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-rw-r--r--fs/exportfs/Makefile6
-rw-r--r--fs/exportfs/expfs.c540
2 files changed, 546 insertions, 0 deletions
diff --git a/fs/exportfs/Makefile b/fs/exportfs/Makefile
new file mode 100644
index 00000000000..d7c5d4ddb34
--- /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 00000000000..c49d6254379
--- /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");
generated by cgit v1.2.3 (git 2.25.1) at 2024-11-21 21:20:24 +0000