Root/fs/ntfs/namei.c

1/*
2 * namei.c - NTFS kernel directory inode operations. Part of the Linux-NTFS
3 * project.
4 *
5 * Copyright (c) 2001-2006 Anton Altaparmakov
6 *
7 * This program/include file is free software; you can redistribute it and/or
8 * modify it under the terms of the GNU General Public License as published
9 * by the Free Software Foundation; either version 2 of the License, or
10 * (at your option) any later version.
11 *
12 * This program/include file is distributed in the hope that it will be
13 * useful, but WITHOUT ANY WARRANTY; without even the implied warranty
14 * of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
15 * GNU General Public License for more details.
16 *
17 * You should have received a copy of the GNU General Public License
18 * along with this program (in the main directory of the Linux-NTFS
19 * distribution in the file COPYING); if not, write to the Free Software
20 * Foundation,Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
21 */
22
23#include <linux/dcache.h>
24#include <linux/exportfs.h>
25#include <linux/security.h>
26#include <linux/slab.h>
27
28#include "attrib.h"
29#include "debug.h"
30#include "dir.h"
31#include "mft.h"
32#include "ntfs.h"
33
34/**
35 * ntfs_lookup - find the inode represented by a dentry in a directory inode
36 * @dir_ino: directory inode in which to look for the inode
37 * @dent: dentry representing the inode to look for
38 * @nd: lookup nameidata
39 *
40 * In short, ntfs_lookup() looks for the inode represented by the dentry @dent
41 * in the directory inode @dir_ino and if found attaches the inode to the
42 * dentry @dent.
43 *
44 * In more detail, the dentry @dent specifies which inode to look for by
45 * supplying the name of the inode in @dent->d_name.name. ntfs_lookup()
46 * converts the name to Unicode and walks the contents of the directory inode
47 * @dir_ino looking for the converted Unicode name. If the name is found in the
48 * directory, the corresponding inode is loaded by calling ntfs_iget() on its
49 * inode number and the inode is associated with the dentry @dent via a call to
50 * d_splice_alias().
51 *
52 * If the name is not found in the directory, a NULL inode is inserted into the
53 * dentry @dent via a call to d_add(). The dentry is then termed a negative
54 * dentry.
55 *
56 * Only if an actual error occurs, do we return an error via ERR_PTR().
57 *
58 * In order to handle the case insensitivity issues of NTFS with regards to the
59 * dcache and the dcache requiring only one dentry per directory, we deal with
60 * dentry aliases that only differ in case in ->ntfs_lookup() while maintaining
61 * a case sensitive dcache. This means that we get the full benefit of dcache
62 * speed when the file/directory is looked up with the same case as returned by
63 * ->ntfs_readdir() but that a lookup for any other case (or for the short file
64 * name) will not find anything in dcache and will enter ->ntfs_lookup()
65 * instead, where we search the directory for a fully matching file name
66 * (including case) and if that is not found, we search for a file name that
67 * matches with different case and if that has non-POSIX semantics we return
68 * that. We actually do only one search (case sensitive) and keep tabs on
69 * whether we have found a case insensitive match in the process.
70 *
71 * To simplify matters for us, we do not treat the short vs long filenames as
72 * two hard links but instead if the lookup matches a short filename, we
73 * return the dentry for the corresponding long filename instead.
74 *
75 * There are three cases we need to distinguish here:
76 *
77 * 1) @dent perfectly matches (i.e. including case) a directory entry with a
78 * file name in the WIN32 or POSIX namespaces. In this case
79 * ntfs_lookup_inode_by_name() will return with name set to NULL and we
80 * just d_splice_alias() @dent.
81 * 2) @dent matches (not including case) a directory entry with a file name in
82 * the WIN32 namespace. In this case ntfs_lookup_inode_by_name() will return
83 * with name set to point to a kmalloc()ed ntfs_name structure containing
84 * the properly cased little endian Unicode name. We convert the name to the
85 * current NLS code page, search if a dentry with this name already exists
86 * and if so return that instead of @dent. At this point things are
87 * complicated by the possibility of 'disconnected' dentries due to NFS
88 * which we deal with appropriately (see the code comments). The VFS will
89 * then destroy the old @dent and use the one we returned. If a dentry is
90 * not found, we allocate a new one, d_splice_alias() it, and return it as
91 * above.
