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0001 // SPDX-License-Identifier: GPL-2.0
0002 /*
0003  *  linux/fs/ext2/dir.c
0004  *
0005  * Copyright (C) 1992, 1993, 1994, 1995
0006  * Remy Card (card@masi.ibp.fr)
0007  * Laboratoire MASI - Institut Blaise Pascal
0008  * Universite Pierre et Marie Curie (Paris VI)
0009  *
0010  *  from
0011  *
0012  *  linux/fs/minix/dir.c
0013  *
0014  *  Copyright (C) 1991, 1992  Linus Torvalds
0015  *
0016  *  ext2 directory handling functions
0017  *
0018  *  Big-endian to little-endian byte-swapping/bitmaps by
0019  *        David S. Miller (davem@caip.rutgers.edu), 1995
0020  *
0021  * All code that works with directory layout had been switched to pagecache
0022  * and moved here. AV
0023  */
0024 
0025 #include "ext2.h"
0026 #include <linux/buffer_head.h>
0027 #include <linux/pagemap.h>
0028 #include <linux/swap.h>
0029 #include <linux/iversion.h>
0030 
0031 typedef struct ext2_dir_entry_2 ext2_dirent;
0032 
0033 /*
0034  * Tests against MAX_REC_LEN etc were put in place for 64k block
0035  * sizes; if that is not possible on this arch, we can skip
0036  * those tests and speed things up.
0037  */
0038 static inline unsigned ext2_rec_len_from_disk(__le16 dlen)
0039 {
0040     unsigned len = le16_to_cpu(dlen);
0041 
0042 #if (PAGE_SIZE >= 65536)
0043     if (len == EXT2_MAX_REC_LEN)
0044         return 1 << 16;
0045 #endif
0046     return len;
0047 }
0048 
0049 static inline __le16 ext2_rec_len_to_disk(unsigned len)
0050 {
0051 #if (PAGE_SIZE >= 65536)
0052     if (len == (1 << 16))
0053         return cpu_to_le16(EXT2_MAX_REC_LEN);
0054     else
0055         BUG_ON(len > (1 << 16));
0056 #endif
0057     return cpu_to_le16(len);
0058 }
0059 
0060 /*
0061  * ext2 uses block-sized chunks. Arguably, sector-sized ones would be
0062  * more robust, but we have what we have
0063  */
0064 static inline unsigned ext2_chunk_size(struct inode *inode)
0065 {
0066     return inode->i_sb->s_blocksize;
0067 }
0068 
0069 /*
0070  * Return the offset into page `page_nr' of the last valid
0071  * byte in that page, plus one.
0072  */
0073 static unsigned
0074 ext2_last_byte(struct inode *inode, unsigned long page_nr)
0075 {
0076     unsigned last_byte = inode->i_size;
0077 
0078     last_byte -= page_nr << PAGE_SHIFT;
0079     if (last_byte > PAGE_SIZE)
0080         last_byte = PAGE_SIZE;
0081     return last_byte;
0082 }
0083 
0084 static int ext2_commit_chunk(struct page *page, loff_t pos, unsigned len)
0085 {
0086     struct address_space *mapping = page->mapping;
0087     struct inode *dir = mapping->host;
0088     int err = 0;
0089 
0090     inode_inc_iversion(dir);
0091     block_write_end(NULL, mapping, pos, len, len, page, NULL);
0092 
0093     if (pos+len > dir->i_size) {
0094         i_size_write(dir, pos+len);
0095         mark_inode_dirty(dir);
0096     }
0097 
0098     if (IS_DIRSYNC(dir)) {
0099         err = write_one_page(page);
0100         if (!err)
0101             err = sync_inode_metadata(dir, 1);
0102     } else {
0103         unlock_page(page);
0104     }
0105 
0106     return err;
0107 }
0108 
0109 static bool ext2_check_page(struct page *page, int quiet, char *kaddr)
0110 {
0111     struct inode *dir = page->mapping->host;
0112     struct super_block *sb = dir->i_sb;
0113     unsigned chunk_size = ext2_chunk_size(dir);
0114     u32 max_inumber = le32_to_cpu(EXT2_SB(sb)->s_es->s_inodes_count);
0115     unsigned offs, rec_len;
0116     unsigned limit = PAGE_SIZE;
0117     ext2_dirent *p;
0118     char *error;
0119 
0120     if ((dir->i_size >> PAGE_SHIFT) == page->index) {
