dir.c 16.3 KB
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/*
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 *  linux/fs/ext4/dir.c
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 *
 * Copyright (C) 1992, 1993, 1994, 1995
 * Remy Card (card@masi.ibp.fr)
 * Laboratoire MASI - Institut Blaise Pascal
 * Universite Pierre et Marie Curie (Paris VI)
 *
 *  from
 *
 *  linux/fs/minix/dir.c
 *
 *  Copyright (C) 1991, 1992  Linus Torvalds
 *
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 *  ext4 directory handling functions
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 *
 *  Big-endian to little-endian byte-swapping/bitmaps by
 *        David S. Miller (davem@caip.rutgers.edu), 1995
 *
 * Hash Tree Directory indexing (c) 2001  Daniel Phillips
 *
 */

#include <linux/fs.h>
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#include <linux/jbd2.h>
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#include <linux/buffer_head.h>
#include <linux/slab.h>
#include <linux/rbtree.h>
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#include "ext4.h"
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static unsigned char ext4_filetype_table[] = {
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	DT_UNKNOWN, DT_REG, DT_DIR, DT_CHR, DT_BLK, DT_FIFO, DT_SOCK, DT_LNK
};

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static int ext4_dx_readdir(struct file *filp,
			   void *dirent, filldir_t filldir);
37 38 39

static unsigned char get_dtype(struct super_block *sb, int filetype)
{
40 41
	if (!EXT4_HAS_INCOMPAT_FEATURE(sb, EXT4_FEATURE_INCOMPAT_FILETYPE) ||
	    (filetype >= EXT4_FT_MAX))
42 43
		return DT_UNKNOWN;

44
	return (ext4_filetype_table[filetype]);
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}

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/**
 * Check if the given dir-inode refers to an htree-indexed directory
 * (or a directory which chould potentially get coverted to use htree
 * indexing).
 *
 * Return 1 if it is a dx dir, 0 if not
 */
static int is_dx_dir(struct inode *inode)
{
	struct super_block *sb = inode->i_sb;

	if (EXT4_HAS_COMPAT_FEATURE(inode->i_sb,
		     EXT4_FEATURE_COMPAT_DIR_INDEX) &&
	    ((ext4_test_inode_flag(inode, EXT4_INODE_INDEX)) ||
	     ((inode->i_size >> sb->s_blocksize_bits) == 1)))
		return 1;

	return 0;
}

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/*
 * Return 0 if the directory entry is OK, and 1 if there is a problem
 *
 * Note: this is the opposite of what ext2 and ext3 historically returned...
 */
72
int __ext4_check_dir_entry(const char *function, unsigned int line,
73
			   struct inode *dir, struct file *filp,
74
			   struct ext4_dir_entry_2 *de,
75
			   struct buffer_head *bh, char *buf, int size,
76
			   unsigned int offset)
77
{
78
	const char *error_msg = NULL;
79 80
	const int rlen = ext4_rec_len_from_disk(de->rec_len,
						dir->i_sb->s_blocksize);
81

82
	if (unlikely(rlen < EXT4_DIR_REC_LEN(1)))
83
		error_msg = "rec_len is smaller than minimal";
84
	else if (unlikely(rlen % 4 != 0))
85
		error_msg = "rec_len % 4 != 0";
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	else if (unlikely(rlen < EXT4_DIR_REC_LEN(de->name_len)))
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		error_msg = "rec_len is too small for name_len";
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	else if (unlikely(((char *) de - buf) + rlen > size))
		error_msg = "directory entry across range";
90 91
	else if (unlikely(le32_to_cpu(de->inode) >
			le32_to_cpu(EXT4_SB(dir->i_sb)->s_es->s_inodes_count)))
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		error_msg = "inode out of bounds";
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	else
		return 0;

96
	if (filp)
97
		ext4_error_file(filp, function, line, bh->b_blocknr,
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				"bad entry in directory: %s - offset=%u(%u), "
				"inode=%u, rec_len=%d, name_len=%d",
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				error_msg, (unsigned) (offset % size),
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				offset, le32_to_cpu(de->inode),
				rlen, de->name_len);
	else
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		ext4_error_inode(dir, function, line, bh->b_blocknr,
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				"bad entry in directory: %s - offset=%u(%u), "
				"inode=%u, rec_len=%d, name_len=%d",
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				error_msg, (unsigned) (offset % size),
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				offset, le32_to_cpu(de->inode),
				rlen, de->name_len);

