1// SPDX-License-Identifier: GPL-2.0-only
  2/* fs/fat/nfs.c
  3 */
  4
  5#include <linux/exportfs.h>
  6#include "fat.h"
  7
  8struct fat_fid {
  9	u32 i_gen;
 10	u32 i_pos_low;
 11	u16 i_pos_hi;
 12	u16 parent_i_pos_hi;
 13	u32 parent_i_pos_low;
 14	u32 parent_i_gen;
 15};
 16
 17#define FAT_FID_SIZE_WITHOUT_PARENT 3
 18#define FAT_FID_SIZE_WITH_PARENT (sizeof(struct fat_fid)/sizeof(u32))
 19
 20/**
 21 * Look up a directory inode given its starting cluster.
 22 */
 23static struct inode *fat_dget(struct super_block *sb, int i_logstart)
 24{
 25	struct msdos_sb_info *sbi = MSDOS_SB(sb);
 26	struct hlist_head *head;
 27	struct msdos_inode_info *i;
 28	struct inode *inode = NULL;
 29
 30	head = sbi->dir_hashtable + fat_dir_hash(i_logstart);
 31	spin_lock(&sbi->dir_hash_lock);
 32	hlist_for_each_entry(i, head, i_dir_hash) {
 33		BUG_ON(i->vfs_inode.i_sb != sb);
 34		if (i->i_logstart != i_logstart)
 35			continue;
 36		inode = igrab(&i->vfs_inode);
 37		if (inode)
 38			break;
 39	}
 40	spin_unlock(&sbi->dir_hash_lock);
 41	return inode;
 42}
 43
 44static struct inode *fat_ilookup(struct super_block *sb, u64 ino, loff_t i_pos)
 45{
 46	if (MSDOS_SB(sb)->options.nfs == FAT_NFS_NOSTALE_RO)
 47		return fat_iget(sb, i_pos);
 48
 49	else {
 50		if ((ino < MSDOS_ROOT_INO) || (ino == MSDOS_FSINFO_INO))
 51			return NULL;
 52		return ilookup(sb, ino);
 53	}
 54}
 55
 56static struct inode *__fat_nfs_get_inode(struct super_block *sb,
 57				       u64 ino, u32 generation, loff_t i_pos)
 58{
 59	struct inode *inode = fat_ilookup(sb, ino, i_pos);
 60
 61	if (inode && generation && (inode->i_generation != generation)) {
 62		iput(inode);
 63		inode = NULL;
 64	}
 65	if (inode == NULL && MSDOS_SB(sb)->options.nfs == FAT_NFS_NOSTALE_RO) {
 66		struct buffer_head *bh = NULL;
 67		struct msdos_dir_entry *de ;
 68		sector_t blocknr;
 69		int offset;
 70		fat_get_blknr_offset(MSDOS_SB(sb), i_pos, &blocknr, &offset);
 71		bh = sb_bread(sb, blocknr);
 72		if (!bh) {
 73			fat_msg(sb, KERN_ERR,
 74				"unable to read block(%llu) for building NFS inode",
 75				(llu)blocknr);
 76			return inode;
 77		}
 78		de = (struct msdos_dir_entry *)bh->b_data;
 79		/* If a file is deleted on server and client is not updated
 80		 * yet, we must not build the inode upon a lookup call.
 81		 */
 82		if (IS_FREE(de[offset].name))
 83			inode = NULL;
 84		else
 85			inode = fat_build_inode(sb, &de[offset], i_pos);
 86		brelse(bh);
 87	}
 88
 89	return inode;
 90}
 91
 92static struct inode *fat_nfs_get_inode(struct super_block *sb,
 93				       u64 ino, u32 generation)
 94{
 95
 96	return __fat_nfs_get_inode(sb, ino, generation, 0);
 97}
 98
 99static int
100fat_encode_fh_nostale(struct inode *inode, __u32 *fh, int *lenp,
101		      struct inode *parent)
102{
103	int len = *lenp;
104	struct msdos_sb_info *sbi = MSDOS_SB(inode->i_sb);
105	struct fat_fid *fid = (struct fat_fid *) fh;
106	loff_t i_pos;
107	int type = FILEID_FAT_WITHOUT_PARENT;
108
109	if (parent) {
110		if (len < FAT_FID_SIZE_WITH_PARENT) {
111			*lenp = FAT_FID_SIZE_WITH_PARENT;
112			return FILEID_INVALID;
113		}
114	} else {
115		if (len < FAT_FID_SIZE_WITHOUT_PARENT) {
116			*lenp = FAT_FID_SIZE_WITHOUT_PARENT;
117			return FILEID_INVALID;
118		}
119	}
120
121	i_pos = fat_i_pos_read(sbi, inode);
122	*lenp = FAT_FID_SIZE_WITHOUT_PARENT;
123	fid->i_gen = inode->i_generation;
124	fid->i_pos_low = i_pos & 0xFFFFFFFF;
125	fid->i_pos_hi = (i_pos >> 32) & 0xFFFF;
126	if (parent) {
127		i_pos = fat_i_pos_read(sbi, parent);
128		fid->parent_i_pos_hi = (i_pos >> 32) & 0xFFFF;
129		fid->parent_i_pos_low = i_pos & 0xFFFFFFFF;
130		fid->parent_i_gen = parent->i_generation;
131		type = FILEID_FAT_WITH_PARENT;
132		*lenp = FAT_FID_SIZE_WITH_PARENT;
133	}
134
135	return type;
136}
137
138/**
139 * Map a NFS file handle to a corresponding dentry.
