From 73b5394e2e4af3bbe01e221fa395373facc67f78 Mon Sep 17 00:00:00 2001 From: Peter Lieven Date: Thu, 16 Apr 2015 16:08:29 +0200 Subject: [PATCH] block/iscsi: optimize WRITE10/16 if cache.writeback is not set SCSI allowes to tell the target to not return from a write command if the date is not written to the disk. Use this so called FUA bit if it is supported to optimize WRITE commands if writeback is not allowed. In this case qemu always issues a WRITE followed by a FLUSH. This is 2 round trip times. If we set the FUA bit we can ignore the following FLUSH. Signed-off-by: Peter Lieven Message-id: 1429193313-4263-6-git-send-email-pl@kamp.de Signed-off-by: Stefan Hajnoczi Signed-off-by: Kevin Wolf --- block/iscsi.c | 18 +++++++++++++++--- 1 file changed, 15 insertions(+), 3 deletions(-) diff --git a/block/iscsi.c b/block/iscsi.c index 237faa1f05..6033330e3d 100644 --- a/block/iscsi.c +++ b/block/iscsi.c @@ -68,6 +68,7 @@ typedef struct IscsiLun { bool lbprz; bool dpofua; bool has_write_same; + bool force_next_flush; } IscsiLun; typedef struct IscsiTask { @@ -80,6 +81,7 @@ typedef struct IscsiTask { QEMUBH *bh; IscsiLun *iscsilun; QEMUTimer retry_timer; + bool force_next_flush; } IscsiTask; typedef struct IscsiAIOCB { @@ -200,6 +202,8 @@ iscsi_co_generic_cb(struct iscsi_context *iscsi, int status, } } error_report("iSCSI Failure: %s", iscsi_get_error(iscsi)); + } else { + iTask->iscsilun->force_next_flush |= iTask->force_next_flush; } out: @@ -370,6 +374,7 @@ static int coroutine_fn iscsi_co_writev(BlockDriverState *bs, struct IscsiTask iTask; uint64_t lba; uint32_t num_sectors; + int fua; if (!is_request_lun_aligned(sector_num, nb_sectors, iscsilun)) { return -EINVAL; @@ -385,15 +390,17 @@ static int coroutine_fn iscsi_co_writev(BlockDriverState *bs, num_sectors = sector_qemu2lun(nb_sectors, iscsilun); iscsi_co_init_iscsitask(iscsilun, &iTask); retry: + fua = iscsilun->dpofua && !bs->enable_write_cache; + iTask.force_next_flush = !fua; if (iscsilun->use_16_for_rw) { iTask.task = iscsi_write16_task(iscsilun->iscsi, iscsilun->lun, lba, NULL, num_sectors * iscsilun->block_size, - iscsilun->block_size, 0, 0, 0, 0, 0, + iscsilun->block_size, 0, 0, fua, 0, 0, iscsi_co_generic_cb, &iTask); } else { iTask.task = iscsi_write10_task(iscsilun->iscsi, iscsilun->lun, lba, NULL, num_sectors * iscsilun->block_size, - iscsilun->block_size, 0, 0, 0, 0, 0, + iscsilun->block_size, 0, 0, fua, 0, 0, iscsi_co_generic_cb, &iTask); } if (iTask.task == NULL) { @@ -621,8 +628,12 @@ static int coroutine_fn iscsi_co_flush(BlockDriverState *bs) return 0; } - iscsi_co_init_iscsitask(iscsilun, &iTask); + if (!iscsilun->force_next_flush) { + return 0; + } + iscsilun->force_next_flush = false; + iscsi_co_init_iscsitask(iscsilun, &iTask); retry: if (iscsi_synchronizecache10_task(iscsilun->iscsi, iscsilun->lun, 0, 0, 0, 0, iscsi_co_generic_cb, &iTask) == NULL) { @@ -918,6 +929,7 @@ coroutine_fn iscsi_co_write_zeroes(BlockDriverState *bs, int64_t sector_num, } iscsi_co_init_iscsitask(iscsilun, &iTask); + iTask.force_next_flush = true; retry: if (use_16_for_ws) { iTask.task = iscsi_writesame16_task(iscsilun->iscsi, iscsilun->lun, lba,