2 files changed, 546 insertions, 0 deletions

diff --git a/fs/exportfs/Makefile b/fs/exportfs/Makefile
new file mode 100644
index 000000000000..d7c5d4ddb34b
--- /dev/null
+++ b/fs/exportfs/Makefile
@@ -0,0 +1,6 @@
+#
+# Makefile for the filesystem export support routines.
+
+obj-$(CONFIG_EXPORTFS) += exportfs.o
+
+exportfs-objs := expfs.o
diff --git a/fs/exportfs/expfs.c b/fs/exportfs/expfs.c
new file mode 100644
index 000000000000..c49d6254379a
--- /dev/null
+++ b/fs/exportfs/expfs.c
@@ -0,0 +1,540 @@
+
+#include <linux/fs.h>
+#include <linux/file.h>
+#include <linux/module.h>
+#include <linux/smp_lock.h>
+#include <linux/namei.h>
+
+struct export_operations export_op_default;
+
+#define CALL(ops,fun) ((ops->fun)?(ops->fun):export_op_default.fun)
+
+#define dprintk(fmt, args...) do{}while(0)
+
+/**
+ * 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;
+        struct export_operations *nops = sb->s_export_op;
+        struct list_head *le, *head;
+        struct dentry *toput = NULL;
+        int noprogress;
+        char nbuf[NAME_MAX+1];
+
+        /*
+         * Attempt to find the inode.
+         */
+        result = CALL(sb->s_export_op,get_dentry)(sb,obj);
+        err = -ESTALE;
+        if (result == NULL)
+                goto err_out;
+        if (IS_ERR(result)) {
+                err = PTR_ERR(result);
+                goto err_out;
+        }
+        if (S_ISDIR(result->d_inode->i_mode) &&
+            (result->d_flags & DCACHE_DISCONNECTED)) {
+                /* it is an unconnected directory, we must connect it */
+                ;
+        } else {
+                if (acceptable(context, result))
+                        return result;
+                if (S_ISDIR(result->d_inode->i_mode)) {
+                        /* there is no other dentry, so fail */
+                        goto err_result;
+                }
+                /* try any other aliases */
+                spin_lock(&dcache_lock);
+                head = &result->d_inode->i_dentry;
+                list_for_each(le, head) {
+                        struct dentry *dentry = list_entry(le, struct dentry, d_alias);
+                        dget_locked(dentry);
+                        spin_unlock(&dcache_lock);
+                        if (toput)
+                                dput(toput);
+                        toput = NULL;
+                        if (dentry != result &&
+                            acceptable(context, dentry)) {
+                                dput(result);
+                                return dentry;
+                        }
+                        spin_lock(&dcache_lock);
+                        toput = dentry;
+                }
+                spin_unlock(&dcache_lock);
+                if (toput)
+                        dput(toput);
+        }                       
+
+        /* It's a directory, or we are required to confirm the file's
+         * location in the tree based on the parent information
+         */
+        dprintk("find_exported_dentry: need to look harder for %s/%d\n",sb->s_id,*(int*)obj);
+        if (S_ISDIR(result->d_inode->i_mode))
+                target_dir = dget(result);
+        else {
+                if (parent == NULL)
+                        goto err_result;
+
+                target_dir = CALL(sb->s_export_op,get_dentry)(sb,parent);
+                if (IS_ERR(target_dir))
+                        err = PTR_ERR(target_dir);
+                if (target_dir == NULL || IS_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
+                         * note: 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
+                         */
+                        struct dentry *ppd;
+                        struct dentry *npd;
+
+                        down(&pd->d_inode->i_sem);
+                        ppd = CALL(nops,get_parent)(pd);
+                        up(&pd->d_inode->i_sem);
+
+                        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 = CALL(nops,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);
+                        down(&ppd->d_inode->i_sem);
+                        npd = lookup_one_len(nbuf, ppd, strlen(nbuf));
+                        up(&ppd->d_inode->i_sem);
+                        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 = CALL(nops,get_name)(target_dir, nbuf, result);
+                if (!err) {
+                        down(&target_dir->d_inode->i_sem);
+                        nresult = lookup_one_len(nbuf, target_dir, strlen(nbuf));
+                        up(&target_dir->d_inode->i_sem);
+                        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;
+        /* one last try of the aliases.. */
+        spin_lock(&dcache_lock);
+        toput = NULL;
+        head = &result->d_inode->i_dentry;
+        list_for_each(le, head) {
+                struct dentry *dentry = list_entry(le, struct 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);
+
+        /* 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);
+ err_out:
+        return ERR_PTR(err);
+}
+
+
+
+static struct dentry *get_parent(struct dentry *child)
+{
+        /* get_parent cannot be supported generically, the locking
+         * is too icky.
+         * instead, we just return EACCES.  If server reboots or inodes
+         * get flushed, you lose
+         */
+        return ERR_PTR(-EACCES);
+}
+
+
+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, ino_t 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;
+}
+
+
+static struct dentry *export_iget(struct super_block *sb, unsigned long ino, __u32 generation)
+{
+
+        /* iget isn't really right if the inode is currently unallocated!!
+         * This should really all be done inside each filesystem
+         *
+         * ext2fs' read_inode has been strengthed to return a bad_inode if
+         * the inode had been deleted.
+         *
+         * Currently we don't know the generation for parent directory, so
+         * a generation of 0 means "accept any"
+         */
+        struct inode *inode;
+        struct dentry *result;
+        if (ino == 0)
+                return ERR_PTR(-ESTALE);
+        inode = iget(sb, ino);
+        if (inode == NULL)
+                return ERR_PTR(-ENOMEM);
+        if (is_bad_inode(inode)
+            || (generation && inode->i_generation != generation)
+                ) {
+                /* we didn't find the right inode.. */
+                dprintk("fh_verify: Inode %lu, Bad count: %d %d or version  %u %u\n",
+                        inode->i_ino,
+                        inode->i_nlink, atomic_read(&inode->i_count),
+                        inode->i_generation,
+                        generation);
+
+                iput(inode);
+                return ERR_PTR(-ESTALE);
+        }
+        /* now to find a dentry.
+         * If possible, get a well-connected one
+         */
+        result = d_alloc_anon(inode);
+        if (!result) {
+                iput(inode);
+                return ERR_PTR(-ENOMEM);
+        }
+        return result;
+}
+
+
+static struct dentry *get_object(struct super_block *sb, void *vobjp)
+{
+        __u32 *objp = vobjp;
+        unsigned long ino = objp[0];
+        __u32 generation = objp[1];
+
+        return export_iget(sb, ino, generation);
+}
+
+
+/**
+ * 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);
+}
+
+struct export_operations export_op_default = {
+        .decode_fh      = export_decode_fh,
+        .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");