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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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