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	return 1;
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}

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static int ext4_readdir(struct file *filp,
			 void *dirent, filldir_t filldir)
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{
	int error = 0;
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	unsigned int offset;
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	int i, stored;
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	struct ext4_dir_entry_2 *de;
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	int err;
122
	struct inode *inode = filp->f_path.dentry->d_inode;
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	struct super_block *sb = inode->i_sb;
124
	int ret = 0;
125
	int dir_has_error = 0;
126

127
	if (is_dx_dir(inode)) {
128
		err = ext4_dx_readdir(filp, dirent, filldir);
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		if (err != ERR_BAD_DX_DIR) {
			ret = err;
			goto out;
		}
		/*
		 * We don't set the inode dirty flag since it's not
		 * critical that it get flushed back to the disk.
		 */
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		ext4_clear_inode_flag(filp->f_path.dentry->d_inode,
				      EXT4_INODE_INDEX);
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	}
	stored = 0;
	offset = filp->f_pos & (sb->s_blocksize - 1);

	while (!error && !stored && filp->f_pos < inode->i_size) {
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		struct ext4_map_blocks map;
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		struct buffer_head *bh = NULL;

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		map.m_lblk = filp->f_pos >> EXT4_BLOCK_SIZE_BITS(sb);
		map.m_len = 1;
		err = ext4_map_blocks(NULL, inode, &map, 0);
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		if (err > 0) {
151
			pgoff_t index = map.m_pblk >>
152 153
					(PAGE_CACHE_SHIFT - inode->i_blkbits);
			if (!ra_has_index(&filp->f_ra, index))
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				page_cache_sync_readahead(
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					sb->s_bdev->bd_inode->i_mapping,
					&filp->f_ra, filp,
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					index, 1);
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			filp->f_ra.prev_pos = (loff_t)index << PAGE_CACHE_SHIFT;
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			bh = ext4_bread(NULL, inode, map.m_lblk, 0, &err);
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		}

		/*
		 * We ignore I/O errors on directories so users have a chance
		 * of recovering data when there's a bad sector
		 */
		if (!bh) {
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			if (!dir_has_error) {
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				EXT4_ERROR_FILE(filp, 0,
						"directory contains a "
						"hole at offset %llu",
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					   (unsigned long long) filp->f_pos);
				dir_has_error = 1;
			}
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			/* corrupt size?  Maybe no more blocks to read */
			if (filp->f_pos > inode->i_blocks << 9)
				break;
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			filp->f_pos += sb->s_blocksize - offset;
			continue;
		}

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		/* Check the checksum */
		if (!buffer_verified(bh) &&
		    !ext4_dirent_csum_verify(inode,
				(struct ext4_dir_entry *)bh->b_data)) {
			EXT4_ERROR_FILE(filp, 0, "directory fails checksum "
					"at offset %llu",
					(unsigned long long)filp->f_pos);
			filp->f_pos += sb->s_blocksize - offset;
			continue;
		}
		set_buffer_verified(bh);

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revalidate:
		/* If the dir block has changed since the last call to
		 * readdir(2), then we might be pointing to an invalid
		 * dirent right now.  Scan from the start of the block
		 * to make sure. */
		if (filp->f_version != inode->i_version) {
			for (i = 0; i < sb->s_blocksize && i < offset; ) {
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				de = (struct ext4_dir_entry_2 *)
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					(bh->b_data + i);
				/* It's too expensive to do a full
				 * dirent test each time round this
				 * loop, but we do have to test at
				 * least that it is non-zero.  A
				 * failure will be detected in the
				 * dirent test below. */
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				if (ext4_rec_len_from_disk(de->rec_len,
					sb->s_blocksize) < EXT4_DIR_REC_LEN(1))
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					break;
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				i += ext4_rec_len_from_disk(de->rec_len,
							    sb->s_blocksize);
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			}
			offset = i;
			filp->f_pos = (filp->f_pos & ~(sb->s_blocksize - 1))
				| offset;
			filp->f_version = inode->i_version;
		}

