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0001 // SPDX-License-Identifier: GPL-2.0-only
0002 /*
0003  *  linux/fs/fat/inode.c
0004  *
0005  *  Written 1992,1993 by Werner Almesberger
0006  *  VFAT extensions by Gordon Chaffee, merged with msdos fs by Henrik Storner
0007  *  Rewritten for the constant inumbers support by Al Viro
0008  *
0009  *  Fixes:
0010  *
0011  *  Max Cohan: Fixed invalid FSINFO offset when info_sector is 0
0012  */
0013 
0014 #include <linux/module.h>
0015 #include <linux/pagemap.h>
0016 #include <linux/mpage.h>
0017 #include <linux/vfs.h>
0018 #include <linux/seq_file.h>
0019 #include <linux/parser.h>
0020 #include <linux/uio.h>
0021 #include <linux/blkdev.h>
0022 #include <linux/backing-dev.h>
0023 #include <asm/unaligned.h>
0024 #include <linux/random.h>
0025 #include <linux/iversion.h>
0026 #include "fat.h"
0027 
0028 #ifndef CONFIG_FAT_DEFAULT_IOCHARSET
0029 /* if user don't select VFAT, this is undefined. */
0030 #define CONFIG_FAT_DEFAULT_IOCHARSET    ""
0031 #endif
0032 
0033 #define KB_IN_SECTORS 2
0034 
0035 /* DOS dates from 1980/1/1 through 2107/12/31 */
0036 #define FAT_DATE_MIN (0<<9 | 1<<5 | 1)
0037 #define FAT_DATE_MAX (127<<9 | 12<<5 | 31)
0038 #define FAT_TIME_MAX (23<<11 | 59<<5 | 29)
0039 
0040 /*
0041  * A deserialized copy of the on-disk structure laid out in struct
0042  * fat_boot_sector.
0043  */
0044 struct fat_bios_param_block {
0045     u16 fat_sector_size;
0046     u8  fat_sec_per_clus;
0047     u16 fat_reserved;
0048     u8  fat_fats;
0049     u16 fat_dir_entries;
0050     u16 fat_sectors;
0051     u16 fat_fat_length;
0052     u32 fat_total_sect;
0053 
0054     u8  fat16_state;
0055     u32 fat16_vol_id;
0056 
0057     u32 fat32_length;
0058     u32 fat32_root_cluster;
0059     u16 fat32_info_sector;
0060     u8  fat32_state;
0061     u32 fat32_vol_id;
0062 };
0063 
0064 static int fat_default_codepage = CONFIG_FAT_DEFAULT_CODEPAGE;
0065 static char fat_default_iocharset[] = CONFIG_FAT_DEFAULT_IOCHARSET;
0066 
0067 static struct fat_floppy_defaults {
0068     unsigned nr_sectors;
0069     unsigned sec_per_clus;
0070     unsigned dir_entries;
0071     unsigned media;
0072     unsigned fat_length;
0073 } floppy_defaults[] = {
0074 {
0075     .nr_sectors = 160 * KB_IN_SECTORS,
0076     .sec_per_clus = 1,
0077     .dir_entries = 64,
0078     .media = 0xFE,
0079     .fat_length = 1,
0080 },
0081 {
0082     .nr_sectors = 180 * KB_IN_SECTORS,
0083     .sec_per_clus = 1,
0084     .dir_entries = 64,
0085     .media = 0xFC,
0086     .fat_length = 2,
0087 },
0088 {
0089     .nr_sectors = 320 * KB_IN_SECTORS,
0090     .sec_per_clus = 2,
0091     .dir_entries = 112,
0092     .media = 0xFF,
0093     .fat_length = 1,
0094 },
0095 {
0096     .nr_sectors = 360 * KB_IN_SECTORS,
0097     .sec_per_clus = 2,
0098     .dir_entries = 112,
0099     .media = 0xFD,
0100     .fat_length = 2,
0101 },
0102 };
0103 
0104 int fat_add_cluster(struct inode *inode)
0105 {
0106     int err, cluster;
0107 
0108     err = fat_alloc_clusters(inode, &cluster, 1);
0109     if (err)
0110         return err;
0111     /* FIXME: this cluster should be added after data of this
0112      * cluster is writed */
0113     err = fat_chain_add(inode, cluster, 1);
0114     if (err)
0115         fat_free_clusters(inode, cluster);
0116     return err;
0117 }
0118 
0119 static inline int __fat_get_block(struct inode *inode, sector_t iblock,
0120                   unsigned long *max_blocks,
0121                   struct buffer_head *bh_result, int create)
0122 {
0123     struct super_block *sb = inode->i_sb;
0124     struct msdos_sb_info *sbi = MSDOS_SB(sb);
0125     unsigned long mapped_blocks;
0126     sector_t phys, last_block;
0127     int err, offset;
0128 
0129     err = fat_bmap(inode, iblock, &phys, &mapped_blocks, create, false);
0130     if (err)
0131         return err;
0132     if (phys) {
0133         map_bh(bh_result, sb, phys);
0134         *max_blocks = min(mapped_blocks, *max_blocks);
0135         return 0;
0136     }
0137     if (!create)
0138         return 0;
0139 
0140     if (iblock != MSDOS_I(inode)->mmu_private >> sb->s_blocksize_bits) {
0141         fat_fs_error(sb, "corrupted file size (i_pos %lld, %lld)",
0142             MSDOS_I(inode)->i_pos, MSDOS_I(inode)->mmu_private);
0143         return -EIO;
0144     }
0145 
0146     last_block = inode->i_blocks >> (sb->s_blocksize_bits - 9);
0147     offset = (unsigned long)iblock & (sbi->sec_per_clus - 1);
0148     /*
0149      * allocate a cluster according to the following.
0150      * 1) no more available blocks
0151      * 2) not part of fallocate region
0152      */
0153     if (!offset && !(iblock < last_block)) {
0154         /* TODO: multiple cluster allocation would be desirable. */
0155         err = fat_add_cluster(inode);
0156         if (err)
0157             return err;
0158     }
0159     /* available blocks on this cluster */
0160     mapped_blocks = sbi->sec_per_clus - offset;
0161 
0162     *max_blocks = min(mapped_blocks, *max_blocks);
0163     MSDOS_I(inode)->mmu_private += *max_blocks << sb->s_blocksize_bits;
0164 
0165     err = fat_bmap(inode, iblock, &phys, &mapped_blocks, create, false);
0166     if (err)
0167         return err;
0168     if (!phys) {
0169         fat_fs_error(sb,
0170                  "invalid FAT chain (i_pos %lld, last_block %llu)",
0171                  MSDOS_I(inode)->i_pos,
0172                  (unsigned long long)last_block);
0173         return -EIO;
0174     }
0175 
0176     BUG_ON(*max_blocks != mapped_blocks);
0177     set_buffer_new(bh_result);
0178     map_bh(bh_result, sb, phys);
0179 
0180     return 0;
0181 }
0182 
0183 static int fat_get_block(struct inode *inode, sector_t iblock,
0184              struct buffer_head *bh_result, int create)
0185 {
0186     struct super_block *sb = inode->i_sb;
0187     unsigned long max_blocks = bh_result->b_size >> inode->i_blkbits;
0188     int err;
0189 
0190     err = __fat_get_block(inode, iblock, &max_blocks, bh_result, create);
0191     if (err)
0192         return err;
0193     bh_result->b_size = max_blocks << sb->s_blocksize_bits;
0194     return 0;
0195 }
0196 
0197 static int fat_writepage(struct page *page, struct writeback_control *wbc)
0198 {
0199     return block_write_full_page(page, fat_get_block, wbc);
0200 }
0201 
0202 static int fat_writepages(struct address_space *mapping,
0203               struct writeback_control *wbc)
0204 {
0205     return mpage_writepages(mapping, wbc, fat_get_block);
0206 }
0207 
0208 static int fat_read_folio(struct file *file, struct folio *folio)
0209 {
0210     return mpage_read_folio(folio, fat_get_block);
0211 }
0212 
0213 static void fat_readahead(struct readahead_control *rac)
0214 {
0215     mpage_readahead(rac, fat_get_block);
0216 }
0217 
0218 static void fat_write_failed(struct address_space *mapping, loff_t to)
0219 {
0220     struct inode *inode = mapping->host;
0221 
0222     if (to > inode->i_size) {
0223         truncate_pagecache(inode, inode->i_size);
0224         fat_truncate_blocks(inode, inode->i_size);
0225     }
0226 }
0227 
0228 static int fat_write_begin(struct file *file, struct address_space *mapping,
0229             loff_t pos, unsigned len,
0230             struct page **pagep, void **fsdata)
0231 {
0232     int err;
0233 
0234     *pagep = NULL;
0235     err = cont_write_begin(file, mapping, pos, len,
0236                 pagep, fsdata, fat_get_block,
0237                 &MSDOS_I(mapping->host)->mmu_private);
0238     if (err < 0)
0239         fat_write_failed(mapping, pos + len);
0240     return err;
0241 }
0242 
0243 static int fat_write_end(struct file *file, struct address_space *mapping,
0244             loff_t pos, unsigned len, unsigned copied,
0245             struct page *pagep, void *fsdata)
0246 {
0247     struct inode *inode = mapping->host;
0248     int err;
0249     err = generic_write_end(file, mapping, pos, len, copied, pagep, fsdata);
0250     if (err < len)
0251         fat_write_failed(mapping, pos + len);
0252     if (!(err < 0) && !(MSDOS_I(inode)->i_attrs & ATTR_ARCH)) {
0253         fat_truncate_time(inode, NULL, S_CTIME|S_MTIME);
0254         MSDOS_I(inode)->i_attrs |= ATTR_ARCH;
0255         mark_inode_dirty(inode);
0256     }
0257     return err;
0258 }
0259 
0260 static ssize_t fat_direct_IO(struct kiocb *iocb, struct iov_iter *iter)
0261 {
0262     struct file *file = iocb->ki_filp;
0263     struct address_space *mapping = file->f_mapping;
0264     struct inode *inode = mapping->host;
0265     size_t count = iov_iter_count(iter);
0266     loff_t offset = iocb->ki_pos;
0267     ssize_t ret;
0268 
0269     if (iov_iter_rw(iter) == WRITE) {
0270         /*
0271          * FIXME: blockdev_direct_IO() doesn't use ->write_begin(),
0272          * so we need to update the ->mmu_private to block boundary.