0121         limit = dir->i_size & ~PAGE_MASK;
0122         if (limit & (chunk_size - 1))
0123             goto Ebadsize;
0124         if (!limit)
0125             goto out;
0126     }
0127     for (offs = 0; offs <= limit - EXT2_DIR_REC_LEN(1); offs += rec_len) {
0128         p = (ext2_dirent *)(kaddr + offs);
0129         rec_len = ext2_rec_len_from_disk(p->rec_len);
0130 
0131         if (unlikely(rec_len < EXT2_DIR_REC_LEN(1)))
0132             goto Eshort;
0133         if (unlikely(rec_len & 3))
0134             goto Ealign;
0135         if (unlikely(rec_len < EXT2_DIR_REC_LEN(p->name_len)))
0136             goto Enamelen;
0137         if (unlikely(((offs + rec_len - 1) ^ offs) & ~(chunk_size-1)))
0138             goto Espan;
0139         if (unlikely(le32_to_cpu(p->inode) > max_inumber))
0140             goto Einumber;
0141     }
0142     if (offs != limit)
0143         goto Eend;
0144 out:
0145     SetPageChecked(page);
0146     return true;
0147 
0148     /* Too bad, we had an error */
0149 
0150 Ebadsize:
0151     if (!quiet)
0152         ext2_error(sb, __func__,
0153             "size of directory #%lu is not a multiple "
0154             "of chunk size", dir->i_ino);
0155     goto fail;
0156 Eshort:
0157     error = "rec_len is smaller than minimal";
0158     goto bad_entry;
0159 Ealign:
0160     error = "unaligned directory entry";
0161     goto bad_entry;
0162 Enamelen:
0163     error = "rec_len is too small for name_len";
0164     goto bad_entry;
0165 Espan:
0166     error = "directory entry across blocks";
0167     goto bad_entry;
0168 Einumber:
0169     error = "inode out of bounds";
0170 bad_entry:
0171     if (!quiet)
0172         ext2_error(sb, __func__, "bad entry in directory #%lu: : %s - "
0173             "offset=%lu, inode=%lu, rec_len=%d, name_len=%d",
0174             dir->i_ino, error, (page->index<<PAGE_SHIFT)+offs,
0175             (unsigned long) le32_to_cpu(p->inode),
0176             rec_len, p->name_len);
0177     goto fail;
0178 Eend:
0179     if (!quiet) {
0180         p = (ext2_dirent *)(kaddr + offs);
0181         ext2_error(sb, "ext2_check_page",
0182             "entry in directory #%lu spans the page boundary"
0183             "offset=%lu, inode=%lu",
0184             dir->i_ino, (page->index<<PAGE_SHIFT)+offs,
0185             (unsigned long) le32_to_cpu(p->inode));
0186     }
0187 fail:
0188     SetPageError(page);
0189     return false;
0190 }
0191 
0192 /*
0193  * Calls to ext2_get_page()/ext2_put_page() must be nested according to the
0194  * rules documented in kmap_local_page()/kunmap_local().
0195  *
0196  * NOTE: ext2_find_entry() and ext2_dotdot() act as a call to ext2_get_page()
0197  * and should be treated as a call to ext2_get_page() for nesting purposes.
0198  */
0199 static struct page * ext2_get_page(struct inode *dir, unsigned long n,
0200                    int quiet, void **page_addr)
0201 {
0202     struct address_space *mapping = dir->i_mapping;
0203     struct folio *folio = read_mapping_folio(mapping, n, NULL);
0204 
0205     if (IS_ERR(folio))
0206         return &folio->page;
0207     *page_addr = kmap_local_folio(folio, n & (folio_nr_pages(folio) - 1));
0208     if (unlikely(!folio_test_checked(folio))) {
0209         if (!ext2_check_page(&folio->page, quiet, *page_addr))
0210             goto fail;
0211     }
0212     return &folio->page;
0213 
0214 fail:
0215     ext2_put_page(&folio->page, *page_addr);
0216     return ERR_PTR(-EIO);
0217 }
0218 
0219 /*
0220  * NOTE! unlike strncmp, ext2_match returns 1 for success, 0 for failure.