92 * 3) @dent matches either perfectly or not (i.e. we don't care about case) a
93 * directory entry with a file name in the DOS namespace. In this case
94 * ntfs_lookup_inode_by_name() will return with name set to point to a
95 * kmalloc()ed ntfs_name structure containing the mft reference (cpu endian)
96 * of the inode. We use the mft reference to read the inode and to find the
97 * file name in the WIN32 namespace corresponding to the matched short file
98 * name. We then convert the name to the current NLS code page, and proceed
99 * searching for a dentry with this name, etc, as in case 2), above.
100 *
101 * Locking: Caller must hold i_mutex on the directory.
102 */
103static struct dentry *ntfs_lookup(struct inode *dir_ino, struct dentry *dent,
104        struct nameidata *nd)
105{
106    ntfs_volume *vol = NTFS_SB(dir_ino->i_sb);
107    struct inode *dent_inode;
108    ntfschar *uname;
109    ntfs_name *name = NULL;
110    MFT_REF mref;
111    unsigned long dent_ino;
112    int uname_len;
113
114    ntfs_debug("Looking up %s in directory inode 0x%lx.",
115            dent->d_name.name, dir_ino->i_ino);
116    /* Convert the name of the dentry to Unicode. */
117    uname_len = ntfs_nlstoucs(vol, dent->d_name.name, dent->d_name.len,
118            &uname);
119    if (uname_len < 0) {
120        if (uname_len != -ENAMETOOLONG)
121            ntfs_error(vol->sb, "Failed to convert name to "
122                    "Unicode.");
123        return ERR_PTR(uname_len);
124    }
125    mref = ntfs_lookup_inode_by_name(NTFS_I(dir_ino), uname, uname_len,
126            &name);
127    kmem_cache_free(ntfs_name_cache, uname);
128    if (!IS_ERR_MREF(mref)) {
129        dent_ino = MREF(mref);
130        ntfs_debug("Found inode 0x%lx. Calling ntfs_iget.", dent_ino);
131        dent_inode = ntfs_iget(vol->sb, dent_ino);
132        if (likely(!IS_ERR(dent_inode))) {
133            /* Consistency check. */
134            if (is_bad_inode(dent_inode) || MSEQNO(mref) ==
135                    NTFS_I(dent_inode)->seq_no ||
136                    dent_ino == FILE_MFT) {
137                /* Perfect WIN32/POSIX match. -- Case 1. */
138                if (!name) {
139                    ntfs_debug("Done. (Case 1.)");
140                    return d_splice_alias(dent_inode, dent);
141                }
142                /*
143                 * We are too indented. Handle imperfect
144                 * matches and short file names further below.
145                 */
146                goto handle_name;
147            }
148            ntfs_error(vol->sb, "Found stale reference to inode "
149                    "0x%lx (reference sequence number = "
150                    "0x%x, inode sequence number = 0x%x), "
151                    "returning -EIO. Run chkdsk.",
152                    dent_ino, MSEQNO(mref),
153                    NTFS_I(dent_inode)->seq_no);
154            iput(dent_inode);
155            dent_inode = ERR_PTR(-EIO);
156        } else
157            ntfs_error(vol->sb, "ntfs_iget(0x%lx) failed with "
158                    "error code %li.", dent_ino,
159                    PTR_ERR(dent_inode));
160        kfree(name);
161        /* Return the error code. */
162        return (struct dentry *)dent_inode;
163    }
164    /* It is guaranteed that @name is no longer allocated at this point. */
165    if (MREF_ERR(mref) == -ENOENT) {
166        ntfs_debug("Entry was not found, adding negative dentry.");
167        /* The dcache will handle negative entries. */
168        d_add(dent, NULL);
169        ntfs_debug("Done.");
170        return NULL;
171    }
172    ntfs_error(vol->sb, "ntfs_lookup_ino_by_name() failed with error "
173            "code %i.", -MREF_ERR(mref));
174    return ERR_PTR(MREF_ERR(mref));
175    // TODO: Consider moving this lot to a separate function! (AIA)
176handle_name:
177   {
178    MFT_RECORD *m;
179    ntfs_attr_search_ctx *ctx;
180    ntfs_inode *ni = NTFS_I(dent_inode);
181    int err;
182    struct qstr nls_name;
183
184    nls_name.name = NULL;
185    if (name->type != FILE_NAME_DOS) { /* Case 2. */
186        ntfs_debug("Case 2.");