0273          *
0274          * But we must fill the remaining area or hole by nul for
0275          * updating ->mmu_private.
0276          *
0277          * Return 0, and fallback to normal buffered write.
0278          */
0279         loff_t size = offset + count;
0280         if (MSDOS_I(inode)->mmu_private < size)
0281             return 0;
0282     }
0283 
0284     /*
0285      * FAT need to use the DIO_LOCKING for avoiding the race
0286      * condition of fat_get_block() and ->truncate().
0287      */
0288     ret = blockdev_direct_IO(iocb, inode, iter, fat_get_block);
0289     if (ret < 0 && iov_iter_rw(iter) == WRITE)
0290         fat_write_failed(mapping, offset + count);
0291 
0292     return ret;
0293 }
0294 
0295 static int fat_get_block_bmap(struct inode *inode, sector_t iblock,
0296         struct buffer_head *bh_result, int create)
0297 {
0298     struct super_block *sb = inode->i_sb;
0299     unsigned long max_blocks = bh_result->b_size >> inode->i_blkbits;
0300     int err;
0301     sector_t bmap;
0302     unsigned long mapped_blocks;
0303 
0304     BUG_ON(create != 0);
0305 
0306     err = fat_bmap(inode, iblock, &bmap, &mapped_blocks, create, true);
0307     if (err)
0308         return err;
0309 
0310     if (bmap) {
0311         map_bh(bh_result, sb, bmap);
0312         max_blocks = min(mapped_blocks, max_blocks);
0313     }
0314 
0315     bh_result->b_size = max_blocks << sb->s_blocksize_bits;
0316 
0317     return 0;
0318 }
0319 
0320 static sector_t _fat_bmap(struct address_space *mapping, sector_t block)
0321 {
0322     sector_t blocknr;
0323 
0324     /* fat_get_cluster() assumes the requested blocknr isn't truncated. */
0325     down_read(&MSDOS_I(mapping->host)->truncate_lock);
0326     blocknr = generic_block_bmap(mapping, block, fat_get_block_bmap);
0327     up_read(&MSDOS_I(mapping->host)->truncate_lock);
0328 
0329     return blocknr;
0330 }
0331 
0332 /*
0333  * fat_block_truncate_page() zeroes out a mapping from file offset `from'
0334  * up to the end of the block which corresponds to `from'.
0335  * This is required during truncate to physically zeroout the tail end
0336  * of that block so it doesn't yield old data if the file is later grown.
0337  * Also, avoid causing failure from fsx for cases of "data past EOF"
0338  */
0339 int fat_block_truncate_page(struct inode *inode, loff_t from)
0340 {
0341     return block_truncate_page(inode->i_mapping, from, fat_get_block);
0342 }
0343 
0344 static const struct address_space_operations fat_aops = {
0345     .dirty_folio    = block_dirty_folio,
0346     .invalidate_folio = block_invalidate_folio,
0347     .read_folio = fat_read_folio,
0348     .readahead  = fat_readahead,
0349     .writepage  = fat_writepage,
0350     .writepages = fat_writepages,
0351     .write_begin    = fat_write_begin,
0352     .write_end  = fat_write_end,
0353     .direct_IO  = fat_direct_IO,
0354     .bmap       = _fat_bmap
0355 };
0356 
0357 /*
0358  * New FAT inode stuff. We do the following:
0359  *  a) i_ino is constant and has nothing with on-disk location.
0360  *  b) FAT manages its own cache of directory entries.
0361  *  c) *This* cache is indexed by on-disk location.
0362  *  d) inode has an associated directory entry, all right, but
0363  *      it may be unhashed.
0364  *  e) currently entries are stored within struct inode. That should
0365  *      change.
0366  *  f) we deal with races in the following way:
0367  *      1. readdir() and lookup() do FAT-dir-cache lookup.
0368  *      2. rename() unhashes the F-d-c entry and rehashes it in
0369  *          a new place.
0370  *      3. unlink() and rmdir() unhash F-d-c entry.
0371  *      4. fat_write_inode() checks whether the thing is unhashed.
0372  *          If it is we silently return. If it isn't we do bread(),
0373  *          check if the location is still valid and retry if it
0374  *          isn't. Otherwise we do changes.
0375  *      5. Spinlock is used to protect hash/unhash/location check/lookup
0376  *      6. fat_evict_inode() unhashes the F-d-c entry.
0377  *      7. lookup() and readdir() do igrab() if they find a F-d-c entry
0378  *          and consider negative result as cache miss.
0379  */
0380 
0381 static void fat_hash_init(struct super_block *sb)
0382 {
0383     struct msdos_sb_info *sbi = MSDOS_SB(sb);
0384     int i;
0385 
0386     spin_lock_init(&sbi->inode_hash_lock);
0387     for (i = 0; i < FAT_HASH_SIZE; i++)
0388         INIT_HLIST_HEAD(&sbi->inode_hashtable[i]);
0389 }
0390 
0391 static inline unsigned long fat_hash(loff_t i_pos)
0392 {
0393     return hash_32(i_pos, FAT_HASH_BITS);
0394 }
0395 
0396 static void dir_hash_init(struct super_block *sb)
0397 {
0398     struct msdos_sb_info *sbi = MSDOS_SB(sb);
0399     int i;
0400 
0401     spin_lock_init(&sbi->dir_hash_lock);
0402     for (i = 0; i < FAT_HASH_SIZE; i++)
0403         INIT_HLIST_HEAD(&sbi->dir_hashtable[i]);
0404 }
0405 
0406 void fat_attach(struct inode *inode, loff_t i_pos)
0407 {
0408     struct msdos_sb_info *sbi = MSDOS_SB(inode->i_sb);
0409 
0410     if (inode->i_ino != MSDOS_ROOT_INO) {
0411         struct hlist_head *head =   sbi->inode_hashtable
0412                       + fat_hash(i_pos);
0413 
0414         spin_lock(&sbi->inode_hash_lock);
0415         MSDOS_I(inode)->i_pos = i_pos;
0416         hlist_add_head(&MSDOS_I(inode)->i_fat_hash, head);
0417         spin_unlock(&sbi->inode_hash_lock);
0418     }
0419 
0420     /* If NFS support is enabled, cache the mapping of start cluster
0421      * to directory inode. This is used during reconnection of
0422      * dentries to the filesystem root.
0423      */
0424     if (S_ISDIR(inode->i_mode) && sbi->options.nfs) {
0425         struct hlist_head *d_head = sbi->dir_hashtable;
0426         d_head += fat_dir_hash(MSDOS_I(inode)->i_logstart);
0427 
0428         spin_lock(&sbi->dir_hash_lock);
0429         hlist_add_head(&MSDOS_I(inode)->i_dir_hash, d_head);
0430         spin_unlock(&sbi->dir_hash_lock);
0431     }
0432 }
0433 EXPORT_SYMBOL_GPL(fat_attach);
0434 
0435 void fat_detach(struct inode *inode)
0436 {
0437     struct msdos_sb_info *sbi = MSDOS_SB(inode->i_sb);
0438     spin_lock(&sbi->inode_hash_lock);
0439     MSDOS_I(inode)->i_pos = 0;
0440     hlist_del_init(&MSDOS_I(inode)->i_fat_hash);
0441     spin_unlock(&sbi->inode_hash_lock);
0442 
0443     if (S_ISDIR(inode->i_mode) && sbi->options.nfs) {
0444         spin_lock(&sbi->dir_hash_lock);
0445         hlist_del_init(&MSDOS_I(inode)->i_dir_hash);
0446         spin_unlock(&sbi->dir_hash_lock);
0447     }
0448 }
0449 EXPORT_SYMBOL_GPL(fat_detach);
0450 
0451 struct inode *fat_iget(struct super_block *sb, loff_t i_pos)
0452 {
0453     struct msdos_sb_info *sbi = MSDOS_SB(sb);
0454     struct hlist_head *head = sbi->inode_hashtable + fat_hash(i_pos);
0455     struct msdos_inode_info *i;
0456     struct inode *inode = NULL;
0457 
0458     spin_lock(&sbi->inode_hash_lock);
0459     hlist_for_each_entry(i, head, i_fat_hash) {
0460         BUG_ON(i->vfs_inode.i_sb != sb);
0461         if (i->i_pos != i_pos)
0462             continue;
0463         inode = igrab(&i->vfs_inode);
0464         if (inode)
0465             break;
0466     }
0467     spin_unlock(&sbi->inode_hash_lock);
0468     return inode;
0469 }
0470 
0471 static int is_exec(unsigned char *extension)
0472 {
0473     unsigned char exe_extensions[] = "EXECOMBAT", *walk;
0474 
0475     for (walk = exe_extensions; *walk; walk += 3)
0476         if (!strncmp(extension, walk, 3))
0477             return 1;
0478     return 0;
0479 }
0480 
0481 static int fat_calc_dir_size(struct inode *inode)
0482 {
0483     struct msdos_sb_info *sbi = MSDOS_SB(inode->i_sb);
0484     int ret, fclus, dclus;
0485 
0486     inode->i_size = 0;
0487     if (MSDOS_I(inode)->i_start == 0)
0488         return 0;
0489 
0490     ret = fat_get_cluster(inode, FAT_ENT_EOF, &fclus, &dclus);
0491     if (ret < 0)
0492         return ret;
0493     inode->i_size = (fclus + 1) << sbi->cluster_bits;
0494 
0495     return 0;
0496 }
0497 
0498 static int fat_validate_dir(struct inode *dir)
0499 {
0500     struct super_block *sb = dir->i_sb;
0501 
0502     if (dir->i_nlink < 2) {
0503         /* Directory should have "."/".." entries at least. */
0504         fat_fs_error(sb, "corrupted directory (invalid entries)");
0505         return -EIO;
0506     }
0507     if (MSDOS_I(dir)->i_start == 0 ||
0508         MSDOS_I(dir)->i_start == MSDOS_SB(sb)->root_cluster) {
0509         /* Directory should point valid cluster. */
0510         fat_fs_error(sb, "corrupted directory (invalid i_start)");
0511         return -EIO;
0512     }
0513     return 0;
0514 }
0515 
0516 /* doesn't deal with root inode */
0517 int fat_fill_inode(struct inode *inode, struct msdos_dir_entry *de)
0518 {
0519     struct msdos_sb_info *sbi = MSDOS_SB(inode->i_sb);
0520     int error;
0521 
0522     MSDOS_I(inode)->i_pos = 0;
0523     inode->i_uid = sbi->options.fs_uid;
0524     inode->i_gid = sbi->options.fs_gid;
0525     inode_inc_iversion(inode);
0526     inode->i_generation = prandom_u32();
0527 
0528     if ((de->attr & ATTR_DIR) && !IS_FREE(de->name)) {
