Implement fallocate(2)

Closes #225

PiperOrigin-RevId: 247508791
Change-Id: I04f47cf2770b30043e5a272aba4ba6e11d0476cc

2 files changed, 34 insertions, 1 deletions

diff --git a/pkg/sentry/fs/tmpfs/inode_file.go b/pkg/sentry/fs/tmpfs/inode_file.go
index f89d86c83..c90062a22 100644
--- a/pkg/sentry/fs/tmpfs/inode_file.go
+++ b/pkg/sentry/fs/tmpfs/inode_file.go
@@ -259,6 +259,33 @@ func (f *fileInodeOperations) Truncate(ctx context.Context, _ *fs.Inode, size in
 	return nil
 }
 
+// Allocate implements fs.InodeOperations.Allocate.
+func (f *fileInodeOperations) Allocate(ctx context.Context, _ *fs.Inode, offset, length int64) error {
+	newSize := offset + length
+
+	f.attrMu.Lock()
+	defer f.attrMu.Unlock()
+	f.dataMu.Lock()
+	defer f.dataMu.Unlock()
+
+	if newSize <= f.attr.Size {
+		return nil
+	}
+
+	// Check if current seals allow growth.
+	if f.seals&linux.F_SEAL_GROW != 0 {
+		return syserror.EPERM
+	}
+
+	f.attr.Size = newSize
+
+	now := ktime.NowFromContext(ctx)
+	f.attr.ModificationTime = now
+	f.attr.StatusChangeTime = now
+
+	return nil
+}
+
 // AddLink implements fs.InodeOperations.AddLink.
 func (f *fileInodeOperations) AddLink() {
 	f.attrMu.Lock()
diff --git a/pkg/sentry/fs/tmpfs/tmpfs.go b/pkg/sentry/fs/tmpfs/tmpfs.go
index 832914453..6ad5c5adb 100644
--- a/pkg/sentry/fs/tmpfs/tmpfs.go
+++ b/pkg/sentry/fs/tmpfs/tmpfs.go
@@ -242,11 +242,16 @@ func (d *Dir) Rename(ctx context.Context, oldParent *fs.Inode, oldName string, n
 	return rename(ctx, oldParent, oldName, newParent, newName, replacement)
 }
 
-// StatFS implments fs.InodeOperations.StatFS.
+// StatFS implements fs.InodeOperations.StatFS.
 func (*Dir) StatFS(context.Context) (fs.Info, error) {
 	return fsInfo, nil
 }
 
+// Allocate implements fs.InodeOperations.Allocate.
+func (d *Dir) Allocate(ctx context.Context, node *fs.Inode, offset, length int64) error {
+	return d.ramfsDir.Allocate(ctx, node, offset, length)
+}
+
 // Symlink is a symlink.
 //
 // +stateify savable
@@ -281,6 +286,7 @@ func (s *Symlink) StatFS(context.Context) (fs.Info, error) {
 type Socket struct {
 	ramfs.Socket
 	fsutil.InodeNotTruncatable `state:"nosave"`
+	fsutil.InodeNotAllocatable `state:"nosave"`
 }
 
 // NewSocket returns a new socket with the provided permissions.