[PATCH 24/35] Unionfs: Readdir state

["Josef 'Jeff' Sipek" <jsipek@cs.sunysb.edu>]

From: Josef "Jeff" Sipek <jsipek@cs.sunysb.edu>

This file contains the routines for maintaining readdir state.

Signed-off-by: Josef "Jeff" Sipek <jsipek@cs.sunysb.edu>
Signed-off-by: David Quigley <dquigley@fsl.cs.sunysb.edu>
Signed-off-by: Erez Zadok <ezk@cs.sunysb.edu>
---
 fs/unionfs/rdstate.c |  282 ++++++++++++++++++++++++++++++++++++++++++++++++++
 1 files changed, 282 insertions(+), 0 deletions(-)

diff --git a/fs/unionfs/rdstate.c b/fs/unionfs/rdstate.c
new file mode 100644
index 0000000..5a19157
--- /dev/null
+++ b/fs/unionfs/rdstate.c
@@ -0,0 +1,282 @@
+/*
+ * Copyright (c) 2003-2006 Erez Zadok
+ * Copyright (c) 2003-2006 Charles P. Wright
+ * Copyright (c) 2005-2006 Josef 'Jeff' Sipek
+ * Copyright (c) 2005-2006 Junjiro Okajima
+ * Copyright (c) 2005      Arun M. Krishnakumar
+ * Copyright (c) 2004-2006 David P. Quigley
+ * Copyright (c) 2003-2004 Mohammad Nayyer Zubair
+ * Copyright (c) 2003      Puja Gupta
+ * Copyright (c) 2003      Harikesavan Krishnan
+ * Copyright (c) 2003-2006 Stony Brook University
+ * Copyright (c) 2003-2006 The Research Foundation of State University of New York
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ */
+
+#include "union.h"
+
+/* This file contains the routines for maintaining readdir state. */
+/* There are two structures here, rdstate which is a hash table
+ * of the second structure which is a filldir_node. */
+
+/* This is a struct kmem_cache for filldir nodes, because we allocate a lot
+ * of them and they shouldn't waste memory.  If the node has a small name
+ * (as defined by the dentry structure), then we use an inline name to
+ * preserve kmalloc space. */
+static struct kmem_cache *unionfs_filldir_cachep;
+int init_filldir_cache(void)
+{
+	unionfs_filldir_cachep =
+	    kmem_cache_create("unionfs_filldir", sizeof(struct filldir_node), 0,
+			      SLAB_RECLAIM_ACCOUNT, NULL, NULL);
+
+	return (unionfs_filldir_cachep ? 0 : -ENOMEM);
+}
+
+void destroy_filldir_cache(void)
+{
+	if (unionfs_filldir_cachep)
+		kmem_cache_destroy(unionfs_filldir_cachep);
+}
+
+/* This is a tuning parameter that tells us roughly how big to make the
+ * hash table in directory entries per page.  This isn't perfect, but
+ * at least we get a hash table size that shouldn't be too overloaded.
+ * The following averages are based on my home directory.
+ * 14.44693	Overall
+ * 12.29	Single Page Directories
+ * 117.93	Multi-page directories
+ */
+#define DENTPAGE 4096
+#define DENTPERONEPAGE 12
+#define DENTPERPAGE 118
+#define MINHASHSIZE 1
+static int guesstimate_hash_size(struct inode *inode)
+{
+	struct inode *hidden_inode;
+	int bindex;
+	int hashsize = MINHASHSIZE;
+
+	if (UNIONFS_I(inode)->hashsize > 0)
+		return UNIONFS_I(inode)->hashsize;
+
+	for (bindex = ibstart(inode); bindex <= ibend(inode); bindex++) {
+		if (!(hidden_inode = unionfs_lower_inode_idx(inode, bindex)))
+			continue;
+
+		if (hidden_inode->i_size == DENTPAGE)
+			hashsize += DENTPERONEPAGE;
+		else
+			hashsize += (hidden_inode->i_size / DENTPAGE) * DENTPERPAGE;
+	}
+
+	return hashsize;
+}
+
+int init_rdstate(struct file *file)
+{
+	BUG_ON(sizeof(loff_t) != (sizeof(unsigned int) + sizeof(unsigned int)));
+	BUG_ON(UNIONFS_F(file)->rdstate != NULL);
+
+	UNIONFS_F(file)->rdstate = alloc_rdstate(file->f_dentry->d_inode,
+						 fbstart(file));
+	
+	return (UNIONFS_F(file)->rdstate ? 0 : -ENOMEM);
+}
+
+struct unionfs_dir_state *find_rdstate(struct inode *inode, loff_t fpos)
+{
+	struct unionfs_dir_state *rdstate = NULL;
+	struct list_head *pos;
+
+	spin_lock(&UNIONFS_I(inode)->rdlock);
+	list_for_each(pos, &UNIONFS_I(inode)->readdircache) {
+		struct unionfs_dir_state *r =
+		    list_entry(pos, struct unionfs_dir_state, cache);
+		if (fpos == rdstate2offset(r)) {
+			UNIONFS_I(inode)->rdcount--;
+			list_del(&r->cache);
+			rdstate = r;
+			break;
+		}
+	}
+	spin_unlock(&UNIONFS_I(inode)->rdlock);
+	return rdstate;
+}
+
+struct unionfs_dir_state *alloc_rdstate(struct inode *inode, int bindex)
+{
+	int i = 0;
+	int hashsize;
+	int mallocsize = sizeof(struct unionfs_dir_state);
