Root/fs/ext3/dir.c

1/*
2 * linux/fs/ext3/dir.c
3 *
4 * Copyright (C) 1992, 1993, 1994, 1995
5 * Remy Card (card@masi.ibp.fr)
6 * Laboratoire MASI - Institut Blaise Pascal
7 * Universite Pierre et Marie Curie (Paris VI)
8 *
9 * from
10 *
11 * linux/fs/minix/dir.c
12 *
13 * Copyright (C) 1991, 1992 Linus Torvalds
14 *
15 * ext3 directory handling functions
16 *
17 * Big-endian to little-endian byte-swapping/bitmaps by
18 * David S. Miller (davem@caip.rutgers.edu), 1995
19 *
20 * Hash Tree Directory indexing (c) 2001 Daniel Phillips
21 *
22 */
23
24#include <linux/fs.h>
25#include <linux/jbd.h>
26#include <linux/ext3_fs.h>
27#include <linux/buffer_head.h>
28#include <linux/slab.h>
29#include <linux/rbtree.h>
30
31static unsigned char ext3_filetype_table[] = {
32    DT_UNKNOWN, DT_REG, DT_DIR, DT_CHR, DT_BLK, DT_FIFO, DT_SOCK, DT_LNK
33};
34
35static int ext3_readdir(struct file *, void *, filldir_t);
36static int ext3_dx_readdir(struct file * filp,
37               void * dirent, filldir_t filldir);
38static int ext3_release_dir (struct inode * inode,
39                struct file * filp);
40
41const struct file_operations ext3_dir_operations = {
42    .llseek = generic_file_llseek,
43    .read = generic_read_dir,
44    .readdir = ext3_readdir, /* we take BKL. needed?*/
45    .unlocked_ioctl = ext3_ioctl,
46#ifdef CONFIG_COMPAT
47    .compat_ioctl = ext3_compat_ioctl,
48#endif
49    .fsync = ext3_sync_file, /* BKL held */
50    .release = ext3_release_dir,
51};
52
53
54static unsigned char get_dtype(struct super_block *sb, int filetype)
55{
56    if (!EXT3_HAS_INCOMPAT_FEATURE(sb, EXT3_FEATURE_INCOMPAT_FILETYPE) ||
57        (filetype >= EXT3_FT_MAX))
58        return DT_UNKNOWN;
59
60    return (ext3_filetype_table[filetype]);
61}
62
63
64int ext3_check_dir_entry (const char * function, struct inode * dir,
65              struct ext3_dir_entry_2 * de,
66              struct buffer_head * bh,
67              unsigned long offset)
68{
69    const char * error_msg = NULL;
70    const int rlen = ext3_rec_len_from_disk(de->rec_len);
71
72    if (unlikely(rlen < EXT3_DIR_REC_LEN(1)))
73        error_msg = "rec_len is smaller than minimal";
74    else if (unlikely(rlen % 4 != 0))
75        error_msg = "rec_len % 4 != 0";
76    else if (unlikely(rlen < EXT3_DIR_REC_LEN(de->name_len)))
77        error_msg = "rec_len is too small for name_len";
78    else if (unlikely((((char *) de - bh->b_data) + rlen > dir->i_sb->s_blocksize)))
79        error_msg = "directory entry across blocks";
80    else if (unlikely(le32_to_cpu(de->inode) >
81            le32_to_cpu(EXT3_SB(dir->i_sb)->s_es->s_inodes_count)))
82        error_msg = "inode out of bounds";
83
84    if (unlikely(error_msg != NULL))
85        ext3_error (dir->i_sb, function,
86            "bad entry in directory #%lu: %s - "
87            "offset=%lu, inode=%lu, rec_len=%d, name_len=%d",
88            dir->i_ino, error_msg, offset,
89            (unsigned long) le32_to_cpu(de->inode),
90            rlen, de->name_len);
91
92    return error_msg == NULL ? 1 : 0;
93}
94
95static int ext3_readdir(struct file * filp,
96             void * dirent, filldir_t filldir)
97{
98    int error = 0;
99    unsigned long offset;
100    int i, stored;
101    struct ext3_dir_entry_2 *de;
102    struct super_block *sb;
103    int err;
104    struct inode *inode = filp->f_path.dentry->d_inode;
105    int ret = 0;
106    int dir_has_error = 0;
107
108    sb = inode->i_sb;
109
110    if (EXT3_HAS_COMPAT_FEATURE(inode->i_sb,
111                    EXT3_FEATURE_COMPAT_DIR_INDEX) &&
112        ((EXT3_I(inode)->i_flags & EXT3_INDEX_FL) ||
113         ((inode->i_size >> sb->s_blocksize_bits) == 1))) {
114        err = ext3_dx_readdir(filp, dirent, filldir);
115        if (err != ERR_BAD_DX_DIR) {
116            ret = err;
117            goto out;
118        }
119        /*
120         * We don't set the inode dirty flag since it's not
121         * critical that it get flushed back to the disk.
