru);
+
static unsigned d_flags_for_inode(struct inode *inode)
{
unsigned add_flags = DCACHE_FILE_TYPE;
@@ -1691,7 +1707,8 @@
unsigned add_flags = d_flags_for_inode(inode);
spin_lock(&dentry->d_lock);
- __d_set_type(dentry, add_flags);
+ dentry->d_flags &= ~(DCACHE_ENTRY_TYPE | DCACHE_FALLTHRU);
+ dentry->d_flags |= add_flags;
if (inode)
hlist_add_head(&dentry->d_u.d_alias, &inode->i_dentry);
dentry->d_inode = inode;
diff --git a/include/linux/dcache.h b/include/linux/dcache.h
index 98d2a94..728f5d3 100644
--- a/include/linux/dcache.h
+++ b/include/linux/dcache.h
@@ -223,6 +223,7 @@
#define DCACHE_FILE_TYPE 0x00500000 /* Other file type (or fallthru to such) */
#define DCACHE_MAY_FREE 0x00800000
+#define DCACHE_FALLTHRU 0x01000000 /* Fall through to lower layer */
extern seqlock_t rename_lock;
@@ -470,6 +471,14 @@
return !d_is_negative(dentry);
}
+extern void d_set_fallthru(struct dentry *dentry);
+
+static inline bool d_is_fallthru(const struct dentry *dentry)
+{
+ return dentry->d_flags & DCACHE_FALLTHRU;
+}
+
+
extern int sysctl_vfs_cache_pressure;
static inline unsigned long vfs_pressure_ratio(unsigned long val)
