dir.c

来自「Linux Kernel 2.6.9 for OMAP1710」· C语言 代码 · 共 667 行 · 第 1/2 页

/* dir.c: AFS filesystem directory handling
 *
 * Copyright (C) 2002 Red Hat, Inc. All Rights Reserved.
 * Written by David Howells ([e-mail])
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version
 * 2 of the License, or (at your option) any later version.
 */

#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/init.h>
#include <linux/sched.h>
#include <linux/slab.h>
#include <linux/fs.h>
#include <linux/pagemap.h>
#include <linux/smp_lock.h>
#include "vnode.h"
#include "volume.h"
#include <rxrpc/call.h>
#include "super.h"
#include "internal.h"

static struct dentry *afs_dir_lookup(struct inode *dir, struct dentry *dentry,
				     struct nameidata *nd);
static int afs_dir_open(struct inode *inode, struct file *file);
static int afs_dir_readdir(struct file *file, void *dirent, filldir_t filldir);
static int afs_d_revalidate(struct dentry *dentry, struct nameidata *nd);
static int afs_d_delete(struct dentry *dentry);
static int afs_dir_lookup_filldir(void *_cookie, const char *name, int nlen,
				  loff_t fpos, ino_t ino, unsigned dtype);

struct file_operations afs_dir_file_operations = {
	.open		= afs_dir_open,
	.readdir	= afs_dir_readdir,
};

struct inode_operations afs_dir_inode_operations = {
	.lookup		= afs_dir_lookup,
	.getattr	= afs_inode_getattr,
#if 0 /* TODO */
	.create		= afs_dir_create,
	.link		= afs_dir_link,
	.unlink		= afs_dir_unlink,
	.symlink	= afs_dir_symlink,
	.mkdir		= afs_dir_mkdir,
	.rmdir		= afs_dir_rmdir,
	.mknod		= afs_dir_mknod,
	.rename		= afs_dir_rename,
#endif
};

static struct dentry_operations afs_fs_dentry_operations = {
	.d_revalidate	= afs_d_revalidate,
	.d_delete	= afs_d_delete,
};

#define AFS_DIR_HASHTBL_SIZE	128
#define AFS_DIR_DIRENT_SIZE	32
#define AFS_DIRENT_PER_BLOCK	64

union afs_dirent {
	struct {
		uint8_t		valid;
		uint8_t		unused[1];
		__be16		hash_next;
		__be32		vnode;
		__be32		unique;
		uint8_t		name[16];
		uint8_t		overflow[4];	/* if any char of the name (inc
						 * NUL) reaches here, consume
						 * the next dirent too */
	} u;
	uint8_t	extended_name[32];
};

/* AFS directory page header (one at the beginning of every 2048-byte chunk) */
struct afs_dir_pagehdr {
	__be16		npages;
	__be16		magic;
#define AFS_DIR_MAGIC htons(1234)
	uint8_t		nentries;
	uint8_t		bitmap[8];
	uint8_t		pad[19];
};

/* directory block layout */
union afs_dir_block {

	struct afs_dir_pagehdr pagehdr;

	struct {
		struct afs_dir_pagehdr	pagehdr;
		uint8_t			alloc_ctrs[128];
		/* dir hash table */
		uint16_t		hashtable[AFS_DIR_HASHTBL_SIZE];
	} hdr;

	union afs_dirent dirents[AFS_DIRENT_PER_BLOCK];
};

/* layout on a linux VM page */
struct afs_dir_page {
	union afs_dir_block blocks[PAGE_SIZE / sizeof(union afs_dir_block)];
};

struct afs_dir_lookup_cookie {
	struct afs_fid	fid;
	const char	*name;
	size_t		nlen;
	int		found;
};

/*****************************************************************************/
/*
 * check that a directory page is valid
 */
static inline void afs_dir_check_page(struct inode *dir, struct page *page)
{
	struct afs_dir_page *dbuf;
	loff_t latter;
	int tmp, qty;

#if 0
	/* check the page count */
	qty = desc.size / sizeof(dbuf->blocks[0]);
	if (qty == 0)
		goto error;

	if (page->index==0 && qty!=ntohs(dbuf->blocks[0].pagehdr.npages)) {
		printk("kAFS: %s(%lu): wrong number of dir blocks %d!=%hu\n",
		       __FUNCTION__,dir->i_ino,qty,ntohs(dbuf->blocks[0].pagehdr.npages));
		goto error;
	}
#endif

	/* determine how many magic numbers there should be in this page */
	latter = dir->i_size - (page->index << PAGE_CACHE_SHIFT);
	if (latter >= PAGE_SIZE)
		qty = PAGE_SIZE;
	else
		qty = latter;
	qty /= sizeof(union afs_dir_block);

	/* check them */
	dbuf = page_address(page);
	for (tmp = 0; tmp < qty; tmp++) {
		if (dbuf->blocks[tmp].pagehdr.magic != AFS_DIR_MAGIC) {
			printk("kAFS: %s(%lu): bad magic %d/%d is %04hx\n",
			       __FUNCTION__, dir->i_ino, tmp, qty,
			       ntohs(dbuf->blocks[tmp].pagehdr.magic));
			goto error;
		}
	}

