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Commit d7dab39b authored by Eric Sandeen's avatar Eric Sandeen Committed by Jan Kara
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ext3: return 32/64-bit dir name hash according to usage type 



This is based on commit d1f5273e
ext4: return 32/64-bit dir name hash according to usage type
by Fan Yong <yong.fan@whamcloud.com>

Traditionally ext2/3/4 has returned a 32-bit hash value from llseek()
to appease NFSv2, which can only handle a 32-bit cookie for seekdir()
and telldir().  However, this causes problems if there are 32-bit hash
collisions, since the NFSv2 server can get stuck resending the same
entries from the directory repeatedly.

Allow ext3 to return a full 64-bit hash (both major and minor) for
telldir to decrease the chance of hash collisions.

This patch does implement a new ext3_dir_llseek op, because with 64-bit
hashes, nfs will attempt to seek to a hash "offset" which is much
larger than ext3's s_maxbytes.  So for dx dirs, we call
generic_file_llseek_size() with the appropriate max hash value as the
maximum seekable size.  Otherwise we just pass through to
generic_file_llseek().

Patch-updated-by: default avatarBernd Schubert <bernd.schubert@itwm.fraunhofer.de>
Patch-updated-by: default avatarEric Sandeen <sandeen@redhat.com>
(blame us if something is not correct)

Signed-off-by: default avatarEric Sandeen <sandeen@redhat.com>
Signed-off-by: default avatarJan Kara <jack@suse.cz>
parent a80b12c3

fs/ext3/dir.c

+122 −45
Original line number Diff line number Diff line
@@ -21,30 +21,15 @@ 
 *

 */



#include <linux/compat.h>

#include "ext3.h"



static unsigned char ext3_filetype_table[] = {

	DT_UNKNOWN, DT_REG, DT_DIR, DT_CHR, DT_BLK, DT_FIFO, DT_SOCK, DT_LNK

};



static int ext3_readdir(struct file *, void *, filldir_t);

static int ext3_dx_readdir(struct file * filp,

			   void * dirent, filldir_t filldir);

static int ext3_release_dir (struct inode * inode,

				struct file * filp);



const struct file_operations ext3_dir_operations = {

	.llseek		= generic_file_llseek,

	.read		= generic_read_dir,

	.readdir	= ext3_readdir,		/* we take BKL. needed?*/

	.unlocked_ioctl	= ext3_ioctl,

#ifdef CONFIG_COMPAT

	.compat_ioctl	= ext3_compat_ioctl,

#endif

	.fsync		= ext3_sync_file,	/* BKL held */

	.release	= ext3_release_dir,

};





static unsigned char get_dtype(struct super_block *sb, int filetype)

{
@@ -55,6 +40,25 @@ static unsigned char get_dtype(struct super_block *sb, int filetype) 
	return (ext3_filetype_table[filetype]);

}



/**

 * 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 (EXT3_HAS_COMPAT_FEATURE(inode->i_sb,

		     EXT3_FEATURE_COMPAT_DIR_INDEX) &&

	    ((EXT3_I(inode)->i_flags & EXT3_INDEX_FL) ||

	     ((inode->i_size >> sb->s_blocksize_bits) == 1)))

		return 1;



	return 0;

}



int ext3_check_dir_entry (const char * function, struct inode * dir,

			  struct ext3_dir_entry_2 * de,
@@ -94,18 +98,13 @@ static int ext3_readdir(struct file * filp, 
	unsigned long offset;

	int i, stored;

	struct ext3_dir_entry_2 *de;

	struct super_block *sb;

	int err;

	struct inode *inode = filp->f_path.dentry->d_inode;

	struct super_block *sb = inode->i_sb;

	int ret = 0;

	int dir_has_error = 0;



	sb = inode->i_sb;



	if (EXT3_HAS_COMPAT_FEATURE(inode->i_sb,

				    EXT3_FEATURE_COMPAT_DIR_INDEX) &&

	    ((EXT3_I(inode)->i_flags & EXT3_INDEX_FL) ||

	     ((inode->i_size >> sb->s_blocksize_bits) == 1))) {

	if (is_dx_dir(inode)) {

		err = ext3_dx_readdir(filp, dirent, filldir);

		if (err != ERR_BAD_DX_DIR) {

			ret = err;
@@ -227,22 +226,87 @@ out: 
	return ret;

}



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.

 * value for dx directories

 *

 * Currently we only use major hash numer.  This is unfortunate, but

 * on 32-bit machines, the same VFS interface is used for lseek and

 * llseek, so if we use the 64 bit offset, then the 32-bit versions of

 * lseek/telldir/seekdir will blow out spectacularly, and from within

 * the ext2 low-level routine, we don't know if we're being called by

 * a 64-bit version of the system call or the 32-bit version of the

 * system call.  Worse yet, NFSv2 only allows for a 32-bit readdir

 * cookie.  Sigh.

 * Upper layer (for example NFS) should specify FMODE_32BITHASH or

 * FMODE_64BITHASH explicitly. On the other hand, we allow ext3 to be mounted

 * directly on both 32-bit and 64-bit nodes, under such case, neither

 * FMODE_32BITHASH nor FMODE_64BITHASH is specified.

