[Ext4 Secure Delete 2/7v4] ext4: Secure Delete: Add ext4_ind_hole_lookup function

[Allison Henderson <achender@linux.vnet.ibm.com>]

This patch adds a new ext4_ind_hole_lookup function that
will be used to identify and skip over holes during a
secure delete operation

Signed-off-by: Allison Henderson <achender@linux.vnet.ibm.com>
---
:100644 100644 db54ce4... 5c9f88c... M	fs/ext4/ext4.h
:100644 100644 0962642... 2fe9dfd... M	fs/ext4/indirect.c
:100644 100644 c4da98a... 9dc8c14... M	fs/ext4/inode.c
 fs/ext4/ext4.h     |    5 +++
 fs/ext4/indirect.c |    2 +-
 fs/ext4/inode.c    |   73 ++++++++++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 79 insertions(+), 1 deletions(-)

diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
index db54ce4..5c9f88c 100644
--- a/fs/ext4/ext4.h
+++ b/fs/ext4/ext4.h
@@ -2241,6 +2241,11 @@ extern int ext4_bio_write_page(struct ext4_io_submit *io,
 /* mmp.c */
 extern int ext4_multi_mount_protect(struct super_block *, ext4_fsblk_t);
 
+/* indirects.c */
+extern int ext4_block_to_path(struct inode *inode,
+			ext4_lblk_t i_block,
+			ext4_lblk_t offsets[4], int *boundary);
+
 /* BH_Uninit flag: blocks are allocated but uninitialized on disk */
 enum ext4_state_bits {
 	BH_Uninit	/* blocks are allocated but uninitialized on disk */
diff --git a/fs/ext4/indirect.c b/fs/ext4/indirect.c
index 0962642..2fe9dfd 100644
--- a/fs/ext4/indirect.c
+++ b/fs/ext4/indirect.c
@@ -69,7 +69,7 @@ static inline void add_chain(Indirect *p, struct buffer_head *bh, __le32 *v)
  * get there at all.
  */
 
-static int ext4_block_to_path(struct inode *inode,
+int ext4_block_to_path(struct inode *inode,
 			      ext4_lblk_t i_block,
 			      ext4_lblk_t offsets[4], int *boundary)
 {
diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index c4da98a..9dc8c14 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -640,6 +640,79 @@ struct buffer_head *ext4_getblk(handle_t *handle, struct inode *inode,
 	return bh;
 }
 
+/*
+ * ext4_in_hole_lookup
+ *
+ * Returns the size of the hole located at the given block up to
+ * the first boundry, or 0 if there is no hole. Returns negative on err.
+ */
+static int ext4_ind_hole_lookup(struct inode *inode, ext4_lblk_t block)
+{
+	struct super_block *sb = inode->i_sb;
+	struct buffer_head *bh;
+	ext4_lblk_t offsets[4];
+	ext4_lblk_t offset;
+	__le32 *children;
+	__le32 blk;
+	int blocks_to_boundary = 0;
+	int depth = 0;
+	int hole_size = 0;
+	unsigned int i, j;
+
+	depth = ext4_block_to_path(inode, block, offsets, &blocks_to_boundary);
+
+	if (depth == 0)
+		return 0;
+
+	offset = offsets[0];
+	blk = EXT4_I(inode)->i_data[offset];
+	if (blk == 0) {
+		for (i = *offsets; i < EXT4_NDIR_BLOCKS; i++) {
+			if (EXT4_I(inode)->i_data[i] == 0)
+				hole_size++;
+			else
+				break;
+		}
+		return hole_size;
+	}
+
+
+	for (j = 1; j < depth; j++) {
+		offset = offsets[j];
+		bh = sb_getblk(sb, le32_to_cpu(blk));
+		if (unlikely(!bh))
+			return -EIO;
+
+		if (!bh_uptodate_or_lock(bh)) {
+			if (bh_submit_read(bh) < 0) {
+				put_bh(bh);
+				return -EIO;
+			}
+			/* validate block references */
+			if (ext4_check_indirect_blockref(inode, bh)) {
+				put_bh(bh);
+				return -EIO;
+			}
+		}
+
+		blk = ((__le32 *)bh->b_data)[offset];
+		/* Reader: end */
+		if (blk == 0) {
+			children = (__le32 *)(bh->b_data);
+			for (i = offset; i < offset +
+					blocks_to_boundary; i++) {
+				if (children[i] == 0)
+					hole_size++;
+				else
+					break;
+			}
+			return hole_size;
+		}
+	}
+
+	return 0;
+}
+
 struct buffer_head *ext4_bread(handle_t *handle, struct inode *inode,
 			       ext4_lblk_t block, int create, int *err)
 {
-- 
1.7.1