122         */
123        EXT3_I(filp->f_path.dentry->d_inode)->i_flags &= ~EXT3_INDEX_FL;
124    }
125    stored = 0;
126    offset = filp->f_pos & (sb->s_blocksize - 1);
127
128    while (!error && !stored && filp->f_pos < inode->i_size) {
129        unsigned long blk = filp->f_pos >> EXT3_BLOCK_SIZE_BITS(sb);
130        struct buffer_head map_bh;
131        struct buffer_head *bh = NULL;
132
133        map_bh.b_state = 0;
134        err = ext3_get_blocks_handle(NULL, inode, blk, 1, &map_bh, 0);
135        if (err > 0) {
136            pgoff_t index = map_bh.b_blocknr >>
137                    (PAGE_CACHE_SHIFT - inode->i_blkbits);
138            if (!ra_has_index(&filp->f_ra, index))
139                page_cache_sync_readahead(
140                    sb->s_bdev->bd_inode->i_mapping,
141                    &filp->f_ra, filp,
142                    index, 1);
143            filp->f_ra.prev_pos = (loff_t)index << PAGE_CACHE_SHIFT;
144            bh = ext3_bread(NULL, inode, blk, 0, &err);
145        }
146
147        /*
148         * We ignore I/O errors on directories so users have a chance
149         * of recovering data when there's a bad sector
150         */
151        if (!bh) {
152            if (!dir_has_error) {
153                ext3_error(sb, __func__, "directory #%lu "
154                    "contains a hole at offset %lld",
155                    inode->i_ino, filp->f_pos);
156                dir_has_error = 1;
157            }
158            /* corrupt size? Maybe no more blocks to read */
159            if (filp->f_pos > inode->i_blocks << 9)
160                break;
161            filp->f_pos += sb->s_blocksize - offset;
162            continue;
163        }
164
165revalidate:
166        /* If the dir block has changed since the last call to
167         * readdir(2), then we might be pointing to an invalid
168         * dirent right now. Scan from the start of the block
169         * to make sure. */
170        if (filp->f_version != inode->i_version) {
171            for (i = 0; i < sb->s_blocksize && i < offset; ) {
172                de = (struct ext3_dir_entry_2 *)
173                    (bh->b_data + i);
174                /* It's too expensive to do a full
175                 * dirent test each time round this
176                 * loop, but we do have to test at
177                 * least that it is non-zero. A
178                 * failure will be detected in the
179                 * dirent test below. */
180                if (ext3_rec_len_from_disk(de->rec_len) <
181                        EXT3_DIR_REC_LEN(1))
182                    break;
183                i += ext3_rec_len_from_disk(de->rec_len);
184            }
185            offset = i;
186            filp->f_pos = (filp->f_pos & ~(sb->s_blocksize - 1))
187                | offset;
188            filp->f_version = inode->i_version;
189        }
190
191        while (!error && filp->f_pos < inode->i_size
192               && offset < sb->s_blocksize) {
193            de = (struct ext3_dir_entry_2 *) (bh->b_data + offset);
194            if (!ext3_check_dir_entry ("ext3_readdir", inode, de,
195                           bh, offset)) {
196                /* On error, skip the f_pos to the
197                                   next block. */
198                filp->f_pos = (filp->f_pos |
199                        (sb->s_blocksize - 1)) + 1;
200                brelse (bh);
201                ret = stored;
202                goto out;
203            }
204            offset += ext3_rec_len_from_disk(de->rec_len);
205            if (le32_to_cpu(de->inode)) {
206                /* We might block in the next section
207                 * if the data destination is
208                 * currently swapped out. So, use a
209                 * version stamp to detect whether or
210                 * not the directory has been modified
211                 * during the copy operation.
212                 */
213                u64 version = filp->f_version;
214
215                error = filldir(dirent, de->name,
216                        de->name_len,
217                        filp->f_pos,
218                        le32_to_cpu(de->inode),
219                        get_dtype(sb, de->file_type));
220                if (error)
221                    break;
222                if (version != filp->f_version)
223                    goto revalidate;
224                stored ++;
225            }
226            filp->f_pos += ext3_rec_len_from_disk(de->rec_len);
227        }
228        offset = 0;
229        brelse (bh);
230    }
231out:
232    return ret;
233}
234
235/*
236 * These functions convert from the major/minor hash to an f_pos
237 * value.
