blockdev: enable discard by default

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>

diff --git a/hw/block-common.h b/hw/block-common.h
index bb808f7f56136f4b0f7f2a7bd6cae7d7129bbb58..dd115320c9580c60bd7e791cb10afb3218a3d7b4 100644 (file)
--- 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 c436b38bcbf0520ed1b03df7606d59a4e9dd9faa..fd06da7003aac407c19921efe6de9daa59f1c1e4 100644 (file)
--- 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 28e75bbf5bc73f3a629d4176f331474f6f5271f4..d41158693e023fa7e483649c00d8d6f613879de8 100644 (file)
--- 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());
     }