ext: Added extent tree building logic.

PiperOrigin-RevId: 259628657

2 files changed, 9 insertions, 8 deletions

diff --git a/pkg/sentry/fs/ext/disklayout/inode.go b/pkg/sentry/fs/ext/disklayout/inode.go
index b48001910..9ab9a4988 100644
--- a/pkg/sentry/fs/ext/disklayout/inode.go
+++ b/pkg/sentry/fs/ext/disklayout/inode.go
@@ -107,16 +107,17 @@ type Inode interface {
 	// Flags returns InodeFlags which represents the inode flags.
 	Flags() InodeFlags
 
-	// Blocks returns the underlying inode.i_block array. This field is special
-	// and is used to store various kinds of things depending on the filesystem
-	// version and inode type.
+	// Data returns the underlying inode.i_block array as a slice so it's
+	// modifiable. This field is special and is used to store various kinds of
+	// things depending on the filesystem version and inode type. The underlying
+	// field name in Linux is a little misleading.
 	//   - In ext2/ext3, it contains the block map.
-	//   - In ext4, it contains the extent tree.
+	//   - In ext4, it contains the extent tree root node.
 	//   - For inline files, it contains the file contents.
 	//   - For symlinks, it contains the link path (if it fits here).
 	//
 	// See https://www.kernel.org/doc/html/latest/filesystems/ext4/dynamic.html#the-contents-of-inode-i-block.
-	Blocks() [60]byte
+	Data() []byte
 }
 
 // Inode flags. This is not comprehensive and flags which were not used in
diff --git a/pkg/sentry/fs/ext/disklayout/inode_old.go b/pkg/sentry/fs/ext/disklayout/inode_old.go
index dc4c9d8e4..7d7cc9143 100644
--- a/pkg/sentry/fs/ext/disklayout/inode_old.go
+++ b/pkg/sentry/fs/ext/disklayout/inode_old.go
@@ -47,7 +47,7 @@ type InodeOld struct {
 	BlocksCountLo uint32
 	FlagsRaw      uint32
 	VersionLo     uint32 // This is OS dependent.
-	BlocksRaw     [60]byte
+	DataRaw       [60]byte
 	Generation    uint32
 	FileACLLo     uint32
 	SizeHi        uint32
@@ -113,5 +113,5 @@ func (in *InodeOld) LinksCount() uint16 { return in.LinksCountRaw }
 // Flags implements Inode.Flags.
 func (in *InodeOld) Flags() InodeFlags { return InodeFlagsFromInt(in.FlagsRaw) }
 
-// Blocks implements Inode.Blocks.
-func (in *InodeOld) Blocks() [60]byte { return in.BlocksRaw }
+// Data implements Inode.Data.
+func (in *InodeOld) Data() []byte { return in.DataRaw[:] }