238 *
239 * Currently we only use major hash numer. This is unfortunate, but
240 * on 32-bit machines, the same VFS interface is used for lseek and
241 * llseek, so if we use the 64 bit offset, then the 32-bit versions of
242 * lseek/telldir/seekdir will blow out spectacularly, and from within
243 * the ext2 low-level routine, we don't know if we're being called by
244 * a 64-bit version of the system call or the 32-bit version of the
245 * system call. Worse yet, NFSv2 only allows for a 32-bit readdir
246 * cookie. Sigh.
247 */
248#define hash2pos(major, minor) (major >> 1)
249#define pos2maj_hash(pos) ((pos << 1) & 0xffffffff)
250#define pos2min_hash(pos) (0)
251
252/*
253 * This structure holds the nodes of the red-black tree used to store
254 * the directory entry in hash order.
255 */
256struct fname {
257    __u32 hash;
258    __u32 minor_hash;
259    struct rb_node rb_hash;
260    struct fname *next;
261    __u32 inode;
262    __u8 name_len;
263    __u8 file_type;
264    char name[0];
265};
266
267/*
268 * This functoin implements a non-recursive way of freeing all of the
269 * nodes in the red-black tree.
270 */
271static void free_rb_tree_fname(struct rb_root *root)
272{
273    struct rb_node *n = root->rb_node;
274    struct rb_node *parent;
275    struct fname *fname;
276
277    while (n) {
278        /* Do the node's children first */
279        if (n->rb_left) {
280            n = n->rb_left;
281            continue;
282        }
283        if (n->rb_right) {
284            n = n->rb_right;
285            continue;
286        }
287        /*
288         * The node has no children; free it, and then zero
289         * out parent's link to it. Finally go to the
290         * beginning of the loop and try to free the parent
291         * node.
292         */
293        parent = rb_parent(n);
294        fname = rb_entry(n, struct fname, rb_hash);
295        while (fname) {
296            struct fname * old = fname;
297            fname = fname->next;
298            kfree (old);
299        }
300        if (!parent)
301            *root = RB_ROOT;
302        else if (parent->rb_left == n)
303            parent->rb_left = NULL;
304        else if (parent->rb_right == n)
305            parent->rb_right = NULL;
306        n = parent;
307    }
308}
309
310
311static struct dir_private_info *ext3_htree_create_dir_info(loff_t pos)
312{
313    struct dir_private_info *p;
314
315    p = kzalloc(sizeof(struct dir_private_info), GFP_KERNEL);
316    if (!p)
317        return NULL;
318    p->curr_hash = pos2maj_hash(pos);
319    p->curr_minor_hash = pos2min_hash(pos);
320    return p;
321}
322
323void ext3_htree_free_dir_info(struct dir_private_info *p)
324{
325    free_rb_tree_fname(&p->root);
326    kfree(p);
327}
328
329/*
330 * Given a directory entry, enter it into the fname rb tree.
331 */
332int ext3_htree_store_dirent(struct file *dir_file, __u32 hash,
333                 __u32 minor_hash,
334                 struct ext3_dir_entry_2 *dirent)
335{
336    struct rb_node **p, *parent = NULL;
337    struct fname * fname, *new_fn;
338    struct dir_private_info *info;
339    int len;
340
341    info = (struct dir_private_info *) dir_file->private_data;
342    p = &info->root.rb_node;
343
344    /* Create and allocate the fname structure */
345    len = sizeof(struct fname) + dirent->name_len + 1;
346    new_fn = kzalloc(len, GFP_KERNEL);
347    if (!new_fn)
348        return -ENOMEM;
349    new_fn->hash = hash;
350    new_fn->minor_hash = minor_hash;
351    new_fn->inode = le32_to_cpu(dirent->inode);
352    new_fn->name_len = dirent->name_len;
353    new_fn->file_type = dirent->file_type;
354    memcpy(new_fn->name, dirent->name, dirent->name_len);
355    new_fn->name[dirent->name_len] = 0;
356
357    while (*p) {
358        parent = *p;
359        fname = rb_entry(parent, struct fname, rb_hash);
360
361        /*
362         * If the hash and minor hash match up, then we put
363         * them on a linked list. This rarely happens...
