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1// SPDX-License-Identifier: GPL-2.02/*3 * linux/fs/sysv/dir.c4 *5 * minix/dir.c6 * Copyright (C) 1991, 1992 Linus Torvalds7 *8 * coh/dir.c9 * Copyright (C) 1993 Pascal Haible, Bruno Haible10 *11 * sysv/dir.c12 * Copyright (C) 1993 Bruno Haible13 *14 * SystemV/Coherent directory handling functions15 */16 17#include <linux/pagemap.h>18#include <linux/highmem.h>19#include <linux/swap.h>20#include "sysv.h"21 22static int sysv_readdir(struct file *, struct dir_context *);23 24const struct file_operations sysv_dir_operations = {25 .llseek = generic_file_llseek,26 .read = generic_read_dir,27 .iterate_shared = sysv_readdir,28 .fsync = generic_file_fsync,29};30 31static void dir_commit_chunk(struct folio *folio, loff_t pos, unsigned len)32{33 struct address_space *mapping = folio->mapping;34 struct inode *dir = mapping->host;35 36 block_write_end(NULL, mapping, pos, len, len, folio, NULL);37 if (pos+len > dir->i_size) {38 i_size_write(dir, pos+len);39 mark_inode_dirty(dir);40 }41 folio_unlock(folio);42}43 44static int sysv_handle_dirsync(struct inode *dir)45{46 int err;47 48 err = filemap_write_and_wait(dir->i_mapping);49 if (!err)50 err = sync_inode_metadata(dir, 1);51 return err;52}53 54/*55 * Calls to dir_get_folio()/folio_release_kmap() must be nested according to the56 * rules documented in mm/highmem.rst.57 *58 * NOTE: sysv_find_entry() and sysv_dotdot() act as calls to dir_get_folio()59 * and must be treated accordingly for nesting purposes.60 */61static void *dir_get_folio(struct inode *dir, unsigned long n,62 struct folio **foliop)63{64 struct folio *folio = read_mapping_folio(dir->i_mapping, n, NULL);65 66 if (IS_ERR(folio))67 return ERR_CAST(folio);68 *foliop = folio;69 return kmap_local_folio(folio, 0);70}71 72static int sysv_readdir(struct file *file, struct dir_context *ctx)73{74 unsigned long pos = ctx->pos;75 struct inode *inode = file_inode(file);76 struct super_block *sb = inode->i_sb;77 unsigned long npages = dir_pages(inode);78 unsigned offset;79 unsigned long n;80 81 ctx->pos = pos = (pos + SYSV_DIRSIZE-1) & ~(SYSV_DIRSIZE-1);82 if (pos >= inode->i_size)83 return 0;84 85 offset = pos & ~PAGE_MASK;86 n = pos >> PAGE_SHIFT;87 88 for ( ; n < npages; n++, offset = 0) {89 char *kaddr, *limit;90 struct sysv_dir_entry *de;91 struct folio *folio;92 93 kaddr = dir_get_folio(inode, n, &folio);94 if (IS_ERR(kaddr))95 continue;96 de = (struct sysv_dir_entry *)(kaddr+offset);97 limit = kaddr + PAGE_SIZE - SYSV_DIRSIZE;98 for ( ;(char*)de <= limit; de++, ctx->pos += sizeof(*de)) {99 char *name = de->name;100 101 if (!de->inode)102 continue;103 104 if (!dir_emit(ctx, name, strnlen(name,SYSV_NAMELEN),105 fs16_to_cpu(SYSV_SB(sb), de->inode),106 DT_UNKNOWN)) {107 folio_release_kmap(folio, kaddr);108 return 0;109 }110 }111 folio_release_kmap(folio, kaddr);112 }113 return 0;114}115 116/* compare strings: name[0..len-1] (not zero-terminated) and117 * buffer[0..] (filled with zeroes up to buffer[0..maxlen-1])118 */119static inline int namecompare(int len, int maxlen,120 const char * name, const char * buffer)121{122 if (len < maxlen && buffer[len])123 return 0;124 return !memcmp(name, buffer, len);125}126 127/*128 * sysv_find_entry()129 *130 * finds an entry in the specified directory