--- /dev/null
+/*
+ * Copyright (C) Neil Brown 2002
+ * Copyright (C) Christoph Hellwig 2007
+ *
+ * This file contains the code mapping from inodes to NFS file handles,
+ * and for mapping back from file handles to dentries.
+ *
+ * For details on why we do all the strange and hairy things in here
+ * take a look at Documentation/filesystems/nfs/Exporting.
+ */
+#include <linux/exportfs.h>
+#include <linux/fs.h>
+#include <linux/file.h>
+#include <linux/module.h>
+#include <linux/mount.h>
+#include <linux/namei.h>
+#include <linux/sched.h>
+
+#define dprintk(fmt, args...) do{}while(0)
+
+
+static int get_name(const struct path *path, char *name, struct dentry *child);
+
+
+static int exportfs_get_name(struct vfsmount *mnt, struct dentry *dir,
+ char *name, struct dentry *child)
+{
+ const struct export_operations *nop = dir->d_sb->s_export_op;
+ struct path path = {.mnt = mnt, .dentry = dir};
+
+ if (nop->get_name)
+ return nop->get_name(dir, name, child);
+ else
+ return get_name(&path, name, child);
+}
+
+/*
+ * Check if the dentry or any of it's aliases is acceptable.
+ */
+static struct dentry *
+find_acceptable_alias(struct dentry *result,
+ int (*acceptable)(void *context, struct dentry *dentry),
+ void *context)
+{
+ struct dentry *dentry, *toput = NULL;
+ struct inode *inode;
+
+ if (acceptable(context, result))
+ return result;
+
+ inode = result->d_inode;
+ spin_lock(&inode->i_lock);
+ hlist_for_each_entry(dentry, &inode->i_dentry, d_u.d_alias) {
+ dget(dentry);
+ spin_unlock(&inode->i_lock);
+ if (toput)
+ dput(toput);
+ if (dentry != result && acceptable(context, dentry)) {
+ dput(result);
+ return dentry;
+ }
+ spin_lock(&inode->i_lock);
+ toput = dentry;
+ }
+ spin_unlock(&inode->i_lock);
+
+ if (toput)
+ dput(toput);
+ return NULL;
+}
+
+static bool dentry_connected(struct dentry *dentry)
+{
+ dget(dentry);
+ while (dentry->d_flags & DCACHE_DISCONNECTED) {
+ struct dentry *parent = dget_parent(dentry);
+
+ dput(dentry);
+ if (IS_ROOT(dentry)) {
+ dput(parent);
+ return false;
+ }
+ dentry = parent;
+ }
+ dput(dentry);
+ return true;
+}
+
+static void clear_disconnected(struct dentry *dentry)
+{
+ dget(dentry);
+ while (dentry->d_flags & DCACHE_DISCONNECTED) {
+ struct dentry *parent = dget_parent(dentry);
+
+ WARN_ON_ONCE(IS_ROOT(dentry));
+
+ spin_lock(&dentry->d_lock);
+ dentry->d_flags &= ~DCACHE_DISCONNECTED;
+ spin_unlock(&dentry->d_lock);
+
+ dput(dentry);
+ dentry = parent;
+ }
+ dput(dentry);
+}
+
+/*
+ * Reconnect a directory dentry with its parent.
+ *
+ * This can return a dentry, or NULL, or an error.
+ *
+ * In the first case the returned dentry is the parent of the given
+ * dentry, and may itself need to be reconnected to its parent.
+ *
+ * In the NULL case, a concurrent VFS operation has either renamed or
+ * removed this directory. The concurrent operation has reconnected our
+ * dentry, so we no longer need to.