364         */
365        if ((new_fn->hash == fname->hash) &&
366            (new_fn->minor_hash == fname->minor_hash)) {
367            new_fn->next = fname->next;
368            fname->next = new_fn;
369            return 0;
370        }
371
372        if (new_fn->hash < fname->hash)
373            p = &(*p)->rb_left;
374        else if (new_fn->hash > fname->hash)
375            p = &(*p)->rb_right;
376        else if (new_fn->minor_hash < fname->minor_hash)
377            p = &(*p)->rb_left;
378        else /* if (new_fn->minor_hash > fname->minor_hash) */
379            p = &(*p)->rb_right;
380    }
381
382    rb_link_node(&new_fn->rb_hash, parent, p);
383    rb_insert_color(&new_fn->rb_hash, &info->root);
384    return 0;
385}
386
387
388
389/*
390 * This is a helper function for ext3_dx_readdir. It calls filldir
391 * for all entres on the fname linked list. (Normally there is only
392 * one entry on the linked list, unless there are 62 bit hash collisions.)
393 */
394static int call_filldir(struct file * filp, void * dirent,
395            filldir_t filldir, struct fname *fname)
396{
397    struct dir_private_info *info = filp->private_data;
398    loff_t curr_pos;
399    struct inode *inode = filp->f_path.dentry->d_inode;
400    struct super_block * sb;
401    int error;
402
403    sb = inode->i_sb;
404
405    if (!fname) {
406        printk("call_filldir: called with null fname?!?\n");
407        return 0;
408    }
409    curr_pos = hash2pos(fname->hash, fname->minor_hash);
410    while (fname) {
411        error = filldir(dirent, fname->name,
412                fname->name_len, curr_pos,
413                fname->inode,
414                get_dtype(sb, fname->file_type));
415        if (error) {
416            filp->f_pos = curr_pos;
417            info->extra_fname = fname;
418            return error;
419        }
420        fname = fname->next;
421    }
422    return 0;
423}
424
425static int ext3_dx_readdir(struct file * filp,
426             void * dirent, filldir_t filldir)
427{
428    struct dir_private_info *info = filp->private_data;
429    struct inode *inode = filp->f_path.dentry->d_inode;
430    struct fname *fname;
431    int ret;
432
433    if (!info) {
434        info = ext3_htree_create_dir_info(filp->f_pos);
435        if (!info)
436            return -ENOMEM;
437        filp->private_data = info;
438    }
439
440    if (filp->f_pos == EXT3_HTREE_EOF)
441        return 0; /* EOF */
442
443    /* Some one has messed with f_pos; reset the world */
444    if (info->last_pos != filp->f_pos) {
445        free_rb_tree_fname(&info->root);
446        info->curr_node = NULL;
447        info->extra_fname = NULL;
448        info->curr_hash = pos2maj_hash(filp->f_pos);
449        info->curr_minor_hash = pos2min_hash(filp->f_pos);
450    }
451
452    /*
453     * If there are any leftover names on the hash collision
454     * chain, return them first.
455     */
456    if (info->extra_fname) {
457        if (call_filldir(filp, dirent, filldir, info->extra_fname))
458            goto finished;
459        info->extra_fname = NULL;
460        goto next_node;
461    } else if (!info->curr_node)
462        info->curr_node = rb_first(&info->root);
463
464    while (1) {
465        /*
466         * Fill the rbtree if we have no more entries,
467         * or the inode has changed since we last read in the
468         * cached entries.
469         */
470        if ((!info->curr_node) ||
471            (filp->f_version != inode->i_version)) {
472            info->curr_node = NULL;
473            free_rb_tree_fname(&info->root);
474            filp->f_version = inode->i_version;
475            ret = ext3_htree_fill_tree(filp, info->curr_hash,
476                           info->curr_minor_hash,
477                           &info->next_hash);
478            if (ret < 0)
479                return ret;
480            if (ret == 0) {
481                filp->f_pos = EXT3_HTREE_EOF;
482                break;
483            }
484            info->curr_node = rb_first(&info->root);
485        }
486
487        fname = rb_entry(info->curr_node, struct fname, rb_hash);
488        info->curr_hash = fname->hash;
489        info->curr_minor_hash = fname->minor_hash;
490        if (call_filldir(filp, dirent, filldir, fname))
491            break;
492    next_node:
493        info->curr_node = rb_next(info->curr_node);
494        if (info->curr_node) {
495            fname = rb_entry(info->curr_node, struct fname,
496                     rb_hash);
497            info->curr_hash = fname->hash;
498            info->curr_minor_hash = fname->minor_hash;
499        } else {
500            if (info->next_hash == ~0) {
501                filp->f_pos = EXT3_HTREE_EOF;
502                break;
503            }
504            info->curr_hash = info->next_hash;
505            info->curr_minor_hash = 0;
506        }
507    }
508finished:
509    info->last_pos = filp->f_pos;
510    return 0;
511}
512
513static int ext3_release_dir (struct inode * inode, struct file * filp)
514{
515       if (filp->private_data)
516        ext3_htree_free_dir_info(filp->private_data);
517
518    return 0;
519}
520

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