		while (!error && filp->f_pos < inode->i_size
		       && offset < sb->s_blocksize) {
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			de = (struct ext4_dir_entry_2 *) (bh->b_data + offset);
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			if (ext4_check_dir_entry(inode, filp, de, bh,
						 bh->b_data, bh->b_size,
						 offset)) {
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				/*
				 * On error, skip the f_pos to the next block
				 */
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				filp->f_pos = (filp->f_pos |
						(sb->s_blocksize - 1)) + 1;
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				brelse(bh);
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				ret = stored;
				goto out;
			}
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			offset += ext4_rec_len_from_disk(de->rec_len,
					sb->s_blocksize);
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			if (le32_to_cpu(de->inode)) {
				/* We might block in the next section
				 * if the data destination is
				 * currently swapped out.  So, use a
				 * version stamp to detect whether or
				 * not the directory has been modified
				 * during the copy operation.
				 */
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				u64 version = filp->f_version;
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				error = filldir(dirent, de->name,
						de->name_len,
						filp->f_pos,
						le32_to_cpu(de->inode),
						get_dtype(sb, de->file_type));
				if (error)
					break;
				if (version != filp->f_version)
					goto revalidate;
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				stored++;
257
			}
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			filp->f_pos += ext4_rec_len_from_disk(de->rec_len,
						sb->s_blocksize);
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		}
		offset = 0;
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		brelse(bh);
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	}
out:
	return ret;
}

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static inline int is_32bit_api(void)
{
#ifdef CONFIG_COMPAT
	return is_compat_task();
#else
	return (BITS_PER_LONG == 32);
#endif
}

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/*
 * These functions convert from the major/minor hash to an f_pos
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 * value for dx directories
 *
 * Upper layer (for example NFS) should specify FMODE_32BITHASH or
 * FMODE_64BITHASH explicitly. On the other hand, we allow ext4 to be mounted
 * directly on both 32-bit and 64-bit nodes, under such case, neither
 * FMODE_32BITHASH nor FMODE_64BITHASH is specified.
 */
static inline loff_t hash2pos(struct file *filp, __u32 major, __u32 minor)
{
	if ((filp->f_mode & FMODE_32BITHASH) ||
	    (!(filp->f_mode & FMODE_64BITHASH) && is_32bit_api()))
		return major >> 1;
	else
		return ((__u64)(major >> 1) << 32) | (__u64)minor;
}

static inline __u32 pos2maj_hash(struct file *filp, loff_t pos)
{
	if ((filp->f_mode & FMODE_32BITHASH) ||
	    (!(filp->f_mode & FMODE_64BITHASH) && is_32bit_api()))
		return (pos << 1) & 0xffffffff;
	else
		return ((pos >> 32) << 1) & 0xffffffff;
}

static inline __u32 pos2min_hash(struct file *filp, loff_t pos)
{
	if ((filp->f_mode & FMODE_32BITHASH) ||
	    (!(filp->f_mode & FMODE_64BITHASH) && is_32bit_api()))
		return 0;
	else
		return pos & 0xffffffff;
}

/*
 * Return 32- or 64-bit end-of-file for dx directories
 */
static inline loff_t ext4_get_htree_eof(struct file *filp)
{
	if ((filp->f_mode & FMODE_32BITHASH) ||
	    (!(filp->f_mode & FMODE_64BITHASH) && is_32bit_api()))
		return EXT4_HTREE_EOF_32BIT;
	else
		return EXT4_HTREE_EOF_64BIT;
}


/*
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 * ext4_dir_llseek() calls generic_file_llseek_size to handle htree
 * directories, where the "offset" is in terms of the filename hash
 * value instead of the byte offset.
330
 *
331 332 333 334 335
 * Because we may return a 64-bit hash that is well beyond offset limits,
 * we need to pass the max hash as the maximum allowable offset in
 * the htree directory case.
 *
 * For non-htree, ext4_llseek already chooses the proper max offset.
336
 */
337 338 339 340
loff_t ext4_dir_llseek(struct file *file, loff_t offset, int origin)
{
	struct inode *inode = file->f_mapping->host;
	int dx_dir = is_dx_dir(inode);
341
	loff_t htree_max = ext4_get_htree_eof(file);
342

343 344 345 346 347
	if (likely(dx_dir))
		return generic_file_llseek_size(file, offset, origin,
						    htree_max, htree_max);
	else
		return ext4_llseek(file, offset, origin);
348
}
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/*
 * This structure holds the nodes of the red-black tree used to store
 * the directory entry in hash order.
 */
struct fname {
	__u32		hash;
	__u32		minor_hash;
	struct rb_node	rb_hash;
	struct fname	*next;
	__u32		inode;
	__u8		name_len;
	__u8		file_type;
	char		name[0];
};

