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Subject[PATCH 20/42] Unionfs: readdir state helpers
Date
Includes duplicate name elimination and whiteout-handling code.

Signed-off-by: Erez Zadok <ezk@cs.sunysb.edu>
---
fs/unionfs/rdstate.c | 285 ++++++++++++++++++++++++++++++++++++++++++++++++++
1 files changed, 285 insertions(+), 0 deletions(-)
create mode 100644 fs/unionfs/rdstate.c
diff --git a/fs/unionfs/rdstate.c b/fs/unionfs/rdstate.c
new file mode 100644
index 0000000..7ba1e1a
--- /dev/null
+++ b/fs/unionfs/rdstate.c
@@ -0,0 +1,285 @@
+/*
+ * Copyright (c) 2003-2007 Erez Zadok
+ * Copyright (c) 2003-2006 Charles P. Wright
+ * Copyright (c) 2005-2007 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) 2003-2007 Stony Brook University
+ * Copyright (c) 2003-2007 The Research Foundation of SUNY
+ *
+ * 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 unionfs_init_filldir_cache(void)
+{
+ unionfs_filldir_cachep =
+ kmem_cache_create("unionfs_filldir",
+ sizeof(struct filldir_node), 0,
+ SLAB_RECLAIM_ACCOUNT, NULL);
+
+ return (unionfs_filldir_cachep ? 0 : -ENOMEM);
+}
+
+void unionfs_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 *lower_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++) {
+ lower_inode = unionfs_lower_inode_idx(inode, bindex);
+ if (!lower_inode)
+ continue;
+
+ if (i_size_read(lower_inode) == DENTPAGE)
+ hashsize += DENTPERONEPAGE;
+ else
+ hashsize += (i_size_read(lower_inode) / 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_path.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;
+ unsigned long mallocsize = sizeof(struct unionfs_dir_state);
+ struct unionfs_dir_state *rdstate;
+
+ hashsize = guesstimate_hash_size(inode);
+ mallocsize += hashsize * sizeof(struct list_head);
+ mallocsize = __roundup_pow_of_two(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 (unlikely(!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 is_whiteout)
+{
+ 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 a duplicate is found in this branch, and is
+ * not due to the caller looking for an entry to
+ * whiteout, then the file system may be corrupted.
+ */
+ if (unlikely(!is_whiteout &&
+ cursor->bindex == rdstate->bindex))
+ printk(KERN_ERR "unionfs: filldir: possible "
+ "I/O error: a file is duplicated "
+ "in the same branch %d: %s\n",
+ rdstate->bindex, cursor->name);
+ break;
+ }
+ }
+
+ if (!found)
+ cursor = NULL;
+
+ return cursor;
+}
+
+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 = kmem_cache_alloc(unionfs_filldir_cachep, GFP_KERNEL);
+ if (unlikely(!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 (unlikely(!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;
+}
--
1.5.2.2


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