533 lines
14 KiB
C
533 lines
14 KiB
C
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#include <linux/fs.h>
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#include <linux/file.h>
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#include <linux/module.h>
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#include <linux/namei.h>
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struct export_operations export_op_default;
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#define CALL(ops,fun) ((ops->fun)?(ops->fun):export_op_default.fun)
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#define dprintk(fmt, args...) do{}while(0)
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static struct dentry *
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find_acceptable_alias(struct dentry *result,
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int (*acceptable)(void *context, struct dentry *dentry),
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void *context)
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{
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struct dentry *dentry, *toput = NULL;
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spin_lock(&dcache_lock);
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list_for_each_entry(dentry, &result->d_inode->i_dentry, d_alias) {
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dget_locked(dentry);
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spin_unlock(&dcache_lock);
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if (toput)
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dput(toput);
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if (dentry != result && acceptable(context, dentry)) {
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dput(result);
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return dentry;
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}
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spin_lock(&dcache_lock);
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toput = dentry;
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}
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spin_unlock(&dcache_lock);
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if (toput)
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dput(toput);
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return NULL;
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}
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/**
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* find_exported_dentry - helper routine to implement export_operations->decode_fh
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* @sb: The &super_block identifying the filesystem
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* @obj: An opaque identifier of the object to be found - passed to
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* get_inode
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* @parent: An optional opqaue identifier of the parent of the object.
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* @acceptable: A function used to test possible &dentries to see if they are
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* acceptable
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* @context: A parameter to @acceptable so that it knows on what basis to
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* judge.
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*
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* find_exported_dentry is the central helper routine to enable file systems
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* to provide the decode_fh() export_operation. It's main task is to take
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* an &inode, find or create an appropriate &dentry structure, and possibly
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* splice this into the dcache in the correct place.
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*
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* The decode_fh() operation provided by the filesystem should call
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* find_exported_dentry() with the same parameters that it received except
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* that instead of the file handle fragment, pointers to opaque identifiers
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* for the object and optionally its parent are passed. The default decode_fh
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* routine passes one pointer to the start of the filehandle fragment, and
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* one 8 bytes into the fragment. It is expected that most filesystems will
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* take this approach, though the offset to the parent identifier may well be
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* different.
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*
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* find_exported_dentry() will call get_dentry to get an dentry pointer from
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* the file system. If any &dentry in the d_alias list is acceptable, it will
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* be returned. Otherwise find_exported_dentry() will attempt to splice a new
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* &dentry into the dcache using get_name() and get_parent() to find the
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* appropriate place.
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*/
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struct dentry *
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find_exported_dentry(struct super_block *sb, void *obj, void *parent,
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int (*acceptable)(void *context, struct dentry *de),
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void *context)
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{
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struct dentry *result = NULL;
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struct dentry *target_dir;
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int err;
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struct export_operations *nops = sb->s_export_op;
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struct dentry *alias;
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int noprogress;
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char nbuf[NAME_MAX+1];
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/*
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* Attempt to find the inode.
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*/
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result = CALL(sb->s_export_op,get_dentry)(sb,obj);
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err = -ESTALE;
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if (result == NULL)
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goto err_out;
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if (IS_ERR(result)) {
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err = PTR_ERR(result);
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goto err_out;
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}
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if (S_ISDIR(result->d_inode->i_mode) &&
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(result->d_flags & DCACHE_DISCONNECTED)) {
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/* it is an unconnected directory, we must connect it */
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;
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} else {
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if (acceptable(context, result))
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return result;
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if (S_ISDIR(result->d_inode->i_mode)) {
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err = -EACCES;
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goto err_result;
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}
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alias = find_acceptable_alias(result, acceptable, context);
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if (alias)
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return alias;
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}
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/* It's a directory, or we are required to confirm the file's
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* location in the tree based on the parent information
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*/
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dprintk("find_exported_dentry: need to look harder for %s/%d\n",sb->s_id,*(int*)obj);
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if (S_ISDIR(result->d_inode->i_mode))
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target_dir = dget(result);
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else {
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if (parent == NULL)
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goto err_result;
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target_dir = CALL(sb->s_export_op,get_dentry)(sb,parent);
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if (IS_ERR(target_dir))
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err = PTR_ERR(target_dir);
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if (target_dir == NULL || IS_ERR(target_dir))
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goto err_result;
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}
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/*
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* Now we need to make sure that target_dir is properly connected.