140 * The dentry may or may not be connected to the filesystem root.
141 */
142static struct dentry *fat_fh_to_dentry(struct super_block *sb, struct fid *fid,
143				int fh_len, int fh_type)
144{
145	return generic_fh_to_dentry(sb, fid, fh_len, fh_type,
146				    fat_nfs_get_inode);
147}
148
149static struct dentry *fat_fh_to_dentry_nostale(struct super_block *sb,
150					       struct fid *fh, int fh_len,
151					       int fh_type)
152{
153	struct inode *inode = NULL;
154	struct fat_fid *fid = (struct fat_fid *)fh;
155	loff_t i_pos;
156
157	switch (fh_type) {
158	case FILEID_FAT_WITHOUT_PARENT:
159		if (fh_len < FAT_FID_SIZE_WITHOUT_PARENT)
160			return NULL;
161		break;
162	case FILEID_FAT_WITH_PARENT:
163		if (fh_len < FAT_FID_SIZE_WITH_PARENT)
164			return NULL;
165		break;
166	default:
167		return NULL;
168	}
169	i_pos = fid->i_pos_hi;
170	i_pos = (i_pos << 32) | (fid->i_pos_low);
171	inode = __fat_nfs_get_inode(sb, 0, fid->i_gen, i_pos);
172
173	return d_obtain_alias(inode);
174}
175
176/*
177 * Find the parent for a file specified by NFS handle.
178 * This requires that the handle contain the i_ino of the parent.
179 */
180static struct dentry *fat_fh_to_parent(struct super_block *sb, struct fid *fid,
181				int fh_len, int fh_type)
182{
183	return generic_fh_to_parent(sb, fid, fh_len, fh_type,
184				    fat_nfs_get_inode);
185}
186
187static struct dentry *fat_fh_to_parent_nostale(struct super_block *sb,
188					       struct fid *fh, int fh_len,
189					       int fh_type)
190{
191	struct inode *inode = NULL;
192	struct fat_fid *fid = (struct fat_fid *)fh;
193	loff_t i_pos;
194
195	if (fh_len < FAT_FID_SIZE_WITH_PARENT)
196		return NULL;
197
198	switch (fh_type) {
199	case FILEID_FAT_WITH_PARENT:
200		i_pos = fid->parent_i_pos_hi;
201		i_pos = (i_pos << 32) | (fid->parent_i_pos_low);
202		inode = __fat_nfs_get_inode(sb, 0, fid->parent_i_gen, i_pos);
203		break;
204	}
205
206	return d_obtain_alias(inode);
207}
208
209/*
210 * Rebuild the parent for a directory that is not connected
211 *  to the filesystem root
212 */
213static
214struct inode *fat_rebuild_parent(struct super_block *sb, int parent_logstart)
215{
216	int search_clus, clus_to_match;
217	struct msdos_dir_entry *de;
218	struct inode *parent = NULL;
219	struct inode *dummy_grand_parent = NULL;
220	struct fat_slot_info sinfo;
221	struct msdos_sb_info *sbi = MSDOS_SB(sb);
222	sector_t blknr = fat_clus_to_blknr(sbi, parent_logstart);
223	struct buffer_head *parent_bh = sb_bread(sb, blknr);
224	if (!parent_bh) {
225		fat_msg(sb, KERN_ERR,
226			"unable to read cluster of parent directory");
227		return NULL;
228	}
229
230	de = (struct msdos_dir_entry *) parent_bh->b_data;
231	clus_to_match = fat_get_start(sbi, &de[0]);
232	search_clus = fat_get_start(sbi, &de[1]);
233
234	dummy_grand_parent = fat_dget(sb, search_clus);
235	if (!dummy_grand_parent) {
236		dummy_grand_parent = new_inode(sb);
237		if (!dummy_grand_parent) {
238			brelse(parent_bh);
239			return parent;
240		}
241
242		dummy_grand_parent->i_ino = iunique(sb, MSDOS_ROOT_INO);
243		fat_fill_inode(dummy_grand_parent, &de[1]);
244		MSDOS_I(dummy_grand_parent)->i_pos = -1;
245	}
246
247	if (!fat_scan_logstart(dummy_grand_parent, clus_to_match, &sinfo))
248		parent = fat_build_inode(sb, sinfo.de, sinfo.i_pos);
249
250	brelse(parent_bh);
251	iput(dummy_grand_parent);
252
253	return parent;
254}
255
256/*
257 * Find the parent for a directory that is not currently connected to
258 * the filesystem root.
