hfsplus: prevent btree data loss on ENOSPC

Inserting or deleting a record in a btree may require splitting several of
its nodes.  If we hit ENOSPC halfway through, the new nodes will be left
orphaned and their records will be lost.  This could mean lost inodes,
extents or xattrs.

Henceforth, check the available disk space before making any changes.
This still leaves the potential problem of corruption on ENOMEM.

The patch can be tested with xfstests generic/027.

Link: http://lkml.kernel.org/r/4596eef22fbda137b4ffa0272d92f0da15364421.1536269129.git.ernesto.mnd.fernandez@gmail.com
Signed-off-by: Ernesto A. Fernández <ernesto.mnd.fernandez@gmail.com>
Cc: Christoph Hellwig <hch@lst.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

fs/hfsplus/attributes.c

@@ -217,6 +217,11 @@ int hfsplus_create_attr(struct inode *inode,
 	if (err)
 		goto failed_init_create_attr;
 
+	/* Fail early and avoid ENOSPC during the btree operation */
+	err = hfs_bmap_reserve(fd.tree, fd.tree->depth + 1);
+	if (err)
+		goto failed_create_attr;
+
 	if (name) {
 		err = hfsplus_attr_build_key(sb, fd.search_key,
 						inode->i_ino, name);
@@ -313,6 +318,11 @@ int hfsplus_delete_attr(struct inode *inode, const char *name)
 	if (err)
 		return err;
 
+	/* Fail early and avoid ENOSPC during the btree operation */
+	err = hfs_bmap_reserve(fd.tree, fd.tree->depth);
+	if (err)
+		goto out;
+
 	if (name) {
 		err = hfsplus_attr_build_key(sb, fd.search_key,
 						inode->i_ino, name);

fs/hfsplus/btree.c

@@ -342,6 +342,34 @@ static struct hfs_bnode *hfs_bmap_new_bmap(struct hfs_bnode *prev, u32 idx)
 	return node;
 }
 
+/* Make sure @tree has enough space for the @rsvd_nodes */
+int hfs_bmap_reserve(struct hfs_btree *tree, int rsvd_nodes)
+{
+	struct inode *inode = tree->inode;
+	struct hfsplus_inode_info *hip = HFSPLUS_I(inode);
+	u32 count;
+	int res;
+
+	if (rsvd_nodes <= 0)
+		return 0;
+
+	while (tree->free_nodes < rsvd_nodes) {
+		res = hfsplus_file_extend(inode, hfs_bnode_need_zeroout(tree));
+		if (res)
+			return res;
+		hip->phys_size = inode->i_size =
+			(loff_t)hip->alloc_blocks <<
+				HFSPLUS_SB(tree->sb)->alloc_blksz_shift;
+		hip->fs_blocks =
+			hip->alloc_blocks << HFSPLUS_SB(tree->sb)->fs_shift;
+		inode_set_bytes(inode, inode->i_size);
+		count = inode->i_size >> tree->node_size_shift;
+		tree->free_nodes += count - tree->node_count;
+		tree->node_count = count;
+	}
+	return 0;
+}
+
 struct hfs_bnode *hfs_bmap_alloc(struct hfs_btree *tree)
 {
 	struct hfs_bnode *node, *next_node;
@@ -351,27 +379,11 @@ struct hfs_bnode *hfs_bmap_alloc(struct hfs_btree *tree)
 	u16 off16;
 	u16 len;
 	u8 *data, byte, m;
-	int i;
+	int i, res;
 
-	while (!tree->free_nodes) {
-		struct inode *inode = tree->inode;
-		struct hfsplus_inode_info *hip = HFSPLUS_I(inode);
-		u32 count;
-		int res;
-
-		res = hfsplus_file_extend(inode, hfs_bnode_need_zeroout(tree));
-		if (res)
-			return ERR_PTR(res);
-		hip->phys_size = inode->i_size =
-			(loff_t)hip->alloc_blocks <<
-				HFSPLUS_SB(tree->sb)->alloc_blksz_shift;
-		hip->fs_blocks =
-			hip->alloc_blocks << HFSPLUS_SB(tree->sb)->fs_shift;
-		inode_set_bytes(inode, inode->i_size);
-		count = inode->i_size >> tree->node_size_shift;
-		tree->free_nodes = count - tree->node_count;
-		tree->node_count = count;
-	}
+	res = hfs_bmap_reserve(tree, 1);
+	if (res)
+		return ERR_PTR(res);
 
