Commit 5917af81 authored by Peter Lieven's avatar Peter Lieven Committed by Paolo Bonzini
Browse files

block/iscsi: clarify the meaning of ISCSI_CHECKALLOC_THRES 



Signed-off-by: default avatarPeter Lieven <pl@kamp.de>
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
parent b03c3805

block/iscsi.c

+10 −2
Original line number Diff line number Diff line
@@ -95,7 +95,15 @@ typedef struct IscsiAIOCB { 
#define NOP_INTERVAL 5000

#define MAX_NOP_FAILURES 3

#define ISCSI_CMD_RETRIES 5

#define ISCSI_CHECKALLOC_THRES 63



/* this threshhold is a trade-off knob to choose between

 * the potential additional overhead of an extra GET_LBA_STATUS request

 * vs. unnecessarily reading a lot of zero sectors over the wire.

 * If a read request is greater or equal than ISCSI_CHECKALLOC_THRES

 * sectors we check the allocation status of the area covered by the

 * request first if the allocationmap indicates that the area might be

 * unallocated. */

#define ISCSI_CHECKALLOC_THRES 64



static void

iscsi_bh_cb(void *p)
@@ -505,7 +513,7 @@ static int coroutine_fn iscsi_co_readv(BlockDriverState *bs, 
    }



#if defined(LIBISCSI_FEATURE_IOVECTOR)

    if (iscsilun->lbprz && nb_sectors > ISCSI_CHECKALLOC_THRES &&

    if (iscsilun->lbprz && nb_sectors >= ISCSI_CHECKALLOC_THRES &&

        !iscsi_allocationmap_is_allocated(iscsilun, sector_num, nb_sectors)) {

        int64_t ret;

        int pnum;