How are you testing this?
--b.
On Thu, Apr 26, 2012 at 01:10:39PM -0500, Eric Sandeen wrote:
> This is based on commit d1f5273e9adb40724a85272f248f210dc4ce919a
> ext4: return 32/64-bit dir name hash according to usage type
> by Fan Yong <yong.fan@xxxxxxxxxxxxx>
>
> 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: Bernd Schubert <bernd.schubert@xxxxxxxxxxxxxxxxxx>
> Patch-updated-by: Eric Sandeen <sandeen@xxxxxxxxxx>
> (blame us if something is not correct)
>
> Signed-off-by: Eric Sandeen <sandeen@xxxxxxxxxx>
> ---
>
> diff --git a/fs/ext3/dir.c b/fs/ext3/dir.c
> index cc761ad..92490e9 100644
> --- a/fs/ext3/dir.c
> +++ b/fs/ext3/dir.c
> @@ -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,
> +};
> diff --git a/fs/ext3/ext3.h b/fs/ext3/ext3.h
> index b6515fd..fe5bef7 100644
> --- a/fs/ext3/ext3.h
> +++ b/fs/ext3/ext3.h
> @@ -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
> diff --git a/fs/ext3/hash.c b/fs/ext3/hash.c
> index d10231d..ede315c 100644
> --- a/fs/ext3/hash.c
> +++ b/fs/ext3/hash.c
> @@ -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;
>
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