Function Ext2TruncateExtent

Ext4Fsd/ext4/extents.c:199–244

NTSTATUS
Ext2TruncateExtent(
    PEXT2_IRP_CONTEXT IrpContext,
    PEXT2_VCB         Vcb,
    PEXT2_MCB         Mcb,
    PLARGE_INTEGER    Size
    )
{
    NTSTATUS Status = STATUS_SUCCESS;

    ULONG    Extra = 0;
    ULONG    Wanted = 0;
    ULONG    End;
    ULONG    Removed;
    int      err;

    /* translate file size to block */
    End = Vcb->max_data_blocks;
    Wanted = (ULONG)((Size->QuadPart + BLOCK_SIZE - 1) >> BLOCK_BITS);

    /* calculate blocks to be freed */
    Extra = End - Wanted;

    err = ext4_ext_truncate(IrpContext, &Mcb->Inode, Wanted);
    if (err == 0) {
        if (!Ext2RemoveBlockExtent(Vcb, Mcb, Wanted, Extra)) {
            ClearFlag(Mcb->Flags, MCB_ZONE_INITED);
            Ext2ClearAllExtents(&Mcb->Extents);
        }
        Extra = 0;
    } else {
        Status = STATUS_INSUFFICIENT_RESOURCES;
    }

    if (!NT_SUCCESS(Status)) {
        Size->QuadPart += ((ULONGLONG)Extra << BLOCK_BITS);
    }

    if (Mcb->Inode.i_size > (loff_t)(Size->QuadPart))
        Mcb->Inode.i_size = (loff_t)(Size->QuadPart);

    /* Save modifications on i_blocks field and i_size field of the inode. */
    Ext2SaveInode(IrpContext, Vcb, &Mcb->Inode);

    return Status;
}