+ */
+static struct dentry *reconnect_one(struct vfsmount *mnt,
+ struct dentry *dentry, char *nbuf)
+{
+ struct dentry *parent;
+ struct dentry *tmp;
+ int err;
+
+ parent = ERR_PTR(-EACCES);
+ mutex_lock(&dentry->d_inode->i_mutex);
+ if (mnt->mnt_sb->s_export_op->get_parent)
+ parent = mnt->mnt_sb->s_export_op->get_parent(dentry);
+ mutex_unlock(&dentry->d_inode->i_mutex);
+
+ if (IS_ERR(parent)) {
+ dprintk("%s: get_parent of %ld failed, err %d\n",
+ __func__, dentry->d_inode->i_ino, PTR_ERR(parent));
+ return parent;
+ }
+
+ dprintk("%s: find name of %lu in %lu\n", __func__,
+ dentry->d_inode->i_ino, parent->d_inode->i_ino);
+ err = exportfs_get_name(mnt, parent, nbuf, dentry);
+ if (err == -ENOENT)
+ goto out_reconnected;
+ if (err)
+ goto out_err;
+ dprintk("%s: found name: %s\n", __func__, nbuf);
+ mutex_lock(&parent->d_inode->i_mutex);
+ tmp = lookup_one_len(nbuf, parent, strlen(nbuf));
+ mutex_unlock(&parent->d_inode->i_mutex);
+ if (IS_ERR(tmp)) {
+ dprintk("%s: lookup failed: %d\n", __func__, PTR_ERR(tmp));
+ goto out_err;
+ }
+ if (tmp != dentry) {
+ dput(tmp);
+ goto out_reconnected;
+ }
+ dput(tmp);
+ if (IS_ROOT(dentry)) {
+ err = -ESTALE;
+ goto out_err;
+ }
+ return parent;
+
+out_err:
+ dput(parent);
+ return ERR_PTR(err);
+out_reconnected:
+ dput(parent);
+ /*
+ * Someone must have renamed our entry into another parent, in
+ * which case it has been reconnected by the rename.
+ *
+ * Or someone removed it entirely, in which case filehandle
+ * lookup will succeed but the directory is now IS_DEAD and
+ * subsequent operations on it will fail.
+ *
+ * Alternatively, maybe there was no race at all, and the
+ * filesystem is just corrupt and gave us a parent that doesn't
+ * actually contain any entry pointing to this inode. So,
+ * double check that this worked and return -ESTALE if not:
+ */
+ if (!dentry_connected(dentry))
+ return ERR_PTR(-ESTALE);
+ return NULL;
+}
+
+/*
+ * Make sure target_dir is fully connected to the dentry tree.
+ *
+ * On successful return, DCACHE_DISCONNECTED will be cleared on
+ * target_dir, and target_dir->d_parent->...->d_parent will reach the
+ * root of the filesystem.
+ *
+ * Whenever DCACHE_DISCONNECTED is unset, target_dir is fully connected.
+ * But the converse is not true: target_dir may have DCACHE_DISCONNECTED
+ * set but already be connected. In that case we'll verify the
+ * connection to root and then clear the flag.
+ *
+ * Note that target_dir could be removed by a concurrent operation. In
+ * that case reconnect_path may still succeed with target_dir fully
+ * connected, but further operations using the filehandle will fail when
+ * necessary (due to S_DEAD being set on the directory).
