virtio_blk: check for hardsector size from host

Currently virtio_blk assumes a 512 byte hard sector size. This can cause trouble / performance issues if the backing has a different block size (like a file on an ext3 file system formatted with 4k block size or a dasd). Lets add a feature flag that tells the guest to use a different hard sector size than 512 byte. Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com> Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

virtio_blk: check for hardsector size from host
Currently virtio_blk assumes a 512 byte hard sector size. This can cause trouble / performance issues if the backing has a different block size (like a file on an ext3 file system formatted with 4k block size or a dasd). Lets add a feature flag that tells the guest to use a different hard sector size than 512 byte. Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com> Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Christian Borntraeger · Rusty Russell
1 parent e962fa660d
Showing 2 changed files with 12 additions and 1 deletions Side-by-side Diff
drivers/block/virtio_blk.c
include/linux/virtio_blk.h
@@ -196,6 +196,7 @@
 	int err;
 	u64 cap;
 	u32 v;
+	u32 blk_size;
  
 	if (index_to_minor(index) >= 1 << MINORBITS)
 		return -ENOSPC;
@@ -290,6 +291,13 @@
 	if (!err)
 		blk_queue_max_hw_segments(vblk->disk->queue, v);
  
+	/* Host can optionally specify the block size of the device */
+	err = virtio_config_val(vdev, VIRTIO_BLK_F_BLK_SIZE,
+				offsetof(struct virtio_blk_config, blk_size),
+				&blk_size);
+	if (!err)
+		blk_queue_hardsect_size(vblk->disk->queue, blk_size);
+
 	add_disk(vblk->disk);
 	return 0;
  
@@ -330,7 +338,7 @@
  
 static unsigned int features[] = {
 	VIRTIO_BLK_F_BARRIER, VIRTIO_BLK_F_SEG_MAX, VIRTIO_BLK_F_SIZE_MAX,
-	VIRTIO_BLK_F_GEOMETRY, VIRTIO_BLK_F_RO,
+	VIRTIO_BLK_F_GEOMETRY, VIRTIO_BLK_F_RO, VIRTIO_BLK_F_BLK_SIZE,
 };
  
 static struct virtio_driver virtio_blk = {
@@ -13,6 +13,7 @@
 #define VIRTIO_BLK_F_SEG_MAX	2	/* Indicates maximum # of segments */
 #define VIRTIO_BLK_F_GEOMETRY	4	/* Legacy geometry available  */
 #define VIRTIO_BLK_F_RO		5	/* Disk is read-only */
+#define VIRTIO_BLK_F_BLK_SIZE	6	/* Block size of disk is available*/
  
 struct virtio_blk_config
 {
@@ -28,6 +29,8 @@
 		__u8 heads;
 		__u8 sectors;
 	} geometry;
+	/* block size of device (if VIRTIO_BLK_F_BLK_SIZE) */
+	__u32 blk_size;
 } __attribute__((packed));
  
 /* These two define direction. */
...	...	@@ -196,6 +196,7 @@
196	196	int err;
197	197	u64 cap;
198	198	u32 v;
	199	+ u32 blk_size;
199	200
200	201	if (index_to_minor(index) >= 1 << MINORBITS)
201	202	return -ENOSPC;
...	...	@@ -290,6 +291,13 @@
290	291	if (!err)
291	292	blk_queue_max_hw_segments(vblk->disk->queue, v);
292	293
	294	+ /* Host can optionally specify the block size of the device */
	295	+ err = virtio_config_val(vdev, VIRTIO_BLK_F_BLK_SIZE,
	296	+ offsetof(struct virtio_blk_config, blk_size),
	297	+ &blk_size);
	298	+ if (!err)
	299	+ blk_queue_hardsect_size(vblk->disk->queue, blk_size);
	300	+
293	301	add_disk(vblk->disk);
294	302	return 0;
295	303
...	...	@@ -330,7 +338,7 @@
330	338
331	339	static unsigned int features[] = {
332	340	VIRTIO_BLK_F_BARRIER, VIRTIO_BLK_F_SEG_MAX, VIRTIO_BLK_F_SIZE_MAX,
333		- VIRTIO_BLK_F_GEOMETRY, VIRTIO_BLK_F_RO,
	341	+ VIRTIO_BLK_F_GEOMETRY, VIRTIO_BLK_F_RO, VIRTIO_BLK_F_BLK_SIZE,
334	342	};
335	343
336	344	static struct virtio_driver virtio_blk = {
...	...	@@ -13,6 +13,7 @@
13	13	#define VIRTIO_BLK_F_SEG_MAX 2 /* Indicates maximum # of segments */
14	14	#define VIRTIO_BLK_F_GEOMETRY 4 /* Legacy geometry available */
15	15	#define VIRTIO_BLK_F_RO 5 /* Disk is read-only */
	16	+#define VIRTIO_BLK_F_BLK_SIZE 6 /* Block size of disk is available*/
16	17
17	18	struct virtio_blk_config
18	19	{
...	...	@@ -28,6 +29,8 @@
28	29	__u8 heads;
29	30	__u8 sectors;
30	31	} geometry;
	32	+ /* block size of device (if VIRTIO_BLK_F_BLK_SIZE) */
	33	+ __u32 blk_size;
31	34	} __attribute__((packed));
32	35
33	36	/* These two define direction. */