0221  *
0222  * len <= EXT2_NAME_LEN and de != NULL are guaranteed by caller.
0223  */
0224 static inline int ext2_match (int len, const char * const name,
0225                     struct ext2_dir_entry_2 * de)
0226 {
0227     if (len != de->name_len)
0228         return 0;
0229     if (!de->inode)
0230         return 0;
0231     return !memcmp(name, de->name, len);
0232 }
0233 
0234 /*
0235  * p is at least 6 bytes before the end of page
0236  */
0237 static inline ext2_dirent *ext2_next_entry(ext2_dirent *p)
0238 {
0239     return (ext2_dirent *)((char *)p +
0240             ext2_rec_len_from_disk(p->rec_len));
0241 }
0242 
0243 static inline unsigned 
0244 ext2_validate_entry(char *base, unsigned offset, unsigned mask)
0245 {
0246     ext2_dirent *de = (ext2_dirent*)(base + offset);
0247     ext2_dirent *p = (ext2_dirent*)(base + (offset&mask));
0248     while ((char*)p < (char*)de) {
0249         if (p->rec_len == 0)
0250             break;
0251         p = ext2_next_entry(p);
0252     }
0253     return (char *)p - base;
0254 }
0255 
0256 static inline void ext2_set_de_type(ext2_dirent *de, struct inode *inode)
0257 {
0258     if (EXT2_HAS_INCOMPAT_FEATURE(inode->i_sb, EXT2_FEATURE_INCOMPAT_FILETYPE))
0259         de->file_type = fs_umode_to_ftype(inode->i_mode);
0260     else
0261         de->file_type = 0;
0262 }
0263 
0264 static int
0265 ext2_readdir(struct file *file, struct dir_context *ctx)
0266 {
0267     loff_t pos = ctx->pos;
0268     struct inode *inode = file_inode(file);
0269     struct super_block *sb = inode->i_sb;
0270     unsigned int offset = pos & ~PAGE_MASK;
0271     unsigned long n = pos >> PAGE_SHIFT;
0272     unsigned long npages = dir_pages(inode);
0273     unsigned chunk_mask = ~(ext2_chunk_size(inode)-1);
0274     bool need_revalidate = !inode_eq_iversion(inode, file->f_version);
0275     bool has_filetype;
0276 
0277     if (pos > inode->i_size - EXT2_DIR_REC_LEN(1))
0278         return 0;
0279 
0280     has_filetype =
0281         EXT2_HAS_INCOMPAT_FEATURE(sb, EXT2_FEATURE_INCOMPAT_FILETYPE);
0282 
0283     for ( ; n < npages; n++, offset = 0) {
0284         char *kaddr, *limit;
0285         ext2_dirent *de;
0286         struct page *page = ext2_get_page(inode, n, 0, (void **)&kaddr);
0287 
0288         if (IS_ERR(page)) {
0289             ext2_error(sb, __func__,
0290                    "bad page in #%lu",
0291                    inode->i_ino);
0292             ctx->pos += PAGE_SIZE - offset;
0293             return PTR_ERR(page);
0294         }
0295         if (unlikely(need_revalidate)) {
0296             if (offset) {
0297                 offset = ext2_validate_entry(kaddr, offset, chunk_mask);
0298                 ctx->pos = (n<<PAGE_SHIFT) + offset;
0299             }
0300             file->f_version = inode_query_iversion(inode);
0301             need_revalidate = false;
0302         }
0303         de = (ext2_dirent *)(kaddr+offset);
0304         limit = kaddr + ext2_last_byte(inode, n) - EXT2_DIR_REC_LEN(1);
0305         for ( ;(char*)de <= limit; de = ext2_next_entry(de)) {
0306             if (de->rec_len == 0) {
0307                 ext2_error(sb, __func__,
0308                     "zero-length directory entry");
0309                 ext2_put_page(page, kaddr);
0310                 return -EIO;
0311             }
0312             if (de->inode) {
0313                 unsigned char d_type = DT_UNKNOWN;
0314 
0315                 if (has_filetype)
0316                     d_type = fs_ftype_to_dtype(de->file_type);
0317 
0318                 if (!dir_emit(ctx, de->name, de->name_len,
0319                         le32_to_cpu(de->inode),
0320                         d_type)) {
0321                     ext2_put_page(page, kaddr);
0322                     return 0;
0323                 }
0324             }
0325             ctx->pos += ext2_rec_len_from_disk(de->rec_len);
0326         }
0327         ext2_put_page(page, kaddr);
0328     }
0329     return 0;
0330 }
0331 
0332 /*
0333  *  ext2_find_entry()
0334  *
0335  * finds an entry in the specified directory with the wanted name. It
0336  * returns the page in which the entry was found (as a parameter - res_page),
0337  * and the entry itself. Page is returned mapped and unlocked.
