block: rename buffer_alignment to guest_block_size

The alignment field is now set to the value that is promised to the
guest, rather than required by the host.  The next patches will make
QEMU aware of the host-provided values, so make this clear.

The alignment is also not about memory buffers, but about the sectors on
the disk, change the documentation of the field.

At this point, the field is set by the device emulation, but completely
ignored by the block layer.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Wenchao Xia <xiawenc@linux.vnet.ibm.com>
Reviewed-by: Max Reitz <mreitz@redhat.com>
Reviewed-by: Benoit Canet <benoit@irqsave.net>

block.c

@@ -851,7 +851,7 @@ static int bdrv_open_common(BlockDriverState *bs, BlockDriverState *file,
     }
 
     bs->open_flags = flags;
-    bs->buffer_alignment = 512;
+    bs->guest_block_size = 512;
     bs->zero_beyond_eof = true;
     open_flags = bdrv_open_flags(bs, flags);
     bs->read_only = !(open_flags & BDRV_O_RDWR);
@@ -1796,7 +1796,7 @@ static void bdrv_move_feature_fields(BlockDriverState *bs_dest,
     bs_dest->dev_ops            = bs_src->dev_ops;
     bs_dest->dev_opaque         = bs_src->dev_opaque;
     bs_dest->dev                = bs_src->dev;
-    bs_dest->buffer_alignment   = bs_src->buffer_alignment;
+    bs_dest->guest_block_size   = bs_src->guest_block_size;
     bs_dest->copy_on_read       = bs_src->copy_on_read;
 
     bs_dest->enable_write_cache = bs_src->enable_write_cache;
@@ -1953,7 +1953,7 @@ void bdrv_detach_dev(BlockDriverState *bs, void *dev)
     bs->dev = NULL;
     bs->dev_ops = NULL;
     bs->dev_opaque = NULL;
-    bs->buffer_alignment = 512;
+    bs->guest_block_size = 512;
 }
 
 /* TODO change to return DeviceState * when all users are qdevified */
@@ -4806,9 +4806,9 @@ BlockDriverAIOCB *bdrv_aio_ioctl(BlockDriverState *bs,
     return NULL;
 }
 
-void bdrv_set_buffer_alignment(BlockDriverState *bs, int align)
+void bdrv_set_guest_block_size(BlockDriverState *bs, int align)
 {
-    bs->buffer_alignment = align;
+    bs->guest_block_size = align;
 }
 
 void *qemu_blockalign(BlockDriverState *bs, size_t size)

hw/block/virtio-blk.c

@@ -731,7 +731,7 @@ static void virtio_blk_device_realize(DeviceState *dev, Error **errp)
     register_savevm(dev, "virtio-blk", virtio_blk_id++, 2,
                     virtio_blk_save, virtio_blk_load, s);
     bdrv_set_dev_ops(s->bs, &virtio_block_ops, s);
-    bdrv_set_buffer_alignment(s->bs, s->conf->logical_block_size);
+    bdrv_set_guest_block_size(s->bs, s->conf->logical_block_size);
 
     bdrv_iostatus_enable(s->bs);
 

hw/ide/core.c

@@ -2103,7 +2103,7 @@ int ide_init_drive(IDEState *s, BlockDriverState *bs, IDEDriveKind kind,
     s->smart_selftest_count = 0;
     if (kind == IDE_CD) {
         bdrv_set_dev_ops(bs, &ide_cd_block_ops, s);
-        bdrv_set_buffer_alignment(bs, 2048);
+        bdrv_set_guest_block_size(bs, 2048);
     } else {
         if (!bdrv_is_inserted(s->bs)) {
             error_report("Device needs media, but drive is empty");

hw/scsi/scsi-disk.c

@@ -2254,7 +2254,7 @@ static int scsi_initfn(SCSIDevice *dev)
     } else {
         bdrv_set_dev_ops(s->qdev.conf.bs, &scsi_disk_block_ops, s);
     }
-    bdrv_set_buffer_alignment(s->qdev.conf.bs, s->qdev.blocksize);
+    bdrv_set_guest_block_size(s->qdev.conf.bs, s->qdev.blocksize);
 
     bdrv_iostatus_enable(s->qdev.conf.bs);
     add_boot_device_path(s->qdev.conf.bootindex, &dev->qdev, NULL);

hw/scsi/scsi-generic.c

@@ -210,7 +210,7 @@ static void scsi_read_complete(void * opaque, int ret)
             s->blocksize = ldl_be_p(&r->buf[8]);
             s->max_lba = ldq_be_p(&r->buf[0]);
         }
-        bdrv_set_buffer_alignment(s->conf.bs, s->blocksize);
+        bdrv_set_guest_block_size(s->conf.bs, s->blocksize);
 
         scsi_req_data(&r->req, len);
         if (!r->req.io_canceled) {

include/block/block.h

@@ -431,7 +431,7 @@ void bdrv_img_create(const char *filename, const char *fmt,
 /* Returns the alignment in bytes that is required so that no bounce buffer
  * is required throughout the stack */
 size_t bdrv_opt_mem_align(BlockDriverState *bs);
-void bdrv_set_buffer_alignment(BlockDriverState *bs, int align);
+void bdrv_set_guest_block_size(BlockDriverState *bs, int align);
 void *qemu_blockalign(BlockDriverState *bs, size_t size);
 bool bdrv_qiov_is_aligned(BlockDriverState *bs, QEMUIOVector *qiov);
 

include/block/block_int.h

@@ -325,8 +325,8 @@ struct BlockDriverState {
     /* Whether produces zeros when read beyond eof */
     bool zero_beyond_eof;
 
-    /* the memory alignment required for the buffers handled by this driver */
-    int buffer_alignment;
+    /* the block size for which the guest device expects atomicity */
+    int guest_block_size;
 
     /* do we need to tell the quest if we have a volatile write cache? */
     int enable_write_cache;