+ */
+static int
+reconnect_path(struct vfsmount *mnt, struct dentry *target_dir, char *nbuf)
+{
+ struct dentry *dentry, *parent;
+
+ dentry = dget(target_dir);
+
+ while (dentry->d_flags & DCACHE_DISCONNECTED) {
+ BUG_ON(dentry == mnt->mnt_sb->s_root);
+
+ if (IS_ROOT(dentry))
+ parent = reconnect_one(mnt, dentry, nbuf);
+ else
+ parent = dget_parent(dentry);
+
+ if (!parent)
+ break;
+ dput(dentry);
+ if (IS_ERR(parent))
+ return PTR_ERR(parent);
+ dentry = parent;
+ }
+ dput(dentry);
+ clear_disconnected(target_dir);
+ return 0;
+}
+
+struct getdents_callback {
+ struct dir_context ctx;
+ char *name; /* name that was found. It already points to a
+ buffer NAME_MAX+1 is size */
+ u64 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(struct dir_context *ctx, const char *name, int len,
+ loff_t pos, u64 ino, unsigned int d_type)
+{
+ struct getdents_callback *buf =
+ container_of(ctx, struct getdents_callback, ctx);
+ int result = 0;
+
+ buf->sequence++;
+ if (buf->ino == ino && len <= NAME_MAX) {
+ memcpy(buf->name, name, len);
+ buf->name[len] = '\0';
+ buf->found = 1;
+ result = -1;
+ }
+ return result;
+}
+
+/**
+ * get_name - default export_operations->get_name function
+ * @path: 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(const struct path *path, char *name, struct dentry *child)
+{
+ const struct cred *cred = current_cred();
+ struct inode *dir = path->dentry->d_inode;
+ int error;
+ struct file *file;
+ struct kstat stat;
+ struct path child_path = {
+ .mnt = path->mnt,
+ .dentry = child,
+ };
+ struct getdents_callback buffer = {
+ .ctx.actor = filldir_one,
+ .name = name,
+ };
+
+ error = -ENOTDIR;
+ if (!dir || !S_ISDIR(dir->i_mode))
+ goto out;
+ error = -EINVAL;
+ if (!dir->i_fop)
+ goto out;
+ /*
+ * inode->i_ino is unsigned long, kstat->ino is u64, so the
+ * former would be insufficient on 32-bit hosts when the
+ * filesystem supports 64-bit inode numbers. So we need to
+ * actually call ->getattr, not just read i_ino:
+ */
+ error = vfs_getattr_nosec(&child_path, &stat);
+ if (error)
+ return error;
+ buffer.ino = stat.ino;
+ /*
+ * Open the directory ...
+ */
+ file = dentry_open(path, O_RDONLY, cred);
+ error = PTR_ERR(file);
+ if (IS_ERR(file))
+ goto out;
+
+ error = -EINVAL;
+ if (!file->f_op->iterate)
+ goto out_close;
+
+ buffer.sequence = 0;
+ while (1) {
+ int old_seq = buffer.sequence;
+
+ error = iterate_dir(file, &buffer.ctx);
+ if (buffer.found) {
+ error = 0;
+ break;
+ }
+
+ if (error < 0)
+ 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
+ * @inode: the object to encode
+ * @fid: where to store the file handle fragment
+ * @max_len: maximum length to store there
+ * @parent: parent directory inode, if wanted
+ *
+ * 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 inode *inode, struct fid *fid,
+ int *max_len, struct inode *parent)
+{
+ int len = *max_len;
+ int type = FILEID_INO32_GEN;
+
+ if (parent && (len < 4)) {
+ *max_len = 4;
+ return FILEID_INVALID;
+ } else if (len < 2) {
+ *max_len = 2;
+ return FILEID_INVALID;
+ }
+
+ len = 2;
+ fid->i32.ino = inode->i_ino;
+ fid->i32.gen = inode->i_generation;
+ if (parent) {
+ fid->i32.parent_ino = parent->i_ino;
+ fid->i32.parent_gen = parent->i_generation;
+ len = 4;
+ type = FILEID_INO32_GEN_PARENT;
+ }
+ *max_len = len;
+ return type;
+}
+
+int exportfs_encode_inode_fh(struct inode *inode, struct fid *fid,
+ int *max_len, struct inode *parent)
+{
+ const struct export_operations *nop = inode->i_sb->s_export_op;
+
+ if (nop && nop->encode_fh)
+ return nop->encode_fh(inode, fid->raw, max_len, parent);
+
+ return export_encode_fh(inode, fid, max_len, parent);
+}
+EXPORT_SYMBOL_GPL(exportfs_encode_inode_fh);
+
+int exportfs_encode_fh(struct dentry *dentry, struct fid *fid, int *max_len,
+ int connectable)
+{
+ int error;
+ struct dentry *p = NULL;
+ struct inode *inode = dentry->d_inode, *parent = NULL;
+
+ if (connectable && !S_ISDIR(inode->i_mode)) {
+ p = dget_parent(dentry);
+ /*
+ * note that while p might've ceased to be our parent already,
+ * it's still pinned by and still positive.
