fs: add a DCACHE_NEED_LOOKUP flag for d_flags

index 22a0ef4..7fc0e30 100644
@@ -343,6 +343,24 @@ void d_drop(struct dentry *dentry)
 EXPORT_SYMBOL(d_drop);
 
 /*
+ * d_clear_need_lookup - drop a dentry from cache and clear the need lookup flag
+ * @dentry: dentry to drop
+ *
+ * This is called when we do a lookup on a placeholder dentry that needed to be
+ * looked up.  The dentry should have been hashed in order for it to be found by
+ * the lookup code, but now needs to be unhashed while we do the actual lookup
+ * and clear the DCACHE_NEED_LOOKUP flag.
+ */
+void d_clear_need_lookup(struct dentry *dentry)
+{
+	spin_lock(&dentry->d_lock);
+	__d_drop(dentry);
+	dentry->d_flags &= ~DCACHE_NEED_LOOKUP;
+	spin_unlock(&dentry->d_lock);
+}
+EXPORT_SYMBOL(d_clear_need_lookup);
+
+/*
  * Finish off a dentry we've decided to kill.
  * dentry->d_lock must be held, returns with it unlocked.
  * If ref is non-zero, then decrement the refcount too.

@@ -431,8 +449,13 @@ repeat:
  	if (d_unhashed(dentry))
 		goto kill_it;
 
-	/* Otherwise leave it cached and ensure it's on the LRU */
-	dentry->d_flags |= DCACHE_REFERENCED;
+	/*
+	 * If this dentry needs lookup, don't set the referenced flag so that it
+	 * is more likely to be cleaned up by the dcache shrinker in case of
+	 * memory pressure.
+	 */
+	if (!d_need_lookup(dentry))
+		dentry->d_flags |= DCACHE_REFERENCED;
 	dentry_lru_add(dentry);
 
 	dentry->d_count--;

@@ -1703,6 +1726,13 @@ struct dentry *d_add_ci(struct dentry *dentry, struct inode *inode,
 	}
 
 	/*
+	 * We are going to instantiate this dentry, unhash it and clear the
+	 * lookup flag so we can do that.
+	 */
+	if (unlikely(d_need_lookup(found)))
+		d_clear_need_lookup(found);
+
+	/*
 	 * Negative dentry: instantiate it unless the inode is a directory and
 	 * already has a dentry.
 	 */

81 lines not on this page · raw message

index 19d90a5..5fa5bd3 100644
@@ -216,6 +216,7 @@ struct dentry_operations {
 #define DCACHE_MOUNTED		0x10000	/* is a mountpoint */
 #define DCACHE_NEED_AUTOMOUNT	0x20000	/* handle automount on this dir */
 #define DCACHE_MANAGE_TRANSIT	0x40000	/* manage transit from this dirent */
+#define DCACHE_NEED_LOOKUP	0x80000 /* dentry requires i_op->lookup */
 #define DCACHE_MANAGED_DENTRY \
 	(DCACHE_MOUNTED|DCACHE_NEED_AUTOMOUNT|DCACHE_MANAGE_TRANSIT)
 

@@ -416,6 +417,12 @@ static inline bool d_mountpoint(struct dentry *dentry)
 	return dentry->d_flags & DCACHE_MOUNTED;
 }
 
+static inline bool d_need_lookup(struct dentry *dentry)
+{
+	return dentry->d_flags & DCACHE_NEED_LOOKUP;
+}
+
+extern void d_clear_need_lookup(struct dentry *dentry);
 extern struct dentry *lookup_create(struct nameidata *nd, int is_dir);
 
 extern int sysctl_vfs_cache_pressure;

index 6228a30..2a1a028 100644
@@ -4120,12 +4120,19 @@ struct inode *btrfs_lookup_dentry(struct inode *dir, struct dentry *dentry)
 	struct btrfs_root *sub_root = root;
 	struct btrfs_key location;
 	int index;
-	int ret;
+	int ret = 0;
 
 	if (dentry->d_name.len > BTRFS_NAME_LEN)
 		return ERR_PTR(-ENAMETOOLONG);
 
-	ret = btrfs_inode_by_name(dir, dentry, &location);
+	if (unlikely(d_need_lookup(dentry))) {
+		memcpy(&location, dentry->d_fsdata, sizeof(struct btrfs_key));
+		kfree(dentry->d_fsdata);
+		dentry->d_fsdata = NULL;
+		d_clear_need_lookup(dentry);
+	} else {
+		ret = btrfs_inode_by_name(dir, dentry, &location);
+	}
 
 	if (ret < 0)
 		return ERR_PTR(ret);

@@ -4180,6 +4187,12 @@ static int btrfs_dentry_delete(const struct dentry *dentry)
 	return 0;
 }
 
+static void btrfs_dentry_release(struct dentry *dentry)
+{
+	if (dentry->d_fsdata)
+		kfree(dentry->d_fsdata);
+}
+
 static struct dentry *btrfs_lookup(struct inode *dir, struct dentry *dentry,
 				   struct nameidata *nd)
 {

@@ -4206,6 +4219,7 @@ static int btrfs_real_readdir(struct file *filp, void *dirent,
 	struct btrfs_key key;
 	struct btrfs_key found_key;
 	struct btrfs_path *path;
+	struct qstr q;
 	int ret;
 	struct extent_buffer *leaf;
 	int slot;

@@ -4284,6 +4298,7 @@ static int btrfs_real_readdir(struct file *filp, void *dirent,
 
 		while (di_cur < di_total) {
 			struct btrfs_key location;
+			struct dentry *tmp;
 
 			if (verify_dir_item(root, leaf, di))
 				break;

@@ -4304,6 +4319,33 @@ static int btrfs_real_readdir(struct file *filp, void *dirent,
 			d_type = btrfs_filetype_table[btrfs_dir_type(leaf, di)];
 			btrfs_dir_item_key_to_cpu(leaf, di, &location);
 
+			q.name = name_ptr;
+			q.len = name_len;
+			q.hash = full_name_hash(q.name, q.len);
+			tmp = d_lookup(filp->f_dentry, &q);
+			if (!tmp) {
+				struct btrfs_key *newkey;
+
+				newkey = kzalloc(sizeof(struct btrfs_key),
+						 GFP_NOFS);
+				if (!newkey)
+					goto no_dentry;
+				tmp = d_alloc(filp->f_dentry, &q);
+				if (!tmp) {
+					kfree(newkey);
+					dput(tmp);
+					goto no_dentry;
+				}
+				memcpy(newkey, &location,
+				       sizeof(struct btrfs_key));
+				tmp->d_fsdata = newkey;
+				tmp->d_flags |= DCACHE_NEED_LOOKUP;
+				d_rehash(tmp);
+				dput(tmp);
+			} else {
+				dput(tmp);
+			}
+no_dentry:
 			/* is this a reference to our own snapshot? If so
 			 * skip it
 			 */

@@ -7566,4 +7608,5 @@ static const struct inode_operations btrfs_symlink_inode_operations = {
 
 const struct dentry_operations btrfs_dentry_operations = {
 	.d_delete	= btrfs_dentry_delete,
+	.d_release	= btrfs_dentry_release,
 };