with the wanted name.131 * It does NOT read the inode of the132 * entry - you'll have to do that yourself if you want to.133 *134 * On Success folio_release_kmap() should be called on *foliop.135 *136 * sysv_find_entry() acts as a call to dir_get_folio() and must be treated137 * accordingly for nesting purposes.138 */139struct sysv_dir_entry *sysv_find_entry(struct dentry *dentry, struct folio **foliop)140{141 const char * name = dentry->d_name.name;142 int namelen = dentry->d_name.len;143 struct inode * dir = d_inode(dentry->d_parent);144 unsigned long start, n;145 unsigned long npages = dir_pages(dir);146 struct sysv_dir_entry *de;147 148 start = SYSV_I(dir)->i_dir_start_lookup;149 if (start >= npages)150 start = 0;151 n = start;152 153 do {154 char *kaddr = dir_get_folio(dir, n, foliop);155 156 if (!IS_ERR(kaddr)) {157 de = (struct sysv_dir_entry *)kaddr;158 kaddr += folio_size(*foliop) - SYSV_DIRSIZE;159 for ( ; (char *) de <= kaddr ; de++) {160 if (!de->inode)161 continue;162 if (namecompare(namelen, SYSV_NAMELEN,163 name, de->name))164 goto found;165 }166 folio_release_kmap(*foliop, kaddr);167 }168 169 if (++n >= npages)170 n = 0;171 } while (n != start);172 173 return NULL;174 175found:176 SYSV_I(dir)->i_dir_start_lookup = n;177 return de;178}179 180int sysv_add_link(struct dentry *dentry, struct inode *inode)181{182 struct inode *dir = d_inode(dentry->d_parent);183 const char * name = dentry->d_name.name;184 int namelen = dentry->d_name.len;185 struct folio *folio = NULL;186 struct sysv_dir_entry * de;187 unsigned long npages = dir_pages(dir);188 unsigned long n;189 char *kaddr;190 loff_t pos;191 int err;192 193 /* We take care of directory expansion in the same loop */194 for (n = 0; n <= npages; n++) {195 kaddr = dir_get_folio(dir, n, &folio);196 if (IS_ERR(kaddr))197 return PTR_ERR(kaddr);198 de = (struct sysv_dir_entry *)kaddr;199 kaddr += PAGE_SIZE - SYSV_DIRSIZE;200 while ((char *)de <= kaddr) {201 if (!de->inode)202 goto got_it;203 err = -EEXIST;204 if (namecompare(namelen, SYSV_NAMELEN, name, de->name)) 205 goto out_folio;206 de++;207 }208 folio_release_kmap(folio, kaddr);209 }210 BUG();211 return -EINVAL;212 213got_it:214 pos = folio_pos(folio) + offset_in_folio(folio, de);215 folio_lock(folio);216 err = sysv_prepare_chunk(folio, pos, SYSV_DIRSIZE);217 if (err)218 goto out_unlock;219 memcpy (de->name, name, namelen);220 memset (de->name + namelen, 0, SYSV_DIRSIZE - namelen - 2);221 de->inode = cpu_to_fs16(SYSV_SB(inode->i_sb), inode->i_ino);222 dir_commit_chunk(folio, pos, SYSV_DIRSIZE);223 inode_set_mtime_to_ts(dir, inode_set_ctime_current(dir));224 mark_inode_dirty(dir);225 err = sysv_handle_dirsync(dir);226out_folio:227 folio_release_kmap(folio, kaddr);228 return err;229out_unlock:230 folio_unlock(folio);231 goto out_folio;232}233 234int sysv_delete_entry(struct sysv_dir_entry *de, struct folio *folio)235{236 struct inode *inode = folio->mapping->host;237 loff_t pos = folio_pos(folio) + offset_in_folio(folio, de);238 int err;239 240 folio_lock(folio);241 err = sysv_prepare_chunk(folio, pos, SYSV_DIRSIZE);242 if (err) {243 folio_unlock(folio);244 return err;245 }246 de->inode = 0;247 dir_commit_chunk(folio, pos, SYSV_DIRSIZE);248 inode_set_mtime_to_ts(inode, inode_set_ctime_current(inode));249 mark_inode_dirty(inode);250 