0338  * Entry is guaranteed to be valid.
0339  *
0340  * On Success ext2_put_page() should be called on *res_page.
0341  *
0342  * NOTE: Calls to ext2_get_page()/ext2_put_page() must be nested according to
0343  * the rules documented in kmap_local_page()/kunmap_local().
0344  *
0345  * ext2_find_entry() and ext2_dotdot() act as a call to ext2_get_page() and
0346  * should be treated as a call to ext2_get_page() for nesting purposes.
0347  */
0348 struct ext2_dir_entry_2 *ext2_find_entry (struct inode *dir,
0349             const struct qstr *child, struct page **res_page,
0350             void **res_page_addr)
0351 {
0352     const char *name = child->name;
0353     int namelen = child->len;
0354     unsigned reclen = EXT2_DIR_REC_LEN(namelen);
0355     unsigned long start, n;
0356     unsigned long npages = dir_pages(dir);
0357     struct page *page = NULL;
0358     struct ext2_inode_info *ei = EXT2_I(dir);
0359     ext2_dirent * de;
0360     void *page_addr;
0361 
0362     if (npages == 0)
0363         goto out;
0364 
0365     /* OFFSET_CACHE */
0366     *res_page = NULL;
0367     *res_page_addr = NULL;
0368 
0369     start = ei->i_dir_start_lookup;
0370     if (start >= npages)
0371         start = 0;
0372     n = start;
0373     do {
0374         char *kaddr;
0375         page = ext2_get_page(dir, n, 0, &page_addr);
0376         if (IS_ERR(page))
0377             return ERR_CAST(page);
0378 
0379         kaddr = page_addr;
0380         de = (ext2_dirent *) kaddr;
0381         kaddr += ext2_last_byte(dir, n) - reclen;
0382         while ((char *) de <= kaddr) {
0383             if (de->rec_len == 0) {
0384                 ext2_error(dir->i_sb, __func__,
0385                     "zero-length directory entry");
0386                 ext2_put_page(page, page_addr);
0387                 goto out;
0388             }
0389             if (ext2_match(namelen, name, de))
0390                 goto found;
0391             de = ext2_next_entry(de);
0392         }
0393         ext2_put_page(page, page_addr);
0394 
0395         if (++n >= npages)
0396             n = 0;
0397         /* next page is past the blocks we've got */
0398         if (unlikely(n > (dir->i_blocks >> (PAGE_SHIFT - 9)))) {
0399             ext2_error(dir->i_sb, __func__,
0400                 "dir %lu size %lld exceeds block count %llu",
0401                 dir->i_ino, dir->i_size,
0402                 (unsigned long long)dir->i_blocks);
0403             goto out;
0404         }
0405     } while (n != start);
0406 out:
0407     return ERR_PTR(-ENOENT);
0408 
0409 found:
0410     *res_page = page;
0411     *res_page_addr = page_addr;
0412     ei->i_dir_start_lookup = n;
0413     return de;
0414 }
0415 
0416 /**
0417  * Return the '..' directory entry and the page in which the entry was found
0418  * (as a parameter - p).
