ncpfs: get rid of d_validate() nonsense

What we want is to have non-counting references to children in
pagecache of parent directory, and avoid picking them after a child
has been freed.  Fine, so let's just have ->d_prune() clear
parent's inode "has directory contents in page cache" flag.
That way we don't need ->d_fsdata for storing offsets, so we can
use it as a quick and dirty "is it referenced from page cache"
flag.
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

fs/ncpfs/dir.c

@@ -77,6 +77,7 @@ static int ncp_hash_dentry(const struct dentry *, struct qstr *);
 static int ncp_compare_dentry(const struct dentry *, const struct dentry *,
 		unsigned int, const char *, const struct qstr *);
 static int ncp_delete_dentry(const struct dentry *);
+static void ncp_d_prune(struct dentry *dentry);
 
 const struct dentry_operations ncp_dentry_operations =
 {
@@ -84,6 +85,7 @@ const struct dentry_operations ncp_dentry_operations =
 	.d_hash		= ncp_hash_dentry,
 	.d_compare	= ncp_compare_dentry,
 	.d_delete	= ncp_delete_dentry,
+	.d_prune	= ncp_d_prune,
 };
 
 #define ncp_namespace(i)	(NCP_SERVER(i)->name_space[NCP_FINFO(i)->volNumber])
@@ -384,42 +386,6 @@ ncp_lookup_validate(struct dentry *dentry, unsigned int flags)
 	return val;
 }
 
-static struct dentry *
-ncp_dget_fpos(struct dentry *dentry, struct dentry *parent, unsigned long fpos)
-{
-	struct dentry *dent = dentry;
-
-	if (d_validate(dent, parent)) {
-		if (dent->d_name.len <= NCP_MAXPATHLEN &&
-		    (unsigned long)dent->d_fsdata == fpos) {
-			if (!dent->d_inode) {
-				dput(dent);
-				dent = NULL;
-			}
-			return dent;
-		}
-		dput(dent);
-	}
-
-	/* If a pointer is invalid, we search the dentry. */
-	spin_lock(&parent->d_lock);
-	list_for_each_entry(dent, &parent->d_subdirs, d_child) {
-		if ((unsigned long)dent->d_fsdata == fpos) {
-			if (dent->d_inode)
-				dget(dent);
-			else
-				dent = NULL;
-			spin_unlock(&parent->d_lock);
-			goto out;
-		}
-	}
-	spin_unlock(&parent->d_lock);
-	return NULL;
-
-out:
-	return dent;
-}
-
 static time_t ncp_obtain_mtime(struct dentry *dentry)
 {
 	struct inode *inode = dentry->d_inode;
@@ -435,6 +401,20 @@ static time_t ncp_obtain_mtime(struct dentry *dentry)
 	return ncp_date_dos2unix(i.modifyTime, i.modifyDate);
 }
 
+static inline void
+ncp_invalidate_dircache_entries(struct dentry *parent)
+{
+	struct ncp_server *server = NCP_SERVER(parent->d_inode);
+	struct dentry *dentry;
+
+	spin_lock(&parent->d_lock);
+	list_for_each_entry(dentry, &parent->d_subdirs, d_child) {
+		dentry->d_fsdata = NULL;
+		ncp_age_dentry(server, dentry);
+	}
+	spin_unlock(&parent->d_lock);
+}
+
 static int ncp_readdir(struct file *file, struct dir_context *ctx)
 {
 	struct dentry *dentry = file->f_path.dentry;
@@ -500,10 +480,21 @@ static int ncp_readdir(struct file *file, struct dir_context *ctx)
 			struct dentry *dent;
 			bool over;
 
-			dent = ncp_dget_fpos(ctl.cache->dentry[ctl.idx],
-						dentry, ctx->pos);
-			if (!dent)
+			spin_lock(&dentry->d_lock);
+			if (!(NCP_FINFO(inode)->flags & NCPI_DIR_CACHE)) { 
+				spin_unlock(&dentry->d_lock);
+				goto invalid_cache;
+			}
+			dent = ctl.cache->dentry[ctl.idx];
+			if (unlikely(!lockref_get_not_dead(&dent->d_lockref))) {
+				spin_unlock(&dentry->d_lock);
+				goto invalid_cache;
+			}
+			spin_unlock(&dentry->d_lock);
+			if (!dent->d_inode) {
+				dput(dent);
 				goto invalid_cache;
+			}
 			over = !dir_emit(ctx, dent->d_name.name,
 					dent->d_name.len,
 					dent->d_inode->i_ino, DT_UNKNOWN);
@@ -548,6 +539,9 @@ static int ncp_readdir(struct file *file, struct dir_context *ctx)
 	ctl.filled = 0;
 	ctl.valid  = 1;
 read_really:
+	spin_lock(&dentry->d_lock);
+	NCP_FINFO(inode)->flags |= NCPI_DIR_CACHE;
+	spin_unlock(&dentry->d_lock);
 	if (ncp_is_server_root(inode)) {
 		ncp_read_volume_list(file, ctx, &ctl);
 	} else {
@@ -573,6 +567,13 @@ static int ncp_readdir(struct file *file, struct dir_context *ctx)
 	return result;
 }
 
