Add the guts for the new filesystem API to exportfs.
There's now a fh_to_dentry method that returns a dentry for the
object looked for given a filehandle fragment, and a fh_to_parent
operation that returns the dentry for the encoded parent directory
in case the file handle contains it.
There are default implementations for these methods that only take
a callback for an nfs-enhanced iget variant and implement the
rest of the semantics.
Signed-off-by: Christoph Hellwig <hch@xxxxxx>
Index: linux-2.6/include/linux/exportfs.h
===================================================================
--- linux-2.6.orig/include/linux/exportfs.h 2007-03-13 19:23:03.000000000 +0100
+++ linux-2.6/include/linux/exportfs.h 2007-03-13 19:23:05.000000000 +0100
@@ -4,6 +4,7 @@
#include <linux/types.h>
struct dentry;
+struct inode;
struct super_block;
struct vfsmount;
@@ -101,6 +102,21 @@ struct fid {
* the filehandle fragment. encode_fh() should return the number of bytes
* stored or a negative error code such as %-ENOSPC
*
+ * fh_to_dentry:
+ * @fh_to_dentry is given a &struct super_block (@sb) and a file handle
+ * fragment (@fh, @fh_len). It should return a &struct dentry which refers
+ * to the same file that the file handle fragment refers to. If it cannot,
+ * it should return a %NULL pointer if the file was found but no acceptable
+ * &dentries were available, or an %ERR_PTR error code indicating why it
+ * couldn't be found (e.g. %ENOENT or %ENOMEM). Any suitable dentry can be
+ * returned including, if necessary, a new dentry created with d_alloc_root.
+ * The caller can then find any other extant dentries by following the
+ * d_alias links.
+ *
+ * fh_to_parent:
+ * Same as @fh_to_dentry, except that it returns a pointer to the parent
+ * dentry if it was encoded into the filehandle fragment by @encode_fh.
+ *
* get_name:
* @get_name should find a name for the given @child in the given @parent
* directory. The name should be stored in the @name (with the
@@ -139,6 +155,10 @@ struct export_operations {
void *context);
int (*encode_fh)(struct dentry *de, __u32 *fh, int *max_len,
int connectable);
+ struct dentry * (*fh_to_dentry)(struct super_block *sb, struct fid *fid,
+ int fh_len, int fh_type);
+ struct dentry * (*fh_to_parent)(struct super_block *sb, struct fid *fid,
+ int fh_len, int fh_type);
int (*get_name)(struct dentry *parent, char *name,
struct dentry *child);
struct dentry * (*get_parent)(struct dentry *child);
@@ -161,4 +181,14 @@ extern struct dentry *exportfs_decode_fh
int fh_len, int fileid_type, int (*acceptable)(void *, struct dentry *),
void *context);
+/*
+ * Generic helpers for filesystems.
+ */
+extern struct dentry *generic_fh_to_dentry(struct super_block *sb,
+ struct fid *fid, int fh_len, int fh_type,
+ struct inode *(*get_inode) (struct super_block *sb, u64 ino, u32 gen));
+extern struct dentry *generic_fh_to_parent(struct super_block *sb,
+ struct fid *fid, int fh_len, int fh_type,
+ struct inode *(*get_inode) (struct super_block *sb, u64 ino, u32 gen));
+
#endif /* LINUX_EXPORTFS_H */
Index: linux-2.6/fs/exportfs/expfs.c
===================================================================
--- linux-2.6.orig/fs/exportfs/expfs.c 2007-03-13 19:23:03.000000000 +0100
+++ linux-2.6/fs/exportfs/expfs.c 2007-03-13 19:23:05.000000000 +0100
@@ -496,6 +496,71 @@ static struct dentry *export_decode_fh(s
acceptable, context);
}
+static struct dentry *exportfs_d_alloc(struct inode *inode)
+{
+ struct dentry *dentry;
+
+ if (!inode)
+ return NULL;
+ if (IS_ERR(inode))
+ return ERR_PTR(PTR_ERR(inode));
+
+ dentry = d_alloc_anon(inode);
+ if (!dentry) {
+ iput(inode);
+ dentry = ERR_PTR(-ENOMEM);
+ }
+ return dentry;
+}
+
+/*
+ * Generic helper for the fh_to_dentry export operation.