0419  *
0420  * On Success ext2_put_page() should be called on *p.
0421  *
0422  * NOTE: Calls to ext2_get_page()/ext2_put_page() must be nested according to
0423  * the rules documented in kmap_local_page()/kunmap_local().
0424  *
0425  * ext2_find_entry() and ext2_dotdot() act as a call to ext2_get_page() and
0426  * should be treated as a call to ext2_get_page() for nesting purposes.
0427  */
0428 struct ext2_dir_entry_2 *ext2_dotdot(struct inode *dir, struct page **p,
0429                      void **pa)
0430 {
0431     void *page_addr;
0432     struct page *page = ext2_get_page(dir, 0, 0, &page_addr);
0433     ext2_dirent *de = NULL;
0434 
0435     if (!IS_ERR(page)) {
0436         de = ext2_next_entry((ext2_dirent *) page_addr);
0437         *p = page;
0438         *pa = page_addr;
0439     }
0440     return de;
0441 }
0442 
0443 int ext2_inode_by_name(struct inode *dir, const struct qstr *child, ino_t *ino)
0444 {
0445     struct ext2_dir_entry_2 *de;
0446     struct page *page;
0447     void *page_addr;
0448     
0449     de = ext2_find_entry(dir, child, &page, &page_addr);
0450     if (IS_ERR(de))
0451         return PTR_ERR(de);
0452 
0453     *ino = le32_to_cpu(de->inode);
0454     ext2_put_page(page, page_addr);
0455     return 0;
0456 }
0457 
0458 static int ext2_prepare_chunk(struct page *page, loff_t pos, unsigned len)
0459 {
0460     return __block_write_begin(page, pos, len, ext2_get_block);
0461 }
0462 
0463 void ext2_set_link(struct inode *dir, struct ext2_dir_entry_2 *de,
0464            struct page *page, void *page_addr, struct inode *inode,
0465            int update_times)
0466 {
0467     loff_t pos = page_offset(page) +
0468             (char *) de - (char *) page_addr;
0469     unsigned len = ext2_rec_len_from_disk(de->rec_len);
0470     int err;
0471 
0472     lock_page(page);
0473     err = ext2_prepare_chunk(page, pos, len);
0474     BUG_ON(err);
0475     de->inode = cpu_to_le32(inode->i_ino);
0476     ext2_set_de_type(de, inode);
0477     err = ext2_commit_chunk(page, pos, len);
0478     if (update_times)
0479         dir->i_mtime = dir->i_ctime = current_time(dir);
0480     EXT2_I(dir)->i_flags &= ~EXT2_BTREE_FL;
0481     mark_inode_dirty(dir);
0482 }
0483 
0484 /*
0485  *  Parent is locked.
0486  */
0487 int ext2_add_link (struct dentry *dentry, struct inode *inode)
0488 {
0489     struct inode *dir = d_inode(dentry->d_parent);
0490     const char *name = dentry->d_name.name;
0491     int namelen = dentry->d_name.len;
0492     unsigned chunk_size = ext2_chunk_size(dir);
0493     unsigned reclen = EXT2_DIR_REC_LEN(namelen);
0494     unsigned short rec_len, name_len;
0495     struct page *page = NULL;
0496     void *page_addr = NULL;
0497     ext2_dirent * de;
0498     unsigned long npages = dir_pages(dir);
0499     unsigned long n;
0500     loff_t pos;
0501     int err;
0502 
0503     /*
0504      * We take care of directory expansion in the same loop.
0505      * This code plays outside i_size, so it locks the page
0506      * to protect that region.
