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Blame SOURCES/kvm-scsi-disk-add-UNMAP-limits-to-block-limits-VPD-page.patch

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From de979b1f256be8488f49a78646dee1ded06251ef Mon Sep 17 00:00:00 2001
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From: Paolo Bonzini <pbonzini@redhat.com>
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Date: Mon, 20 Jan 2014 12:49:40 +0100
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Subject: [PATCH 2/4] scsi-disk: add UNMAP limits to block limits VPD page
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RH-Author: Paolo Bonzini <pbonzini@redhat.com>
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Message-id: <1390222180-24891-1-git-send-email-pbonzini@redhat.com>
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Patchwork-id: 56831
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O-Subject: [RHEL 7.0 qemu-kvm PATCH] scsi-disk: add UNMAP limits to block limits VPD page
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Bugzilla: 1037503
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RH-Acked-by: Orit Wasserman <owasserm@redhat.com>
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RH-Acked-by: Stefan Hajnoczi <stefanha@redhat.com>
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RH-Acked-by: Fam Zheng <famz@redhat.com>
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Bugzilla: 1037503
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Brew build: 6896455
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Linux prefers WRITE SAME to UNMAP if the limits are zero, and WRITE
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SAME does not discard anything unless the device can guarantee that
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the resulting block is zero.
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Setting the maximum unmap block and descriptor counts to non-zero
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makes Linux choose UNMAP and fixes thin provisioning on glusterfs.
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While the maximum unmap block count can have some effect on performance,
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the (suggested) maximum number of descriptors is not particularly
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important so I didn't add a customization option.  SCSI drivers are
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used to online firmware updates so I'm not yet adding versioning support
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for SCSI, but we're probably getting close to the point when it's worth
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thinking about it.
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Reported-by: Bharata B Rao <bharata@linux.vnet.ibm.com>
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Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
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(cherry picked from commit 8a1bd2973ed5f99a3c37c9afdff823c4a22152b1)
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---
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 hw/scsi/scsi-disk.c | 20 ++++++++++++++++++++
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 1 file changed, 20 insertions(+)
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Signed-off-by: Miroslav Rezanina <mrezanin@redhat.com>
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---
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 hw/scsi/scsi-disk.c |   20 ++++++++++++++++++++
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 1 files changed, 20 insertions(+), 0 deletions(-)
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diff --git a/hw/scsi/scsi-disk.c b/hw/scsi/scsi-disk.c
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index 7653411..bce617c 100644
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--- a/hw/scsi/scsi-disk.c
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+++ b/hw/scsi/scsi-disk.c
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@@ -47,6 +47,7 @@ do { printf("scsi-disk: " fmt , ## __VA_ARGS__); } while (0)
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 #define SCSI_MAX_MODE_LEN           256
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 #define DEFAULT_DISCARD_GRANULARITY 4096
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+#define DEFAULT_MAX_UNMAP_SIZE      (1 << 30)   /* 1 GB */
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 typedef struct SCSIDiskState SCSIDiskState;
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@@ -74,6 +75,7 @@ struct SCSIDiskState
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     bool media_event;
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     bool eject_request;
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     uint64_t wwn;
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+    uint64_t max_unmap_size;
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     QEMUBH *bh;
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     char *version;
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     char *serial;
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@@ -625,6 +627,8 @@ static int scsi_disk_emulate_inquiry(SCSIRequest *req, uint8_t *outbuf)
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                     s->qdev.conf.min_io_size / s->qdev.blocksize;
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             unsigned int opt_io_size =
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                     s->qdev.conf.opt_io_size / s->qdev.blocksize;
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+            unsigned int max_unmap_sectors =
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+                    s->max_unmap_size / s->qdev.blocksize;
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             if (s->qdev.type == TYPE_ROM) {
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                 DPRINTF("Inquiry (EVPD[%02X] not supported for CDROM\n",
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@@ -647,6 +651,18 @@ static int scsi_disk_emulate_inquiry(SCSIRequest *req, uint8_t *outbuf)
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             outbuf[14] = (opt_io_size >> 8) & 0xff;
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             outbuf[15] = opt_io_size & 0xff;
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+            /* max unmap LBA count, default is 1GB */
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+            outbuf[20] = (max_unmap_sectors >> 24) & 0xff;
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+            outbuf[21] = (max_unmap_sectors >> 16) & 0xff;
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+            outbuf[22] = (max_unmap_sectors >> 8) & 0xff;
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+            outbuf[23] = max_unmap_sectors & 0xff;
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+
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+            /* max unmap descriptors, 255 fit in 4 kb with an 8-byte header.  */
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+            outbuf[24] = 0;
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+            outbuf[25] = 0;
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+            outbuf[26] = 0;
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+            outbuf[27] = 255;
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+
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             /* optimal unmap granularity */
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             outbuf[28] = (unmap_sectors >> 24) & 0xff;
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             outbuf[29] = (unmap_sectors >> 16) & 0xff;
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@@ -2519,6 +2535,8 @@ static Property scsi_hd_properties[] = {
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     DEFINE_PROP_BIT("dpofua", SCSIDiskState, features,
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                     SCSI_DISK_F_DPOFUA, false),
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     DEFINE_PROP_HEX64("wwn", SCSIDiskState, wwn, 0),
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+    DEFINE_PROP_UINT64("max_unmap_size", SCSIDiskState, max_unmap_size,
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+                       DEFAULT_MAX_UNMAP_SIZE),
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     DEFINE_BLOCK_CHS_PROPERTIES(SCSIDiskState, qdev.conf),
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     DEFINE_PROP_END_OF_LIST(),
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 };
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@@ -2628,6 +2646,8 @@ static Property scsi_disk_properties[] = {
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     DEFINE_PROP_BIT("dpofua", SCSIDiskState, features,
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                     SCSI_DISK_F_DPOFUA, false),
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     DEFINE_PROP_HEX64("wwn", SCSIDiskState, wwn, 0),
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+    DEFINE_PROP_UINT64("max_unmap_size", SCSIDiskState, max_unmap_size,
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+                       DEFAULT_MAX_UNMAP_SIZE),
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     DEFINE_PROP_END_OF_LIST(),
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 };
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-- 
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1.7.1
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