0529         inode->i_generation &= ~1;
0530         inode->i_mode = fat_make_mode(sbi, de->attr, S_IRWXUGO);
0531         inode->i_op = sbi->dir_ops;
0532         inode->i_fop = &fat_dir_operations;
0533 
0534         MSDOS_I(inode)->i_start = fat_get_start(sbi, de);
0535         MSDOS_I(inode)->i_logstart = MSDOS_I(inode)->i_start;
0536         error = fat_calc_dir_size(inode);
0537         if (error < 0)
0538             return error;
0539         MSDOS_I(inode)->mmu_private = inode->i_size;
0540 
0541         set_nlink(inode, fat_subdirs(inode));
0542 
0543         error = fat_validate_dir(inode);
0544         if (error < 0)
0545             return error;
0546     } else { /* not a directory */
0547         inode->i_generation |= 1;
0548         inode->i_mode = fat_make_mode(sbi, de->attr,
0549             ((sbi->options.showexec && !is_exec(de->name + 8))
0550              ? S_IRUGO|S_IWUGO : S_IRWXUGO));
0551         MSDOS_I(inode)->i_start = fat_get_start(sbi, de);
0552 
0553         MSDOS_I(inode)->i_logstart = MSDOS_I(inode)->i_start;
0554         inode->i_size = le32_to_cpu(de->size);
0555         inode->i_op = &fat_file_inode_operations;
0556         inode->i_fop = &fat_file_operations;
0557         inode->i_mapping->a_ops = &fat_aops;
0558         MSDOS_I(inode)->mmu_private = inode->i_size;
0559     }
0560     if (de->attr & ATTR_SYS) {
0561         if (sbi->options.sys_immutable)
0562             inode->i_flags |= S_IMMUTABLE;
0563     }
0564     fat_save_attrs(inode, de->attr);
0565 
0566     inode->i_blocks = ((inode->i_size + (sbi->cluster_size - 1))
0567                & ~((loff_t)sbi->cluster_size - 1)) >> 9;
0568 
0569     fat_time_fat2unix(sbi, &inode->i_mtime, de->time, de->date, 0);
0570     inode->i_ctime = inode->i_mtime;
0571     if (sbi->options.isvfat) {
0572         fat_time_fat2unix(sbi, &inode->i_atime, 0, de->adate, 0);
0573         fat_time_fat2unix(sbi, &MSDOS_I(inode)->i_crtime, de->ctime,
0574                   de->cdate, de->ctime_cs);
0575     } else
0576         inode->i_atime = fat_truncate_atime(sbi, &inode->i_mtime);
0577 
0578     return 0;
0579 }
0580 
0581 static inline void fat_lock_build_inode(struct msdos_sb_info *sbi)
0582 {
0583     if (sbi->options.nfs == FAT_NFS_NOSTALE_RO)
0584         mutex_lock(&sbi->nfs_build_inode_lock);
0585 }
0586 
0587 static inline void fat_unlock_build_inode(struct msdos_sb_info *sbi)
0588 {
0589     if (sbi->options.nfs == FAT_NFS_NOSTALE_RO)
0590         mutex_unlock(&sbi->nfs_build_inode_lock);
0591 }
0592 
0593 struct inode *fat_build_inode(struct super_block *sb,
0594             struct msdos_dir_entry *de, loff_t i_pos)
0595 {
0596     struct inode *inode;
0597     int err;
0598 
0599     fat_lock_build_inode(MSDOS_SB(sb));
0600     inode = fat_iget(sb, i_pos);
0601     if (inode)
0602         goto out;
0603     inode = new_inode(sb);
0604     if (!inode) {
0605         inode = ERR_PTR(-ENOMEM);
0606         goto out;
0607     }
0608     inode->i_ino = iunique(sb, MSDOS_ROOT_INO);
0609     inode_set_iversion(inode, 1);
0610     err = fat_fill_inode(inode, de);
0611     if (err) {
0612         iput(inode);
0613         inode = ERR_PTR(err);
0614         goto out;
0615     }
0616     fat_attach(inode, i_pos);
0617     insert_inode_hash(inode);
0618 out:
0619     fat_unlock_build_inode(MSDOS_SB(sb));
0620     return inode;
0621 }
0622 
0623 EXPORT_SYMBOL_GPL(fat_build_inode);
0624 
0625 static int __fat_write_inode(struct inode *inode, int wait);
0626 
0627 static void fat_free_eofblocks(struct inode *inode)
0628 {
0629     /* Release unwritten fallocated blocks on inode eviction. */
0630     if ((inode->i_blocks << 9) >
0631             round_up(MSDOS_I(inode)->mmu_private,
0632                 MSDOS_SB(inode->i_sb)->cluster_size)) {
0633         int err;
0634 
0635         fat_truncate_blocks(inode, MSDOS_I(inode)->mmu_private);
0636         /* Fallocate results in updating the i_start/iogstart
0637          * for the zero byte file. So, make it return to
0638          * original state during evict and commit it to avoid
0639          * any corruption on the next access to the cluster
0640          * chain for the file.
0641          */
0642         err = __fat_write_inode(inode, inode_needs_sync(inode));
0643         if (err) {
0644             fat_msg(inode->i_sb, KERN_WARNING, "Failed to "
0645                     "update on disk inode for unused "
0646                     "fallocated blocks, inode could be "
0647                     "corrupted. Please run fsck");
0648         }
0649 
0650     }
0651 }
0652 
0653 static void fat_evict_inode(struct inode *inode)
0654 {
0655     truncate_inode_pages_final(&inode->i_data);
0656     if (!inode->i_nlink) {
0657         inode->i_size = 0;
0658         fat_truncate_blocks(inode, 0);
0659     } else
0660         fat_free_eofblocks(inode);
0661 
0662     invalidate_inode_buffers(inode);
0663     clear_inode(inode);
0664     fat_cache_inval_inode(inode);
0665     fat_detach(inode);
0666 }
0667 
0668 static void fat_set_state(struct super_block *sb,
0669             unsigned int set, unsigned int force)
0670 {
0671     struct buffer_head *bh;
0672     struct fat_boot_sector *b;
0673     struct msdos_sb_info *sbi = MSDOS_SB(sb);
0674 
0675     /* do not change any thing if mounted read only */
0676     if (sb_rdonly(sb) && !force)
0677         return;
0678 
0679     /* do not change state if fs was dirty */
0680     if (sbi->dirty) {
0681         /* warn only on set (mount). */
0682         if (set)
0683             fat_msg(sb, KERN_WARNING, "Volume was not properly "
0684                 "unmounted. Some data may be corrupt. "
0685                 "Please run fsck.");
0686         return;
0687     }
0688 
0689     bh = sb_bread(sb, 0);
0690     if (bh == NULL) {
0691         fat_msg(sb, KERN_ERR, "unable to read boot sector "
0692             "to mark fs as dirty");
0693         return;
0694     }
0695 
0696     b = (struct fat_boot_sector *) bh->b_data;
0697 
0698     if (is_fat32(sbi)) {
0699         if (set)
0700             b->fat32.state |= FAT_STATE_DIRTY;
0701         else
0702             b->fat32.state &= ~FAT_STATE_DIRTY;
0703     } else /* fat 16 and 12 */ {
0704         if (set)
0705             b->fat16.state |= FAT_STATE_DIRTY;
0706         else
0707             b->fat16.state &= ~FAT_STATE_DIRTY;
0708     }
0709 
0710     mark_buffer_dirty(bh);
0711     sync_dirty_buffer(bh);
0712     brelse(bh);
0713 }
0714 
0715 static void fat_reset_iocharset(struct fat_mount_options *opts)
0716 {
0717     if (opts->iocharset != fat_default_iocharset) {
0718         /* Note: opts->iocharset can be NULL here */
0719         kfree(opts->iocharset);
0720         opts->iocharset = fat_default_iocharset;
0721     }
0722 }
0723 
0724 static void delayed_free(struct rcu_head *p)
0725 {
0726     struct msdos_sb_info *sbi = container_of(p, struct msdos_sb_info, rcu);
0727     unload_nls(sbi->nls_disk);
0728     unload_nls(sbi->nls_io);
0729     fat_reset_iocharset(&sbi->options);
0730     kfree(sbi);
0731 }
0732 
0733 static void fat_put_super(struct super_block *sb)
0734 {
0735     struct msdos_sb_info *sbi = MSDOS_SB(sb);
0736 
0737     fat_set_state(sb, 0, 0);
0738 
0739     iput(sbi->fsinfo_inode);
0740     iput(sbi->fat_inode);
0741 
0742     call_rcu(&sbi->rcu, delayed_free);
0743 }
0744 
0745 static struct kmem_cache *fat_inode_cachep;
0746 
0747 static struct inode *fat_alloc_inode(struct super_block *sb)
0748 {
0749     struct msdos_inode_info *ei;
0750     ei = alloc_inode_sb(sb, fat_inode_cachep, GFP_NOFS);
0751     if (!ei)
0752         return NULL;
0753 
0754     init_rwsem(&ei->truncate_lock);
0755     /* Zeroing to allow iput() even if partial initialized inode. */
0756     ei->mmu_private = 0;
0757     ei->i_start = 0;
0758     ei->i_logstart = 0;
0759     ei->i_attrs = 0;
0760     ei->i_pos = 0;
0761     ei->i_crtime.tv_sec = 0;
0762     ei->i_crtime.tv_nsec = 0;
0763 
0764     return &ei->vfs_inode;
0765 }
0766 
0767 static void fat_free_inode(struct inode *inode)
0768 {
0769     kmem_cache_free(fat_inode_cachep, MSDOS_I(inode));
0770 }
0771 
0772 static void init_once(void *foo)
0773 {
0774     struct msdos_inode_info *ei = (struct msdos_inode_info *)foo;
0775 
0776     spin_lock_init(&ei->cache_lru_lock);
0777     ei->nr_caches = 0;
0778     ei->cache_valid_id = FAT_CACHE_VALID + 1;
0779     INIT_LIST_HEAD(&ei->cache_lru);
0780     INIT_HLIST_NODE(&ei->i_fat_hash);
0781     INIT_HLIST_NODE(&ei->i_dir_hash);
0782     inode_init_once(&ei->vfs_inode);
0783 }
0784 
0785 static int __init fat_init_inodecache(void)
0786 {
0787     fat_inode_cachep = kmem_cache_create("fat_inode_cache",
0788                          sizeof(struct msdos_inode_info),
0789                          0, (SLAB_RECLAIM_ACCOUNT|
0790                         SLAB_MEM_SPREAD|SLAB_ACCOUNT),
0791                          init_once);
0792     if (fat_inode_cachep == NULL)
0793         return -ENOMEM;
0794     return 0;
0795 }
0796 
0797 static void __exit fat_destroy_inodecache(void)
0798 {
0799     /*
0800      * Make sure all delayed rcu free inodes are flushed before we
0801      * destroy cache.