0507      */
0508     for (n = 0; n <= npages; n++) {
0509         char *kaddr;
0510         char *dir_end;
0511 
0512         page = ext2_get_page(dir, n, 0, &page_addr);
0513         err = PTR_ERR(page);
0514         if (IS_ERR(page))
0515             goto out;
0516         lock_page(page);
0517         kaddr = page_addr;
0518         dir_end = kaddr + ext2_last_byte(dir, n);
0519         de = (ext2_dirent *)kaddr;
0520         kaddr += PAGE_SIZE - reclen;
0521         while ((char *)de <= kaddr) {
0522             if ((char *)de == dir_end) {
0523                 /* We hit i_size */
0524                 name_len = 0;
0525                 rec_len = chunk_size;
0526                 de->rec_len = ext2_rec_len_to_disk(chunk_size);
0527                 de->inode = 0;
0528                 goto got_it;
0529             }
0530             if (de->rec_len == 0) {
0531                 ext2_error(dir->i_sb, __func__,
0532                     "zero-length directory entry");
0533                 err = -EIO;
0534                 goto out_unlock;
0535             }
0536             err = -EEXIST;
0537             if (ext2_match (namelen, name, de))
0538                 goto out_unlock;
0539             name_len = EXT2_DIR_REC_LEN(de->name_len);
0540             rec_len = ext2_rec_len_from_disk(de->rec_len);
0541             if (!de->inode && rec_len >= reclen)
0542                 goto got_it;
0543             if (rec_len >= name_len + reclen)
0544                 goto got_it;
0545             de = (ext2_dirent *) ((char *) de + rec_len);
0546         }
0547         unlock_page(page);
0548         ext2_put_page(page, page_addr);
0549     }
0550     BUG();
0551     return -EINVAL;
0552 
0553 got_it:
0554     pos = page_offset(page) +
0555         (char *)de - (char *)page_addr;
0556     err = ext2_prepare_chunk(page, pos, rec_len);
0557     if (err)
0558         goto out_unlock;
0559     if (de->inode) {
0560         ext2_dirent *de1 = (ext2_dirent *) ((char *) de + name_len);
0561         de1->rec_len = ext2_rec_len_to_disk(rec_len - name_len);
0562         de->rec_len = ext2_rec_len_to_disk(name_len);
0563         de = de1;
0564     }
0565     de->name_len = namelen;
0566     memcpy(de->name, name, namelen);
0567     de->inode = cpu_to_le32(inode->i_ino);
0568     ext2_set_de_type (de, inode);
0569     err = ext2_commit_chunk(page, pos, rec_len);
0570     dir->i_mtime = dir->i_ctime = current_time(dir);
0571     EXT2_I(dir)->i_flags &= ~EXT2_BTREE_FL;
0572     mark_inode_dirty(dir);
0573     /* OFFSET_CACHE */
0574 out_put:
0575     ext2_put_page(page, page_addr);
0576 out:
0577     return err;
0578 out_unlock:
0579     unlock_page(page);
0580     goto out_put;
0581 }
0582 
0583 /*
0584  * ext2_delete_entry deletes a directory entry by merging it with the
0585  * previous entry. Page is up-to-date.
0586  */
0587 int ext2_delete_entry (struct ext2_dir_entry_2 *dir, struct page *page,
0588             char *kaddr)
0589 {
0590     struct inode *inode = page->mapping->host;
0591     unsigned from = ((char*)dir - kaddr) & ~(ext2_chunk_size(inode)-1);
0592     unsigned to = ((char *)dir - kaddr) +
0593                 ext2_rec_len_from_disk(dir->rec_len);
0594     loff_t pos;
0595     ext2_dirent * pde = NULL;
0596     ext2_dirent * de = (ext2_dirent *) (kaddr + from);
0597     int err;
0598 
0599     while ((char*)de < (char*)dir) {
0600         if (de->rec_len == 0) {
0601             ext2_error(inode->i_sb, __func__,
0602                 "zero-length directory entry");
0603             err = -EIO;
0604             goto out;
0605         }
0606         pde = de;
0607         de = ext2_next_entry(de);
0608     }
0609     if (pde)
0610         from = (char *)pde - kaddr;
0611     pos = page_offset(page) + from;
0612     lock_page(page);
0613     err = ext2_prepare_chunk(page, pos, to - from);
0614     BUG_ON(err);
0615     if (pde)
0616         pde->rec_len = ext2_rec_len_to_disk(to - from);
0617     dir->inode = 0;
0618     err = ext2_commit_chunk(page, pos, to - from);
0619     inode->i_ctime = inode->i_mtime = current_time(inode);
0620     EXT2_I(inode)->i_flags &= ~EXT2_BTREE_FL;
0621     mark_inode_dirty(inode);
0622 out:
0623     return err;
0624 }
0625 
0626 /*
0627  * Set the first fragment of directory.
