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