259 *
260 * On entry, the caller holds d_inode(child_dir)->i_mutex.
261 */
262static struct dentry *fat_get_parent(struct dentry *child_dir)
263{
264	struct super_block *sb = child_dir->d_sb;
265	struct buffer_head *bh = NULL;
266	struct msdos_dir_entry *de;
267	struct inode *parent_inode = NULL;
268	struct msdos_sb_info *sbi = MSDOS_SB(sb);
269
270	if (!fat_get_dotdot_entry(d_inode(child_dir), &bh, &de)) {
271		int parent_logstart = fat_get_start(sbi, de);
272		parent_inode = fat_dget(sb, parent_logstart);
273		if (!parent_inode && sbi->options.nfs == FAT_NFS_NOSTALE_RO)
274			parent_inode = fat_rebuild_parent(sb, parent_logstart);
275	}
276	brelse(bh);
277
278	return d_obtain_alias(parent_inode);
279}
280
281const struct export_operations fat_export_ops = {
282	.fh_to_dentry   = fat_fh_to_dentry,
283	.fh_to_parent   = fat_fh_to_parent,
284	.get_parent     = fat_get_parent,
285};
286
287const struct export_operations fat_export_ops_nostale = {
288	.encode_fh      = fat_encode_fh_nostale,
289	.fh_to_dentry   = fat_fh_to_dentry_nostale,
290	.fh_to_parent   = fat_fh_to_parent_nostale,
291	.get_parent     = fat_get_parent,
292};

  1// SPDX-License-Identifier: GPL-2.0-only
  2/* fs/fat/nfs.c
  3 */
  4
  5#include <linux/exportfs.h>
  6#include "fat.h"
  7
  8struct fat_fid {
  9	u32 i_gen;
 10	u32 i_pos_low;
 11	u16 i_pos_hi;
 12	u16 parent_i_pos_hi;
 13	u32 parent_i_pos_low;
 14	u32 parent_i_gen;
 15};
 16
 17#define FAT_FID_SIZE_WITHOUT_PARENT 3
 18#define FAT_FID_SIZE_WITH_PARENT (sizeof(struct fat_fid)/sizeof(u32))
 19
 20/**
 21 * Look up a directory inode given its starting cluster.
 22 */
 23static struct inode *fat_dget(struct super_block *sb, int i_logstart)
 24{
 25	struct msdos_sb_info *sbi = MSDOS_SB(sb);
 26	struct hlist_head *head;
 27	struct msdos_inode_info *i;
 28	struct inode *inode = NULL;
 29
 30	head = sbi->dir_hashtable + fat_dir_hash(i_logstart);
 31	spin_lock(&sbi->dir_hash_lock);
 32	hlist_for_each_entry(i, head, i_dir_hash) {
 33		BUG_ON(i->vfs_inode.i_sb != sb);
 34		if (i->i_logstart != i_logstart)
 35			continue;
 36		inode = igrab(&i->vfs_inode);
 37		if (inode)
 38			break;
 39	}
 40	spin_unlock(&sbi->dir_hash_lock);
 41	return inode;
 42}
 43
 44static struct inode *fat_ilookup(struct super_block *sb, u64 ino, loff_t i_pos)
 45{
 46	if (MSDOS_SB(sb)->options.nfs == FAT_NFS_NOSTALE_RO)
 47		return fat_iget(sb, i_pos);
 48
 49	else {
 50		if ((ino < MSDOS_ROOT_INO) || (ino == MSDOS_FSINFO_INO))
 51			return NULL;
 52		return ilookup(sb, ino);
 53	}
 54}
 55
 56static struct inode *__fat_nfs_get_inode(struct super_block *sb,
 57				       u64 ino, u32 generation, loff_t i_pos)
 58{
 59	struct inode *inode = fat_ilookup(sb, ino, i_pos);
 60
 61	if (inode && generation && (inode->i_generation != generation)) {
 62		iput(inode);
 63		inode = NULL;
 64	}
 65	if (inode == NULL && MSDOS_SB(sb)->options.nfs == FAT_NFS_NOSTALE_RO) {
 66		struct buffer_head *bh = NULL;
 67		struct msdos_dir_entry *de ;
 68		sector_t blocknr;
 69		int offset;
 70		fat_get_blknr_offset(MSDOS_SB(sb), i_pos, &blocknr, &offset);
 71		bh = sb_bread(sb, blocknr);
 72		if (!bh) {
 73			fat_msg(sb, KERN_ERR,
 74				"unable to read block(%llu) for building NFS inode",
 75				(llu)blocknr);
 76			return inode;
 77		}
 78		de = (struct msdos_dir_entry *)bh->b_data;
 79		/* If a file is deleted on server and client is not updated
 80		 * yet, we must not build the inode upon a lookup call.