0628  */
0629 int ext2_make_empty(struct inode *inode, struct inode *parent)
0630 {
0631     struct page *page = grab_cache_page(inode->i_mapping, 0);
0632     unsigned chunk_size = ext2_chunk_size(inode);
0633     struct ext2_dir_entry_2 * de;
0634     int err;
0635     void *kaddr;
0636 
0637     if (!page)
0638         return -ENOMEM;
0639 
0640     err = ext2_prepare_chunk(page, 0, chunk_size);
0641     if (err) {
0642         unlock_page(page);
0643         goto fail;
0644     }
0645     kaddr = kmap_atomic(page);
0646     memset(kaddr, 0, chunk_size);
0647     de = (struct ext2_dir_entry_2 *)kaddr;
0648     de->name_len = 1;
0649     de->rec_len = ext2_rec_len_to_disk(EXT2_DIR_REC_LEN(1));
0650     memcpy (de->name, ".\0\0", 4);
0651     de->inode = cpu_to_le32(inode->i_ino);
0652     ext2_set_de_type (de, inode);
0653 
0654     de = (struct ext2_dir_entry_2 *)(kaddr + EXT2_DIR_REC_LEN(1));
0655     de->name_len = 2;
0656     de->rec_len = ext2_rec_len_to_disk(chunk_size - EXT2_DIR_REC_LEN(1));
0657     de->inode = cpu_to_le32(parent->i_ino);
0658     memcpy (de->name, "..\0", 4);
0659     ext2_set_de_type (de, inode);
0660     kunmap_atomic(kaddr);
0661     err = ext2_commit_chunk(page, 0, chunk_size);
0662 fail:
0663     put_page(page);
0664     return err;
0665 }
0666 
0667 /*
0668  * routine to check that the specified directory is empty (for rmdir)
0669  */
0670 int ext2_empty_dir (struct inode * inode)
0671 {
0672     void *page_addr = NULL;
0673     struct page *page = NULL;
0674     unsigned long i, npages = dir_pages(inode);
0675 
0676     for (i = 0; i < npages; i++) {
0677         char *kaddr;
0678         ext2_dirent * de;
0679         page = ext2_get_page(inode, i, 0, &page_addr);
0680 
0681         if (IS_ERR(page))
0682             goto not_empty;
0683 
0684         kaddr = page_addr;
0685         de = (ext2_dirent *)kaddr;
0686         kaddr += ext2_last_byte(inode, i) - EXT2_DIR_REC_LEN(1);
0687 
0688         while ((char *)de <= kaddr) {
0689             if (de->rec_len == 0) {
0690                 ext2_error(inode->i_sb, __func__,
0691                     "zero-length directory entry");
0692                 printk("kaddr=%p, de=%p\n", kaddr, de);
0693                 goto not_empty;
0694             }
0695             if (de->inode != 0) {
0696                 /* check for . and .. */
0697                 if (de->name[0] != '.')
0698                     goto not_empty;
0699                 if (de->name_len > 2)
0700                     goto not_empty;
0701                 if (de->name_len < 2) {
0702                     if (de->inode !=
0703                         cpu_to_le32(inode->i_ino))
0704                         goto not_empty;
0705                 } else if (de->name[1] != '.')
0706                     goto not_empty;
0707             }
0708             de = ext2_next_entry(de);
0709         }
0710         ext2_put_page(page, page_addr);
0711     }
0712     return 1;
0713 
0714 not_empty:
0715     ext2_put_page(page, page_addr);
0716     return 0;
0717 }
0718 
0719 const struct file_operations ext2_dir_operations = {
0720     .llseek     = generic_file_llseek,
0721     .read       = generic_read_dir,
0722     .iterate_shared = ext2_readdir,
0723     .unlocked_ioctl = ext2_ioctl,
0724 #ifdef CONFIG_COMPAT
0725     .compat_ioctl   = ext2_compat_ioctl,
0726 #endif
0727     .fsync      = ext2_fsync,
0728 };
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