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Linux/fs/freevxfs/vxfs_lookup.c

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  1 /*
  2  * Copyright (c) 2000-2001 Christoph Hellwig.
  3  * All rights reserved.
  4  *
  5  * Redistribution and use in source and binary forms, with or without
  6  * modification, are permitted provided that the following conditions
  7  * are met:
  8  * 1. Redistributions of source code must retain the above copyright
  9  *    notice, this list of conditions, and the following disclaimer,
 10  *    without modification.
 11  * 2. The name of the author may not be used to endorse or promote products
 12  *    derived from this software without specific prior written permission.
 13  *
 14  * Alternatively, this software may be distributed under the terms of the
 15  * GNU General Public License ("GPL").
 16  *
 17  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
 18  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 19  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 20  * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE FOR
 21  * ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 22  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 23  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 24  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 25  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 26  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 27  * SUCH DAMAGE.
 28  */
 29 
 30 /*
 31  * Veritas filesystem driver - lookup and other directory related code.
 32  */
 33 #include <linux/fs.h>
 34 #include <linux/time.h>
 35 #include <linux/mm.h>
 36 #include <linux/highmem.h>
 37 #include <linux/kernel.h>
 38 #include <linux/pagemap.h>
 39 
 40 #include "vxfs.h"
 41 #include "vxfs_dir.h"
 42 #include "vxfs_inode.h"
 43 #include "vxfs_extern.h"
 44 
 45 /*
 46  * Number of VxFS blocks per page.
 47  */
 48 #define VXFS_BLOCK_PER_PAGE(sbp)  ((PAGE_CACHE_SIZE / (sbp)->s_blocksize))
 49 
 50 
 51 static struct dentry *  vxfs_lookup(struct inode *, struct dentry *, unsigned int);
 52 static int              vxfs_readdir(struct file *, struct dir_context *);
 53 
 54 const struct inode_operations vxfs_dir_inode_ops = {
 55         .lookup =               vxfs_lookup,
 56 };
 57 
 58 const struct file_operations vxfs_dir_operations = {
 59         .llseek =               generic_file_llseek,
 60         .read =                 generic_read_dir,
 61         .iterate =              vxfs_readdir,
 62 };
 63 
 64  
 65 static inline u_long
 66 dir_pages(struct inode *inode)
 67 {
 68         return (inode->i_size + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
 69 }
 70  
 71 static inline u_long
 72 dir_blocks(struct inode *ip)
 73 {
 74         u_long                  bsize = ip->i_sb->s_blocksize;
 75         return (ip->i_size + bsize - 1) & ~(bsize - 1);
 76 }
 77 
 78 /*
 79  * NOTE! unlike strncmp, vxfs_match returns 1 for success, 0 for failure.
 80  *
 81  * len <= VXFS_NAMELEN and de != NULL are guaranteed by caller.
 82  */
 83 static inline int
 84 vxfs_match(int len, const char * const name, struct vxfs_direct *de)
 85 {
 86         if (len != de->d_namelen)
 87                 return 0;
 88         if (!de->d_ino)
 89                 return 0;
 90         return !memcmp(name, de->d_name, len);
 91 }
 92 
 93 static inline struct vxfs_direct *
 94 vxfs_next_entry(struct vxfs_direct *de)
 95 {
 96         return ((struct vxfs_direct *)((char*)de + de->d_reclen));
 97 }
 98 
 99 /**
100  * vxfs_find_entry - find a mathing directory entry for a dentry
101  * @ip:         directory inode
102  * @dp:         dentry for which we want to find a direct
103  * @ppp:        gets filled with the page the return value sits in
104  *
105  * Description:
106  *   vxfs_find_entry finds a &struct vxfs_direct for the VFS directory
107  *   cache entry @dp.  @ppp will be filled with the page the return
108  *   value resides in.
109  *
110  * Returns:
111  *   The wanted direct on success, else a NULL pointer.
112  */
113 static struct vxfs_direct *
114 vxfs_find_entry(struct inode *ip, struct dentry *dp, struct page **ppp)
115 {
116         u_long                          npages, page, nblocks, pblocks, block;
117         u_long                          bsize = ip->i_sb->s_blocksize;
118         const char                      *name = dp->d_name.name;
119         int                             namelen = dp->d_name.len;
120 
121         npages = dir_pages(ip);
122         nblocks = dir_blocks(ip);
123         pblocks = VXFS_BLOCK_PER_PAGE(ip->i_sb);
124         
125         for (page = 0; page < npages; page++) {
126                 caddr_t                 kaddr;
127                 struct page             *pp;
128 
129                 pp = vxfs_get_page(ip->i_mapping, page);
130                 if (IS_ERR(pp))
131                         continue;
132                 kaddr = (caddr_t)page_address(pp);
133 
134                 for (block = 0; block <= nblocks && block <= pblocks; block++) {
135                         caddr_t                 baddr, limit;
136                         struct vxfs_dirblk      *dbp;
137                         struct vxfs_direct      *de;
138 
139                         baddr = kaddr + (block * bsize);
140                         limit = baddr + bsize - VXFS_DIRLEN(1);
141                         
142                         dbp = (struct vxfs_dirblk *)baddr;
143                         de = (struct vxfs_direct *)(baddr + VXFS_DIRBLKOV(dbp));
144 
145                         for (; (caddr_t)de <= limit; de = vxfs_next_entry(de)) {
146                                 if (!de->d_reclen)
147                                         break;
148                                 if (!de->d_ino)
149                                         continue;
150                                 if (vxfs_match(namelen, name, de)) {
151                                         *ppp = pp;
152                                         return (de);
153                                 }
154                         }
155                 }
156                 vxfs_put_page(pp);
157         }
158 
159         return NULL;
160 }
161 
162 /**
163  * vxfs_inode_by_name - find inode number for dentry
164  * @dip:        directory to search in
165  * @dp:         dentry we search for
166  *
167  * Description:
168  *   vxfs_inode_by_name finds out the inode number of
169  *   the path component described by @dp in @dip.
