knfsd: exportfs: remove iget abuse

When the exportfs interface was added the expectation was that filesystems
provide an operation to convert from a file handle to an inode/dentry, but it
kept a backwards compat option that still calls into iget.

Calling into iget from non-filesystem code is very bad, because it gives too
little information to filesystem, and simply crashes if the filesystem doesn't
implement the ->read_inode routine.

Fortunately there are only two filesystems left using this fallback: efs and
jfs.  This patch moves a copy of export_iget to each of those to implement the
get_dentry method.

While this is a temporary increase of lines of code in the kernel it allows
for a much cleaner interface and important code restructuring in later
patches.

[akpm@linux-foundation.org: add jfs_get_inode_flags() declaration]
Signed-off-by: Dave Kleikamp <shaggy@linux.vnet.ibm.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Neil Brown <neilb@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

3 files changed, 34 insertions, 0 deletions

diff --git a/fs/jfs/jfs_inode.h b/fs/jfs/jfs_inode.h
index 2374b595f2e..f0ec72b263f 100644
--- a/fs/jfs/jfs_inode.h
+++ b/fs/jfs/jfs_inode.h
@@ -32,6 +32,7 @@ extern void jfs_truncate_nolock(struct inode *, loff_t);
 extern void jfs_free_zero_link(struct inode *);
 extern struct dentry *jfs_get_parent(struct dentry *dentry);
 extern void jfs_get_inode_flags(struct jfs_inode_info *);
+extern struct dentry *jfs_get_dentry(struct super_block *sb, void *vobjp);
 extern void jfs_set_inode_flags(struct inode *);
 extern int jfs_get_block(struct inode *, sector_t, struct buffer_head *, int);
 
diff --git a/fs/jfs/namei.c b/fs/jfs/namei.c
index 25161c4121e..932797ba433 100644
--- a/fs/jfs/namei.c
+++ b/fs/jfs/namei.c
@@ -1477,6 +1477,38 @@ static struct dentry *jfs_lookup(struct inode *dip, struct dentry *dentry, struc
 	return dentry;
 }
 
+struct dentry *jfs_get_dentry(struct super_block *sb, void *vobjp)
+{
+	__u32 *objp = vobjp;
+	unsigned long ino = objp[0];
+	__u32 generation = objp[1];
+	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)) {
+	    	result = ERR_PTR(-ESTALE);
+		goto out_iput;
+	}
+
+	result = d_alloc_anon(inode);
+	if (!result) {
+		result = ERR_PTR(-ENOMEM);
+		goto out_iput;
+	}
+	return result;
+
+ out_iput:
+	iput(inode);
+	return result;
+}
+
 struct dentry *jfs_get_parent(struct dentry *dentry)
 {
 	struct super_block *sb = dentry->d_inode->i_sb;
diff --git a/fs/jfs/super.c b/fs/jfs/super.c
index 49b652bd96b..929fceca799 100644
--- a/fs/jfs/super.c
+++ b/fs/jfs/super.c
@@ -738,6 +738,7 @@ static const struct super_operations jfs_super_operations = {
 };
 
 static struct export_operations jfs_export_operations = {
+	.get_dentry	= jfs_get_dentry,
 	.get_parent	= jfs_get_parent,
 };