187        nls_name.len = (unsigned)ntfs_ucstonls(vol,
188                (ntfschar*)&name->name, name->len,
189                (unsigned char**)&nls_name.name, 0);
190        kfree(name);
191    } else /* if (name->type == FILE_NAME_DOS) */ { /* Case 3. */
192        FILE_NAME_ATTR *fn;
193
194        ntfs_debug("Case 3.");
195        kfree(name);
196
197        /* Find the WIN32 name corresponding to the matched DOS name. */
198        ni = NTFS_I(dent_inode);
199        m = map_mft_record(ni);
200        if (IS_ERR(m)) {
201            err = PTR_ERR(m);
202            m = NULL;
203            ctx = NULL;
204            goto err_out;
205        }
206        ctx = ntfs_attr_get_search_ctx(ni, m);
207        if (unlikely(!ctx)) {
208            err = -ENOMEM;
209            goto err_out;
210        }
211        do {
212            ATTR_RECORD *a;
213            u32 val_len;
214
215            err = ntfs_attr_lookup(AT_FILE_NAME, NULL, 0, 0, 0,
216                    NULL, 0, ctx);
217            if (unlikely(err)) {
218                ntfs_error(vol->sb, "Inode corrupt: No WIN32 "
219                        "namespace counterpart to DOS "
220                        "file name. Run chkdsk.");
221                if (err == -ENOENT)
222                    err = -EIO;
223                goto err_out;
224            }
225            /* Consistency checks. */
226            a = ctx->attr;
227            if (a->non_resident || a->flags)
228                goto eio_err_out;
229            val_len = le32_to_cpu(a->data.resident.value_length);
230            if (le16_to_cpu(a->data.resident.value_offset) +
231                    val_len > le32_to_cpu(a->length))
232                goto eio_err_out;
233            fn = (FILE_NAME_ATTR*)((u8*)ctx->attr + le16_to_cpu(
234                    ctx->attr->data.resident.value_offset));
235            if ((u32)(fn->file_name_length * sizeof(ntfschar) +
236                    sizeof(FILE_NAME_ATTR)) > val_len)
237                goto eio_err_out;
238        } while (fn->file_name_type != FILE_NAME_WIN32);
239
240        /* Convert the found WIN32 name to current NLS code page. */
241        nls_name.len = (unsigned)ntfs_ucstonls(vol,
242                (ntfschar*)&fn->file_name, fn->file_name_length,
243                (unsigned char**)&nls_name.name, 0);
244
245        ntfs_attr_put_search_ctx(ctx);
246        unmap_mft_record(ni);
247    }
248    m = NULL;
249    ctx = NULL;
250
251    /* Check if a conversion error occurred. */
252    if ((signed)nls_name.len < 0) {
253        err = (signed)nls_name.len;
254        goto err_out;
255    }
256    nls_name.hash = full_name_hash(nls_name.name, nls_name.len);
257
258    dent = d_add_ci(dent, dent_inode, &nls_name);
259    kfree(nls_name.name);
260    return dent;
261
262eio_err_out:
263    ntfs_error(vol->sb, "Illegal file name attribute. Run chkdsk.");
264    err = -EIO;
265err_out:
266    if (ctx)
267        ntfs_attr_put_search_ctx(ctx);
268    if (m)
269        unmap_mft_record(ni);
270    iput(dent_inode);
271    ntfs_error(vol->sb, "Failed, returning error code %i.", err);
272    return ERR_PTR(err);
273   }
274}
275
276/**
277 * Inode operations for directories.
278 */
279const struct inode_operations ntfs_dir_inode_ops = {
280    .lookup = ntfs_lookup, /* VFS: Lookup directory. */
281};
282
283/**
284 * ntfs_get_parent - find the dentry of the parent of a given directory dentry
285 * @child_dent: dentry of the directory whose parent directory to find
286 *
287 * Find the dentry for the parent directory of the directory specified by the
288 * dentry @child_dent. This function is called from
289 * fs/exportfs/expfs.c::find_exported_dentry() which in turn is called from the
290 * default ->decode_fh() which is export_decode_fh() in the same file.
291 *
292 * The code is based on the ext3 ->get_parent() implementation found in
293 * fs/ext3/namei.c::ext3_get_parent().
294 *
295 * Note: ntfs_get_parent() is called with @child_dent->d_inode->i_mutex down.
296 *
297 * Return the dentry of the parent directory on success or the error code on
298 * error (IS_ERR() is true).