170  *
171  * Returns:
172  *   The wanted inode number on success, else Zero.
173  */
174 static ino_t
175 vxfs_inode_by_name(struct inode *dip, struct dentry *dp)
176 {
177         struct vxfs_direct              *de;
178         struct page                     *pp;
179         ino_t                           ino = 0;
180 
181         de = vxfs_find_entry(dip, dp, &pp);
182         if (de) {
183                 ino = de->d_ino;
184                 kunmap(pp);
185                 page_cache_release(pp);
186         }
187         
188         return (ino);
189 }
190 
191 /**
192  * vxfs_lookup - lookup pathname component
193  * @dip:        dir in which we lookup
194  * @dp:         dentry we lookup
195  * @nd:         lookup nameidata
196  *
197  * Description:
198  *   vxfs_lookup tries to lookup the pathname component described
199  *   by @dp in @dip.
200  *
201  * Returns:
202  *   A NULL-pointer on success, else an negative error code encoded
203  *   in the return pointer.
204  */
205 static struct dentry *
206 vxfs_lookup(struct inode *dip, struct dentry *dp, unsigned int flags)
207 {
208         struct inode            *ip = NULL;
209         ino_t                   ino;
210                          
211         if (dp->d_name.len > VXFS_NAMELEN)
212                 return ERR_PTR(-ENAMETOOLONG);
213                                  
214         ino = vxfs_inode_by_name(dip, dp);
215         if (ino) {
216                 ip = vxfs_iget(dip->i_sb, ino);
217                 if (IS_ERR(ip))
218                         return ERR_CAST(ip);
219         }
220         d_add(dp, ip);
221         return NULL;
222 }
223 
224 /**
225  * vxfs_readdir - read a directory
226  * @fp:         the directory to read
227  * @retp:       return buffer
228  * @filler:     filldir callback
229  *
230  * Description:
231  *   vxfs_readdir fills @retp with directory entries from @fp
232  *   using the VFS supplied callback @filler.
233  *
234  * Returns:
235  *   Zero.
236  */
237 static int
238 vxfs_readdir(struct file *fp, struct dir_context *ctx)
239 {
240         struct inode            *ip = file_inode(fp);
241         struct super_block      *sbp = ip->i_sb;
242         u_long                  bsize = sbp->s_blocksize;
243         u_long                  page, npages, block, pblocks, nblocks, offset;
244         loff_t                  pos;
245 
246         if (ctx->pos == 0) {
247                 if (!dir_emit_dot(fp, ctx))
248                         return 0;
249                 ctx->pos = 1;
250         }
251         if (ctx->pos == 1) {
252                 if (!dir_emit(ctx, "..", 2, VXFS_INO(ip)->vii_dotdot, DT_DIR))
253                         return 0;
254                 ctx->pos = 2;
255         }
256         pos = ctx->pos - 2;
257         
258         if (pos > VXFS_DIRROUND(ip->i_size))
259                 return 0;
260 
261         npages = dir_pages(ip);
262         nblocks = dir_blocks(ip);
263         pblocks = VXFS_BLOCK_PER_PAGE(sbp);
264 
265         page = pos >> PAGE_CACHE_SHIFT;
266         offset = pos & ~PAGE_CACHE_MASK;
267         block = (u_long)(pos >> sbp->s_blocksize_bits) % pblocks;
268 
269         for (; page < npages; page++, block = 0) {
270                 char                    *kaddr;
271                 struct page             *pp;
272 
273                 pp = vxfs_get_page(ip->i_mapping, page);
274                 if (IS_ERR(pp))
275                         continue;
276                 kaddr = (char *)page_address(pp);
277 
278                 for (; block <= nblocks && block <= pblocks; block++) {
279                         char                    *baddr, *limit;
280                         struct vxfs_dirblk      *dbp;
281                         struct vxfs_direct      *de;
282 
283                         baddr = kaddr + (block * bsize);
284                         limit = baddr + bsize - VXFS_DIRLEN(1);
285         
286                         dbp = (struct vxfs_dirblk *)baddr;
287                         de = (struct vxfs_direct *)
288                                 (offset ?
289                                  (kaddr + offset) :
290                                  (baddr + VXFS_DIRBLKOV(dbp)));
291 
292                         for (; (char *)de <= limit; de = vxfs_next_entry(de)) {
293                                 if (!de->d_reclen)
294                                         break;
295                                 if (!de->d_ino)
296                                         continue;
297 
298                                 offset = (char *)de - kaddr;
299                                 ctx->pos = ((page << PAGE_CACHE_SHIFT) | offset) + 2;
300                                 if (!dir_emit(ctx, de->d_name, de->d_namelen,
301                                         de->d_ino, DT_UNKNOWN)) {
302                                         vxfs_put_page(pp);
303                                         return 0;
304                                 }
305                         }
306                         offset = 0;
307                 }
308                 vxfs_put_page(pp);
309                 offset = 0;
310         }
311         ctx->pos = ((page << PAGE_CACHE_SHIFT) | offset) + 2;
312         return 0;
313 }
314 

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