return sysv_handle_dirsync(inode);251}252 253int sysv_make_empty(struct inode *inode, struct inode *dir)254{255 struct folio *folio = filemap_grab_folio(inode->i_mapping, 0);256 struct sysv_dir_entry * de;257 char *kaddr;258 int err;259 260 if (IS_ERR(folio))261 return PTR_ERR(folio);262 err = sysv_prepare_chunk(folio, 0, 2 * SYSV_DIRSIZE);263 if (err) {264 folio_unlock(folio);265 goto fail;266 }267 kaddr = kmap_local_folio(folio, 0);268 memset(kaddr, 0, folio_size(folio));269 270 de = (struct sysv_dir_entry *)kaddr;271 de->inode = cpu_to_fs16(SYSV_SB(inode->i_sb), inode->i_ino);272 strcpy(de->name,".");273 de++;274 de->inode = cpu_to_fs16(SYSV_SB(inode->i_sb), dir->i_ino);275 strcpy(de->name,"..");276 277 kunmap_local(kaddr);278 dir_commit_chunk(folio, 0, 2 * SYSV_DIRSIZE);279 err = sysv_handle_dirsync(inode);280fail:281 folio_put(folio);282 return err;283}284 285/*286 * routine to check that the specified directory is empty (for rmdir)287 */288int sysv_empty_dir(struct inode * inode)289{290 struct super_block *sb = inode->i_sb;291 struct folio *folio = NULL;292 unsigned long i, npages = dir_pages(inode);293 char *kaddr;294 295 for (i = 0; i < npages; i++) {296 struct sysv_dir_entry *de;297 298 kaddr = dir_get_folio(inode, i, &folio);299 if (IS_ERR(kaddr))300 continue;301 302 de = (struct sysv_dir_entry *)kaddr;303 kaddr += folio_size(folio) - SYSV_DIRSIZE;304 305 for ( ;(char *)de <= kaddr; de++) {306 if (!de->inode)307 continue;308 /* check for . and .. */309 if (de->name[0] != '.')310 goto not_empty;311 if (!de->name[1]) {312 if (de->inode == cpu_to_fs16(SYSV_SB(sb),313 inode->i_ino))314 continue;315 goto not_empty;316 }317 if (de->name[1] != '.' || de->name[2])318 goto not_empty;319 }320 folio_release_kmap(folio, kaddr);321 }322 return 1;323 324not_empty:325 folio_release_kmap(folio, kaddr);326 return 0;327}328 329/* Releases the page */330int sysv_set_link(struct sysv_dir_entry *de, struct folio *folio,331 struct inode *inode)332{333 struct inode *dir = folio->mapping->host;334 loff_t pos = folio_pos(folio) + offset_in_folio(folio, de);335 int err;336 337 folio_lock(folio);338 err = sysv_prepare_chunk(folio, pos, SYSV_DIRSIZE);339 if (err) {340 folio_unlock(folio);341 return err;342 }343 de->inode = cpu_to_fs16(SYSV_SB(inode->i_sb), inode->i_ino);344 dir_commit_chunk(folio, pos, SYSV_DIRSIZE);345 inode_set_mtime_to_ts(dir, inode_set_ctime_current(dir));346 mark_inode_dirty(dir);347 return sysv_handle_dirsync(inode);348}349 350/*351 * Calls to dir_get_folio()/folio_release_kmap() must be nested according to the352 * rules documented in mm/highmem.rst.353 *354 * sysv_dotdot() acts as a call to dir_get_folio() and must be treated355 * accordingly for nesting purposes.356 */357struct sysv_dir_entry *sysv_dotdot(struct inode *dir, struct folio **foliop)358{359 struct sysv_dir_entry *de = dir_get_folio(dir, 0, foliop);360 361 if (IS_ERR(de))362 return NULL;363 /* ".." is the second directory entry */364 return de + 1;365}366 367ino_t sysv_inode_by_name(struct dentry *dentry)368{369 struct folio *folio;370 struct sysv_dir_entry *de = sysv_find_entry (dentry, &folio);371 ino_t res = 0;372 373 if (de) {374 res = fs16_to_cpu(SYSV_SB(dentry->d_sb), de->inode);375 folio_release_kmap(folio, de);376 }377 return res;378}379