fs/ext4/dir.c - kernel/common - Git at Google

 /*
  *  linux/fs/ext4/dir.c
  *
  * Copyright (C) 1992, 1993, 1994, 1995
  * Remy Card ([email protected])
  * Laboratoire MASI - Institut Blaise Pascal
  * Universite Pierre et Marie Curie (Paris VI)
  *
  *  from
  *
  *  linux/fs/minix/dir.c
  *
  *  Copyright (C) 1991, 1992  Linus Torvalds
  *
  *  ext4 directory handling functions
  *
  *  Big-endian to little-endian byte-swapping/bitmaps by
  *        David S. Miller ([email protected]), 1995
  *
  * Hash Tree Directory indexing (c) 2001  Daniel Phillips
  *
  */

 #include <linux/fs.h>
 #include <linux/jbd2.h>
 #include <linux/buffer_head.h>
 #include <linux/slab.h>
 #include <linux/rbtree.h>
 #include "ext4.h"
 #include "xattr.h"

 static int ext4_dx_readdir(struct file *, struct dir_context *);

 /**
  * 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) ||
 	     ext4_has_inline_data(inode)))
 		return 1;

 	return 0;
 }

 /*
  * 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...
  *
  * bh passed here can be an inode block or a dir data block, depending
  * on the inode inline data flag.
  */
 int __ext4_check_dir_entry(const char *function, unsigned int line,
 			   struct inode *dir, struct file *filp,
 			   struct ext4_dir_entry_2 *de,
 			   struct buffer_head *bh, char *buf, int size,
 			   unsigned int offset)
 {
 	const char *error_msg = NULL;
 	const int rlen = ext4_rec_len_from_disk(de->rec_len,
 						dir->i_sb->s_blocksize);

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

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

 	return 1;
 }

 static int ext4_readdir(struct file *file, struct dir_context *ctx)
 {
 	unsigned int offset;
 	int i, stored;
 	struct ext4_dir_entry_2 *de;
 	int err;
 	struct inode *inode = file_inode(file);
 	struct super_block *sb = inode->i_sb;
 	int dir_has_error = 0;

 	if (is_dx_dir(inode)) {
 		err = ext4_dx_readdir(file, ctx);
 		if (err != ERR_BAD_DX_DIR) {
 			return err;
 		}
 		/*
 		 * We don't set the inode dirty flag since it's not
 		 * critical that it get flushed back to the disk.
 		 */
 		ext4_clear_inode_flag(file_inode(file),
 				      EXT4_INODE_INDEX);
 	}

 	if (ext4_has_inline_data(inode)) {
 		int has_inline_data = 1;
 		int ret = ext4_read_inline_dir(file, ctx,
 					   &has_inline_data);
 		if (has_inline_data)
 			return ret;
 	}

 	stored = 0;
 	offset = ctx->pos & (sb->s_blocksize - 1);

 	while (ctx->pos < inode->i_size) {
 		struct ext4_map_blocks map;
 		struct buffer_head *bh = NULL;

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

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

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

 		/* 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 (file->f_version != inode->i_version) {
 			for (i = 0; i < sb->s_blocksize && i < offset; ) {
 				de = (struct ext4_dir_entry_2 *)
 					(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. */
 				if (ext4_rec_len_from_disk(de->rec_len,
 					sb->s_blocksize) < EXT4_DIR_REC_LEN(1))
 					break;
 				i += ext4_rec_len_from_disk(de->rec_len,
 							    sb->s_blocksize);
 			}
 			offset = i;
 			ctx->pos = (ctx->pos & ~(sb->s_blocksize - 1))
 				| offset;
 			file->f_version = inode->i_version;
 		}

 		while (ctx->pos < inode->i_size
 		       && offset < sb->s_blocksize) {
 			de = (struct ext4_dir_entry_2 *) (bh->b_data + offset);
 			if (ext4_check_dir_entry(inode, file, de, bh,
 						 bh->b_data, bh->b_size,
 						 offset)) {
 				/*
 				 * On error, skip to the next block
 				 */
 				ctx->pos = (ctx->pos |
 						(sb->s_blocksize - 1)) + 1;
 				break;
 			}
 			offset += ext4_rec_len_from_disk(de->rec_len,
 					sb->s_blocksize);
 			if (le32_to_cpu(de->inode)) {
 				if (!dir_emit(ctx, de->name,
 						de->name_len,
 						le32_to_cpu(de->inode),
 						get_dtype(sb, de->file_type))) {
 					brelse(bh);
 					return 0;
 				}
 			}
 			ctx->pos += ext4_rec_len_from_disk(de->rec_len,
 						sb->s_blocksize);
 		}
 		offset = 0;
 		brelse(bh);
 		if (ctx->pos < inode->i_size) {
 			if (!dir_relax(inode))
 				return 0;
 		}
 	}
 	return 0;
 }

