-
+/*
+ * 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/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>
-struct export_operations export_op_default;
+#define dprintk(fmt, args...) do{}while(0)
-#define CALL(ops,fun) ((ops->fun)?(ops->fun):export_op_default.fun)
-#define dprintk(fmt, args...) do{}while(0)
+static int get_name(struct vfsmount *mnt, struct dentry *dentry, 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;
+
+ if (nop->get_name)
+ return nop->get_name(dir, name, child);
+ else
+ return get_name(mnt, dir, 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),
{
struct dentry *dentry, *toput = NULL;
+ if (acceptable(context, result))
+ return result;
+
spin_lock(&dcache_lock);
list_for_each_entry(dentry, &result->d_inode->i_dentry, d_alias) {
dget_locked(dentry);
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.
+/*
+ * Find root of a disconnected subtree and return a reference to it.
*/
-
-struct dentry *
-find_exported_dentry(struct super_block *sb, void *obj, void *parent,
- int (*acceptable)(void *context, struct dentry *de),
- void *context)
+static struct dentry *
+find_disconnected_root(struct dentry *dentry)
{
- struct dentry *result = NULL;
- struct dentry *target_dir;
- int err;
- struct export_operations *nops = sb->s_export_op;
- struct dentry *alias;
- 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;
+ dget(dentry);
+ spin_lock(&dentry->d_lock);
+ while (!IS_ROOT(dentry) &&
+ (dentry->d_parent->d_flags & DCACHE_DISCONNECTED)) {
+ struct dentry *parent = dentry->d_parent;
+ dget(parent);
+ spin_unlock(&dentry->d_lock);
+ dput(dentry);
+ dentry = parent;
+ spin_lock(&dentry->d_lock);
}
- 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)) {
- err = -EACCES;
- goto err_result;
- }
+ spin_unlock(&dentry->d_lock);
+ return dentry;
+}
- alias = find_acceptable_alias(result, acceptable, context);
- if (alias)
- return alias;
- }
-
- /* 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.
- */
+/*
+ * Make sure target_dir is fully connected to the dentry tree.
+ *
+ * It may already be, as the flag isn't always updated when connection happens.
+ */
+static int
+reconnect_path(struct vfsmount *mnt, struct dentry *target_dir)
+{
+ char nbuf[NAME_MAX+1];
+ int noprogress = 0;
+ int err = -ESTALE;
- /* it is possible that a confused file system might not let us complete
+ /*
+ * 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);
+ struct dentry *pd = find_disconnected_root(target_dir);
if (!IS_ROOT(pd)) {
/* must have found a connected parent - great */
pd->d_flags &= ~DCACHE_DISCONNECTED;
spin_unlock(&pd->d_lock);
noprogress = 0;
- } else if (pd == sb->s_root) {
+ } else if (pd == mnt->mnt_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
+ /*
+ * 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;
+ struct dentry *ppd = ERR_PTR(-EACCES);
struct dentry *npd;
mutex_lock(&pd->d_inode->i_mutex);
- ppd = CALL(nops,get_parent)(pd);
+ if (mnt->mnt_sb->s_export_op->get_parent)
+ ppd = mnt->mnt_sb->s_export_op->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);
+ dprintk("%s: get_parent of %ld failed, err %d\n",
+ __func__, 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);
+
+ dprintk("%s: find name of %lu in %lu\n", __func__,
+ pd->d_inode->i_ino, ppd->d_inode->i_ino);
+ err = exportfs_get_name(mnt, ppd, nbuf, pd);
if (err) {
dput(ppd);
dput(pd);
continue;
break;
}
- dprintk("find_exported_dentry: found name: %s\n", nbuf);
+ dprintk("%s: found name: %s\n", __func__, 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);
+ dprintk("%s: lookup failed: %d\n",
+ __func__, err);
dput(ppd);
dput(pd);
break;
if (npd == pd)
noprogress = 0;
else
- printk("find_exported_dentry: npd != pd\n");
+ printk("%s: npd != pd\n", __func__);
dput(npd);
dput(ppd);
if (IS_ROOT(pd)) {
/* 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) {
- 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);
- }
- }
+ return err;
}
- 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);
- 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);
+ return 0;
}
-
struct getdents_callback {
char *name; /* name that was found. It already points to a
buffer NAME_MAX+1 is size */
* 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)
+static int get_name(struct vfsmount *mnt, struct dentry *dentry,
+ char *name, struct dentry *child)
{
struct inode *dir = dentry->d_inode;
int error;
/*
* Open the directory ...
*/
- file = dentry_open(dget(dentry), NULL, O_RDONLY);
+ file = dentry_open(dget(dentry), mntget(mnt), O_RDONLY);
error = PTR_ERR(file);
if (IS_ERR(file))
goto 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
* 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)
+static int export_encode_fh(struct dentry *dentry, struct fid *fid,
+ int *max_len, int connectable)
{
struct inode * inode = dentry->d_inode;
int len = *max_len;
- int type = 1;
+ int type = FILEID_INO32_GEN;
if (len < 2 || (connectable && len < 4))
return 255;
len = 2;
- fh[0] = inode->i_ino;
- fh[1] = inode->i_generation;
+ fid->i32.ino = inode->i_ino;
+ fid->i32.gen = 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;
+ fid->i32.parent_ino = parent->i_ino;
+ fid->i32.parent_gen = parent->i_generation;
spin_unlock(&dentry->d_lock);
len = 4;
- type = 2;
+ type = FILEID_INO32_GEN_PARENT;
}
*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)
+int exportfs_encode_fh(struct dentry *dentry, struct fid *fid, int *max_len,
+ int connectable)
{
- __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);
+ const struct export_operations *nop = dentry->d_sb->s_export_op;
+ int error;
+
+ if (nop->encode_fh)
+ error = nop->encode_fh(dentry, fid->raw, max_len, connectable);
+ else
+ error = export_encode_fh(dentry, fid, max_len, connectable);
+
+ 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;
+ int err;
-struct export_operations export_op_default = {
- .decode_fh = export_decode_fh,
- .encode_fh = export_encode_fh,
+ /*
+ * Try to get any dentry for the given file handle from the filesystem.
+ */
+ result = nop->fh_to_dentry(mnt->mnt_sb, fid, fh_len, fileid_type);
+ if (IS_ERR(result))
+ return result;
- .get_name = get_name,
- .get_parent = get_parent,
- .get_dentry = get_object,
-};
+ if (S_ISDIR(result->d_inode->i_mode)) {
+ /*
+ * 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);
+ if (err)
+ goto err_result;
+ }
-EXPORT_SYMBOL(export_op_default);
-EXPORT_SYMBOL(find_exported_dentry);
+ 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;
+ char nbuf[NAME_MAX+1];
+
+ /*
+ * 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);
+ 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);
+ 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");