dir.c

Go to the documentation of this file.

/*
 *  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"

static unsigned char ext4_filetype_table[] = {
    DT_UNKNOWN, DT_REG, DT_DIR, DT_CHR, DT_BLK, DT_FIFO, DT_SOCK, DT_LNK
};

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

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

    return (ext4_filetype_table[filetype]);
}

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;
}

/*
 * 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...
 */
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,
               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 - bh->b_data) + rlen >
              dir->i_sb->s_blocksize))
        error_msg = "directory entry across blocks";
    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 % bh->b_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 % bh->b_size),
                offset, le32_to_cpu(de->inode),
                rlen, de->name_len);

    return 1;
}

static int ext4_readdir(struct file *filp,
             void *dirent, filldir_t filldir)
{
    int error = 0;
    unsigned int offset;
    int i, stored;
    struct ext4_dir_entry_2 *de;
    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;

    if (is_dx_dir(inode)) {
        err = ext4_dx_readdir(filp, dirent, filldir);
        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.
         */
        ext4_clear_inode_flag(filp->f_path.dentry->d_inode,
                      EXT4_INODE_INDEX);
    }
    stored = 0;
    offset = filp->f_pos & (sb->s_blocksize - 1);

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

        map.m_lblk = filp->f_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(&filp->f_ra, index))
                page_cache_sync_readahead(
                    sb->s_bdev->bd_inode->i_mapping,
                    &filp->f_ra, filp,
                    index, 1);
            filp->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(filp, 0,
                        "directory contains a "
                        "hole at offset %llu",
                       (unsigned long long) filp->f_pos);
                dir_has_error = 1;
            }
            /* corrupt size?  Maybe no more blocks to read */
            if (filp->f_pos > inode->i_blocks << 9)
                break;
            filp->f_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(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);

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; ) {
                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;
            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) {
            de = (struct ext4_dir_entry_2 *) (bh->b_data + offset);
            if (ext4_check_dir_entry(inode, filp, de,
                         bh, offset)) {
                /*
                 * On error, skip the f_pos to the next block
                 */
                filp->f_pos = (filp->f_pos |
                        (sb->s_blocksize - 1)) + 1;
                brelse(bh);
                ret = stored;
                goto out;
            }
            offset += ext4_rec_len_from_disk(de->rec_len,
                    sb->s_blocksize);
            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.
                 */
                u64 version = filp->f_version;

                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;
                stored++;
            }
            filp->f_pos += ext4_rec_len_from_disk(de->rec_len,
                        sb->s_blocksize);
        }
        offset = 0;
        brelse(bh);
    }
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 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.
 */
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);
    loff_t htree_max = ext4_get_htree_eof(file);

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

/*
 * 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 *filp, void *dirent,
            filldir_t filldir, struct fname *fname)
{
    struct dir_private_info *info = filp->private_data;
    loff_t  curr_pos;
    struct inode *inode = filp->f_path.dentry->d_inode;
    struct super_block *sb;
    int error;

    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;
    }
    curr_pos = hash2pos(filp, fname->hash, fname->minor_hash);
    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;
            info->extra_fname = fname;
            return error;
        }
        fname = fname->next;
    }
    return 0;
}

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

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

    if (filp->f_pos == ext4_get_htree_eof(filp))
        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;
        info->curr_hash = pos2maj_hash(filp, filp->f_pos);
        info->curr_minor_hash = pos2min_hash(filp, filp->f_pos);
    }

    /*
     * If there are any leftover names on the hash collision
     * chain, return them first.
     */
    if (info->extra_fname) {
        if (call_filldir(filp, dirent, filldir, 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) ||
            (filp->f_version != inode->i_version)) {
            info->curr_node = NULL;
            free_rb_tree_fname(&info->root);
            filp->f_version = inode->i_version;
            ret = ext4_htree_fill_tree(filp, info->curr_hash,
                           info->curr_minor_hash,
                           &info->next_hash);
            if (ret < 0)
                return ret;
            if (ret == 0) {
                filp->f_pos = ext4_get_htree_eof(filp);
                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;
    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) {
                filp->f_pos = ext4_get_htree_eof(filp);
                break;
            }
            info->curr_hash = info->next_hash;
            info->curr_minor_hash = 0;
        }
    }
finished:
    info->last_pos = filp->f_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,
    .readdir    = ext4_readdir,
    .unlocked_ioctl = ext4_ioctl,
#ifdef CONFIG_COMPAT
    .compat_ioctl   = ext4_compat_ioctl,
#endif
    .fsync      = ext4_sync_file,
    .release    = ext4_release_dir,
};