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

 /*
  * These functions convert from the major/minor hash to an f_pos
  * 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;
 }


 /*
  * 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.
  *
  * 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.
  */
 static loff_t ext4_dir_llseek(struct file *file, loff_t offset, int whence)
 {
 	struct inode *inode = file->f_mapping->host;
 	int dx_dir = is_dx_dir(inode);
 	loff_t htree_max = ext4_get_htree_eof(file);

 	if (likely(dx_dir))
 		return generic_file_llseek_size(file, offset, whence,
 						    htree_max, htree_max);
 	else
 		return ext4_llseek(file, offset, whence);
 }

 /*
  * 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 */
 		if (n->rb_left) {
 			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) {
 			struct fname *old = fname;
 			fname = fname->next;
 			kfree(old);
 		}
 		if (!parent)
 			*root = RB_ROOT;
 		else if (parent->rb_left == n)
 			parent->rb_left = NULL;
 		else if (parent->rb_right == n)
 			parent->rb_right = NULL;
 		n = parent;
 	}
 }


 static struct dir_private_info *ext4_htree_create_dir_info(struct file *filp,
 							   loff_t pos)
 {
 	struct dir_private_info *p;

 	p = kzalloc(sizeof(struct dir_private_info), GFP_KERNEL);
 	if (!p)
 		return NULL;
 	p->curr_hash = pos2maj_hash(filp, pos);
 	p->curr_minor_hash = pos2min_hash(filp, pos);
 	return p;
 }

 void ext4_htree_free_dir_info(struct dir_private_info *p)
 {
 	free_rb_tree_fname(&p->root);
 	kfree(p);
 }

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

 	info = dir_file->private_data;
 	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;
 }


 /*
  * This is a helper function for ext4_dx_readdir.  It calls filldir
  * 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.)
  */
 static int call_filldir(struct file *file, struct dir_context *ctx,
 			struct fname *fname)
 {
 	struct dir_private_info *info = file->private_data;
 	struct inode *inode = file_inode(file);
 	struct super_block *sb = inode->i_sb;

 	if (!fname) {
 		ext4_msg(sb, KERN_ERR, "%s:%d: inode #%lu: comm %s: "
 			 "called with null fname?!?", __func__, __LINE__,
 			 inode->i_ino, current->comm);
 		return 0;
 	}
 	ctx->pos = hash2pos(file, fname->hash, fname->minor_hash);
 	while (fname) {
 		if (!dir_emit(ctx, fname->name,
 				fname->name_len,
 				fname->inode,
 				get_dtype(sb, fname->file_type))) {
 			info->extra_fname = fname;
 			return 1;
 		}
 		fname = fname->next;
 	}
 	return 0;
 }

 static int ext4_dx_readdir(struct file *file, struct dir_context *ctx)
 {
 	struct dir_private_info *info = file->private_data;
 	struct inode *inode = file_inode(file);
 	struct fname *fname;
 	int	ret;

 	if (!info) {
 		info = ext4_htree_create_dir_info(file, ctx->pos);
 		if (!info)
 			return -ENOMEM;
 		file->private_data = info;
 	}

 	if (ctx->pos == ext4_get_htree_eof(file))
 		return 0;	/* EOF */

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

 	/*
 	 * If there are any leftover names on the hash collision
 	 * chain, return them first.
 	 */
 	if (info->extra_fname) {
 		if (call_filldir(file, ctx, info->extra_fname))
 			goto finished;
 		info->extra_fname = NULL;
 		goto next_node;
 	} else if (!info->curr_node)
 		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) ||
 		    (file->f_version != inode->i_version)) {
 			info->curr_node = NULL;
 			free_rb_tree_fname(&info->root);
 			file->f_version = inode->i_version;
 			ret = ext4_htree_fill_tree(file, info->curr_hash,
 						   info->curr_minor_hash,
 						   &info->next_hash);
 			if (ret < 0)
 				return ret;
 			if (ret == 0) {
 				ctx->pos = ext4_get_htree_eof(file);
 				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(file, ctx, fname))
 			break;
 	next_node:
 		info->curr_node = rb_next(info->curr_node);
 		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 {
 			if (info->next_hash == ~0) {
 				ctx->pos = ext4_get_htree_eof(file);
 				break;
 			}
 			info->curr_hash = info->next_hash;
 			info->curr_minor_hash = 0;
 		}
 	}
 finished:
 	info->last_pos = ctx->pos;
 	return 0;
 }

 static int ext4_release_dir(struct inode *inode, struct file *filp)
 {
 	if (filp->private_data)
 		ext4_htree_free_dir_info(filp->private_data);