 81		 */
 82		if (IS_FREE(de[offset].name))
 83			inode = NULL;
 84		else
 85			inode = fat_build_inode(sb, &de[offset], i_pos);
 86		brelse(bh);
 87	}
 88
 89	return inode;
 90}
 91
 92static struct inode *fat_nfs_get_inode(struct super_block *sb,
 93				       u64 ino, u32 generation)
 94{
 95
 96	return __fat_nfs_get_inode(sb, ino, generation, 0);
 97}
 98
 99static int
100fat_encode_fh_nostale(struct inode *inode, __u32 *fh, int *lenp,
101		      struct inode *parent)
102{
103	int len = *lenp;
104	struct msdos_sb_info *sbi = MSDOS_SB(inode->i_sb);
105	struct fat_fid *fid = (struct fat_fid *) fh;
106	loff_t i_pos;
107	int type = FILEID_FAT_WITHOUT_PARENT;
108
109	if (parent) {
110		if (len < FAT_FID_SIZE_WITH_PARENT) {
111			*lenp = FAT_FID_SIZE_WITH_PARENT;
112			return FILEID_INVALID;
113		}
114	} else {
115		if (len < FAT_FID_SIZE_WITHOUT_PARENT) {
116			*lenp = FAT_FID_SIZE_WITHOUT_PARENT;
117			return FILEID_INVALID;
118		}
119	}
120
121	i_pos = fat_i_pos_read(sbi, inode);
122	*lenp = FAT_FID_SIZE_WITHOUT_PARENT;
123	fid->i_gen = inode->i_generation;
124	fid->i_pos_low = i_pos & 0xFFFFFFFF;
125	fid->i_pos_hi = (i_pos >> 32) & 0xFFFF;
126	if (parent) {
127		i_pos = fat_i_pos_read(sbi, parent);
128		fid->parent_i_pos_hi = (i_pos >> 32) & 0xFFFF;
129		fid->parent_i_pos_low = i_pos & 0xFFFFFFFF;
130		fid->parent_i_gen = parent->i_generation;
131		type = FILEID_FAT_WITH_PARENT;
132		*lenp = FAT_FID_SIZE_WITH_PARENT;
133	}
134
135	return type;
136}
137
138/**
139 * Map a NFS file handle to a corresponding dentry.
140 * The dentry may or may not be connected to the filesystem root.
141 */
142static struct dentry *fat_fh_to_dentry(struct super_block *sb, struct fid *fid,
143				int fh_len, int fh_type)
144{
145	return generic_fh_to_dentry(sb, fid, fh_len, fh_type,
146				    fat_nfs_get_inode);
147}
148
149static struct dentry *fat_fh_to_dentry_nostale(struct super_block *sb,
150					       struct fid *fh, int fh_len,
151					       int fh_type)
152{
153	struct inode *inode = NULL;
154	struct fat_fid *fid = (struct fat_fid *)fh;
155	loff_t i_pos;
156
157	switch (fh_type) {
158	case FILEID_FAT_WITHOUT_PARENT:
159		if (fh_len < FAT_FID_SIZE_WITHOUT_PARENT)
160			return NULL;
161		break;
162	case FILEID_FAT_WITH_PARENT:
163		if (fh_len < FAT_FID_SIZE_WITH_PARENT)
164			return NULL;
165		break;
166	default:
167		return NULL;
168	}
169	i_pos = fid->i_pos_hi;
170	i_pos = (i_pos << 32) | (fid->i_pos_low);
171	inode = __fat_nfs_get_inode(sb, 0, fid->i_gen, i_pos);
172
173	return d_obtain_alias(inode);
174}
175
176/*
177 * Find the parent for a file specified by NFS handle.