 	nidx = 0;
 	node = hfs_bnode_find(tree, nidx);

fs/hfsplus/catalog.c

@@ -265,6 +265,14 @@ int hfsplus_create_cat(u32 cnid, struct inode *dir,
 	if (err)
 		return err;
 
+	/*
+	 * Fail early and avoid ENOSPC during the btree operations. We may
+	 * have to split the root node at most once.
+	 */
+	err = hfs_bmap_reserve(fd.tree, 2 * fd.tree->depth);
+	if (err)
+		goto err2;
+
 	hfsplus_cat_build_key_with_cnid(sb, fd.search_key, cnid);
 	entry_size = hfsplus_fill_cat_thread(sb, &entry,
 		S_ISDIR(inode->i_mode) ?
@@ -333,6 +341,14 @@ int hfsplus_delete_cat(u32 cnid, struct inode *dir, const struct qstr *str)
 	if (err)
 		return err;
 
+	/*
+	 * Fail early and avoid ENOSPC during the btree operations. We may
+	 * have to split the root node at most once.
+	 */
+	err = hfs_bmap_reserve(fd.tree, 2 * (int)fd.tree->depth - 2);
+	if (err)
+		goto out;
+
 	if (!str) {
 		int len;
 
@@ -433,6 +449,14 @@ int hfsplus_rename_cat(u32 cnid,
 		return err;
 	dst_fd = src_fd;
 
+	/*
+	 * Fail early and avoid ENOSPC during the btree operations. We may
+	 * have to split the root node at most twice.
+	 */
+	err = hfs_bmap_reserve(src_fd.tree, 4 * (int)src_fd.tree->depth - 1);
+	if (err)
+		goto out;
+
 	/* find the old dir entry and read the data */
 	err = hfsplus_cat_build_key(sb, src_fd.search_key,
 			src_dir->i_ino, src_name);

fs/hfsplus/extents.c

@@ -100,6 +100,10 @@ static int __hfsplus_ext_write_extent(struct inode *inode,
 	if (hip->extent_state & HFSPLUS_EXT_NEW) {
 		if (res != -ENOENT)
 			return res;
+		/* Fail early and avoid ENOSPC during the btree operation */
+		res = hfs_bmap_reserve(fd->tree, fd->tree->depth + 1);
+		if (res)
+			return res;
 		hfs_brec_insert(fd, hip->cached_extents,
 				sizeof(hfsplus_extent_rec));
 		hip->extent_state &= ~(HFSPLUS_EXT_DIRTY | HFSPLUS_EXT_NEW);

fs/hfsplus/hfsplus_fs.h

@@ -311,6 +311,7 @@ static inline unsigned short hfsplus_min_io_size(struct super_block *sb)
 #define hfs_btree_open hfsplus_btree_open
 #define hfs_btree_close hfsplus_btree_close
 #define hfs_btree_write hfsplus_btree_write
+#define hfs_bmap_reserve hfsplus_bmap_reserve
 #define hfs_bmap_alloc hfsplus_bmap_alloc
 #define hfs_bmap_free hfsplus_bmap_free
 #define hfs_bnode_read hfsplus_bnode_read
@@ -395,6 +396,7 @@ u32 hfsplus_calc_btree_clump_size(u32 block_size, u32 node_size, u64 sectors,
 struct hfs_btree *hfs_btree_open(struct super_block *sb, u32 id);
 void hfs_btree_close(struct hfs_btree *tree);
 int hfs_btree_write(struct hfs_btree *tree);
+int hfs_bmap_reserve(struct hfs_btree *tree, int rsvd_nodes);
 struct hfs_bnode *hfs_bmap_alloc(struct hfs_btree *tree);
 void hfs_bmap_free(struct hfs_bnode *node);