[PATCH 3/6] hfsplus: prevent btree data loss on ENOSPC

["Ernesto A. Fernández" <ernesto.mnd.fernandez@gmail.com>]

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.

>From now on, 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.

Signed-off-by: Ernesto A. Fernández <ernesto.mnd.fernandez@gmail.com>
---
 fs/hfsplus/attributes.c | 10 ++++++++++
 fs/hfsplus/btree.c      | 42 +++++++++++++++++++++++++++---------------
 fs/hfsplus/catalog.c    | 24 ++++++++++++++++++++++++
 fs/hfsplus/extents.c    |  4 ++++
 fs/hfsplus/hfsplus_fs.h |  2 ++
 5 files changed, 67 insertions(+), 15 deletions(-)

diff --git a/fs/hfsplus/attributes.c b/fs/hfsplus/attributes.c
index 2bab6b3cdba4..e6d554476db4 100644
--- a/fs/hfsplus/attributes.c
+++ b/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);
diff --git a/fs/hfsplus/btree.c b/fs/hfsplus/btree.c
index de14b2b6881b..d20902f3e015 100644
--- a/fs/hfsplus/btree.c
+++ b/fs/hfsplus/btree.c
@@ -342,26 +342,21 @@ static struct hfs_bnode *hfs_bmap_new_bmap(struct hfs_bnode *prev, u32 idx)
 	return node;
 }
 
-struct hfs_bnode *hfs_bmap_alloc(struct hfs_btree *tree)
+/* Make sure @tree has enough space for the @rsvd_nodes */
+int hfs_bmap_reserve(struct hfs_btree *tree, int rsvd_nodes)
 {
-	struct hfs_bnode *node, *next_node;
-	struct page **pagep;
-	u32 nidx, idx;
-	unsigned off;
-	u16 off16;
-	u16 len;
-	u8 *data, byte, m;
-	int i;
+	struct inode *inode = tree->inode;
+	struct hfsplus_inode_info *hip = HFSPLUS_I(inode);
+	u32 count;
+	int res;
 
-	while (!tree->free_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 ERR_PTR(res);
+			return res;
 		hip->phys_size = inode->i_size =
 			(loff_t)hip->alloc_blocks <<
 				HFSPLUS_SB(tree->sb)->alloc_blksz_shift;
@@ -372,6 +367,23 @@ struct hfs_bnode *hfs_bmap_alloc(struct hfs_btree *tree)
 		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;
+	struct page **pagep;
+	u32 nidx, idx;
+	unsigned off;
+	u16 off16;
+	u16 len;
+	u8 *data, byte, m;
+	int i, res;
+
+	res = hfs_bmap_reserve(tree, 1);
+	if (res)
+		return ERR_PTR(res);
 
 	nidx = 0;
 	node = hfs_bnode_find(tree, nidx);
diff --git a/fs/hfsplus/catalog.c b/fs/hfsplus/catalog.c
index a196369ba779..35472cba750e 100644
--- a/fs/hfsplus/catalog.c
+++ b/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);
diff --git a/fs/hfsplus/extents.c b/fs/hfsplus/extents.c
index 8e0f59767694..8a8893d522ef 100644
--- a/fs/hfsplus/extents.c
+++ b/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);
diff --git a/fs/hfsplus/hfsplus_fs.h b/fs/hfsplus/hfsplus_fs.h
index 8e039435958a..dd7ad9f13e3a 100644
--- a/fs/hfsplus/hfsplus_fs.h
+++ b/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);
 
-- 
2.11.0