The Design and Implementation of the FreeBSD Operating System, Second Edition
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FreeBSD/Linux Kernel Cross Reference
sys/fs/ntfs/namei.c

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    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  */
  103 static struct dentry *ntfs_lookup(struct inode *dir_ino, struct dentry *dent,
  104                 unsigned int flags)
  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)
  176 handle_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 
  262 eio_err_out:
  263         ntfs_error(vol->sb, "Illegal file name attribute. Run chkdsk.");
  264         err = -EIO;
  265 err_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  */
  279 const 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  */
  300 static 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         }
  322 try_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 
  351 static 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 
  367 static 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 
  374 static 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  */
  400 const 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 };

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