Complete vfs2 implementation of fallocate.

This change includes overlay, special regular gofer files, and hostfs.

Fixes #3589.

PiperOrigin-RevId: 332330860

4 files changed, 43 insertions, 26 deletions

diff --git a/pkg/sentry/fsimpl/gofer/filesystem.go b/pkg/sentry/fsimpl/gofer/filesystem.go
index b01121f9e..4a592175b 100644
--- a/pkg/sentry/fsimpl/gofer/filesystem.go
+++ b/pkg/sentry/fsimpl/gofer/filesystem.go
@@ -1026,7 +1026,7 @@ func (d *dentry) open(ctx context.Context, rp *vfs.ResolvingPath, opts *vfs.Open
 		// step is required even if !d.cachedMetadataAuthoritative() because
 		// d.mappings has to be updated.
 		// d.metadataMu has already been acquired if trunc == true.
-		d.updateFileSizeLocked(0)
+		d.updateSizeLocked(0)
 
 		if d.cachedMetadataAuthoritative() {
 			d.touchCMtimeLocked()
diff --git a/pkg/sentry/fsimpl/gofer/gofer.go b/pkg/sentry/fsimpl/gofer/gofer.go
index 0e21c31a4..aaad9c0d9 100644
--- a/pkg/sentry/fsimpl/gofer/gofer.go
+++ b/pkg/sentry/fsimpl/gofer/gofer.go
@@ -833,7 +833,7 @@ func (d *dentry) updateFromP9AttrsLocked(mask p9.AttrMask, attr *p9.Attr) {
 		atomic.StoreUint32(&d.nlink, uint32(attr.NLink))
 	}
 	if mask.Size {
-		d.updateFileSizeLocked(attr.Size)
+		d.updateSizeLocked(attr.Size)
 	}
 }
 
@@ -987,7 +987,7 @@ func (d *dentry) setStat(ctx context.Context, creds *auth.Credentials, opts *vfs
 				// d.size should be kept up to date, and privatized
 				// copy-on-write mappings of truncated pages need to be
 				// invalidated, even if InteropModeShared is in effect.
-				d.updateFileSizeLocked(stat.Size)
+				d.updateSizeLocked(stat.Size)
 			}
 		}
 		if d.fs.opts.interop == InteropModeShared {
@@ -1024,8 +1024,31 @@ func (d *dentry) setStat(ctx context.Context, creds *auth.Credentials, opts *vfs
 	return nil
 }
 
+// doAllocate performs an allocate operation on d. Note that d.metadataMu will
+// be held when allocate is called.
+func (d *dentry) doAllocate(ctx context.Context, offset, length uint64, allocate func() error) error {
+	d.metadataMu.Lock()
+	defer d.metadataMu.Unlock()
+
+	// Allocating a smaller size is a noop.
+	size := offset + length
+	if d.cachedMetadataAuthoritative() && size <= d.size {
+		return nil
+	}
+
+	err := allocate()
+	if err != nil {
+		return err
+	}
+	d.updateSizeLocked(size)
+	if d.cachedMetadataAuthoritative() {
+		d.touchCMtimeLocked()
+	}
+	return nil
+}
+
 // Preconditions: d.metadataMu must be locked.
-func (d *dentry) updateFileSizeLocked(newSize uint64) {
+func (d *dentry) updateSizeLocked(newSize uint64) {
 	d.dataMu.Lock()
 	oldSize := d.size
 	atomic.StoreUint64(&d.size, newSize)
diff --git a/pkg/sentry/fsimpl/gofer/regular_file.go b/pkg/sentry/fsimpl/gofer/regular_file.go
index a2e9342d5..24f03ee94 100644
--- a/pkg/sentry/fsimpl/gofer/regular_file.go
+++ b/pkg/sentry/fsimpl/gofer/regular_file.go
@@ -79,28 +79,11 @@ func (fd *regularFileFD) OnClose(ctx context.Context) error {
 // Allocate implements vfs.FileDescriptionImpl.Allocate.
 func (fd *regularFileFD) Allocate(ctx context.Context, mode, offset, length uint64) error {
 	d := fd.dentry()
-	d.metadataMu.Lock()
-	defer d.metadataMu.Unlock()
-
-	// Allocating a smaller size is a noop.
-	size := offset + length
-	if d.cachedMetadataAuthoritative() && size <= d.size {
-		return nil
-	}
-
-	d.handleMu.RLock()
-	err := d.writeFile.allocate(ctx, p9.ToAllocateMode(mode), offset, length)
-	d.handleMu.RUnlock()
-	if err != nil {
-		return err
-	}
-	d.dataMu.Lock()
-	atomic.StoreUint64(&d.size, size)
-	d.dataMu.Unlock()
-	if d.cachedMetadataAuthoritative() {
-		d.touchCMtimeLocked()
-	}
-	return nil
+	return d.doAllocate(ctx, offset, length, func() error {
+		d.handleMu.RLock()
+		defer d.handleMu.RUnlock()
+		return d.writeFile.allocate(ctx, p9.ToAllocateMode(mode), offset, length)
+	})
 }
 
 // PRead implements vfs.FileDescriptionImpl.PRead.
diff --git a/pkg/sentry/fsimpl/gofer/special_file.go b/pkg/sentry/fsimpl/gofer/special_file.go
index 3c39aa9b7..dc960e5bf 100644
--- a/pkg/sentry/fsimpl/gofer/special_file.go
+++ b/pkg/sentry/fsimpl/gofer/special_file.go
@@ -22,6 +22,7 @@ import (
 	"gvisor.dev/gvisor/pkg/abi/linux"
 	"gvisor.dev/gvisor/pkg/context"
 	"gvisor.dev/gvisor/pkg/fdnotifier"
+	"gvisor.dev/gvisor/pkg/p9"
 	"gvisor.dev/gvisor/pkg/safemem"
 	"gvisor.dev/gvisor/pkg/sentry/vfs"
 	"gvisor.dev/gvisor/pkg/syserror"
@@ -135,6 +136,16 @@ func (fd *specialFileFD) EventUnregister(e *waiter.Entry) {
 	fd.fileDescription.EventUnregister(e)
 }
 
+func (fd *specialFileFD) Allocate(ctx context.Context, mode, offset, length uint64) error {
+	if fd.isRegularFile {
+		d := fd.dentry()
+		return d.doAllocate(ctx, offset, length, func() error {
+			return fd.handle.file.allocate(ctx, p9.ToAllocateMode(mode), offset, length)
+		})
+	}
+	return fd.FileDescriptionDefaultImpl.Allocate(ctx, mode, offset, length)
+}
+
 // PRead implements vfs.FileDescriptionImpl.PRead.
 func (fd *specialFileFD) PRead(ctx context.Context, dst usermem.IOSequence, offset int64, opts vfs.ReadOptions) (int64, error) {
 	if fd.seekable && offset < 0 {