Function Ext2QueryUnusedBH

Ext4Fsd/memory.c:3162–3207

/* get buffer heads from global Vcb BH list */

BOOLEAN
Ext2QueryUnusedBH(PEXT2_VCB Vcb, PLIST_ENTRY head)
{
    struct buffer_head *bh = NULL;
    PLIST_ENTRY         next = NULL;
    LARGE_INTEGER       start, now;
    BOOLEAN             wake = FALSE;

    KeQuerySystemTime(&start);

    ExAcquireResourceExclusiveLite(&Vcb->bd.bd_bh_lock, TRUE);

    while (!IsListEmpty(&Vcb->bd.bd_bh_free)) {

        KeQuerySystemTime(&now);
        if (now.QuadPart > start.QuadPart + (LONGLONG)10*1000*1000) {
            break;
        }

        next = RemoveHeadList(&Vcb->bd.bd_bh_free);
        bh = CONTAINING_RECORD(next, struct buffer_head, b_link);
        if (atomic_read(&bh->b_count)) {
            InitializeListHead(&bh->b_link);
            /* to be inserted by brelse */
            continue;
        }

        if ( IsFlagOn(Vcb->Flags, VCB_BEING_DROPPED) ||
            (bh->b_ts_drop.QuadPart + (LONGLONG)10*1000*1000*15) > now.QuadPart ||
            (bh->b_ts_creat.QuadPart + (LONGLONG)10*1000*1000*180) > now.QuadPart) {
            InsertTailList(head, &bh->b_link);
            buffer_head_remove(&Vcb->bd, bh);
        } else {
            InsertHeadList(&Vcb->bd.bd_bh_free, &bh->b_link);
            break;
        }
    }

    wake = IsListEmpty(&Vcb->bd.bd_bh_free);
    ExReleaseResourceLite(&Vcb->bd.bd_bh_lock);

    if (wake)
        KeSetEvent(&Vcb->bd.bd_bh_notify, 0, FALSE);

    return IsFlagOn(Vcb->Flags, VCB_BEING_DROPPED);
}


/* Reaper thread to release unused buffer heads */