vfs: add d_prune dentry operation

This adds a d_prune dentry operation that is called by the VFS prior to
pruning (i.e. unhashing and killing) a hashed dentry from the dcache.
Wrap dentry_lru_del() and use the new _prune() helper in the cases where we
are about to unhash and kill the dentry.

This will be used by Ceph to maintain a flag indicating whether the
complete contents of a directory are contained in the dcache, allowing it
to satisfy lookups and readdir without addition server communication.

Renumber a few DCACHE_* #defines to group DCACHE_OP_PRUNE with the other
DCACHE_OP_ bits.

Signed-off-by: Sage Weil <sage@newdream.net>
Signed-off-by: Christoph Hellwig <hch@lst.de>

1 files changed, 5 insertions, 3 deletions

diff --git a/include/linux/dcache.h b/include/linux/dcache.h
index 62157c03caf7..4df926199369 100644
--- a/include/linux/dcache.h
+++ b/include/linux/dcache.h
@@ -165,6 +165,7 @@ struct dentry_operations {
                         unsigned int, const char *, const struct qstr *);
         int (*d_delete)(const struct dentry *);
         void (*d_release)(struct dentry *);
+        void (*d_prune)(struct dentry *);
         void (*d_iput)(struct dentry *, struct inode *);
         char *(*d_dname)(struct dentry *, char *, int);
         struct vfsmount *(*d_automount)(struct path *);
@@ -184,8 +185,9 @@ struct dentry_operations {
 #define DCACHE_OP_COMPARE       0x0002
 #define DCACHE_OP_REVALIDATE    0x0004
 #define DCACHE_OP_DELETE        0x0008
+#define DCACHE_OP_PRUNE         0x0010
 
-#define DCACHE_DISCONNECTED     0x0010
+#define DCACHE_DISCONNECTED     0x0020
      /* This dentry is possibly not currently connected to the dcache tree, in
       * which case its parent will either be itself, or will have this flag as
       * well.  nfsd will not use a dentry with this bit set, but will first
@@ -196,8 +198,8 @@ struct dentry_operations {
       * dentry into place and return that dentry rather than the passed one,
       * typically using d_splice_alias. */
 
-#define DCACHE_REFERENCED       0x0020  /* Recently used, don't discard. */
-#define DCACHE_RCUACCESS        0x0040  /* Entry has ever been RCU-visible */
+#define DCACHE_REFERENCED       0x0040  /* Recently used, don't discard. */
+#define DCACHE_RCUACCESS        0x0080  /* Entry has ever been RCU-visible */
 
 #define DCACHE_CANT_MOUNT       0x0100
 #define DCACHE_GENOCIDE         0x0200