 	return 0;
 }

 const struct file_operations ext4_dir_operations = {
 	.llseek		= ext4_dir_llseek,
 	.read		= generic_read_dir,
 	.iterate	= ext4_readdir,
 	.unlocked_ioctl = ext4_ioctl,
 #ifdef CONFIG_COMPAT
 	.compat_ioctl	= ext4_compat_ioctl,
 #endif
 	.fsync		= ext4_sync_file,
 	.release	= ext4_release_dir,
 };
	/*
	* linux/fs/ext4/dir.c
	*
	* Copyright (C) 1992, 1993, 1994, 1995
	* Remy Card ([email protected])
	* Laboratoire MASI - Institut Blaise Pascal
	* Universite Pierre et Marie Curie (Paris VI)
	*
	* from
	*
	* linux/fs/minix/dir.c
	*
	* Copyright (C) 1991, 1992 Linus Torvalds
	*
	* ext4 directory handling functions
	*
	* Big-endian to little-endian byte-swapping/bitmaps by
	* David S. Miller ([email protected]), 1995
	*
	* Hash Tree Directory indexing (c) 2001 Daniel Phillips
	*
	*/

	#include <linux/fs.h>
	#include <linux/jbd2.h>
	#include <linux/buffer_head.h>
	#include <linux/slab.h>
	#include <linux/rbtree.h>
	#include "ext4.h"
	#include "xattr.h"

	static int ext4_dx_readdir(struct file , struct dir_context );

	/**
	* 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) \|\|
	ext4_has_inline_data(inode)))
	return 1;

	return 0;
	}

	/*
	* 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...
	*
	* bh passed here can be an inode block or a dir data block, depending
	* on the inode inline data flag.
	*/
	int __ext4_check_dir_entry(const char *function, unsigned int line,
	struct inode dir, struct file filp,
	struct ext4_dir_entry_2 *de,
	struct buffer_head bh, char buf, int size,
	unsigned int offset)
	{
	const char *error_msg = NULL;
	const int rlen = ext4_rec_len_from_disk(de->rec_len,
	dir->i_sb->s_blocksize);

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

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

	return 1;
	}

	static int ext4_readdir(struct file file, struct dir_context ctx)
	{
	unsigned int offset;
	int i, stored;
	struct ext4_dir_entry_2 *de;
	int err;
	struct inode *inode = file_inode(file);
	struct super_block *sb = inode->i_sb;
	int dir_has_error = 0;

	if (is_dx_dir(inode)) {
	err = ext4_dx_readdir(file, ctx);
	if (err != ERR_BAD_DX_DIR) {
	return err;
	}
	/*
	* We don't set the inode dirty flag since it's not
	* critical that it get flushed back to the disk.
	*/
	ext4_clear_inode_flag(file_inode(file),
	EXT4_INODE_INDEX);
	}

	if (ext4_has_inline_data(inode)) {
	int has_inline_data = 1;
	int ret = ext4_read_inline_dir(file, ctx,
	&has_inline_data);
	if (has_inline_data)
	return ret;
	}

	stored = 0;
	offset = ctx->pos & (sb->s_blocksize - 1);

	while (ctx->pos < inode->i_size) {
	struct ext4_map_blocks map;
	struct buffer_head *bh = NULL;

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

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

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

	/* 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 (file->f_version != inode->i_version) {
	for (i = 0; i < sb->s_blocksize && i < offset; ) {
	de = (struct ext4_dir_entry_2 *)
	(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. */
	if (ext4_rec_len_from_disk(de->rec_len,
	sb->s_blocksize) < EXT4_DIR_REC_LEN(1))
	break;
	i += ext4_rec_len_from_disk(de->rec_len,
	sb->s_blocksize);
	}
	offset = i;
	ctx->pos = (ctx->pos & ~(sb->s_blocksize - 1))
	\| offset;
	file->f_version = inode->i_version;
	}

	while (ctx->pos < inode->i_size
	&& offset < sb->s_blocksize) {
	de = (struct ext4_dir_entry_2 *) (bh->b_data + offset);
	if (ext4_check_dir_entry(inode, file, de, bh,
	bh->b_data, bh->b_size,
	offset)) {
	/*
	* On error, skip to the next block
	*/
	ctx->pos = (ctx->pos \|
	(sb->s_blocksize - 1)) + 1;
	break;
	}
	offset += ext4_rec_len_from_disk(de->rec_len,
	sb->s_blocksize);
	if (le32_to_cpu(de->inode)) {
	if (!dir_emit(ctx, de->name,
	de->name_len,
	le32_to_cpu(de->inode),
	get_dtype(sb, de->file_type))) {
	brelse(bh);
	return 0;
	}
	}
	ctx->pos += ext4_rec_len_from_disk(de->rec_len,
	sb->s_blocksize);
	}
	offset = 0;
	brelse(bh);
	if (ctx->pos < inode->i_size) {
	if (!dir_relax(inode))
	return 0;
	}
	}
	return 0;
	}