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* It may already be, as the flag isn't always updated when connection
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* happens.
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* So, we walk up parent links until we find a connected directory,
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* or we run out of directories. Then we find the parent, find
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* the name of the child in that parent, and do a lookup.
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* This should connect the child into the parent
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* We then repeat.
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*/
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/* it is possible that a confused file system might not let us complete
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* the path to the root. For example, if get_parent returns a directory
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* in which we cannot find a name for the child. While this implies a
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* very sick filesystem we don't want it to cause knfsd to spin. Hence
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* the noprogress counter. If we go through the loop 10 times (2 is
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* probably enough) without getting anywhere, we just give up
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*/
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noprogress= 0;
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while (target_dir->d_flags & DCACHE_DISCONNECTED && noprogress++ < 10) {
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struct dentry *pd = target_dir;
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dget(pd);
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spin_lock(&pd->d_lock);
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while (!IS_ROOT(pd) &&
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(pd->d_parent->d_flags&DCACHE_DISCONNECTED)) {
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struct dentry *parent = pd->d_parent;
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dget(parent);
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spin_unlock(&pd->d_lock);
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dput(pd);
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pd = parent;
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spin_lock(&pd->d_lock);
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}
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spin_unlock(&pd->d_lock);
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if (!IS_ROOT(pd)) {
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/* must have found a connected parent - great */
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spin_lock(&pd->d_lock);
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pd->d_flags &= ~DCACHE_DISCONNECTED;
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spin_unlock(&pd->d_lock);
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noprogress = 0;
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} else if (pd == sb->s_root) {
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printk(KERN_ERR "export: Eeek filesystem root is not connected, impossible\n");
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spin_lock(&pd->d_lock);
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pd->d_flags &= ~DCACHE_DISCONNECTED;
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spin_unlock(&pd->d_lock);
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noprogress = 0;
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} else {
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/* we have hit the top of a disconnected path. Try
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* to find parent and connect
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* note: racing with some other process renaming a
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* directory isn't much of a problem here. If someone
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* renames the directory, it will end up properly
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* connected, which is what we want
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*/
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struct dentry *ppd;
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struct dentry *npd;
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mutex_lock(&pd->d_inode->i_mutex);
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ppd = CALL(nops,get_parent)(pd);
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mutex_unlock(&pd->d_inode->i_mutex);
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if (IS_ERR(ppd)) {
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err = PTR_ERR(ppd);
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dprintk("find_exported_dentry: get_parent of %ld failed, err %d\n",
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pd->d_inode->i_ino, err);
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dput(pd);
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break;
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}
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dprintk("find_exported_dentry: find name of %lu in %lu\n", pd->d_inode->i_ino, ppd->d_inode->i_ino);
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err = CALL(nops,get_name)(ppd, nbuf, pd);
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if (err) {
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dput(ppd);
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dput(pd);
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if (err == -ENOENT)
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/* some race between get_parent and
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* get_name? just try again
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*/
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continue;
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break;
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}
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dprintk("find_exported_dentry: found name: %s\n", nbuf);
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mutex_lock(&ppd->d_inode->i_mutex);
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npd = lookup_one_len(nbuf, ppd, strlen(nbuf));
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mutex_unlock(&ppd->d_inode->i_mutex);
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if (IS_ERR(npd)) {
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err = PTR_ERR(npd);
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dprintk("find_exported_dentry: lookup failed: %d\n", err);
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dput(ppd);
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dput(pd);
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break;
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}
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/* we didn't really want npd, we really wanted
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* a side-effect of the lookup.