/*
 * This functoin implements a non-recursive way of freeing all of the
 * nodes in the red-black tree.
 */
static void free_rb_tree_fname(struct rb_root *root)
{
	struct rb_node	*n = root->rb_node;
	struct rb_node	*parent;
	struct fname	*fname;

	while (n) {
		/* Do the node's children first */
377
		if (n->rb_left) {
378 379 380 381 382 383 384 385 386 387 388 389 390 391 392 393
			n = n->rb_left;
			continue;
		}
		if (n->rb_right) {
			n = n->rb_right;
			continue;
		}
		/*
		 * The node has no children; free it, and then zero
		 * out parent's link to it.  Finally go to the
		 * beginning of the loop and try to free the parent
		 * node.
		 */
		parent = rb_parent(n);
		fname = rb_entry(n, struct fname, rb_hash);
		while (fname) {
394
			struct fname *old = fname;
395
			fname = fname->next;
396
			kfree(old);
397 398
		}
		if (!parent)
399
			*root = RB_ROOT;
400 401 402 403 404 405 406 407 408
		else if (parent->rb_left == n)
			parent->rb_left = NULL;
		else if (parent->rb_right == n)
			parent->rb_right = NULL;
		n = parent;
	}
}


409 410
static struct dir_private_info *ext4_htree_create_dir_info(struct file *filp,
							   loff_t pos)
411 412 413
{
	struct dir_private_info *p;

414
	p = kzalloc(sizeof(struct dir_private_info), GFP_KERNEL);
415 416
	if (!p)
		return NULL;
417 418
	p->curr_hash = pos2maj_hash(filp, pos);
	p->curr_minor_hash = pos2min_hash(filp, pos);
419 420 421
	return p;
}

422
void ext4_htree_free_dir_info(struct dir_private_info *p)
423 424 425 426 427 428 429 430
{
	free_rb_tree_fname(&p->root);
	kfree(p);
}

/*
 * Given a directory entry, enter it into the fname rb tree.
 */
431
int ext4_htree_store_dirent(struct file *dir_file, __u32 hash,
432
			     __u32 minor_hash,
433
			     struct ext4_dir_entry_2 *dirent)
434 435
{
	struct rb_node **p, *parent = NULL;
436
	struct fname *fname, *new_fn;
437 438 439
	struct dir_private_info *info;
	int len;

440
	info = dir_file->private_data;
441 442 443 444 445 446 447 448 449 450 451 452 453 454 455 456 457 458 459 460 461 462 463 464 465 466 467 468 469 470 471 472 473 474 475 476 477 478 479 480 481 482 483 484 485 486 487 488
	p = &info->root.rb_node;

	/* Create and allocate the fname structure */
	len = sizeof(struct fname) + dirent->name_len + 1;
	new_fn = kzalloc(len, GFP_KERNEL);
	if (!new_fn)
		return -ENOMEM;
	new_fn->hash = hash;
	new_fn->minor_hash = minor_hash;
	new_fn->inode = le32_to_cpu(dirent->inode);
	new_fn->name_len = dirent->name_len;
	new_fn->file_type = dirent->file_type;
	memcpy(new_fn->name, dirent->name, dirent->name_len);
	new_fn->name[dirent->name_len] = 0;

	while (*p) {
		parent = *p;
		fname = rb_entry(parent, struct fname, rb_hash);

		/*
		 * If the hash and minor hash match up, then we put
		 * them on a linked list.  This rarely happens...
		 */
		if ((new_fn->hash == fname->hash) &&
		    (new_fn->minor_hash == fname->minor_hash)) {
			new_fn->next = fname->next;
			fname->next = new_fn;
			return 0;
		}

		if (new_fn->hash < fname->hash)
			p = &(*p)->rb_left;
		else if (new_fn->hash > fname->hash)
			p = &(*p)->rb_right;
		else if (new_fn->minor_hash < fname->minor_hash)
			p = &(*p)->rb_left;
		else /* if (new_fn->minor_hash > fname->minor_hash) */
			p = &(*p)->rb_right;
	}

	rb_link_node(&new_fn->rb_hash, parent, p);
	rb_insert_color(&new_fn->rb_hash, &info->root);
	return 0;
}