+static void ncp_d_prune(struct dentry *dentry)
+{
+	if (!dentry->d_fsdata)	/* not referenced from page cache */
+		return;
+	NCP_FINFO(dentry->d_parent->d_inode)->flags &= ~NCPI_DIR_CACHE;
+}
+
 static int
 ncp_fill_cache(struct file *file, struct dir_context *ctx,
 		struct ncp_cache_control *ctrl, struct ncp_entry_info *entry,
@@ -630,6 +631,10 @@ ncp_fill_cache(struct file *file, struct dir_context *ctx,
 			d_instantiate(newdent, inode);
 			if (!hashed)
 				d_rehash(newdent);
+		} else {
+			spin_lock(&dentry->d_lock);
+			NCP_FINFO(inode)->flags &= ~NCPI_DIR_CACHE;
+			spin_unlock(&dentry->d_lock);
 		}
 	} else {
 		struct inode *inode = newdent->d_inode;
@@ -639,12 +644,6 @@ ncp_fill_cache(struct file *file, struct dir_context *ctx,
 		mutex_unlock(&inode->i_mutex);
 	}
 
-	if (newdent->d_inode) {
-		ino = newdent->d_inode->i_ino;
-		newdent->d_fsdata = (void *) ctl.fpos;
-		ncp_new_dentry(newdent);
-	}
-
 	if (ctl.idx >= NCP_DIRCACHE_SIZE) {
 		if (ctl.page) {
 			kunmap(ctl.page);
@@ -660,7 +659,12 @@ ncp_fill_cache(struct file *file, struct dir_context *ctx,
 			ctl.cache = kmap(ctl.page);
 	}
 	if (ctl.cache) {
+		if (newdent->d_inode) {
+			newdent->d_fsdata = newdent;
 			ctl.cache->dentry[ctl.idx] = newdent;
+			ino = newdent->d_inode->i_ino;
+			ncp_new_dentry(newdent);
+		}
  		valid = 1;
 	}
 	dput(newdent);

fs/ncpfs/ncp_fs_i.h

@@ -22,6 +22,7 @@ struct ncp_inode_info {
 	int	access;
 	int	flags;
 #define NCPI_KLUDGE_SYMLINK	0x0001
+#define NCPI_DIR_CACHE		0x0002
 	__u8	file_handle[6];
 	struct inode vfs_inode;
 };

fs/ncpfs/ncplib_kernel.h

@@ -184,36 +184,6 @@ ncp_new_dentry(struct dentry* dentry)
 	dentry->d_time = jiffies;
 }
 
-static inline void
-ncp_renew_dentries(struct dentry *parent)
-{
-	struct ncp_server *server = NCP_SERVER(parent->d_inode);
-	struct dentry *dentry;
-
-	spin_lock(&parent->d_lock);
-	list_for_each_entry(dentry, &parent->d_subdirs, d_child) {
-		if (dentry->d_fsdata == NULL)
-			ncp_age_dentry(server, dentry);
-		else
-			ncp_new_dentry(dentry);
-	}
-	spin_unlock(&parent->d_lock);
-}
-
-static inline void
-ncp_invalidate_dircache_entries(struct dentry *parent)
-{
-	struct ncp_server *server = NCP_SERVER(parent->d_inode);
-	struct dentry *dentry;
-
-	spin_lock(&parent->d_lock);
-	list_for_each_entry(dentry, &parent->d_subdirs, d_child) {
-		dentry->d_fsdata = NULL;
-		ncp_age_dentry(server, dentry);
-	}
-	spin_unlock(&parent->d_lock);
-}
-
 struct ncp_cache_head {
 	time_t		mtime;
 	unsigned long	time;	/* cache age */