299 */
300static struct dentry *ntfs_get_parent(struct dentry *child_dent)
301{
302    struct inode *vi = child_dent->d_inode;
303    ntfs_inode *ni = NTFS_I(vi);
304    MFT_RECORD *mrec;
305    ntfs_attr_search_ctx *ctx;
306    ATTR_RECORD *attr;
307    FILE_NAME_ATTR *fn;
308    unsigned long parent_ino;
309    int err;
310
311    ntfs_debug("Entering for inode 0x%lx.", vi->i_ino);
312    /* Get the mft record of the inode belonging to the child dentry. */
313    mrec = map_mft_record(ni);
314    if (IS_ERR(mrec))
315        return (struct dentry *)mrec;
316    /* Find the first file name attribute in the mft record. */
317    ctx = ntfs_attr_get_search_ctx(ni, mrec);
318    if (unlikely(!ctx)) {
319        unmap_mft_record(ni);
320        return ERR_PTR(-ENOMEM);
321    }
322try_next:
323    err = ntfs_attr_lookup(AT_FILE_NAME, NULL, 0, CASE_SENSITIVE, 0, NULL,
324            0, ctx);
325    if (unlikely(err)) {
326        ntfs_attr_put_search_ctx(ctx);
327        unmap_mft_record(ni);
328        if (err == -ENOENT)
329            ntfs_error(vi->i_sb, "Inode 0x%lx does not have a "
330                    "file name attribute. Run chkdsk.",
331                    vi->i_ino);
332        return ERR_PTR(err);
333    }
334    attr = ctx->attr;
335    if (unlikely(attr->non_resident))
336        goto try_next;
337    fn = (FILE_NAME_ATTR *)((u8 *)attr +
338            le16_to_cpu(attr->data.resident.value_offset));
339    if (unlikely((u8 *)fn + le32_to_cpu(attr->data.resident.value_length) >
340            (u8*)attr + le32_to_cpu(attr->length)))
341        goto try_next;
342    /* Get the inode number of the parent directory. */
343    parent_ino = MREF_LE(fn->parent_directory);
344    /* Release the search context and the mft record of the child. */
345    ntfs_attr_put_search_ctx(ctx);
346    unmap_mft_record(ni);
347
348    return d_obtain_alias(ntfs_iget(vi->i_sb, parent_ino));
349}
350
351static struct inode *ntfs_nfs_get_inode(struct super_block *sb,
352        u64 ino, u32 generation)
353{
354    struct inode *inode;
355
356    inode = ntfs_iget(sb, ino);
357    if (!IS_ERR(inode)) {
358        if (is_bad_inode(inode) || inode->i_generation != generation) {
359            iput(inode);
360            inode = ERR_PTR(-ESTALE);
361        }
362    }
363
364    return inode;
365}
366
367static struct dentry *ntfs_fh_to_dentry(struct super_block *sb, struct fid *fid,
368        int fh_len, int fh_type)
369{
370    return generic_fh_to_dentry(sb, fid, fh_len, fh_type,
371                    ntfs_nfs_get_inode);
372}
373
374static struct dentry *ntfs_fh_to_parent(struct super_block *sb, struct fid *fid,
375        int fh_len, int fh_type)
376{
377    return generic_fh_to_parent(sb, fid, fh_len, fh_type,
378                    ntfs_nfs_get_inode);
379}
380
381/**
382 * Export operations allowing NFS exporting of mounted NTFS partitions.
383 *
384 * We use the default ->encode_fh() for now. Note that they
385 * use 32 bits to store the inode number which is an unsigned long so on 64-bit
386 * architectures is usually 64 bits so it would all fail horribly on huge
387 * volumes. I guess we need to define our own encode and decode fh functions
388 * that store 64-bit inode numbers at some point but for now we will ignore the
389 * problem...
390 *
391 * We also use the default ->get_name() helper (used by ->decode_fh() via
392 * fs/exportfs/expfs.c::find_exported_dentry()) as that is completely fs
393 * independent.
394 *
395 * The default ->get_parent() just returns -EACCES so we have to provide our
396 * own and the default ->get_dentry() is incompatible with NTFS due to not
397 * allowing the inode number 0 which is used in NTFS for the system file $MFT
398 * and due to using iget() whereas NTFS needs ntfs_iget().
399 */
400const struct export_operations ntfs_export_ops = {
401    .get_parent = ntfs_get_parent, /* Find the parent of a given
402                           directory. */
403    .fh_to_dentry = ntfs_fh_to_dentry,
404    .fh_to_parent = ntfs_fh_to_parent,
405};
406

Archive Download this file



interactive