[Qemu-devel] [PATCH v2] Fix block migration when the device size is not a multiple of 1 MB

[Qemu-devel] [PATCH v2] Fix block migration when the device size is not a multiple of 1 MB

[Pierre Riteau]

b02bea3a85cc939f09aa674a3f1e4f36d418c007 added a check on the return
value of bdrv_write and aborts migration when it fails. However, if the
size of the block device to migrate is not a multiple of BLOCK_SIZE
(currently 1 MB), the last bdrv_write will fail with -EIO.

Fixed by calling bdrv_write with the correct size of the last block.

Signed-off-by: Pierre Riteau <Pierre.Riteau@irisa.fr>
---

This v2 has the following changes:
- use error_report instead of fprintf (comment from Yoshiaki Tamura)
- don't recompute total_sectors when the device hasn't changed since the
  previous iteration (comment from Kevin Wolf)

 block-migration.c |   22 ++++++++++++++++++++--
 1 files changed, 20 insertions(+), 2 deletions(-)

diff --git a/block-migration.c b/block-migration.c
index 1475325..5f1473a 100644
--- a/block-migration.c
+++ b/block-migration.c
@@ -633,8 +633,10 @@ static int block_load(QEMUFile *f, void *opaque, int version_id)
     int len, flags;
     char device_name[256];
     int64_t addr;
-    BlockDriverState *bs;
+    BlockDriverState *bs, *bs_prev = NULL;
     uint8_t *buf;
+    int64_t total_sectors = 0;
+    int nr_sectors;
 
     do {
         addr = qemu_get_be64(f);
@@ -656,10 +658,26 @@ static int block_load(QEMUFile *f, void *opaque, int version_id)
                 return -EINVAL;
             }
 
+            if (bs != bs_prev) {
+                bs_prev = bs;
+                total_sectors = bdrv_getlength(bs) >> BDRV_SECTOR_BITS;
+                if (total_sectors <= 0) {
+                    error_report("Error getting length of block device %s\n",
+                                 device_name);
+                    return -EINVAL;
+                }
+            }
+
+            if (total_sectors - addr < BDRV_SECTORS_PER_DIRTY_CHUNK) {
+                nr_sectors = total_sectors - addr;
+            } else {
+                nr_sectors = BDRV_SECTORS_PER_DIRTY_CHUNK;
+            }
+
             buf = qemu_malloc(BLOCK_SIZE);
 
             qemu_get_buffer(f, buf, BLOCK_SIZE);
-            ret = bdrv_write(bs, addr, buf, BDRV_SECTORS_PER_DIRTY_CHUNK);
+            ret = bdrv_write(bs, addr, buf, nr_sectors);
 
             qemu_free(buf);
             if (ret < 0) {
-- 
1.7.3.5

[Qemu-devel] Re: [PATCH v2] Fix block migration when the device size is not a multiple of 1 MB

[Kevin Wolf]

Am 21.01.2011 12:42, schrieb Pierre Riteau:
> b02bea3a85cc939f09aa674a3f1e4f36d418c007 added a check on the return
> value of bdrv_write and aborts migration when it fails. However, if the
> size of the block device to migrate is not a multiple of BLOCK_SIZE
> (currently 1 MB), the last bdrv_write will fail with -EIO.
> 
> Fixed by calling bdrv_write with the correct size of the last block.
> 
> Signed-off-by: Pierre Riteau <Pierre.Riteau@irisa.fr>

Thanks, applied to the block branch.

Kevin