Implement fallocate(2)

Closes #225

PiperOrigin-RevId: 247508791
Change-Id: I04f47cf2770b30043e5a272aba4ba6e11d0476cc

2 files changed, 31 insertions, 0 deletions

diff --git a/pkg/sentry/fs/gofer/context_file.go b/pkg/sentry/fs/gofer/context_file.go
index 842a34af8..be53ac4d9 100644
--- a/pkg/sentry/fs/gofer/context_file.go
+++ b/pkg/sentry/fs/gofer/context_file.go
@@ -59,6 +59,13 @@ func (c *contextFile) setAttr(ctx context.Context, valid p9.SetAttrMask, attr p9
 	return err
 }
 
+func (c *contextFile) allocate(ctx context.Context, mode p9.AllocateMode, offset, length uint64) error {
+	ctx.UninterruptibleSleepStart(false)
+	err := c.file.Allocate(mode, offset, length)
+	ctx.UninterruptibleSleepFinish(false)
+	return err
+}
+
 func (c *contextFile) rename(ctx context.Context, directory contextFile, name string) error {
 	ctx.UninterruptibleSleepStart(false)
 	err := c.file.Rename(directory.file, name)
diff --git a/pkg/sentry/fs/gofer/inode.go b/pkg/sentry/fs/gofer/inode.go
index f6f20844d..dcb3b2880 100644
--- a/pkg/sentry/fs/gofer/inode.go
+++ b/pkg/sentry/fs/gofer/inode.go
@@ -322,6 +322,15 @@ func (i *inodeFileState) unstableAttr(ctx context.Context) (fs.UnstableAttr, err
 	return unstable(ctx, valid, pattr, i.s.mounter, i.s.client), nil
 }
 
+func (i *inodeFileState) Allocate(ctx context.Context, offset, length int64) error {
+	i.handlesMu.RLock()
+	defer i.handlesMu.RUnlock()
+
+	// No options are supported for now.
+	mode := p9.AllocateMode{}
+	return i.writeHandles.File.allocate(ctx, mode, uint64(offset), uint64(length))
+}
+
 // session extracts the gofer's session from the MountSource.
 func (i *inodeOperations) session() *session {
 	return i.fileState.s
@@ -498,6 +507,21 @@ func (i *inodeOperations) Truncate(ctx context.Context, inode *fs.Inode, length
 	return i.fileState.file.setAttr(ctx, p9.SetAttrMask{Size: true}, p9.SetAttr{Size: uint64(length)})
 }
 
+// Allocate implements fs.InodeOperations.Allocate.
+func (i *inodeOperations) Allocate(ctx context.Context, inode *fs.Inode, offset, length int64) error {
+	// This can only be called for files anyway.
+	if i.session().cachePolicy.useCachingInodeOps(inode) {
+		return i.cachingInodeOps.Allocate(ctx, offset, length)
+	}
+	if i.session().cachePolicy == cacheRemoteRevalidating {
+		return i.fileState.hostMappable.Allocate(ctx, offset, length)
+	}
+
+	// No options are supported for now.
+	mode := p9.AllocateMode{}
+	return i.fileState.file.allocate(ctx, mode, uint64(offset), uint64(length))
+}
+
 // WriteOut implements fs.InodeOperations.WriteOut.
 func (i *inodeOperations) WriteOut(ctx context.Context, inode *fs.Inode) error {
 	if !i.session().cachePolicy.cacheUAttrs(inode) {