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* hopefully, npd == pd, though it isn't really
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* a problem if it isn't
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*/
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if (npd == pd)
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noprogress = 0;
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else
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printk("find_exported_dentry: npd != pd\n");
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dput(npd);
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dput(ppd);
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if (IS_ROOT(pd)) {
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/* something went wrong, we have to give up */
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dput(pd);
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break;
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}
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}
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dput(pd);
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}
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if (target_dir->d_flags & DCACHE_DISCONNECTED) {
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/* something went wrong - oh-well */
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if (!err)
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err = -ESTALE;
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goto err_target;
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}
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/* if we weren't after a directory, have one more step to go */
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if (result != target_dir) {
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struct dentry *nresult;
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err = CALL(nops,get_name)(target_dir, nbuf, result);
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if (!err) {
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mutex_lock(&target_dir->d_inode->i_mutex);
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nresult = lookup_one_len(nbuf, target_dir, strlen(nbuf));
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mutex_unlock(&target_dir->d_inode->i_mutex);
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if (!IS_ERR(nresult)) {
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if (nresult->d_inode) {
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dput(result);
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result = nresult;
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} else
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dput(nresult);
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}
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}
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}
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dput(target_dir);
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/* now result is properly connected, it is our best bet */
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if (acceptable(context, result))
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return result;
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alias = find_acceptable_alias(result, acceptable, context);
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if (alias)
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return alias;
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/* drat - I just cannot find anything acceptable */
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dput(result);
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/* It might be justifiable to return ESTALE here,
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* but the filehandle at-least looks reasonable good
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* and it just be a permission problem, so returning
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* -EACCESS is safer
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*/
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return ERR_PTR(-EACCES);
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err_target:
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dput(target_dir);
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err_result:
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dput(result);
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err_out:
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return ERR_PTR(err);
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}
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static struct dentry *get_parent(struct dentry *child)
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{
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/* get_parent cannot be supported generically, the locking
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* is too icky.
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* instead, we just return EACCES. If server reboots or inodes
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* get flushed, you lose
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*/
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return ERR_PTR(-EACCES);
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}
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struct getdents_callback {
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char *name; /* name that was found. It already points to a
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buffer NAME_MAX+1 is size */
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unsigned long ino; /* the inum we are looking for */
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int found; /* inode matched? */
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int sequence; /* sequence counter */
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};
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/*
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* A rather strange filldir function to capture
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* the name matching the specified inode number.
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*/
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static int filldir_one(void * __buf, const char * name, int len,
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loff_t pos, u64 ino, unsigned int d_type)
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{
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struct getdents_callback *buf = __buf;
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int result = 0;
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buf->sequence++;
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if (buf->ino == ino) {
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memcpy(buf->name, name, len);
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buf->name[len] = '\0';
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buf->found = 1;
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result = -1;
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}
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return result;
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}
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/**
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* get_name - default export_operations->get_name function
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* @dentry: the directory in which to find a name
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* @name: a pointer to a %NAME_MAX+1 char buffer to store the name
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* @child: the dentry for the child directory.
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*
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* calls readdir on the parent until it finds an entry with
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* the same inode number as the child, and returns that.
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*/
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static int get_name(struct dentry *dentry, char *name,
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struct dentry *child)
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{
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struct inode *dir = dentry->d_inode;
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int error;
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struct file *file;
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struct getdents_callback buffer;
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error = -ENOTDIR;
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if (!dir || !S_ISDIR(dir->i_mode))
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goto out;
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error = -EINVAL;
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if (!dir->i_fop)
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goto out;
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/*
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* Open the directory ...
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*/
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file = dentry_open(dget(dentry), NULL, O_RDONLY);
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error = PTR_ERR(file);
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if (IS_ERR(file))
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goto out;
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error = -EINVAL;
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if (!file->f_op->readdir)
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goto out_close;
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buffer.name = name;
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buffer.ino = child->d_inode->i_ino;
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buffer.found = 0;
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buffer.sequence = 0;
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while (1) {
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int old_seq = buffer.sequence;
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error = vfs_readdir(file, filldir_one, &buffer);
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if (error < 0)
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break;
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error = 0;
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if (buffer.found)
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break;
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error = -ENOENT;
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if (old_seq == buffer.sequence)
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break;
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}
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out_close:
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fput(file);
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out:
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return error;
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}
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static struct dentry *export_iget(struct super_block *sb, unsigned long ino, __u32 generation)
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{
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/* iget isn't really right if the inode is currently unallocated!!