	SetPageChecked(page);
	return;

 error:
	SetPageChecked(page);
	SetPageError(page);

} /* end afs_dir_check_page() */

/*****************************************************************************/
/*
 * discard a page cached in the pagecache
 */
static inline void afs_dir_put_page(struct page *page)
{
	kunmap(page);
	page_cache_release(page);

} /* end afs_dir_put_page() */

/*****************************************************************************/
/*
 * get a page into the pagecache
 */
static struct page *afs_dir_get_page(struct inode *dir, unsigned long index)
{
	struct page *page;

	_enter("{%lu},%lu", dir->i_ino, index);

	page = read_cache_page(dir->i_mapping,index,
			       (filler_t *) dir->i_mapping->a_ops->readpage,
			       NULL);
	if (!IS_ERR(page)) {
		wait_on_page_locked(page);
		kmap(page);
		if (!PageUptodate(page))
			goto fail;
		if (!PageChecked(page))
			afs_dir_check_page(dir, page);
		if (PageError(page))
			goto fail;
	}
	return page;

 fail:
	afs_dir_put_page(page);
	return ERR_PTR(-EIO);
} /* end afs_dir_get_page() */

/*****************************************************************************/
/*
 * open an AFS directory file
 */
static int afs_dir_open(struct inode *inode, struct file *file)
{
	_enter("{%lu}", inode->i_ino);

	BUG_ON(sizeof(union afs_dir_block) != 2048);
	BUG_ON(sizeof(union afs_dirent) != 32);

	if (AFS_FS_I(inode)->flags & AFS_VNODE_DELETED)
		return -ENOENT;

	_leave(" = 0");
	return 0;

} /* end afs_dir_open() */

/*****************************************************************************/
/*
 * deal with one block in an AFS directory
 */
static int afs_dir_iterate_block(unsigned *fpos,
				 union afs_dir_block *block,
				 unsigned blkoff,
				 void *cookie,
				 filldir_t filldir)
{
	union afs_dirent *dire;
	unsigned offset, next, curr;
	size_t nlen;
	int tmp, ret;

	_enter("%u,%x,%p,,",*fpos,blkoff,block);

	curr = (*fpos - blkoff) / sizeof(union afs_dirent);

	/* walk through the block, an entry at a time */
	for (offset = AFS_DIRENT_PER_BLOCK - block->pagehdr.nentries;
	     offset < AFS_DIRENT_PER_BLOCK;
	     offset = next
	     ) {
		next = offset + 1;

		/* skip entries marked unused in the bitmap */
		if (!(block->pagehdr.bitmap[offset / 8] &
		      (1 << (offset % 8)))) {
			_debug("ENT[%Zu.%u]: unused\n",
			       blkoff / sizeof(union afs_dir_block), offset);
			if (offset >= curr)
				*fpos = blkoff +
					next * sizeof(union afs_dirent);
			continue;
		}

		/* got a valid entry */
		dire = &block->dirents[offset];
		nlen = strnlen(dire->u.name,
			       sizeof(*block) -
			       offset * sizeof(union afs_dirent));

		_debug("ENT[%Zu.%u]: %s %Zu \"%s\"\n",
		       blkoff / sizeof(union afs_dir_block), offset,
		       (offset < curr ? "skip" : "fill"),
		       nlen, dire->u.name);

		/* work out where the next possible entry is */
		for (tmp = nlen; tmp > 15; tmp -= sizeof(union afs_dirent)) {
			if (next >= AFS_DIRENT_PER_BLOCK) {
				_debug("ENT[%Zu.%u]:"
				       " %u travelled beyond end dir block"
				       " (len %u/%Zu)\n",
				       blkoff / sizeof(union afs_dir_block),
				       offset, next, tmp, nlen);
				return -EIO;
			}
			if (!(block->pagehdr.bitmap[next / 8] &
			      (1 << (next % 8)))) {
				_debug("ENT[%Zu.%u]:"
				       " %u unmarked extension (len %u/%Zu)\n",
				       blkoff / sizeof(union afs_dir_block),
				       offset, next, tmp, nlen);
				return -EIO;
			}

			_debug("ENT[%Zu.%u]: ext %u/%Zu\n",
			       blkoff / sizeof(union afs_dir_block),
			       next, tmp, nlen);
			next++;
		}

		/* skip if starts before the current position */
		if (offset < curr)
			continue;

		/* found the next entry */
		ret = filldir(cookie,
			      dire->u.name,
			      nlen,
			      blkoff + offset * sizeof(union afs_dirent),
			      ntohl(dire->u.vnode),
			      filldir == afs_dir_lookup_filldir ?
			      ntohl(dire->u.unique) : DT_UNKNOWN);
		if (ret < 0) {
			_leave(" = 0 [full]");
			return 0;
		}

		*fpos = blkoff + next * sizeof(union afs_dirent);
	}

	_leave(" = 1 [more]");
	return 1;
} /* end afs_dir_iterate_block() */

/*****************************************************************************/
/*
 * read an AFS directory
 */
static int afs_dir_iterate(struct inode *dir, unsigned *fpos, void *cookie,
			   filldir_t filldir)
{
	union afs_dir_block	*dblock;
	struct afs_dir_page *dbuf;
	struct page *page;
	unsigned blkoff, limit;