0802      */
0803     rcu_barrier();
0804     kmem_cache_destroy(fat_inode_cachep);
0805 }
0806 
0807 static int fat_remount(struct super_block *sb, int *flags, char *data)
0808 {
0809     bool new_rdonly;
0810     struct msdos_sb_info *sbi = MSDOS_SB(sb);
0811     *flags |= SB_NODIRATIME | (sbi->options.isvfat ? 0 : SB_NOATIME);
0812 
0813     sync_filesystem(sb);
0814 
0815     /* make sure we update state on remount. */
0816     new_rdonly = *flags & SB_RDONLY;
0817     if (new_rdonly != sb_rdonly(sb)) {
0818         if (new_rdonly)
0819             fat_set_state(sb, 0, 0);
0820         else
0821             fat_set_state(sb, 1, 1);
0822     }
0823     return 0;
0824 }
0825 
0826 static int fat_statfs(struct dentry *dentry, struct kstatfs *buf)
0827 {
0828     struct super_block *sb = dentry->d_sb;
0829     struct msdos_sb_info *sbi = MSDOS_SB(sb);
0830     u64 id = huge_encode_dev(sb->s_bdev->bd_dev);
0831 
0832     /* If the count of free cluster is still unknown, counts it here. */
0833     if (sbi->free_clusters == -1 || !sbi->free_clus_valid) {
0834         int err = fat_count_free_clusters(dentry->d_sb);
0835         if (err)
0836             return err;
0837     }
0838 
0839     buf->f_type = dentry->d_sb->s_magic;
0840     buf->f_bsize = sbi->cluster_size;
0841     buf->f_blocks = sbi->max_cluster - FAT_START_ENT;
0842     buf->f_bfree = sbi->free_clusters;
0843     buf->f_bavail = sbi->free_clusters;
0844     buf->f_fsid = u64_to_fsid(id);
0845     buf->f_namelen =
0846         (sbi->options.isvfat ? FAT_LFN_LEN : 12) * NLS_MAX_CHARSET_SIZE;
0847 
0848     return 0;
0849 }
0850 
0851 static int __fat_write_inode(struct inode *inode, int wait)
0852 {
0853     struct super_block *sb = inode->i_sb;
0854     struct msdos_sb_info *sbi = MSDOS_SB(sb);
0855     struct buffer_head *bh;
0856     struct msdos_dir_entry *raw_entry;
0857     loff_t i_pos;
0858     sector_t blocknr;
0859     int err, offset;
0860 
0861     if (inode->i_ino == MSDOS_ROOT_INO)
0862         return 0;
0863 
0864 retry:
0865     i_pos = fat_i_pos_read(sbi, inode);
0866     if (!i_pos)
0867         return 0;
0868 
0869     fat_get_blknr_offset(sbi, i_pos, &blocknr, &offset);
0870     bh = sb_bread(sb, blocknr);
0871     if (!bh) {
0872         fat_msg(sb, KERN_ERR, "unable to read inode block "
0873                "for updating (i_pos %lld)", i_pos);
0874         return -EIO;
0875     }
0876     spin_lock(&sbi->inode_hash_lock);
0877     if (i_pos != MSDOS_I(inode)->i_pos) {
0878         spin_unlock(&sbi->inode_hash_lock);
0879         brelse(bh);
0880         goto retry;
0881     }
0882 
0883     raw_entry = &((struct msdos_dir_entry *) (bh->b_data))[offset];
0884     if (S_ISDIR(inode->i_mode))
0885         raw_entry->size = 0;
0886     else
0887         raw_entry->size = cpu_to_le32(inode->i_size);
0888     raw_entry->attr = fat_make_attrs(inode);
0889     fat_set_start(raw_entry, MSDOS_I(inode)->i_logstart);
0890     fat_time_unix2fat(sbi, &inode->i_mtime, &raw_entry->time,
0891               &raw_entry->date, NULL);
0892     if (sbi->options.isvfat) {
0893         __le16 atime;
0894         fat_time_unix2fat(sbi, &inode->i_atime, &atime,
0895                   &raw_entry->adate, NULL);
0896         fat_time_unix2fat(sbi, &MSDOS_I(inode)->i_crtime, &raw_entry->ctime,
0897                   &raw_entry->cdate, &raw_entry->ctime_cs);
0898     }
0899     spin_unlock(&sbi->inode_hash_lock);
0900     mark_buffer_dirty(bh);
0901     err = 0;
0902     if (wait)
0903         err = sync_dirty_buffer(bh);
0904     brelse(bh);
0905     return err;
0906 }
0907 
0908 static int fat_write_inode(struct inode *inode, struct writeback_control *wbc)
0909 {
0910     int err;
0911 
0912     if (inode->i_ino == MSDOS_FSINFO_INO) {
0913         struct super_block *sb = inode->i_sb;
0914 
0915         mutex_lock(&MSDOS_SB(sb)->s_lock);
0916         err = fat_clusters_flush(sb);
0917         mutex_unlock(&MSDOS_SB(sb)->s_lock);
0918     } else
0919         err = __fat_write_inode(inode, wbc->sync_mode == WB_SYNC_ALL);
0920 
0921     return err;
0922 }
0923 
0924 int fat_sync_inode(struct inode *inode)
0925 {
0926     return __fat_write_inode(inode, 1);
0927 }
0928 
0929 EXPORT_SYMBOL_GPL(fat_sync_inode);
0930 
0931 static int fat_show_options(struct seq_file *m, struct dentry *root);
0932 static const struct super_operations fat_sops = {
0933     .alloc_inode    = fat_alloc_inode,
0934     .free_inode = fat_free_inode,
0935     .write_inode    = fat_write_inode,
0936     .evict_inode    = fat_evict_inode,
0937     .put_super  = fat_put_super,
0938     .statfs     = fat_statfs,
0939     .remount_fs = fat_remount,
0940 
0941     .show_options   = fat_show_options,
0942 };
0943 
0944 static int fat_show_options(struct seq_file *m, struct dentry *root)
0945 {
0946     struct msdos_sb_info *sbi = MSDOS_SB(root->d_sb);
0947     struct fat_mount_options *opts = &sbi->options;
0948     int isvfat = opts->isvfat;
0949 
0950     if (!uid_eq(opts->fs_uid, GLOBAL_ROOT_UID))
0951         seq_printf(m, ",uid=%u",
0952                 from_kuid_munged(&init_user_ns, opts->fs_uid));
0953     if (!gid_eq(opts->fs_gid, GLOBAL_ROOT_GID))
0954         seq_printf(m, ",gid=%u",
0955                 from_kgid_munged(&init_user_ns, opts->fs_gid));
0956     seq_printf(m, ",fmask=%04o", opts->fs_fmask);
0957     seq_printf(m, ",dmask=%04o", opts->fs_dmask);
0958     if (opts->allow_utime)
0959         seq_printf(m, ",allow_utime=%04o", opts->allow_utime);
0960     if (sbi->nls_disk)
0961         /* strip "cp" prefix from displayed option */
0962         seq_printf(m, ",codepage=%s", &sbi->nls_disk->charset[2]);
0963     if (isvfat) {
0964         if (sbi->nls_io)
0965             seq_printf(m, ",iocharset=%s", sbi->nls_io->charset);
0966 
0967         switch (opts->shortname) {
0968         case VFAT_SFN_DISPLAY_WIN95 | VFAT_SFN_CREATE_WIN95:
0969             seq_puts(m, ",shortname=win95");
0970             break;
0971         case VFAT_SFN_DISPLAY_WINNT | VFAT_SFN_CREATE_WINNT:
0972             seq_puts(m, ",shortname=winnt");
0973             break;
0974         case VFAT_SFN_DISPLAY_WINNT | VFAT_SFN_CREATE_WIN95:
0975             seq_puts(m, ",shortname=mixed");
0976             break;
0977         case VFAT_SFN_DISPLAY_LOWER | VFAT_SFN_CREATE_WIN95:
0978             seq_puts(m, ",shortname=lower");
0979             break;
0980         default:
0981             seq_puts(m, ",shortname=unknown");
0982             break;
0983         }
0984     }
0985     if (opts->name_check != 'n')
0986         seq_printf(m, ",check=%c", opts->name_check);
0987     if (opts->usefree)
0988         seq_puts(m, ",usefree");
0989     if (opts->quiet)
0990         seq_puts(m, ",quiet");
0991     if (opts->showexec)
0992         seq_puts(m, ",showexec");
0993     if (opts->sys_immutable)
0994         seq_puts(m, ",sys_immutable");
0995     if (!isvfat) {
0996         if (opts->dotsOK)
0997             seq_puts(m, ",dotsOK=yes");
0998         if (opts->nocase)
0999             seq_puts(m, ",nocase");
1000     } else {
1001         if (opts->utf8)
1002             seq_puts(m, ",utf8");
1003         if (opts->unicode_xlate)
1004             seq_puts(m, ",uni_xlate");
1005         if (!opts->numtail)
1006             seq_puts(m, ",nonumtail");
1007         if (opts->rodir)
1008             seq_puts(m, ",rodir");
1009     }
1010     if (opts->flush)
1011         seq_puts(m, ",flush");
1012     if (opts->tz_set) {
1013         if (opts->time_offset)
1014             seq_printf(m, ",time_offset=%d", opts->time_offset);
1015         else
1016             seq_puts(m, ",tz=UTC");
1017     }
1018     if (opts->errors == FAT_ERRORS_CONT)
1019         seq_puts(m, ",errors=continue");
1020     else if (opts->errors == FAT_ERRORS_PANIC)
1021         seq_puts(m, ",errors=panic");
1022     else
1023         seq_puts(m, ",errors=remount-ro");
1024     if (opts->nfs == FAT_NFS_NOSTALE_RO)
1025         seq_puts(m, ",nfs=nostale_ro");
1026     else if (opts->nfs)
1027         seq_puts(m, ",nfs=stale_rw");
1028     if (opts->discard)
1029         seq_puts(m, ",discard");
1030     if (opts->dos1xfloppy)
1031         seq_puts(m, ",dos1xfloppy");
1032 
1033     return 0;
1034 }
1035 
1036 enum {
1037     Opt_check_n, Opt_check_r, Opt_check_s, Opt_uid, Opt_gid,
1038     Opt_umask, Opt_dmask, Opt_fmask, Opt_allow_utime, Opt_codepage,
1039     Opt_usefree, Opt_nocase, Opt_quiet, Opt_showexec, Opt_debug,
1040     Opt_immutable, Opt_dots, Opt_nodots,
