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Re: [Qemu-devel] [PATCH for-2.0] iscsi: always query max WRITE SAME leng
From: |
Peter Lieven |
Subject: |
Re: [Qemu-devel] [PATCH for-2.0] iscsi: always query max WRITE SAME length |
Date: |
Wed, 02 Apr 2014 22:44:41 +0200 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:24.0) Gecko/20100101 Thunderbird/24.2.0 |
Am 02.04.2014 15:44, schrieb Paolo Bonzini:
> Max WRITE SAME length is also used when the UNMAP bit is zero, so it
> should be queried even if LBPWS=0. Same for the optimal transfer
> length.
>
> However, the write_zeroes_alignment only matters for UNMAP=1 so we
> still restrict it to LBPWS=1.
>
> Signed-off-by: Paolo Bonzini <address@hidden>
> ---
> block/iscsi.c | 12 +++++++-----
> 1 file changed, 7 insertions(+), 5 deletions(-)
>
> diff --git a/block/iscsi.c b/block/iscsi.c
> index 00316af..bb88b4b 100644
> --- a/block/iscsi.c
> +++ b/block/iscsi.c
> @@ -1335,18 +1335,20 @@ static int iscsi_refresh_limits(BlockDriverState *bs)
>
> /* We don't actually refresh here, but just return data queried in
> * iscsi_open(): iscsi targets don't change their limits. */
> - if (iscsilun->lbp.lbpu || iscsilun->lbp.lbpws) {
> + if (iscsilun->lbp.lbpu) {
> if (iscsilun->bl.max_unmap < 0xffffffff) {
> bs->bl.max_discard = sector_lun2qemu(iscsilun->bl.max_unmap,
> iscsilun);
> }
> bs->bl.discard_alignment =
> sector_lun2qemu(iscsilun->bl.opt_unmap_gran,
> iscsilun);
> + }
>
> - if (iscsilun->bl.max_ws_len < 0xffffffff) {
> - bs->bl.max_write_zeroes =
> sector_lun2qemu(iscsilun->bl.max_ws_len,
> - iscsilun);
> - }
> + if (iscsilun->bl.max_ws_len < 0xffffffff) {
> + bs->bl.max_write_zeroes = sector_lun2qemu(iscsilun->bl.max_ws_len,
> + iscsilun);
> + }
> + if (iscsilun->lbp.lbpws) {
> bs->bl.write_zeroes_alignment =
> sector_lun2qemu(iscsilun->bl.opt_unmap_gran,
> iscsilun);
> }
Reviewed-by: Peter Lieven <address@hidden>
PS: One thing that came into my mind while looking at this. If a target has
LBPWS == 0 and we
send a write zeroes request with BDRV_REQ_MAY_UNMAP we fail with -ENOTSUP.
Shouldn't
we fall back to WRITESAME without UNMAP if iscsilun->has_write_same == true?
Peter