/*
489
 * This is a helper function for ext4_dx_readdir.  It calls filldir
490 491 492
 * for all entres on the fname linked list.  (Normally there is only
 * one entry on the linked list, unless there are 62 bit hash collisions.)
 */
493
static int call_filldir(struct file *filp, void *dirent,
494 495 496 497
			filldir_t filldir, struct fname *fname)
{
	struct dir_private_info *info = filp->private_data;
	loff_t	curr_pos;
498
	struct inode *inode = filp->f_path.dentry->d_inode;
499
	struct super_block *sb;
500 501 502 503 504
	int error;

	sb = inode->i_sb;

	if (!fname) {
505 506 507
		ext4_msg(sb, KERN_ERR, "%s:%d: inode #%lu: comm %s: "
			 "called with null fname?!?", __func__, __LINE__,
			 inode->i_ino, current->comm);
508 509
		return 0;
	}
510
	curr_pos = hash2pos(filp, fname->hash, fname->minor_hash);
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	while (fname) {
		error = filldir(dirent, fname->name,
				fname->name_len, curr_pos,
				fname->inode,
				get_dtype(sb, fname->file_type));
		if (error) {
			filp->f_pos = curr_pos;
518
			info->extra_fname = fname;
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			return error;
		}
		fname = fname->next;
	}
	return 0;
}

526 527
static int ext4_dx_readdir(struct file *filp,
			 void *dirent, filldir_t filldir)
528 529
{
	struct dir_private_info *info = filp->private_data;
530
	struct inode *inode = filp->f_path.dentry->d_inode;
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	struct fname *fname;
	int	ret;

	if (!info) {
535
		info = ext4_htree_create_dir_info(filp, filp->f_pos);
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		if (!info)
			return -ENOMEM;
		filp->private_data = info;
	}

541
	if (filp->f_pos == ext4_get_htree_eof(filp))
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		return 0;	/* EOF */

	/* Some one has messed with f_pos; reset the world */
	if (info->last_pos != filp->f_pos) {
		free_rb_tree_fname(&info->root);
		info->curr_node = NULL;
		info->extra_fname = NULL;
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		info->curr_hash = pos2maj_hash(filp, filp->f_pos);
		info->curr_minor_hash = pos2min_hash(filp, filp->f_pos);
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	}

	/*
	 * If there are any leftover names on the hash collision
	 * chain, return them first.
	 */
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	if (info->extra_fname) {
		if (call_filldir(filp, dirent, filldir, info->extra_fname))
			goto finished;
		info->extra_fname = NULL;
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		goto next_node;
562
	} else if (!info->curr_node)
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		info->curr_node = rb_first(&info->root);

	while (1) {
		/*
		 * Fill the rbtree if we have no more entries,
		 * or the inode has changed since we last read in the
		 * cached entries.
		 */
		if ((!info->curr_node) ||
		    (filp->f_version != inode->i_version)) {
			info->curr_node = NULL;
			free_rb_tree_fname(&info->root);
			filp->f_version = inode->i_version;
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			ret = ext4_htree_fill_tree(filp, info->curr_hash,
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						   info->curr_minor_hash,
						   &info->next_hash);
			if (ret < 0)
				return ret;
			if (ret == 0) {
582
				filp->f_pos = ext4_get_htree_eof(filp);
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				break;
			}
			info->curr_node = rb_first(&info->root);
		}

		fname = rb_entry(info->curr_node, struct fname, rb_hash);
		info->curr_hash = fname->hash;
		info->curr_minor_hash = fname->minor_hash;
		if (call_filldir(filp, dirent, filldir, fname))
			break;
593
	next_node:
594
		info->curr_node = rb_next(info->curr_node);
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		if (info->curr_node) {
			fname = rb_entry(info->curr_node, struct fname,
					 rb_hash);
			info->curr_hash = fname->hash;
			info->curr_minor_hash = fname->minor_hash;
		} else {
601
			if (info->next_hash == ~0) {
602
				filp->f_pos = ext4_get_htree_eof(filp);
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				break;
			}
			info->curr_hash = info->next_hash;
			info->curr_minor_hash = 0;
		}
	}
finished:
	info->last_pos = filp->f_pos;
	return 0;
}

614
static int ext4_release_dir(struct inode *inode, struct file *filp)
615
{
616
	if (filp->private_data)
617
		ext4_htree_free_dir_info(filp->private_data);
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	return 0;
}
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const struct file_operations ext4_dir_operations = {
	.llseek		= ext4_dir_llseek,
	.read		= generic_read_dir,
	.readdir	= ext4_readdir,
	.unlocked_ioctl = ext4_ioctl,
#ifdef CONFIG_COMPAT
	.compat_ioctl	= ext4_compat_ioctl,
#endif
	.fsync		= ext4_sync_file,
	.release	= ext4_release_dir,
};