1041     Opt_charset, Opt_shortname_lower, Opt_shortname_win95,
1042     Opt_shortname_winnt, Opt_shortname_mixed, Opt_utf8_no, Opt_utf8_yes,
1043     Opt_uni_xl_no, Opt_uni_xl_yes, Opt_nonumtail_no, Opt_nonumtail_yes,
1044     Opt_obsolete, Opt_flush, Opt_tz_utc, Opt_rodir, Opt_err_cont,
1045     Opt_err_panic, Opt_err_ro, Opt_discard, Opt_nfs, Opt_time_offset,
1046     Opt_nfs_stale_rw, Opt_nfs_nostale_ro, Opt_err, Opt_dos1xfloppy,
1047 };
1048 
1049 static const match_table_t fat_tokens = {
1050     {Opt_check_r, "check=relaxed"},
1051     {Opt_check_s, "check=strict"},
1052     {Opt_check_n, "check=normal"},
1053     {Opt_check_r, "check=r"},
1054     {Opt_check_s, "check=s"},
1055     {Opt_check_n, "check=n"},
1056     {Opt_uid, "uid=%u"},
1057     {Opt_gid, "gid=%u"},
1058     {Opt_umask, "umask=%o"},
1059     {Opt_dmask, "dmask=%o"},
1060     {Opt_fmask, "fmask=%o"},
1061     {Opt_allow_utime, "allow_utime=%o"},
1062     {Opt_codepage, "codepage=%u"},
1063     {Opt_usefree, "usefree"},
1064     {Opt_nocase, "nocase"},
1065     {Opt_quiet, "quiet"},
1066     {Opt_showexec, "showexec"},
1067     {Opt_debug, "debug"},
1068     {Opt_immutable, "sys_immutable"},
1069     {Opt_flush, "flush"},
1070     {Opt_tz_utc, "tz=UTC"},
1071     {Opt_time_offset, "time_offset=%d"},
1072     {Opt_err_cont, "errors=continue"},
1073     {Opt_err_panic, "errors=panic"},
1074     {Opt_err_ro, "errors=remount-ro"},
1075     {Opt_discard, "discard"},
1076     {Opt_nfs_stale_rw, "nfs"},
1077     {Opt_nfs_stale_rw, "nfs=stale_rw"},
1078     {Opt_nfs_nostale_ro, "nfs=nostale_ro"},
1079     {Opt_dos1xfloppy, "dos1xfloppy"},
1080     {Opt_obsolete, "conv=binary"},
1081     {Opt_obsolete, "conv=text"},
1082     {Opt_obsolete, "conv=auto"},
1083     {Opt_obsolete, "conv=b"},
1084     {Opt_obsolete, "conv=t"},
1085     {Opt_obsolete, "conv=a"},
1086     {Opt_obsolete, "fat=%u"},
1087     {Opt_obsolete, "blocksize=%u"},
1088     {Opt_obsolete, "cvf_format=%20s"},
1089     {Opt_obsolete, "cvf_options=%100s"},
1090     {Opt_obsolete, "posix"},
1091     {Opt_err, NULL},
1092 };
1093 static const match_table_t msdos_tokens = {
1094     {Opt_nodots, "nodots"},
1095     {Opt_nodots, "dotsOK=no"},
1096     {Opt_dots, "dots"},
1097     {Opt_dots, "dotsOK=yes"},
1098     {Opt_err, NULL}
1099 };
1100 static const match_table_t vfat_tokens = {
1101     {Opt_charset, "iocharset=%s"},
1102     {Opt_shortname_lower, "shortname=lower"},
1103     {Opt_shortname_win95, "shortname=win95"},
1104     {Opt_shortname_winnt, "shortname=winnt"},
1105     {Opt_shortname_mixed, "shortname=mixed"},
1106     {Opt_utf8_no, "utf8=0"},        /* 0 or no or false */
1107     {Opt_utf8_no, "utf8=no"},
1108     {Opt_utf8_no, "utf8=false"},
1109     {Opt_utf8_yes, "utf8=1"},       /* empty or 1 or yes or true */
1110     {Opt_utf8_yes, "utf8=yes"},
1111     {Opt_utf8_yes, "utf8=true"},
1112     {Opt_utf8_yes, "utf8"},
1113     {Opt_uni_xl_no, "uni_xlate=0"},     /* 0 or no or false */
1114     {Opt_uni_xl_no, "uni_xlate=no"},
1115     {Opt_uni_xl_no, "uni_xlate=false"},
1116     {Opt_uni_xl_yes, "uni_xlate=1"},    /* empty or 1 or yes or true */
1117     {Opt_uni_xl_yes, "uni_xlate=yes"},
1118     {Opt_uni_xl_yes, "uni_xlate=true"},
1119     {Opt_uni_xl_yes, "uni_xlate"},
1120     {Opt_nonumtail_no, "nonumtail=0"},  /* 0 or no or false */
1121     {Opt_nonumtail_no, "nonumtail=no"},
1122     {Opt_nonumtail_no, "nonumtail=false"},
1123     {Opt_nonumtail_yes, "nonumtail=1"}, /* empty or 1 or yes or true */
1124     {Opt_nonumtail_yes, "nonumtail=yes"},
1125     {Opt_nonumtail_yes, "nonumtail=true"},
1126     {Opt_nonumtail_yes, "nonumtail"},
1127     {Opt_rodir, "rodir"},
1128     {Opt_err, NULL}
1129 };
1130 
1131 static int parse_options(struct super_block *sb, char *options, int is_vfat,
1132              int silent, int *debug, struct fat_mount_options *opts)
1133 {
1134     char *p;
1135     substring_t args[MAX_OPT_ARGS];
1136     int option;
1137     char *iocharset;
1138 
1139     opts->isvfat = is_vfat;
1140 
1141     opts->fs_uid = current_uid();
1142     opts->fs_gid = current_gid();
1143     opts->fs_fmask = opts->fs_dmask = current_umask();
1144     opts->allow_utime = -1;
1145     opts->codepage = fat_default_codepage;
1146     fat_reset_iocharset(opts);
1147     if (is_vfat) {
1148         opts->shortname = VFAT_SFN_DISPLAY_WINNT|VFAT_SFN_CREATE_WIN95;
1149         opts->rodir = 0;
1150     } else {
1151         opts->shortname = 0;
1152         opts->rodir = 1;
1153     }
1154     opts->name_check = 'n';
1155     opts->quiet = opts->showexec = opts->sys_immutable = opts->dotsOK =  0;
1156     opts->unicode_xlate = 0;
1157     opts->numtail = 1;
1158     opts->usefree = opts->nocase = 0;
1159     opts->tz_set = 0;
1160     opts->nfs = 0;
1161     opts->errors = FAT_ERRORS_RO;
1162     *debug = 0;
1163 
1164     opts->utf8 = IS_ENABLED(CONFIG_FAT_DEFAULT_UTF8) && is_vfat;
1165 
1166     if (!options)
1167         goto out;
1168 
1169     while ((p = strsep(&options, ",")) != NULL) {
1170         int token;
1171         if (!*p)
1172             continue;
1173 
1174         token = match_token(p, fat_tokens, args);
1175         if (token == Opt_err) {
1176             if (is_vfat)
1177                 token = match_token(p, vfat_tokens, args);
1178             else
1179                 token = match_token(p, msdos_tokens, args);
1180         }
1181         switch (token) {
1182         case Opt_check_s:
1183             opts->name_check = 's';
1184             break;
1185         case Opt_check_r:
1186             opts->name_check = 'r';
1187             break;
1188         case Opt_check_n:
1189             opts->name_check = 'n';
1190             break;
1191         case Opt_usefree:
1192             opts->usefree = 1;
1193             break;
1194         case Opt_nocase:
1195             if (!is_vfat)
1196                 opts->nocase = 1;
1197             else {
1198                 /* for backward compatibility */
1199                 opts->shortname = VFAT_SFN_DISPLAY_WIN95
1200                     | VFAT_SFN_CREATE_WIN95;
1201             }
1202             break;
1203         case Opt_quiet:
1204             opts->quiet = 1;
1205             break;
1206         case Opt_showexec:
1207             opts->showexec = 1;
1208             break;
1209         case Opt_debug:
1210             *debug = 1;
1211             break;
1212         case Opt_immutable:
1213             opts->sys_immutable = 1;
1214             break;
1215         case Opt_uid:
1216             if (match_int(&args[0], &option))
1217                 return -EINVAL;
1218             opts->fs_uid = make_kuid(current_user_ns(), option);
1219             if (!uid_valid(opts->fs_uid))
1220                 return -EINVAL;
1221             break;
1222         case Opt_gid:
1223             if (match_int(&args[0], &option))
1224                 return -EINVAL;
1225             opts->fs_gid = make_kgid(current_user_ns(), option);
1226             if (!gid_valid(opts->fs_gid))
1227                 return -EINVAL;
1228             break;
1229         case Opt_umask:
1230             if (match_octal(&args[0], &option))
1231                 return -EINVAL;
1232             opts->fs_fmask = opts->fs_dmask = option;
1233             break;
1234         case Opt_dmask:
1235             if (match_octal(&args[0], &option))
1236                 return -EINVAL;
1237             opts->fs_dmask = option;
1238             break;
1239         case Opt_fmask:
1240             if (match_octal(&args[0], &option))
1241                 return -EINVAL;
1242             opts->fs_fmask = option;
1243             break;
1244         case Opt_allow_utime:
1245             if (match_octal(&args[0], &option))
1246                 return -EINVAL;
1247             opts->allow_utime = option & (S_IWGRP | S_IWOTH);
1248             break;
1249         case Opt_codepage:
1250             if (match_int(&args[0], &option))
1251                 return -EINVAL;
1252             opts->codepage = option;
1253             break;
1254         case Opt_flush:
1255             opts->flush = 1;
1256             break;
1257         case Opt_time_offset:
1258             if (match_int(&args[0], &option))
1259                 return -EINVAL;
1260             /*
1261              * GMT+-12 zones may have DST corrections so at least
1262              * 13 hours difference is needed. Make the limit 24
1263              * just in case someone invents something unusual.