+	struct unionfs_dir_state *rdstate;
+
+	hashsize = guesstimate_hash_size(inode);
+	mallocsize += hashsize * sizeof(struct list_head);
+	/* Round it up to the next highest power of two. */
+	mallocsize--;
+	mallocsize |= mallocsize >> 1;
+	mallocsize |= mallocsize >> 2;
+	mallocsize |= mallocsize >> 4;
+	mallocsize |= mallocsize >> 8;
+	mallocsize |= mallocsize >> 16;
+	mallocsize++;
+
+	/* This should give us about 500 entries anyway. */
+	if (mallocsize > PAGE_SIZE)
+		mallocsize = PAGE_SIZE;
+
+	hashsize = (mallocsize -
+	     sizeof(struct unionfs_dir_state)) / sizeof(struct list_head);
+
+	rdstate = kmalloc(mallocsize, GFP_KERNEL);
+	if (!rdstate)
+		return NULL;
+
+	spin_lock(&UNIONFS_I(inode)->rdlock);
+	if (UNIONFS_I(inode)->cookie >= (MAXRDCOOKIE - 1))
+		UNIONFS_I(inode)->cookie = 1;
+	else
+		UNIONFS_I(inode)->cookie++;
+
+	rdstate->cookie = UNIONFS_I(inode)->cookie;
+	spin_unlock(&UNIONFS_I(inode)->rdlock);
+	rdstate->offset = 1;
+	rdstate->access = jiffies;
+	rdstate->bindex = bindex;
+	rdstate->dirpos = 0;
+	rdstate->hashentries = 0;
+	rdstate->size = hashsize;
+	for (i = 0; i < rdstate->size; i++)
+		INIT_LIST_HEAD(&rdstate->list[i]);
+
+	return rdstate;
+}
+
+static void free_filldir_node(struct filldir_node *node)
+{
+	if (node->namelen >= DNAME_INLINE_LEN_MIN)
+		kfree(node->name);
+	kmem_cache_free(unionfs_filldir_cachep, node);
+}
+
+void free_rdstate(struct unionfs_dir_state *state)
+{
+	struct filldir_node *tmp;
+	int i;
+
+	for (i = 0; i < state->size; i++) {
+		struct list_head *head = &(state->list[i]);
+		struct list_head *pos, *n;
+
+		/* traverse the list and deallocate space */
+		list_for_each_safe(pos, n, head) {
+			tmp = list_entry(pos, struct filldir_node, file_list);
+			list_del(&tmp->file_list);
+			free_filldir_node(tmp);
+		}
+	}
+
+	kfree(state);
+}
+
+struct filldir_node *find_filldir_node(struct unionfs_dir_state *rdstate,
+				       const char *name, int namelen)
+{
+	int index;
+	unsigned int hash;
+	struct list_head *head;
+	struct list_head *pos;
+	struct filldir_node *cursor = NULL;
+	int found = 0;
+
+	BUG_ON(namelen <= 0);
+
+	hash = full_name_hash(name, namelen);
+	index = hash % rdstate->size;
+
+	head = &(rdstate->list[index]);
+	list_for_each(pos, head) {
+		cursor = list_entry(pos, struct filldir_node, file_list);
+
+		if (cursor->namelen == namelen && cursor->hash == hash &&
+		    !strncmp(cursor->name, name, namelen)) {
+			/* a duplicate exists, and hence no need to create
+			 * entry to the list */
+			found = 1;
+
+			/* if the duplicate is in this branch, then the file
+			 * system is corrupted. */
+			if (cursor->bindex == rdstate->bindex) {
+				printk(KERN_DEBUG "Possible I/O error "
+					"unionfs_filldir: a file is duplicated "
+					"in the same branch %d: %s\n",
+					rdstate->bindex, cursor->name);
+			}
+			break;
+		}
+	}
+
+	if (!found)
+		cursor = NULL;
+
+	return cursor;
+}
+
+inline struct filldir_node *alloc_filldir_node(const char *name, int namelen,
+					       unsigned int hash, int bindex)
+{
+	return kmem_cache_alloc(unionfs_filldir_cachep, SLAB_KERNEL);
+}
+
+int add_filldir_node(struct unionfs_dir_state *rdstate, const char *name,
+		     int namelen, int bindex, int whiteout)
+{
+	struct filldir_node *new;
+	unsigned int hash;
+	int index;
+	int err = 0;
+	struct list_head *head;
+
+	BUG_ON(namelen <= 0);
+
+	hash = full_name_hash(name, namelen);
+	index = hash % rdstate->size;
+	head = &(rdstate->list[index]);
+
+	new = alloc_filldir_node(name, namelen, hash, bindex);
+	if (!new) {
+		err = -ENOMEM;
+		goto out;
+	}
+
+	INIT_LIST_HEAD(&new->file_list);
+	new->namelen = namelen;
+	new->hash = hash;
+	new->bindex = bindex;
+	new->whiteout = whiteout;
+
+	if (namelen < DNAME_INLINE_LEN_MIN)
+		new->name = new->iname;
+	else {
+		new->name = kmalloc(namelen + 1, GFP_KERNEL);
+		if (!new->name) {
+			kmem_cache_free(unionfs_filldir_cachep, new);
+			new = NULL;
+			goto out;
+		}
+	}
+
+	memcpy(new->name, name, namelen);
+	new->name[namelen] = '\0';
+
+	rdstate->hashentries++;
+
+	list_add(&(new->file_list), head);
+out:
+	return err;
+}
+
-- 
1.4.3.3