vfs: call d_op->d_prune() before unhashing dentry

The d_prune dentry operation is used to notify filesystem when VFS
about to prune a hashed dentry from the dcache. There are three
code paths that prune dentries: shrink_dcache_for_umount_subtree(),
prune_dcache_sb() and d_prune_aliases(). For the d_prune_aliases()
case, VFS unhashes the dentry first, then call the d_prune dentry
operation. This confuses ceph_d_prune() (ceph uses the d_prune
dentry operation to maintain a flag indicating whether the complete
contents of a directory are in the dcache, pruning unhashed dentry
does not affect dir's completeness)

This patch fixes the issue by calling the d_prune dentry operation
in d_prune_aliases(), before unhashing the dentry. Also make VFS
only call the d_prune dentry operation for hashed dentry, to avoid
calling the d_prune dentry operation twice when dentry is pruned
by d_prune_aliases().

Signed-off-by: Yan, Zheng <zheng.z.yan@intel.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

1 files changed, 11 insertions, 2 deletions

diff --git a/fs/dcache.c b/fs/dcache.c
index 83cfb834db03..2e5f9ca83285 100644
--- a/fs/dcache.c
+++ b/fs/dcache.c
@@ -472,7 +472,7 @@ relock:
          * inform the fs via d_prune that this dentry is about to be
          * unhashed and destroyed.
          */
-        if (dentry->d_flags & DCACHE_OP_PRUNE)
+        if ((dentry->d_flags & DCACHE_OP_PRUNE) && !d_unhashed(dentry))
                 dentry->d_op->d_prune(dentry);
 
         dentry_lru_del(dentry);
@@ -719,6 +719,14 @@ restart:
         hlist_for_each_entry(dentry, &inode->i_dentry, d_alias) {
                 spin_lock(&dentry->d_lock);
                 if (!dentry->d_count) {
+                        /*
+                         * inform the fs via d_prune that this dentry
+                         * is about to be unhashed and destroyed.
+                         */
+                        if ((dentry->d_flags & DCACHE_OP_PRUNE) &&
+                            !d_unhashed(dentry))
+                                dentry->d_op->d_prune(dentry);
+
                         __dget_dlock(dentry);
                         __d_drop(dentry);
                         spin_unlock(&dentry->d_lock);
@@ -907,7 +915,8 @@ static void shrink_dcache_for_umount_subtree(struct dentry *dentry)
                          * inform the fs that this dentry is about to be
                          * unhashed and destroyed.
                          */
-                        if (dentry->d_flags & DCACHE_OP_PRUNE)
+                        if ((dentry->d_flags & DCACHE_OP_PRUNE) &&
+                            !d_unhashed(dentry))
                                 dentry->d_op->d_prune(dentry);
 
                         dentry_lru_del(dentry);