1264              */
1265             if (option < -24 * 60 || option > 24 * 60)
1266                 return -EINVAL;
1267             opts->tz_set = 1;
1268             opts->time_offset = option;
1269             break;
1270         case Opt_tz_utc:
1271             opts->tz_set = 1;
1272             opts->time_offset = 0;
1273             break;
1274         case Opt_err_cont:
1275             opts->errors = FAT_ERRORS_CONT;
1276             break;
1277         case Opt_err_panic:
1278             opts->errors = FAT_ERRORS_PANIC;
1279             break;
1280         case Opt_err_ro:
1281             opts->errors = FAT_ERRORS_RO;
1282             break;
1283         case Opt_nfs_stale_rw:
1284             opts->nfs = FAT_NFS_STALE_RW;
1285             break;
1286         case Opt_nfs_nostale_ro:
1287             opts->nfs = FAT_NFS_NOSTALE_RO;
1288             break;
1289         case Opt_dos1xfloppy:
1290             opts->dos1xfloppy = 1;
1291             break;
1292 
1293         /* msdos specific */
1294         case Opt_dots:
1295             opts->dotsOK = 1;
1296             break;
1297         case Opt_nodots:
1298             opts->dotsOK = 0;
1299             break;
1300 
1301         /* vfat specific */
1302         case Opt_charset:
1303             fat_reset_iocharset(opts);
1304             iocharset = match_strdup(&args[0]);
1305             if (!iocharset)
1306                 return -ENOMEM;
1307             opts->iocharset = iocharset;
1308             break;
1309         case Opt_shortname_lower:
1310             opts->shortname = VFAT_SFN_DISPLAY_LOWER
1311                     | VFAT_SFN_CREATE_WIN95;
1312             break;
1313         case Opt_shortname_win95:
1314             opts->shortname = VFAT_SFN_DISPLAY_WIN95
1315                     | VFAT_SFN_CREATE_WIN95;
1316             break;
1317         case Opt_shortname_winnt:
1318             opts->shortname = VFAT_SFN_DISPLAY_WINNT
1319                     | VFAT_SFN_CREATE_WINNT;
1320             break;
1321         case Opt_shortname_mixed:
1322             opts->shortname = VFAT_SFN_DISPLAY_WINNT
1323                     | VFAT_SFN_CREATE_WIN95;
1324             break;
1325         case Opt_utf8_no:       /* 0 or no or false */
1326             opts->utf8 = 0;
1327             break;
1328         case Opt_utf8_yes:      /* empty or 1 or yes or true */
1329             opts->utf8 = 1;
1330             break;
1331         case Opt_uni_xl_no:     /* 0 or no or false */
1332             opts->unicode_xlate = 0;
1333             break;
1334         case Opt_uni_xl_yes:        /* empty or 1 or yes or true */
1335             opts->unicode_xlate = 1;
1336             break;
1337         case Opt_nonumtail_no:      /* 0 or no or false */
1338             opts->numtail = 1;  /* negated option */
1339             break;
1340         case Opt_nonumtail_yes:     /* empty or 1 or yes or true */
1341             opts->numtail = 0;  /* negated option */
1342             break;
1343         case Opt_rodir:
1344             opts->rodir = 1;
1345             break;
1346         case Opt_discard:
1347             opts->discard = 1;
1348             break;
1349 
1350         /* obsolete mount options */
1351         case Opt_obsolete:
1352             fat_msg(sb, KERN_INFO, "\"%s\" option is obsolete, "
1353                    "not supported now", p);
1354             break;
1355         /* unknown option */
1356         default:
1357             if (!silent) {
1358                 fat_msg(sb, KERN_ERR,
1359                        "Unrecognized mount option \"%s\" "
1360                        "or missing value", p);
1361             }
1362             return -EINVAL;
1363         }
1364     }
1365 
1366 out:
1367     /* UTF-8 doesn't provide FAT semantics */
1368     if (!strcmp(opts->iocharset, "utf8")) {
1369         fat_msg(sb, KERN_WARNING, "utf8 is not a recommended IO charset"
1370                " for FAT filesystems, filesystem will be "
1371                "case sensitive!");
1372     }
1373 
1374     /* If user doesn't specify allow_utime, it's initialized from dmask. */
1375     if (opts->allow_utime == (unsigned short)-1)
1376         opts->allow_utime = ~opts->fs_dmask & (S_IWGRP | S_IWOTH);
1377     if (opts->unicode_xlate)
1378         opts->utf8 = 0;
1379     if (opts->nfs == FAT_NFS_NOSTALE_RO) {
1380         sb->s_flags |= SB_RDONLY;
1381         sb->s_export_op = &fat_export_ops_nostale;
1382     }
1383 
1384     return 0;
1385 }
1386 
1387 static int fat_read_root(struct inode *inode)
1388 {
1389     struct msdos_sb_info *sbi = MSDOS_SB(inode->i_sb);
1390     int error;
1391 
1392     MSDOS_I(inode)->i_pos = MSDOS_ROOT_INO;
1393     inode->i_uid = sbi->options.fs_uid;
1394     inode->i_gid = sbi->options.fs_gid;
1395     inode_inc_iversion(inode);
1396     inode->i_generation = 0;
1397     inode->i_mode = fat_make_mode(sbi, ATTR_DIR, S_IRWXUGO);
1398     inode->i_op = sbi->dir_ops;
1399     inode->i_fop = &fat_dir_operations;
1400     if (is_fat32(sbi)) {
1401         MSDOS_I(inode)->i_start = sbi->root_cluster;
1402         error = fat_calc_dir_size(inode);
1403         if (error < 0)
1404             return error;
1405     } else {
1406         MSDOS_I(inode)->i_start = 0;
1407         inode->i_size = sbi->dir_entries * sizeof(struct msdos_dir_entry);
1408     }
1409     inode->i_blocks = ((inode->i_size + (sbi->cluster_size - 1))
1410                & ~((loff_t)sbi->cluster_size - 1)) >> 9;
1411     MSDOS_I(inode)->i_logstart = 0;
1412     MSDOS_I(inode)->mmu_private = inode->i_size;
1413 
1414     fat_save_attrs(inode, ATTR_DIR);
1415     inode->i_mtime.tv_sec = inode->i_atime.tv_sec = inode->i_ctime.tv_sec = 0;
1416     inode->i_mtime.tv_nsec = inode->i_atime.tv_nsec = inode->i_ctime.tv_nsec = 0;
1417     set_nlink(inode, fat_subdirs(inode)+2);
1418 
1419     return 0;
1420 }
1421 
1422 static unsigned long calc_fat_clusters(struct super_block *sb)
1423 {
1424     struct msdos_sb_info *sbi = MSDOS_SB(sb);
1425 
1426     /* Divide first to avoid overflow */
1427     if (!is_fat12(sbi)) {
1428         unsigned long ent_per_sec = sb->s_blocksize * 8 / sbi->fat_bits;
1429         return ent_per_sec * sbi->fat_length;
1430     }
1431 
1432     return sbi->fat_length * sb->s_blocksize * 8 / sbi->fat_bits;
1433 }
1434 
1435 static bool fat_bpb_is_zero(struct fat_boot_sector *b)
1436 {
1437     if (get_unaligned_le16(&b->sector_size))
1438         return false;
1439     if (b->sec_per_clus)
1440         return false;
1441     if (b->reserved)
1442         return false;
1443     if (b->fats)
1444         return false;
1445     if (get_unaligned_le16(&b->dir_entries))
1446         return false;
1447     if (get_unaligned_le16(&b->sectors))
1448         return false;
1449     if (b->media)
1450         return false;
1451     if (b->fat_length)
1452         return false;
1453     if (b->secs_track)
1454         return false;
1455     if (b->heads)
1456         return false;
1457     return true;
1458 }
1459 
1460 static int fat_read_bpb(struct super_block *sb, struct fat_boot_sector *b,
1461     int silent, struct fat_bios_param_block *bpb)
1462 {
1463     int error = -EINVAL;
1464 
1465     /* Read in BPB ... */
1466     memset(bpb, 0, sizeof(*bpb));
1467     bpb->fat_sector_size = get_unaligned_le16(&b->sector_size);
1468     bpb->fat_sec_per_clus = b->sec_per_clus;
1469     bpb->fat_reserved = le16_to_cpu(b->reserved);
1470     bpb->fat_fats = b->fats;
1471     bpb->fat_dir_entries = get_unaligned_le16(&b->dir_entries);
1472     bpb->fat_sectors = get_unaligned_le16(&b->sectors);
1473     bpb->fat_fat_length = le16_to_cpu(b->fat_length);
1474     bpb->fat_total_sect = le32_to_cpu(b->total_sect);
1475 
1476     bpb->fat16_state = b->fat16.state;
1477     bpb->fat16_vol_id = get_unaligned_le32(b->fat16.vol_id);
1478 
1479     bpb->fat32_length = le32_to_cpu(b->fat32.length);
1480     bpb->fat32_root_cluster = le32_to_cpu(b->fat32.root_cluster);
1481     bpb->fat32_info_sector = le16_to_cpu(b->fat32.info_sector);
1482     bpb->fat32_state = b->fat32.state;
1483     bpb->fat32_vol_id = get_unaligned_le32(b->fat32.vol_id);
1484 
1485     /* Validate this looks like a FAT filesystem BPB */
1486     if (!bpb->fat_reserved) {
1487         if (!silent)
1488             fat_msg(sb, KERN_ERR,
1489                 "bogus number of reserved sectors");
1490         goto out;
1491     }
1492     if (!bpb->fat_fats) {
1493         if (!silent)
1494             fat_msg(sb, KERN_ERR, "bogus number of FAT structure");
1495         goto out;
1496     }
1497 
1498     /*
1499      * Earlier we checked here that b->secs_track and b->head are nonzero,
1500      * but it turns out valid FAT filesystems can have zero there.