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

	/*
	* These functions convert from the major/minor hash to an f_pos
	* 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;
	}


	/*
	* 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.
	*
	* 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.
	*/
	static loff_t ext4_dir_llseek(struct file *file, loff_t offset, int whence)
	{
	struct inode *inode = file->f_mapping->host;
	int dx_dir = is_dx_dir(inode);
	loff_t htree_max = ext4_get_htree_eof(file);

	if (likely(dx_dir))
	return generic_file_llseek_size(file, offset, whence,
	htree_max, htree_max);
	else
	return ext4_llseek(file, offset, whence);
	}

	/*
	* 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 */
	if (n->rb_left) {
	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) {
	struct fname *old = fname;
	fname = fname->next;
	kfree(old);
	}
	if (!parent)
	*root = RB_ROOT;
	else if (parent->rb_left == n)
	parent->rb_left = NULL;
	else if (parent->rb_right == n)
	parent->rb_right = NULL;
	n = parent;
	}
	}


	static struct dir_private_info ext4_htree_create_dir_info(struct file filp,
	loff_t pos)
	{
	struct dir_private_info *p;

	p = kzalloc(sizeof(struct dir_private_info), GFP_KERNEL);
	if (!p)
	return NULL;
	p->curr_hash = pos2maj_hash(filp, pos);
	p->curr_minor_hash = pos2min_hash(filp, pos);
	return p;
	}

	void ext4_htree_free_dir_info(struct dir_private_info *p)
	{
	free_rb_tree_fname(&p->root);
	kfree(p);
	}

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

	info = dir_file->private_data;
	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;
	}



	/*
	* This is a helper function for ext4_dx_readdir. It calls filldir
	* 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.)
	*/
	static int call_filldir(struct file file, struct dir_context ctx,
	struct fname *fname)
	{
	struct dir_private_info *info = file->private_data;
	struct inode *inode = file_inode(file);
	struct super_block *sb = inode->i_sb;

	if (!fname) {
	ext4_msg(sb, KERN_ERR, "%s:%d: inode #%lu: comm %s: "
	"called with null fname?!?", __func__, __LINE__,
	inode->i_ino, current->comm);
	return 0;
	}
	ctx->pos = hash2pos(file, fname->hash, fname->minor_hash);
	while (fname) {
	if (!dir_emit(ctx, fname->name,
	fname->name_len,
	fname->inode,
	get_dtype(sb, fname->file_type))) {
	info->extra_fname = fname;
	return 1;
	}
	fname = fname->next;
	}
	return 0;
	}

	static int ext4_dx_readdir(struct file file, struct dir_context ctx)
	{
	struct dir_private_info *info = file->private_data;
	struct inode *inode = file_inode(file);
	struct fname *fname;
	int ret;

	if (!info) {
	info = ext4_htree_create_dir_info(file, ctx->pos);
	if (!info)
	return -ENOMEM;
	file->private_data = info;
	}

	if (ctx->pos == ext4_get_htree_eof(file))
	return 0; /* EOF */

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

	/*
	* If there are any leftover names on the hash collision
	* chain, return them first.
	*/
	if (info->extra_fname) {
	if (call_filldir(file, ctx, info->extra_fname))
	goto finished;
	info->extra_fname = NULL;
	goto next_node;
	} else if (!info->curr_node)
	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) \|\|
	(file->f_version != inode->i_version)) {
	info->curr_node = NULL;
	free_rb_tree_fname(&info->root);
	file->f_version = inode->i_version;
	ret = ext4_htree_fill_tree(file, info->curr_hash,
	info->curr_minor_hash,
	&info->next_hash);
	if (ret < 0)
	return ret;
	if (ret == 0) {
	ctx->pos = ext4_get_htree_eof(file);
	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(file, ctx, fname))
	break;
	next_node:
	info->curr_node = rb_next(info->curr_node);
	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 {
	if (info->next_hash == ~0) {
	ctx->pos = ext4_get_htree_eof(file);
	break;
	}
	info->curr_hash = info->next_hash;
	info->curr_minor_hash = 0;
	}
	}
	finished:
	info->last_pos = ctx->pos;
	return 0;
	}

	static int ext4_release_dir(struct inode inode, struct file filp)
	{
	if (filp->private_data)
	ext4_htree_free_dir_info(filp->private_data);

	return 0;
	}

	const struct file_operations ext4_dir_operations = {
	.llseek = ext4_dir_llseek,
	.read = generic_read_dir,
	.iterate = ext4_readdir,
	.unlocked_ioctl = ext4_ioctl,
	#ifdef CONFIG_COMPAT
	.compat_ioctl = ext4_compat_ioctl,
	#endif
	.fsync = ext4_sync_file,
	.release = ext4_release_dir,
	};