 */

#define hash2pos(major, minor)	(major >> 1)

#define pos2maj_hash(pos)	((pos << 1) & 0xffffffff)

#define pos2min_hash(pos)	(0)

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 ext3_get_htree_eof(struct file *filp)

{

	if ((filp->f_mode & FMODE_32BITHASH) ||

	    (!(filp->f_mode & FMODE_64BITHASH) && is_32bit_api()))

		return EXT3_HTREE_EOF_32BIT;

	else

		return EXT3_HTREE_EOF_64BIT;

}





/*

 * ext3_dir_llseek() calls generic_file_llseek[_size]() to handle both

 * non-htree and 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 s_maxbytes,

 * we need to pass the max hash as the maximum allowable offset in

 * the htree directory case.

 *

 * NOTE: offsets obtained *before* ext3_set_inode_flag(dir, EXT3_INODE_INDEX)

 *       will be invalid once the directory was converted into a dx directory

 */

loff_t ext3_dir_llseek(struct file *file, loff_t offset, int origin)

{

	struct inode *inode = file->f_mapping->host;

	int dx_dir = is_dx_dir(inode);



	if (likely(dx_dir))

		return generic_file_llseek_size(file, offset, origin,

					        ext3_get_htree_eof(file));

	else

		return generic_file_llseek(file, offset, origin);

}



/*

 * This structure holds the nodes of the red-black tree used to store
@@ -303,15 +367,16 @@ static void free_rb_tree_fname(struct rb_root *root) 
}





static struct dir_private_info *ext3_htree_create_dir_info(loff_t pos)

static struct dir_private_info *ext3_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(pos);

	p->curr_minor_hash = pos2min_hash(pos);

	p->curr_hash = pos2maj_hash(filp, pos);

	p->curr_minor_hash = pos2min_hash(filp, pos);

	return p;

}
@@ -401,7 +466,7 @@ static int call_filldir(struct file * filp, void * dirent, 
		printk("call_filldir: called with null fname?!?\n");

		return 0;

	}

	curr_pos = hash2pos(fname->hash, fname->minor_hash);

	curr_pos = hash2pos(filp, fname->hash, fname->minor_hash);

	while (fname) {

		error = filldir(dirent, fname->name,

				fname->name_len, curr_pos,
@@ -426,13 +491,13 @@ static int ext3_dx_readdir(struct file * filp, 
	int	ret;



	if (!info) {

		info = ext3_htree_create_dir_info(filp->f_pos);

		info = ext3_htree_create_dir_info(filp, filp->f_pos);

		if (!info)

			return -ENOMEM;

		filp->private_data = info;

	}



	if (filp->f_pos == EXT3_HTREE_EOF)

	if (filp->f_pos == ext3_get_htree_eof(filp))

		return 0;	/* EOF */



	/* Some one has messed with f_pos; reset the world */
@@ -440,8 +505,8 @@ static int ext3_dx_readdir(struct file * filp, 
		free_rb_tree_fname(&info->root);

		info->curr_node = NULL;

		info->extra_fname = NULL;

		info->curr_hash = pos2maj_hash(filp->f_pos);

		info->curr_minor_hash = pos2min_hash(filp->f_pos);

		info->curr_hash = pos2maj_hash(filp, filp->f_pos);

		info->curr_minor_hash = pos2min_hash(filp, filp->f_pos);

	}



	/*
@@ -473,7 +538,7 @@ static int ext3_dx_readdir(struct file * filp, 
			if (ret < 0)

				return ret;

			if (ret == 0) {

				filp->f_pos = EXT3_HTREE_EOF;

				filp->f_pos = ext3_get_htree_eof(filp);

				break;

			}

			info->curr_node = rb_first(&info->root);
@@ -493,7 +558,7 @@ static int ext3_dx_readdir(struct file * filp, 
			info->curr_minor_hash = fname->minor_hash;

		} else {

			if (info->next_hash == ~0) {

				filp->f_pos = EXT3_HTREE_EOF;

				filp->f_pos = ext3_get_htree_eof(filp);

				break;

			}

			info->curr_hash = info->next_hash;
@@ -512,3 +577,15 @@ static int ext3_release_dir (struct inode * inode, struct file * filp) 


	return 0;

}



const struct file_operations ext3_dir_operations = {

	.llseek		= ext3_dir_llseek,

	.read		= generic_read_dir,

	.readdir	= ext3_readdir,

	.unlocked_ioctl = ext3_ioctl,

#ifdef CONFIG_COMPAT

	.compat_ioctl	= ext3_compat_ioctl,

#endif

	.fsync		= ext3_sync_file,

	.release	= ext3_release_dir,

};

fs/ext3/ext3.h

+5 −1
Original line number Diff line number Diff line
@@ -920,7 +920,11 @@ struct dx_hash_info 
	u32		*seed;

};



#define EXT3_HTREE_EOF	0x7fffffff



/* 32 and 64 bit signed EOF for dx directories */

#define EXT3_HTREE_EOF_32BIT   ((1UL  << (32 - 1)) - 1)

#define EXT3_HTREE_EOF_64BIT   ((1ULL << (64 - 1)) - 1)





/*

 * Control parameters used by ext3_htree_next_block

fs/ext3/hash.c

+2 −2
Original line number Diff line number Diff line
@@ -198,8 +198,8 @@ int ext3fs_dirhash(const char *name, int len, struct dx_hash_info *hinfo) 
		return -1;

	}

	hash = hash & ~1;

	if (hash == (EXT3_HTREE_EOF << 1))

		hash = (EXT3_HTREE_EOF-1) << 1;

	if (hash == (EXT3_HTREE_EOF_32BIT << 1))

		hash = (EXT3_HTREE_EOF_32BIT - 1) << 1;

	hinfo->hash = hash;

	hinfo->minor_hash = minor_hash;

	return 0;