1501      */
1502 
1503     if (!fat_valid_media(b->media)) {
1504         if (!silent)
1505             fat_msg(sb, KERN_ERR, "invalid media value (0x%02x)",
1506                 (unsigned)b->media);
1507         goto out;
1508     }
1509 
1510     if (!is_power_of_2(bpb->fat_sector_size)
1511         || (bpb->fat_sector_size < 512)
1512         || (bpb->fat_sector_size > 4096)) {
1513         if (!silent)
1514             fat_msg(sb, KERN_ERR, "bogus logical sector size %u",
1515                    (unsigned)bpb->fat_sector_size);
1516         goto out;
1517     }
1518 
1519     if (!is_power_of_2(bpb->fat_sec_per_clus)) {
1520         if (!silent)
1521             fat_msg(sb, KERN_ERR, "bogus sectors per cluster %u",
1522                 (unsigned)bpb->fat_sec_per_clus);
1523         goto out;
1524     }
1525 
1526     if (bpb->fat_fat_length == 0 && bpb->fat32_length == 0) {
1527         if (!silent)
1528             fat_msg(sb, KERN_ERR, "bogus number of FAT sectors");
1529         goto out;
1530     }
1531 
1532     error = 0;
1533 
1534 out:
1535     return error;
1536 }
1537 
1538 static int fat_read_static_bpb(struct super_block *sb,
1539     struct fat_boot_sector *b, int silent,
1540     struct fat_bios_param_block *bpb)
1541 {
1542     static const char *notdos1x = "This doesn't look like a DOS 1.x volume";
1543     sector_t bd_sects = bdev_nr_sectors(sb->s_bdev);
1544     struct fat_floppy_defaults *fdefaults = NULL;
1545     int error = -EINVAL;
1546     unsigned i;
1547 
1548     /* 16-bit DOS 1.x reliably wrote bootstrap short-jmp code */
1549     if (b->ignored[0] != 0xeb || b->ignored[2] != 0x90) {
1550         if (!silent)
1551             fat_msg(sb, KERN_ERR,
1552                 "%s; no bootstrapping code", notdos1x);
1553         goto out;
1554     }
1555 
1556     /*
1557      * If any value in this region is non-zero, it isn't archaic
1558      * DOS.
1559      */
1560     if (!fat_bpb_is_zero(b)) {
1561         if (!silent)
1562             fat_msg(sb, KERN_ERR,
1563                 "%s; DOS 2.x BPB is non-zero", notdos1x);
1564         goto out;
1565     }
1566 
1567     for (i = 0; i < ARRAY_SIZE(floppy_defaults); i++) {
1568         if (floppy_defaults[i].nr_sectors == bd_sects) {
1569             fdefaults = &floppy_defaults[i];
1570             break;
1571         }
1572     }
1573 
1574     if (fdefaults == NULL) {
1575         if (!silent)
1576             fat_msg(sb, KERN_WARNING,
1577                 "This looks like a DOS 1.x volume, but isn't a recognized floppy size (%llu sectors)",
1578                 (u64)bd_sects);
1579         goto out;
1580     }
1581 
1582     if (!silent)
1583         fat_msg(sb, KERN_INFO,
1584             "This looks like a DOS 1.x volume; assuming default BPB values");
1585 
1586     memset(bpb, 0, sizeof(*bpb));
1587     bpb->fat_sector_size = SECTOR_SIZE;
1588     bpb->fat_sec_per_clus = fdefaults->sec_per_clus;
1589     bpb->fat_reserved = 1;
1590     bpb->fat_fats = 2;
1591     bpb->fat_dir_entries = fdefaults->dir_entries;
1592     bpb->fat_sectors = fdefaults->nr_sectors;
1593     bpb->fat_fat_length = fdefaults->fat_length;
1594 
1595     error = 0;
1596 
1597 out:
1598     return error;
1599 }
1600 
1601 /*
1602  * Read the super block of an MS-DOS FS.
1603  */
1604 int fat_fill_super(struct super_block *sb, void *data, int silent, int isvfat,
1605            void (*setup)(struct super_block *))
1606 {
1607     struct inode *root_inode = NULL, *fat_inode = NULL;
1608     struct inode *fsinfo_inode = NULL;
1609     struct buffer_head *bh;
1610     struct fat_bios_param_block bpb;
1611     struct msdos_sb_info *sbi;
1612     u16 logical_sector_size;
1613     u32 total_sectors, total_clusters, fat_clusters, rootdir_sectors;
1614     int debug;
1615     long error;
1616     char buf[50];
1617     struct timespec64 ts;
1618 
1619     /*
1620      * GFP_KERNEL is ok here, because while we do hold the
1621      * superblock lock, memory pressure can't call back into
1622      * the filesystem, since we're only just about to mount
1623      * it and have no inodes etc active!
1624      */
1625     sbi = kzalloc(sizeof(struct msdos_sb_info), GFP_KERNEL);
1626     if (!sbi)
1627         return -ENOMEM;
1628     sb->s_fs_info = sbi;
1629 
1630     sb->s_flags |= SB_NODIRATIME;
1631     sb->s_magic = MSDOS_SUPER_MAGIC;
1632     sb->s_op = &fat_sops;
1633     sb->s_export_op = &fat_export_ops;
1634     /*
1635      * fat timestamps are complex and truncated by fat itself, so
1636      * we set 1 here to be fast
1637      */
1638     sb->s_time_gran = 1;
1639     mutex_init(&sbi->nfs_build_inode_lock);
1640     ratelimit_state_init(&sbi->ratelimit, DEFAULT_RATELIMIT_INTERVAL,
1641                  DEFAULT_RATELIMIT_BURST);
1642 
1643     error = parse_options(sb, data, isvfat, silent, &debug, &sbi->options);
1644     if (error)
1645         goto out_fail;
1646 
1647     setup(sb); /* flavour-specific stuff that needs options */
1648 
1649     error = -EIO;
1650     sb_min_blocksize(sb, 512);
1651     bh = sb_bread(sb, 0);
1652     if (bh == NULL) {
1653         fat_msg(sb, KERN_ERR, "unable to read boot sector");
1654         goto out_fail;
1655     }
1656 
1657     error = fat_read_bpb(sb, (struct fat_boot_sector *)bh->b_data, silent,
1658         &bpb);
1659     if (error == -EINVAL && sbi->options.dos1xfloppy)
1660         error = fat_read_static_bpb(sb,
1661             (struct fat_boot_sector *)bh->b_data, silent, &bpb);
1662     brelse(bh);
1663 
1664     if (error == -EINVAL)
1665         goto out_invalid;
1666     else if (error)
1667         goto out_fail;
1668 
1669     logical_sector_size = bpb.fat_sector_size;
1670     sbi->sec_per_clus = bpb.fat_sec_per_clus;
1671 
1672     error = -EIO;
1673     if (logical_sector_size < sb->s_blocksize) {
1674         fat_msg(sb, KERN_ERR, "logical sector size too small for device"
1675                " (logical sector size = %u)", logical_sector_size);
1676         goto out_fail;
1677     }
1678 
1679     if (logical_sector_size > sb->s_blocksize) {
1680         struct buffer_head *bh_resize;
1681 
1682         if (!sb_set_blocksize(sb, logical_sector_size)) {
1683             fat_msg(sb, KERN_ERR, "unable to set blocksize %u",
1684                    logical_sector_size);
1685             goto out_fail;
1686         }
1687 
1688         /* Verify that the larger boot sector is fully readable */
1689         bh_resize = sb_bread(sb, 0);
1690         if (bh_resize == NULL) {
1691             fat_msg(sb, KERN_ERR, "unable to read boot sector"
1692                    " (logical sector size = %lu)",
1693                    sb->s_blocksize);
1694             goto out_fail;
1695         }
1696         brelse(bh_resize);
1697     }
1698 
1699     mutex_init(&sbi->s_lock);
1700     sbi->cluster_size = sb->s_blocksize * sbi->sec_per_clus;
1701     sbi->cluster_bits = ffs(sbi->cluster_size) - 1;
1702     sbi->fats = bpb.fat_fats;
1703     sbi->fat_bits = 0;      /* Don't know yet */
1704     sbi->fat_start = bpb.fat_reserved;
1705     sbi->fat_length = bpb.fat_fat_length;
1706     sbi->root_cluster = 0;
1707     sbi->free_clusters = -1;    /* Don't know yet */
1708     sbi->free_clus_valid = 0;
1709     sbi->prev_free = FAT_START_ENT;
1710     sb->s_maxbytes = 0xffffffff;
1711     fat_time_fat2unix(sbi, &ts, 0, cpu_to_le16(FAT_DATE_MIN), 0);
1712     sb->s_time_min = ts.tv_sec;
1713 
1714     fat_time_fat2unix(sbi, &ts, cpu_to_le16(FAT_TIME_MAX),
1715               cpu_to_le16(FAT_DATE_MAX), 0);
1716     sb->s_time_max = ts.tv_sec;
1717 
1718     if (!sbi->fat_length && bpb.fat32_length) {
1719         struct fat_boot_fsinfo *fsinfo;
1720         struct buffer_head *fsinfo_bh;
1721 
1722         /* Must be FAT32 */
1723         sbi->fat_bits = 32;
1724         sbi->fat_length = bpb.fat32_length;
1725         sbi->root_cluster = bpb.fat32_root_cluster;
1726 
1727         /* MC - if info_sector is 0, don't multiply by 0 */
1728         sbi->fsinfo_sector = bpb.fat32_info_sector;
1729         if (sbi->fsinfo_sector == 0)
1730             sbi->fsinfo_sector = 1;
1731 
1732         fsinfo_bh = sb_bread(sb, sbi->fsinfo_sector);
1733         if (fsinfo_bh == NULL) {
1734             fat_msg(sb, KERN_ERR, "bread failed, FSINFO block"
1735                    " (sector = %lu)", sbi->fsinfo_sector);
