[Qemu-devel] [RFC PATCH 11/17] ide/scsi: prepare for flipping the discard defaults

[Paolo Bonzini <pbonzini@redhat.com>]

Let a discard_granularity equal to -1 represent "enabled with default
granularity".  Also, Linux requires the discard_granularity to be
a power of two because it uses it with an AND, make the user obey.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
 block.h        |    6 +++---
 hw/ide/qdev.c  |    6 +++++-
 hw/scsi-disk.c |   12 ++++++++++++
 3 files changed, 20 insertions(+), 4 deletions(-)

diff --git a/block.h b/block.h
index e28321e..aa224d3 100644
--- a/block.h
+++ b/block.h
@@ -422,7 +422,7 @@ typedef struct BlockConf {
     uint16_t min_io_size;
     uint32_t opt_io_size;
     int32_t bootindex;
-    uint32_t discard_granularity;
+    int32_t discard_granularity;
     uint32_t discard_zeroes_data;
 } BlockConf;
 
@@ -450,8 +450,8 @@ static inline unsigned int get_physical_block_exp(BlockConf *conf)
     DEFINE_PROP_INT32("bootindex", _state, _conf.bootindex, -1),        \
     DEFINE_PROP_BIT("discard_zeroes_data", _state,                      \
                     _conf.discard_zeroes_data, 0, false),               \
-    DEFINE_PROP_UINT32("discard_granularity", _state,                   \
-                       _conf.discard_granularity, 0)
+    DEFINE_PROP_INT32("discard_granularity", _state,                    \
+                      _conf.discard_granularity, 0)
 
 #endif
 
diff --git a/hw/ide/qdev.c b/hw/ide/qdev.c
index f6a4896..5c7141f 100644
--- a/hw/ide/qdev.c
+++ b/hw/ide/qdev.c
@@ -121,8 +121,12 @@ static int ide_dev_initfn(IDEDevice *dev, IDEDriveKind kind)
     IDEState *s = bus->ifs + dev->unit;
     const char *serial;
     DriveInfo *dinfo;
+    int discard_granularity;
 
-    if (dev->conf.discard_granularity && dev->conf.discard_granularity != 512) {
+    discard_granularity = dev->conf.discard_granularity;
+    if (discard_granularity == -1) {
+        dev->conf.discard_granularity = 512;
+    } else if (discard_granularity && 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 f489078..00d355e 100644
--- a/hw/scsi-disk.c
+++ b/hw/scsi-disk.c
@@ -1577,12 +1577,24 @@ static int scsi_initfn(SCSIDevice *dev)
 {
     SCSIDiskState *s = DO_UPCAST(SCSIDiskState, qdev, dev);
     DriveInfo *dinfo;
+    int discard_granularity;
 
     if (!s->qdev.conf.bs) {
         error_report("drive property not set");
         return -1;
     }
 
+    discard_granularity = s->qdev.conf.discard_granularity;
+    if (discard_granularity == -1) {
+        s->qdev.conf.discard_granularity = s->qdev.conf.logical_block_size;
+    } else if (discard_granularity < s->qdev.conf.logical_block_size) {
+        error_report("scsi-block: invalid discard_granularity");
+        return -1;
+    } else if (discard_granularity & (discard_granularity - 1)) {
+        error_report("scsi-block: discard_granularity not a power of two");
+        return -1;
+    }
+
     if (!s->removable && !bdrv_is_inserted(s->qdev.conf.bs)) {
         error_report("Device needs media, but drive is empty");
         return -1;
-- 
1.7.7.6