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* This should really all be done inside each filesystem
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*
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* ext2fs' read_inode has been strengthed to return a bad_inode if
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* the inode had been deleted.
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*
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* Currently we don't know the generation for parent directory, so
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* a generation of 0 means "accept any"
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*/
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struct inode *inode;
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struct dentry *result;
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if (ino == 0)
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return ERR_PTR(-ESTALE);
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inode = iget(sb, ino);
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if (inode == NULL)
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return ERR_PTR(-ENOMEM);
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if (is_bad_inode(inode)
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|| (generation && inode->i_generation != generation)
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) {
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/* we didn't find the right inode.. */
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dprintk("fh_verify: Inode %lu, Bad count: %d %d or version %u %u\n",
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inode->i_ino,
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inode->i_nlink, atomic_read(&inode->i_count),
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inode->i_generation,
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generation);
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iput(inode);
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return ERR_PTR(-ESTALE);
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}
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/* now to find a dentry.
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* If possible, get a well-connected one
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*/
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result = d_alloc_anon(inode);
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if (!result) {
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iput(inode);
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return ERR_PTR(-ENOMEM);
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}
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return result;
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}
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static struct dentry *get_object(struct super_block *sb, void *vobjp)
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{
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__u32 *objp = vobjp;
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unsigned long ino = objp[0];
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__u32 generation = objp[1];
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return export_iget(sb, ino, generation);
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}
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/**
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* export_encode_fh - default export_operations->encode_fh function
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* @dentry: the dentry to encode
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* @fh: where to store the file handle fragment
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* @max_len: maximum length to store there
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* @connectable: whether to store parent information
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*
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* This default encode_fh function assumes that the 32 inode number
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* is suitable for locating an inode, and that the generation number
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* can be used to check that it is still valid. It places them in the
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* filehandle fragment where export_decode_fh expects to find them.
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*/
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static int export_encode_fh(struct dentry *dentry, __u32 *fh, int *max_len,
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int connectable)
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{
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struct inode * inode = dentry->d_inode;
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int len = *max_len;
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int type = 1;
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if (len < 2 || (connectable && len < 4))
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return 255;
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len = 2;
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fh[0] = inode->i_ino;
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fh[1] = inode->i_generation;
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if (connectable && !S_ISDIR(inode->i_mode)) {
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struct inode *parent;
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spin_lock(&dentry->d_lock);
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parent = dentry->d_parent->d_inode;
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fh[2] = parent->i_ino;
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fh[3] = parent->i_generation;
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spin_unlock(&dentry->d_lock);
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len = 4;
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type = 2;
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}
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*max_len = len;
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return type;
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}
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/**
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* export_decode_fh - default export_operations->decode_fh function
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* @sb: The superblock
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* @fh: pointer to the file handle fragment
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* @fh_len: length of file handle fragment
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* @acceptable: function for testing acceptability of dentrys
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* @context: context for @acceptable
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*
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* This is the default decode_fh() function.
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* a fileid_type of 1 indicates that the filehandlefragment
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* just contains an object identifier understood by get_dentry.
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* a fileid_type of 2 says that there is also a directory
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* identifier 8 bytes in to the filehandlefragement.
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*/
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static struct dentry *export_decode_fh(struct super_block *sb, __u32 *fh, int fh_len,
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int fileid_type,
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int (*acceptable)(void *context, struct dentry *de),
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void *context)
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{
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__u32 parent[2];
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parent[0] = parent[1] = 0;
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if (fh_len < 2 || fileid_type > 2)
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return NULL;
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if (fileid_type == 2) {
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if (fh_len > 2) parent[0] = fh[2];
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if (fh_len > 3) parent[1] = fh[3];
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}
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return find_exported_dentry(sb, fh, parent,
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acceptable, context);
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}
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struct export_operations export_op_default = {
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.decode_fh = export_decode_fh,
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.encode_fh = export_encode_fh,
|
|
|
|
.get_name = get_name,
|
|
.get_parent = get_parent,
|
|
.get_dentry = get_object,
|
|
};
|
|
|
|
EXPORT_SYMBOL(export_op_default);
|
|
EXPORT_SYMBOL(find_exported_dentry);
|
|
|
|
MODULE_LICENSE("GPL");
|