Patchwork [21/22] blockdev: enable discard by default

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Submitter Kevin Wolf
Date Feb. 22, 2013, 9:23 p.m.
Message ID <1361568231-18198-22-git-send-email-kwolf@redhat.com>
Download mbox | patch
Permalink /patch/222657/
State New
Headers show

Comments

Kevin Wolf - Feb. 22, 2013, 9:23 p.m.
From: Paolo Bonzini <pbonzini@redhat.com>

Because discard is now a host parameter, we can always fake it as enabled
in the guest.  This is an extension of the current choice to ignore
"not supported" errors from the host when discard_granularity is set
to nonzero.

The default granularity is set to the logical block size or 4k, whichever
is largest, because cluster sizes below 4k are rarely used and 4K is a
typical block size for files.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
---
 hw/block-common.h |  2 +-
 hw/ide/qdev.c     |  5 ++++-
 hw/scsi-disk.c    | 13 ++++++++++---
 3 files changed, 15 insertions(+), 5 deletions(-)

Patch

diff --git a/hw/block-common.h b/hw/block-common.h
index bb808f7..dd11532 100644
--- a/hw/block-common.h
+++ b/hw/block-common.h
@@ -50,7 +50,7 @@  static inline unsigned int get_physical_block_exp(BlockConf *conf)
     DEFINE_PROP_UINT32("opt_io_size", _state, _conf.opt_io_size, 0),    \
     DEFINE_PROP_INT32("bootindex", _state, _conf.bootindex, -1),        \
     DEFINE_PROP_UINT32("discard_granularity", _state, \
-                       _conf.discard_granularity, 0)
+                       _conf.discard_granularity, -1)
 
 #define DEFINE_BLOCK_CHS_PROPERTIES(_state, _conf)      \
     DEFINE_PROP_UINT32("cyls", _state, _conf.cyls, 0),  \
diff --git a/hw/ide/qdev.c b/hw/ide/qdev.c
index c436b38..fd06da7 100644
--- a/hw/ide/qdev.c
+++ b/hw/ide/qdev.c
@@ -143,7 +143,10 @@  static int ide_dev_initfn(IDEDevice *dev, IDEDriveKind kind)
     IDEBus *bus = DO_UPCAST(IDEBus, qbus, dev->qdev.parent_bus);
     IDEState *s = bus->ifs + dev->unit;
 
-    if (dev->conf.discard_granularity && dev->conf.discard_granularity != 512) {
+    if (dev->conf.discard_granularity == -1) {
+        dev->conf.discard_granularity = 512;
+    } else if (dev->conf.discard_granularity &&
+               dev->conf.discard_granularity != 512) {
         error_report("discard_granularity must be 512 for ide");
         return -1;
     }
diff --git a/hw/scsi-disk.c b/hw/scsi-disk.c
index 28e75bb..d411586 100644
--- a/hw/scsi-disk.c
+++ b/hw/scsi-disk.c
@@ -41,9 +41,11 @@  do { printf("scsi-disk: " fmt , ## __VA_ARGS__); } while (0)
 #include <scsi/sg.h>
 #endif
 
-#define SCSI_DMA_BUF_SIZE    131072
-#define SCSI_MAX_INQUIRY_LEN 256
-#define SCSI_MAX_MODE_LEN    256
+#define SCSI_DMA_BUF_SIZE           131072
+#define SCSI_MAX_INQUIRY_LEN        256
+#define SCSI_MAX_MODE_LEN           256
+
+#define DEFAULT_DISCARD_GRANULARITY 4096
 
 typedef struct SCSIDiskState SCSIDiskState;
 
@@ -2059,6 +2061,11 @@  static int scsi_initfn(SCSIDevice *dev)
         return -1;
     }
 
+    if (s->qdev.conf.discard_granularity == -1) {
+        s->qdev.conf.discard_granularity =
+            MAX(s->qdev.conf.logical_block_size, DEFAULT_DISCARD_GRANULARITY);
+    }
+
     if (!s->version) {
         s->version = g_strdup(qemu_get_version());
     }