Implement FileCompressionInformation for ZFS dataset compression

file_compression_information() now returns proper FILE_COMPRESSION_INFORMATION
for files on compressed datasets. It uses os_compress (the dataset-level
setting) rather than doi_compress (which is 0 for most files even when
compression is active via inheritance), and reports physical block usage
from doi_physical_blocks_512 as the CompressedFileSize.

GetCompressedFileSize() correctly returns the physical compressed size
via this handler. Explorer "Size on disk" continues to show the
cluster-rounded logical size (computed from allocation unit size, not
from FileCompressionInformation or AllocationSize).

allocationsize() is moved out of the inline in zfs_windows.h into
zfs_vnops_windows_lib.c so it can use zfs_blksz() with its fallback
logic, fixing the case where z_blksz is 0 at open time.

Signed-off-by: Jorgen Lundman <lundman@lundman.net>

Author: lundman

include/os/windows/zfs/sys/zfs_windows.h

@@ -140,23 +140,7 @@ extern NTSTATUS zfsdev_release(dev_t dev, PIRP Irp);
 extern int	zfs_vnop_recycle(znode_t *zp, int force);
 extern uint64_t zfs_blksz(znode_t *zp);
 
-inline static uint64_t
-allocationsize(struct znode *zp)
-{
-	if (S_ISDIR(zp->z_mode))
-		return (0ULL);
-
-	if (zp->z_size == 0) {
-		// Did they prealloc?
-		struct vnode *vp = ZTOV(zp);
-		if ((vp != NULL) &&
-		    (vp->FileHeader.AllocationSize.QuadPart > 0ULL))
-			return (vp->FileHeader.AllocationSize.QuadPart);
-		return (0ULL);
-	}
-
-	return (P2ROUNDUP(zp->z_size, zfs_blksz(zp)));
-}
+extern uint64_t allocationsize(struct znode *zp);
 
 extern int	zfs_vnop_mount(PDEVICE_OBJECT DiskDevice, PIRP Irp,
     PIO_STACK_LOCATION IrpSp);

module/os/windows/zfs/zfs_vnops_windows_lib.c

@@ -4853,35 +4853,63 @@ NTSTATUS
 file_compression_information(PDEVICE_OBJECT DeviceObject, PIRP Irp,
     PIO_STACK_LOCATION IrpSp, FILE_COMPRESSION_INFORMATION *fci)
 {
-	dprintf("   %s\n", __func__);
-
 	if (IrpSp->Parameters.QueryFile.Length <
 	    sizeof (FILE_COMPRESSION_INFORMATION)) {
 		Irp->IoStatus.Information =
 		    sizeof (FILE_COMPRESSION_INFORMATION);
 		return (STATUS_BUFFER_TOO_SMALL);
 	}
 
-	if (IrpSp->FileObject && IrpSp->FileObject->FsContext) {
-		struct vnode *vp = IrpSp->FileObject->FsContext;
-		if (VN_HOLD(vp) == 0) {
-			znode_t *zp = VTOZ(vp);
-			zfsvfs_t *zfsvfs = zp->z_zfsvfs;
-
-			memset(fci, 0, sizeof (FILE_COMPRESSION_INFORMATION));
+	if (IrpSp->FileObject == NULL ||
+	    IrpSp->FileObject->FsContext == NULL)
+		return (STATUS_INVALID_PARAMETER);
 
-			// Deal with ads here, and send adsdata.length
-			if (vnode_isdir(vp))
-				fci->CompressedFileSize.QuadPart = zp->z_size;
+	struct vnode *vp = IrpSp->FileObject->FsContext;
+	if (VN_HOLD(vp) != 0)
+		return (STATUS_INVALID_PARAMETER);
 
-			VN_RELE(vp);
-		}
-		Irp->IoStatus.Information =
-		    sizeof (FILE_COMPRESSION_INFORMATION);
-		return (STATUS_SUCCESS);
+	znode_t *zp = VTOZ(vp);
+	memset(fci, 0, sizeof (FILE_COMPRESSION_INFORMATION));
+
+	dmu_object_info_t doi;
+	boolean_t compressed = B_FALSE;
+	uint64_t phys_bytes = 0;
+
+	objset_t *os = zp->z_zfsvfs->z_os;
+	boolean_t ds_compressed = (os != NULL &&
+	    os->os_compress != ZIO_COMPRESS_OFF &&
+	    os->os_compress != ZIO_COMPRESS_EMPTY);
+
+	if (zp->z_sa_hdl != NULL) {
+
+		dmu_object_info_from_db(sa_get_db(zp->z_sa_hdl), &doi);
+		compressed = ds_compressed;
+		phys_bytes = doi.doi_physical_blocks_512 * 512ULL;
+		fci->CompressedFileSize.QuadPart =
+		    (int64_t)(compressed ? phys_bytes : zp->z_size);
+		fci->CompressionFormat = compressed ?
+		    COMPRESSION_FORMAT_DEFAULT : COMPRESSION_FORMAT_NONE;
+		/*
+		 * CompressionUnitShift: log2 of the compression unit size.
+		 * highbit64 returns 1-based position of highest set bit, so
+		 * subtract 1 to get log2.
+		 */
+		fci->CompressionUnitShift =
+		    (UCHAR)(highbit64(doi.doi_data_block_size) - 1);
+		fci->ChunkShift = fci->CompressionUnitShift;
+		fci->ClusterShift = fci->CompressionUnitShift;
+	} else {
+		/* Fallback: no object info, report uncompressed */
+		fci->CompressedFileSize.QuadPart = (int64_t)zp->z_size;
 	}
 
-	return (STATUS_INVALID_PARAMETER);
+	dprintf("%s: phys=%llu logical=%llu fmt=%u\n", __func__,
+	    (unsigned long long)phys_bytes,
+	    (unsigned long long)zp->z_size, fci->CompressionFormat);
+
+	VN_RELE(vp);
+	Irp->IoStatus.Information = sizeof (FILE_COMPRESSION_INFORMATION);
+	return (STATUS_SUCCESS);
 }
 
 uint64_t
@@ -4902,6 +4930,23 @@ zfs_blksz(znode_t *zp)
 	return (512ULL);
 }
 
+uint64_t
+allocationsize(znode_t *zp)
+{
+	if (S_ISDIR(zp->z_mode))
+		return (0ULL);
+
+	if (zp->z_size == 0) {
+		struct vnode *vp = ZTOV(zp);
+		if (vp != NULL &&
+		    vp->FileHeader.AllocationSize.QuadPart > 0ULL)
+			return (vp->FileHeader.AllocationSize.QuadPart);
+		return (0ULL);
+	}
+
+	return (P2ROUNDUP(zp->z_size, zfs_blksz(zp)));
+}
+
 void
 file_standard_information_impl(PDEVICE_OBJECT DeviceObject,
     PFILE_OBJECT FileObject, FILE_STANDARD_INFORMATION *fsi,