178 * This requires that the handle contain the i_ino of the parent.
179 */
180static struct dentry *fat_fh_to_parent(struct super_block *sb, struct fid *fid,
181				int fh_len, int fh_type)
182{
183	return generic_fh_to_parent(sb, fid, fh_len, fh_type,
184				    fat_nfs_get_inode);
185}
186
187static struct dentry *fat_fh_to_parent_nostale(struct super_block *sb,
188					       struct fid *fh, int fh_len,
189					       int fh_type)
190{
191	struct inode *inode = NULL;
192	struct fat_fid *fid = (struct fat_fid *)fh;
193	loff_t i_pos;
194
195	if (fh_len < FAT_FID_SIZE_WITH_PARENT)
196		return NULL;
197
198	switch (fh_type) {
199	case FILEID_FAT_WITH_PARENT:
200		i_pos = fid->parent_i_pos_hi;
201		i_pos = (i_pos << 32) | (fid->parent_i_pos_low);
202		inode = __fat_nfs_get_inode(sb, 0, fid->parent_i_gen, i_pos);
203		break;
204	}
205
206	return d_obtain_alias(inode);
207}
208
209/*
210 * Rebuild the parent for a directory that is not connected
211 *  to the filesystem root
212 */
213static
214struct inode *fat_rebuild_parent(struct super_block *sb, int parent_logstart)
215{
216	int search_clus, clus_to_match;
217	struct msdos_dir_entry *de;
218	struct inode *parent = NULL;
219	struct inode *dummy_grand_parent = NULL;
220	struct fat_slot_info sinfo;
221	struct msdos_sb_info *sbi = MSDOS_SB(sb);
222	sector_t blknr = fat_clus_to_blknr(sbi, parent_logstart);
223	struct buffer_head *parent_bh = sb_bread(sb, blknr);
224	if (!parent_bh) {
225		fat_msg(sb, KERN_ERR,
226			"unable to read cluster of parent directory");
227		return NULL;
228	}
229
230	de = (struct msdos_dir_entry *) parent_bh->b_data;
231	clus_to_match = fat_get_start(sbi, &de[0]);
232	search_clus = fat_get_start(sbi, &de[1]);
233
234	dummy_grand_parent = fat_dget(sb, search_clus);
235	if (!dummy_grand_parent) {
236		dummy_grand_parent = new_inode(sb);
237		if (!dummy_grand_parent) {
238			brelse(parent_bh);
239			return parent;
240		}
241
242		dummy_grand_parent->i_ino = iunique(sb, MSDOS_ROOT_INO);
243		fat_fill_inode(dummy_grand_parent, &de[1]);
244		MSDOS_I(dummy_grand_parent)->i_pos = -1;
245	}
246
247	if (!fat_scan_logstart(dummy_grand_parent, clus_to_match, &sinfo))
248		parent = fat_build_inode(sb, sinfo.de, sinfo.i_pos);
249
250	brelse(parent_bh);
251	iput(dummy_grand_parent);
252
253	return parent;
254}
255
256/*
257 * Find the parent for a directory that is not currently connected to
258 * the filesystem root.
259 *
260 * On entry, the caller holds d_inode(child_dir)->i_mutex.
261 */
262static struct dentry *fat_get_parent(struct dentry *child_dir)
263{
264	struct super_block *sb = child_dir->d_sb;
265	struct buffer_head *bh = NULL;
266	struct msdos_dir_entry *de;
267	struct inode *parent_inode = NULL;
268	struct msdos_sb_info *sbi = MSDOS_SB(sb);
269
270	if (!fat_get_dotdot_entry(d_inode(child_dir), &bh, &de)) {
271		int parent_logstart = fat_get_start(sbi, de);
272		parent_inode = fat_dget(sb, parent_logstart);
273		if (!parent_inode && sbi->options.nfs == FAT_NFS_NOSTALE_RO)
274			parent_inode = fat_rebuild_parent(sb, parent_logstart);
275	}
276	brelse(bh);
277
278	return d_obtain_alias(parent_inode);
279}
280
281const struct export_operations fat_export_ops = {
282	.fh_to_dentry   = fat_fh_to_dentry,
283	.fh_to_parent   = fat_fh_to_parent,
284	.get_parent     = fat_get_parent,
285};
286
287const struct export_operations fat_export_ops_nostale = {
288	.encode_fh      = fat_encode_fh_nostale,
289	.fh_to_dentry   = fat_fh_to_dentry_nostale,
290	.fh_to_parent   = fat_fh_to_parent_nostale,
291	.get_parent     = fat_get_parent,
292};