GIT: unionfs2-2.6.27.y: bug fix: set lower inodes correctly after branch management succeeds

[Erez Zadok]

commit 0cb80df88d7c84f4b2a7bf7624e41511811268f2
Author: Erez Zadok <ezk at bigvaio.(none)>
Date:   Tue May 22 23:52:12 2007 -0400

    bug fix: set lower inodes correctly after branch management succeeds
    
    Signed-off-by: Erez Zadok <ezk at cs.sunysb.edu>

diff --git a/fs/unionfs/super.c b/fs/unionfs/super.c
index 1ca6c54..4b4233c 100644
--- a/fs/unionfs/super.c
+++ b/fs/unionfs/super.c
@@ -351,7 +351,13 @@ found_insertion_point:
 		       new_branch, err);
 		goto out;
 	}
-	/* it's probably safe to check_mode the new branch to insert */
+	/*
+	 * It's probably safe to check_mode the new branch to insert.  Note:
+	 * we don't allow inserting branches which are unionfs's by
+	 * themselves (check_branch returns EINVAL in that case).  This is
+	 * because this code base doesn't support stacking unionfs: the ODF
+	 * code base supports that correctly.
+	 */
 	if ((err = check_branch(&nd))) {
 		printk(KERN_WARNING "unionfs: hidden directory "
 		       "\"%s\" is not a valid branch\n", optarg);
@@ -416,14 +422,16 @@ static int unionfs_remount_fs(struct super_block *sb, int *flags,
 	int i;
 	char *optionstmp, *tmp_to_free;	/* kstrdup'ed of "options" */
 	char *optname;
-	int cur_branches;	/* no. of current branches */
-	int new_branches;	/* no. of branches actually left in the end */
+	int cur_branches = 0;	/* no. of current branches */
+	int new_branches = 0;	/* no. of branches actually left in the end */
 	int add_branches;	/* est. no. of branches to add */
 	int del_branches;	/* est. no. of branches to del */
 	int max_branches;	/* max possible no. of branches */
 	struct unionfs_data *new_data = NULL, *tmp_data = NULL;
 	struct path *new_lower_paths = NULL, *tmp_lower_paths = NULL;
+	struct inode **new_lower_inodes = NULL;
 	int new_high_branch_id;	/* new high branch ID */
+	int old_ibstart, old_ibend;
 
 	unionfs_write_lock(sb);
 
@@ -661,10 +669,7 @@ out_no_change:
 			err = -ENOMEM;
 			goto out_release;
 		}
-		/*
-		 * copy current info into new placeholders, incrementing
-		 * refcounts.
-		 */
+		/* copy current info into new placeholders */
 		memcpy(new_data, tmp_data,
 		       new_branches * sizeof(struct unionfs_data));
 		memcpy(new_lower_paths, tmp_lower_paths,
@@ -676,12 +681,19 @@ out_no_change:
 		 */
 		kfree(tmp_data);
 		kfree(tmp_lower_paths);
-		/* no need to nullify pointers here */
+		/* no need to nullify pointers here (they get reused below) */
 	} else {
 		/* number of branches didn't change, no need to re-alloc */
 		new_data = tmp_data;
 		new_lower_paths = tmp_lower_paths;
 	}
+	/* allocate space for new pointers to lower inodes */
+	new_lower_inodes = kcalloc(new_branches,
+				   sizeof(struct inode *), GFP_KERNEL);
+	if (!new_lower_inodes) {
+		err = -ENOMEM;
+		goto out_release;
+	}
 
 	/*
 	 * OK, just before we actually put the new set of branches in place,
@@ -703,7 +715,7 @@ out_no_change:
 	 * fsync_super() which would not have returned until all dirty pages
 	 * were flushed.
 	 *
-	 * But do w have to worry about locked pages?  Is there any chance
+	 * But do we have to worry about locked pages?  Is there any chance
 	 * that in here we'll get locked pages?
 	 *
 	 * XXX: what about pages mapped into pagetables?  Are these pages
@@ -730,8 +742,31 @@ out_no_change:
 	i = sbmax(sb);		/* save no. of branches to release at end */
 	sbend(sb) = new_branches - 1;
 	set_dbend(sb->s_root, new_branches - 1);
+	old_ibstart = ibstart(sb->s_root->d_inode);
+	old_ibend = ibend(sb->s_root->d_inode);
+	ibend(sb->s_root->d_inode) = new_branches - 1;
 	UNIONFS_D(sb->s_root)->bcount = new_branches;
-	new_branches = i;	/* no. of branches to release below */
+	new_branches = i; /* no. of branches to release below */
+
+	/*
+	 * Update lower inodes: 3 steps
+	 * 1. grab ref on all new lower inodes
+	 */
+	for (i=dbstart(sb->s_root); i<=dbend(sb->s_root); i++) {
+		struct dentry *lower_dentry =
+			unionfs_lower_dentry_idx(sb->s_root, i);
+		atomic_inc(&lower_dentry->d_inode->i_count);
+		new_lower_inodes[i] = lower_dentry->d_inode;
+	}
+	/* 2. release reference on all older lower inodes */
+	for (i=old_ibstart; i<=old_ibend; i++) {
+		iput(unionfs_lower_inode_idx(sb->s_root->d_inode, i));
+		unionfs_set_lower_inode_idx(sb->s_root->d_inode, i, NULL);
+	}
+	kfree(UNIONFS_I(sb->s_root->d_inode)->lower_inodes);
+	/* 3. update root dentry's inode to new lower_inodes array */
+	UNIONFS_I(sb->s_root->d_inode)->lower_inodes = new_lower_inodes;
+	new_lower_inodes = NULL;
 
 	/* maxbytes may have changed */
 	sb->s_maxbytes = unionfs_lower_super_idx(sb, 0)->s_maxbytes;
@@ -764,8 +799,10 @@ out_free:
 	kfree(tmp_data);
 	kfree(new_lower_paths);
 	kfree(new_data);
+	kfree(new_lower_inodes);
 out_error:
 	unionfs_write_unlock(sb);
+	unionfs_check_dentry(sb->s_root);
 	return err;
 }