+ */
+ parent = p->d_inode;
+ }
+
+ error = exportfs_encode_inode_fh(inode, fid, max_len, parent);
+ dput(p);
+
+ return error;
+}
+EXPORT_SYMBOL_GPL(exportfs_encode_fh);
+
+struct dentry *exportfs_decode_fh(struct vfsmount *mnt, struct fid *fid,
+ int fh_len, int fileid_type,
+ int (*acceptable)(void *, struct dentry *), void *context)
+{
+ const struct export_operations *nop = mnt->mnt_sb->s_export_op;
+ struct dentry *result, *alias;
+ char nbuf[NAME_MAX+1];
+ int err;
+
+ /*
+ * Try to get any dentry for the given file handle from the filesystem.
+ */
+ if (!nop || !nop->fh_to_dentry)
+ return ERR_PTR(-ESTALE);
+ result = nop->fh_to_dentry(mnt->mnt_sb, fid, fh_len, fileid_type);
+ if (!result)
+ result = ERR_PTR(-ESTALE);
+ if (IS_ERR(result))
+ return result;
+
+ if (d_is_dir(result)) {
+ /*
+ * This request is for a directory.
+ *
+ * On the positive side there is only one dentry for each
+ * directory inode. On the negative side this implies that we
+ * to ensure our dentry is connected all the way up to the
+ * filesystem root.
+ */
+ if (result->d_flags & DCACHE_DISCONNECTED) {
+ err = reconnect_path(mnt, result, nbuf);
+ if (err)
+ goto err_result;
+ }
+
+ if (!acceptable(context, result)) {
+ err = -EACCES;
+ goto err_result;
+ }
+
+ return result;
+ } else {
+ /*
+ * It's not a directory. Life is a little more complicated.
+ */
+ struct dentry *target_dir, *nresult;
+
+ /*
+ * See if either the dentry we just got from the filesystem
+ * or any alias for it is acceptable. This is always true
+ * if this filesystem is exported without the subtreecheck
+ * option. If the filesystem is exported with the subtree
+ * check option there's a fair chance we need to look at
+ * the parent directory in the file handle and make sure
+ * it's connected to the filesystem root.
+ */
+ alias = find_acceptable_alias(result, acceptable, context);
+ if (alias)
+ return alias;
+
+ /*
+ * Try to extract a dentry for the parent directory from the
+ * file handle. If this fails we'll have to give up.
+ */
+ err = -ESTALE;
+ if (!nop->fh_to_parent)
+ goto err_result;
+
+ target_dir = nop->fh_to_parent(mnt->mnt_sb, fid,
+ fh_len, fileid_type);
+ if (!target_dir)
+ goto err_result;
+ err = PTR_ERR(target_dir);
+ if (IS_ERR(target_dir))
+ goto err_result;
+
+ /*
+ * And as usual we need to make sure the parent directory is
+ * connected to the filesystem root. The VFS really doesn't
+ * like disconnected directories..
+ */
+ err = reconnect_path(mnt, target_dir, nbuf);
+ if (err) {
+ dput(target_dir);
+ goto err_result;
+ }
+
+ /*
+ * Now that we've got both a well-connected parent and a
+ * dentry for the inode we're after, make sure that our
+ * inode is actually connected to the parent.
+ */
+ err = exportfs_get_name(mnt, 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);
+ }
+ }
+
+ /*
+ * At this point we are done with the parent, but it's pinned
+ * by the child dentry anyway.
+ */
+ dput(target_dir);
+
+ /*
+ * And finally make sure the dentry is actually acceptable
+ * to NFSD.
+ */
+ alias = find_acceptable_alias(result, acceptable, context);
+ if (!alias) {
+ err = -EACCES;
+ goto err_result;
+ }
+
+ return alias;
+ }
+
+ err_result:
+ dput(result);
+ return ERR_PTR(err);
+}
+EXPORT_SYMBOL_GPL(exportfs_decode_fh);
+
+MODULE_LICENSE("GPL");
Code Review / kvmfornfv.git / blobdiff