1 /* fs/fat/nfs.c 2 * 3 * This software is licensed under the terms of the GNU General Public 4 * License version 2, as published by the Free Software Foundation, and 5 * may be copied, distributed, and modified under those terms. 6 * 7 * This program is distributed in the hope that it will be useful, 8 * but WITHOUT ANY WARRANTY; without even the implied warranty of 9 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 10 * GNU General Public License for more details. 11 * 12 */ 13 14 #include <linux/exportfs.h> 15 #include "fat.h" 16 17 /** 18 * Look up a directory inode given its starting cluster. 19 */ 20 static struct inode *fat_dget(struct super_block *sb, int i_logstart) 21 { 22 struct msdos_sb_info *sbi = MSDOS_SB(sb); 23 struct hlist_head *head; 24 struct msdos_inode_info *i; 25 struct inode *inode = NULL; 26 27 head = sbi->dir_hashtable + fat_dir_hash(i_logstart); 28 spin_lock(&sbi->dir_hash_lock); 29 hlist_for_each_entry(i, head, i_dir_hash) { 30 BUG_ON(i->vfs_inode.i_sb != sb); 31 if (i->i_logstart != i_logstart) 32 continue; 33 inode = igrab(&i->vfs_inode); 34 if (inode) 35 break; 36 } 37 spin_unlock(&sbi->dir_hash_lock); 38 return inode; 39 } 40 41 static struct inode *fat_nfs_get_inode(struct super_block *sb, 42 u64 ino, u32 generation) 43 { 44 struct inode *inode; 45 46 if ((ino < MSDOS_ROOT_INO) || (ino == MSDOS_FSINFO_INO)) 47 return NULL; 48 49 inode = ilookup(sb, ino); 50 if (inode && generation && (inode->i_generation != generation)) { 51 iput(inode); 52 inode = NULL; 53 } 54 55 return inode; 56 } 57 58 /** 59 * Map a NFS file handle to a corresponding dentry. 60 * The dentry may or may not be connected to the filesystem root. 61 */ 62 struct dentry *fat_fh_to_dentry(struct super_block *sb, struct fid *fid, 63 int fh_len, int fh_type) 64 { 65 return generic_fh_to_dentry(sb, fid, fh_len, fh_type, 66 fat_nfs_get_inode); 67 } 68 69 /* 70 * Find the parent for a file specified by NFS handle. 71 * This requires that the handle contain the i_ino of the parent. 72 */ 73 struct dentry *fat_fh_to_parent(struct super_block *sb, struct fid *fid, 74 int fh_len, int fh_type) 75 { 76 return generic_fh_to_parent(sb, fid, fh_len, fh_type, 77 fat_nfs_get_inode); 78 } 79 80 /* 81 * Find the parent for a directory that is not currently connected to 82 * the filesystem root. 83 * 84 * On entry, the caller holds child_dir->d_inode->i_mutex. 85 */ 86 struct dentry *fat_get_parent(struct dentry *child_dir) 87 { 88 struct super_block *sb = child_dir->d_sb; 89 struct buffer_head *bh = NULL; 90 struct msdos_dir_entry *de; 91 struct inode *parent_inode = NULL; 92 93 if (!fat_get_dotdot_entry(child_dir->d_inode, &bh, &de)) { 94 int parent_logstart = fat_get_start(MSDOS_SB(sb), de); 95 parent_inode = fat_dget(sb, parent_logstart); 96 } 97 brelse(bh); 98 99 return d_obtain_alias(parent_inode); 100 } 101