1736             goto out_fail;
1737         }
1738 
1739         fsinfo = (struct fat_boot_fsinfo *)fsinfo_bh->b_data;
1740         if (!IS_FSINFO(fsinfo)) {
1741             fat_msg(sb, KERN_WARNING, "Invalid FSINFO signature: "
1742                    "0x%08x, 0x%08x (sector = %lu)",
1743                    le32_to_cpu(fsinfo->signature1),
1744                    le32_to_cpu(fsinfo->signature2),
1745                    sbi->fsinfo_sector);
1746         } else {
1747             if (sbi->options.usefree)
1748                 sbi->free_clus_valid = 1;
1749             sbi->free_clusters = le32_to_cpu(fsinfo->free_clusters);
1750             sbi->prev_free = le32_to_cpu(fsinfo->next_cluster);
1751         }
1752 
1753         brelse(fsinfo_bh);
1754     }
1755 
1756     /* interpret volume ID as a little endian 32 bit integer */
1757     if (is_fat32(sbi))
1758         sbi->vol_id = bpb.fat32_vol_id;
1759     else /* fat 16 or 12 */
1760         sbi->vol_id = bpb.fat16_vol_id;
1761 
1762     sbi->dir_per_block = sb->s_blocksize / sizeof(struct msdos_dir_entry);
1763     sbi->dir_per_block_bits = ffs(sbi->dir_per_block) - 1;
1764 
1765     sbi->dir_start = sbi->fat_start + sbi->fats * sbi->fat_length;
1766     sbi->dir_entries = bpb.fat_dir_entries;
1767     if (sbi->dir_entries & (sbi->dir_per_block - 1)) {
1768         if (!silent)
1769             fat_msg(sb, KERN_ERR, "bogus number of directory entries"
1770                    " (%u)", sbi->dir_entries);
1771         goto out_invalid;
1772     }
1773 
1774     rootdir_sectors = sbi->dir_entries
1775         * sizeof(struct msdos_dir_entry) / sb->s_blocksize;
1776     sbi->data_start = sbi->dir_start + rootdir_sectors;
1777     total_sectors = bpb.fat_sectors;
1778     if (total_sectors == 0)
1779         total_sectors = bpb.fat_total_sect;
1780 
1781     total_clusters = (total_sectors - sbi->data_start) / sbi->sec_per_clus;
1782 
1783     if (!is_fat32(sbi))
1784         sbi->fat_bits = (total_clusters > MAX_FAT12) ? 16 : 12;
1785 
1786     /* some OSes set FAT_STATE_DIRTY and clean it on unmount. */
1787     if (is_fat32(sbi))
1788         sbi->dirty = bpb.fat32_state & FAT_STATE_DIRTY;
1789     else /* fat 16 or 12 */
1790         sbi->dirty = bpb.fat16_state & FAT_STATE_DIRTY;
1791 
1792     /* check that FAT table does not overflow */
1793     fat_clusters = calc_fat_clusters(sb);
1794     total_clusters = min(total_clusters, fat_clusters - FAT_START_ENT);
1795     if (total_clusters > max_fat(sb)) {
1796         if (!silent)
1797             fat_msg(sb, KERN_ERR, "count of clusters too big (%u)",
1798                    total_clusters);
1799         goto out_invalid;
1800     }
1801 
1802     sbi->max_cluster = total_clusters + FAT_START_ENT;
1803     /* check the free_clusters, it's not necessarily correct */
1804     if (sbi->free_clusters != -1 && sbi->free_clusters > total_clusters)
1805         sbi->free_clusters = -1;
1806     /* check the prev_free, it's not necessarily correct */
1807     sbi->prev_free %= sbi->max_cluster;
1808     if (sbi->prev_free < FAT_START_ENT)
1809         sbi->prev_free = FAT_START_ENT;
1810 
1811     /* set up enough so that it can read an inode */
1812     fat_hash_init(sb);
1813     dir_hash_init(sb);
1814     fat_ent_access_init(sb);
1815 
1816     /*
1817      * The low byte of the first FAT entry must have the same value as
1818      * the media field of the boot sector. But in real world, too many
1819      * devices are writing wrong values. So, removed that validity check.
1820      *
1821      * The removed check compared the first FAT entry to a value dependent
1822      * on the media field like this:
1823      * == (0x0F00 | media), for FAT12
1824      * == (0XFF00 | media), for FAT16
1825      * == (0x0FFFFF | media), for FAT32
1826      */
1827 
1828     error = -EINVAL;
1829     sprintf(buf, "cp%d", sbi->options.codepage);
1830     sbi->nls_disk = load_nls(buf);
1831     if (!sbi->nls_disk) {
1832         fat_msg(sb, KERN_ERR, "codepage %s not found", buf);
1833         goto out_fail;
1834     }
1835 
1836     /* FIXME: utf8 is using iocharset for upper/lower conversion */
1837     if (sbi->options.isvfat) {
1838         sbi->nls_io = load_nls(sbi->options.iocharset);
1839         if (!sbi->nls_io) {
1840             fat_msg(sb, KERN_ERR, "IO charset %s not found",
1841                    sbi->options.iocharset);
1842             goto out_fail;
1843         }
1844     }
1845 
1846     error = -ENOMEM;
1847     fat_inode = new_inode(sb);
1848     if (!fat_inode)
1849         goto out_fail;
1850     sbi->fat_inode = fat_inode;
1851 
1852     fsinfo_inode = new_inode(sb);
1853     if (!fsinfo_inode)
1854         goto out_fail;
1855     fsinfo_inode->i_ino = MSDOS_FSINFO_INO;
1856     sbi->fsinfo_inode = fsinfo_inode;
1857     insert_inode_hash(fsinfo_inode);
1858 
1859     root_inode = new_inode(sb);
1860     if (!root_inode)
1861         goto out_fail;
1862     root_inode->i_ino = MSDOS_ROOT_INO;
1863     inode_set_iversion(root_inode, 1);
1864     error = fat_read_root(root_inode);
1865     if (error < 0) {
1866         iput(root_inode);
1867         goto out_fail;
1868     }
1869     error = -ENOMEM;
1870     insert_inode_hash(root_inode);
1871     fat_attach(root_inode, 0);
1872     sb->s_root = d_make_root(root_inode);
1873     if (!sb->s_root) {
1874         fat_msg(sb, KERN_ERR, "get root inode failed");
1875         goto out_fail;
1876     }
1877 
1878     if (sbi->options.discard && !bdev_max_discard_sectors(sb->s_bdev))
1879         fat_msg(sb, KERN_WARNING,
1880             "mounting with \"discard\" option, but the device does not support discard");
1881 
1882     fat_set_state(sb, 1, 0);
1883     return 0;
1884 
1885 out_invalid:
1886     error = -EINVAL;
1887     if (!silent)
1888         fat_msg(sb, KERN_INFO, "Can't find a valid FAT filesystem");
1889 
1890 out_fail:
1891     iput(fsinfo_inode);
1892     iput(fat_inode);
1893     unload_nls(sbi->nls_io);
1894     unload_nls(sbi->nls_disk);
1895     fat_reset_iocharset(&sbi->options);
1896     sb->s_fs_info = NULL;
1897     kfree(sbi);
1898     return error;
1899 }
1900 
1901 EXPORT_SYMBOL_GPL(fat_fill_super);
1902 
1903 /*
1904  * helper function for fat_flush_inodes.  This writes both the inode
1905  * and the file data blocks, waiting for in flight data blocks before
1906  * the start of the call.  It does not wait for any io started
1907  * during the call
1908  */
1909 static int writeback_inode(struct inode *inode)
1910 {
1911 
1912     int ret;
1913 
1914     /* if we used wait=1, sync_inode_metadata waits for the io for the
1915     * inode to finish.  So wait=0 is sent down to sync_inode_metadata
1916     * and filemap_fdatawrite is used for the data blocks
1917     */
1918     ret = sync_inode_metadata(inode, 0);
1919     if (!ret)
1920         ret = filemap_fdatawrite(inode->i_mapping);
1921     return ret;
1922 }
1923 
1924 /*
1925  * write data and metadata corresponding to i1 and i2.  The io is
1926  * started but we do not wait for any of it to finish.
1927  *
1928  * filemap_flush is used for the block device, so if there is a dirty
1929  * page for a block already in flight, we will not wait and start the
1930  * io over again
1931  */
1932 int fat_flush_inodes(struct super_block *sb, struct inode *i1, struct inode *i2)
1933 {
1934     int ret = 0;
1935     if (!MSDOS_SB(sb)->options.flush)
1936         return 0;
1937     if (i1)
1938         ret = writeback_inode(i1);
1939     if (!ret && i2)
1940         ret = writeback_inode(i2);
1941     if (!ret)
1942         ret = sync_blockdev_nowait(sb->s_bdev);
1943     return ret;
1944 }
1945 EXPORT_SYMBOL_GPL(fat_flush_inodes);
1946 
1947 static int __init init_fat_fs(void)
1948 {
1949     int err;
1950 
1951     err = fat_cache_init();
1952     if (err)
1953         return err;
1954 
1955     err = fat_init_inodecache();
1956     if (err)
1957         goto failed;
1958 
1959     return 0;
1960 
1961 failed:
1962     fat_cache_destroy();
1963     return err;
1964 }
1965 
1966 static void __exit exit_fat_fs(void)
1967 {
1968     fat_cache_destroy();
1969     fat_destroy_inodecache();
1970 }
1971 
1972 module_init(init_fat_fs)
1973 module_exit(exit_fat_fs)
1974 
1975 MODULE_LICENSE("GPL");
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