reiserfs: journaled xattrs

Deadlocks are possible in the xattr code between the journal lock and the
xattr sems.

This patch implements journalling for xattr operations. The benefit is
twofold:
 * It gets rid of the deadlock possibility by always ensuring that xattr
   write operations are initiated inside a transaction.
 * It corrects the problem where xattr backing files aren't considered any
   differently than normal files, despite the fact they are metadata.

I discussed the added journal load with Chris Mason, and we decided that
since xattrs (versus other journal activity) is fairly rare, the introduction
of larger transactions to support journaled xattrs wouldn't be too big a deal.

Signed-off-by: Jeff Mahoney <jeffm@suse.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 30 insertions, 9 deletions

diff --git a/fs/reiserfs/xattr.c b/fs/reiserfs/xattr.c
index d3ce274..c2e3a92 100644
--- a/fs/reiserfs/xattr.c
+++ b/fs/reiserfs/xattr.c
@@ -632,8 +632,9 @@ out_dput:
  * inode->i_mutex: down
  */
 int
-__reiserfs_xattr_set(struct inode *inode, const char *name, const void *buffer,
-		     size_t buffer_size, int flags)
+reiserfs_xattr_set_handle(struct reiserfs_transaction_handle *th,
+			  struct inode *inode, const char *name,
+			  const void *buffer, size_t buffer_size, int flags)
 {
 	int err = 0;
 	struct dentry *dentry;
@@ -723,14 +724,34 @@ out_unlock:
 	return err;
 }
 
-int
-reiserfs_xattr_set(struct inode *inode, const char *name, const void *buffer,
-		     size_t buffer_size, int flags)
+/* We need to start a transaction to maintain lock ordering */
+int reiserfs_xattr_set(struct inode *inode, const char *name,
+		       const void *buffer, size_t buffer_size, int flags)
 {
-	int err = __reiserfs_xattr_set(inode, name, buffer, buffer_size, flags);
-	if (err == -ENODATA)
-		err = 0;
-	return err;
+
+	struct reiserfs_transaction_handle th;
+	int error, error2;
+	size_t jbegin_count = reiserfs_xattr_nblocks(inode, buffer_size);
+
+	if (!(flags & XATTR_REPLACE))
+		jbegin_count += reiserfs_xattr_jcreate_nblocks(inode);
+
+	reiserfs_write_lock(inode->i_sb);
+	error = journal_begin(&th, inode->i_sb, jbegin_count);
+	if (error) {
+		reiserfs_write_unlock(inode->i_sb);
+		return error;
+	}
+
+	error = reiserfs_xattr_set_handle(&th, inode, name,
+					  buffer, buffer_size, flags);
+
+	error2 = journal_end(&th, inode->i_sb, jbegin_count);
+	if (error == 0)
+		error = error2;
+	reiserfs_write_unlock(inode->i_sb);
+
+	return error;
 }
 
 /*