+ * Needs a callback to get a struct inode for a [sb,ino,gen] tuple.
+ */
+struct dentry *generic_fh_to_dentry(struct super_block *sb, struct fid *fid,
+ int fh_len, int fh_type, struct inode *(*get_inode)
+ (struct super_block *sb, u64 ino, u32 gen))
+{
+ struct inode *inode = NULL;
+
+ if (fh_len < 2)
+ return NULL;
+
+ switch (fh_type) {
+ case FILEID_INO32_GEN:
+ case FILEID_INO32_GEN_PARENT:
+ inode = get_inode(sb, fid->i32.ino, fid->i32.gen);
+ break;
+ }
+
+ return exportfs_d_alloc(inode);
+}
+EXPORT_SYMBOL_GPL(generic_fh_to_dentry);
+
+/*
+ * Generic helper for the fh_to_parent export operation.
+ * Needs a callback to get a struct inode for a [sb,ino,gen] tuple.
+ */
+struct dentry *generic_fh_to_parent(struct super_block *sb, struct fid *fid,
+ int fh_len, int fh_type, struct inode *(*get_inode)
+ (struct super_block *sb, u64 ino, u32 gen))
+{
+ struct inode *inode = NULL;
+
+ if (fh_len <= 2)
+ return NULL;
+
+ switch (fh_type) {
+ case FILEID_INO32_GEN_PARENT:
+ inode = get_inode(sb, fid->i32.parent_ino,
+ (fh_len > 3 ? fid->i32.parent_gen : 0));
+ break;
+ }
+
+ return exportfs_d_alloc(inode);
+}
+EXPORT_SYMBOL_GPL(generic_fh_to_parent);
+
int exportfs_encode_fh(struct dentry *dentry, struct fid *fid, int *max_len,
int connectable)
{
@@ -516,17 +581,138 @@ struct dentry *exportfs_decode_fh(struct
int (*acceptable)(void *, struct dentry *), void *context)
{
struct export_operations *nop = mnt->mnt_sb->s_export_op;
- struct dentry *result;
+ struct dentry *result, *alias;
+ int err;
+
+ /*
+ * Old way of doing things. Will go away soon.
+ */
+ if (!nop->fh_to_dentry) {
+ if (nop->decode_fh) {
+ return nop->decode_fh(mnt->mnt_sb, fid->raw, fh_len,
+ fileid_type, acceptable, context);
+ } else {
+ return export_decode_fh(mnt->mnt_sb, fid->raw, fh_len,
+ fileid_type, acceptable, context);
+ }
+ }
- if (nop->decode_fh) {
- result = nop->decode_fh(mnt->mnt_sb, fid->raw, fh_len, fileid_type,
- acceptable, context);
+ /*
+ * 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 (!result)
+ result = ERR_PTR(-ESTALE);
+ if (IS_ERR(result))
+ return result;
+
+ if (S_ISDIR(result->d_inode->i_mode)) {
+ /*
+ * This request is for a directory. That means there can't be
+ * more than one dentry for an inode, but it also means we always
+ * need to make sure it's connected up to the filesystem root.
+ */
+ if (result->d_flags & DCACHE_DISCONNECTED) {
+ err = reconnect_path(mnt->mnt_sb, result);
+ if (err)
+ goto err_result;
+ }
+
+ if (!acceptable(context, result)) {
+ err = -EACCES;
+ goto err_result;
+ }
+
+ return result;
} else {
- result = export_decode_fh(mnt->mnt_sb, fid->raw, fh_len, fileid_type,
- acceptable, context);
+ /*
+ * 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);
+ 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->mnt_sb, 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(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;
}
- return result;
+ err_result:
+ dput(result);
+ return ERR_PTR(err);
}
EXPORT_SYMBOL_GPL(exportfs_decode_fh);
-
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