[Qemu-devel] [PATCH 19/27] block/parallels: implement incorrect close detection

[Denis V. Lunev]

The software driver must set inuse field in Parallels header to
0x746F6E59 when the image is opened in read-write mode. The presence of
this magic in the header on open forces image consistency check.

There is an unfortunate trick here. We can not check for inuse in
parallels_check as this will happen too late. It is possible to do
that for simple check, but during the fix this would always report
an error as the image was opened in BDRV_O_RDWR mode. Thus we save
the flag in BDRVParallelsState for this.

On the other hand, nothing should be done to clear inuse in
parallels_check. Generic close will do the job right.

Signed-off-by: Denis V. Lunev <d...@openvz.org>
Reviewed-by: Roman Kagan <rka...@parallels.com>
CC: Kevin Wolf <kw...@redhat.com>
CC: Stefan Hajnoczi <stefa...@redhat.com>
---
 block/parallels.c | 50 ++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 50 insertions(+)

diff --git a/block/parallels.c b/block/parallels.c
index 0e5d4c3..bafc74b 100644
--- a/block/parallels.c
+++ b/block/parallels.c
@@ -36,6 +36,7 @@
 #define HEADER_MAGIC "WithoutFreeSpace"
 #define HEADER_MAGIC2 "WithouFreSpacExt"
 #define HEADER_VERSION 2
+#define HEADER_INUSE_MAGIC  (0x746F6E59)
 
 #define DEFAULT_CLUSTER_SIZE 1048576        /* 1 MiB */
 
@@ -59,6 +60,8 @@ typedef struct BDRVParallelsState {
 
     ParallelsHeader *header;
     uint32_t header_size;
+    bool header_unclean;
+
     uint32_t *bat_bitmap;
     unsigned int bat_size;
 
@@ -246,6 +249,17 @@ static int parallels_check(BlockDriverState *bs, 
BdrvCheckResult *res,
         return size;
     }
 
+    if (s->header_unclean) {
+        fprintf(stderr, "%s image was not closed correctly\n",
+                fix & BDRV_FIX_ERRORS ? "Repairing" : "ERROR");
+        res->corruptions++;
+        if (fix & BDRV_FIX_ERRORS) {
+            /* parallels_close will do the job right */
+            res->corruptions_fixed++;
+            s->header_unclean = false;
+        }
+    }
+
     res->bfi.total_clusters = s->bat_size;
     res->bfi.compressed_clusters = 0; /* compression is not supported */
 
@@ -404,6 +418,17 @@ static int parallels_probe(const uint8_t *buf, int 
buf_size,
     return 0;
 }
 
+static int parallels_update_header(BlockDriverState *bs)
+{
+    BDRVParallelsState *s = bs->opaque;
+    unsigned size = MAX(bdrv_opt_mem_align(bs->file), sizeof(ParallelsHeader));
+
+    if (size > s->header_size) {
+        size = s->header_size;
+    }
+    return bdrv_pwrite_sync(bs->file, 0, s->header, size);
+}
+
 static int parallels_open(BlockDriverState *bs, QDict *options, int flags,
                           Error **errp)
 {
@@ -468,6 +493,25 @@ static int parallels_open(BlockDriverState *bs, QDict 
*options, int flags,
     }
     s->bat_bitmap = (uint32_t *)(s->header + 1);
 
+    if (le32_to_cpu(ph.inuse) == HEADER_INUSE_MAGIC) {
+        /* Image was not closed correctly. The check is mandatory */
+        s->header_unclean = true;
+        if ((flags & BDRV_O_RDWR) && !(flags & BDRV_O_CHECK)) {
+            error_setg(errp, "parallels: Image was not closed correctly; "
+                       "cannot be opened read/write");
+            ret = -EACCES;
+            goto fail;
+        }
+    }
+
+    if (flags & BDRV_O_RDWR) {
+        s->header->inuse = cpu_to_le32(HEADER_INUSE_MAGIC);
+        ret = parallels_update_header(bs);
+        if (ret < 0) {
+            goto fail;
+        }
+    }
+
     qemu_co_mutex_init(&s->lock);
     return 0;
 
@@ -483,6 +527,12 @@ fail:
 static void parallels_close(BlockDriverState *bs)
 {
     BDRVParallelsState *s = bs->opaque;
+
+    if (bs->open_flags & BDRV_O_RDWR) {
+        s->header->inuse = 0;
+        parallels_update_header(bs);
+    }
+
     qemu_vfree(s->header);
 }
 
-- 
1.9.1