[PATCH v8 5/7] copy-on-read: limit guest writes to base in COR driver

[Andrey Shinkevich]

Limit the guest's COR operations by the base node in the backing chain
during a stream job.

Signed-off-by: Andrey Shinkevich <andrey.shinkevich@virtuozzo.com>
---
 block/copy-on-read.c | 49 +++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 49 insertions(+)

diff --git a/block/copy-on-read.c b/block/copy-on-read.c
index 1f858bb..ecbd1f8 100644
--- a/block/copy-on-read.c
+++ b/block/copy-on-read.c
@@ -57,6 +57,37 @@ static BlockDriverState *get_base_by_name(BlockDriverState 
*bs,
     return base_bs;
 }
 
+/*
+ * Returns 1 if the block is allocated in a node between 
cor_filter_bs->file->bs
+ * and the base_bs in the backing chain. Otherwise, returns 0.
+ * The COR operation is allowed if the base_bs is not specified - return 1.
+ * Returns negative errno on failure.
+ */
+static int node_above_base(BlockDriverState *cor_filter_bs, uint64_t offset,
+                           uint64_t bytes)
+{
+    int ret;
+    int64_t dummy;
+    BlockDriverState *file = NULL;
+    BDRVStateCOR *state = cor_filter_bs->opaque;
+
+    if (!state->base_bs) {
+        return 1;
+    }
+
+    ret = bdrv_block_status_above(cor_filter_bs->file->bs, state->base_bs,
+                                  offset, bytes, &dummy, NULL, &file);
+    if (ret < 0) {
+        return ret;
+    }
+
+    if (file) {
+        return 1;
+    }
+
+    return 0;
+}
+
 static int cor_open(BlockDriverState *bs, QDict *options, int flags,
                     Error **errp)
 {
@@ -153,6 +184,12 @@ static int coroutine_fn 
cor_co_pwritev_part(BlockDriverState *bs,
                                             QEMUIOVector *qiov,
                                             size_t qiov_offset, int flags)
 {
+    int ret = node_above_base(bs, offset, bytes);
+
+    if (!ret || ret < 0) {
+        return ret;
+    }
+
     return bdrv_co_pwritev_part(bs->file, offset, bytes, qiov, qiov_offset,
                                 flags);
 }
@@ -162,6 +199,12 @@ static int coroutine_fn 
cor_co_pwrite_zeroes(BlockDriverState *bs,
                                              int64_t offset, int bytes,
                                              BdrvRequestFlags flags)
 {
+    int ret = node_above_base(bs, offset, bytes);
+
+    if (!ret || ret < 0) {
+        return ret;
+    }
+
     return bdrv_co_pwrite_zeroes(bs->file, offset, bytes, flags);
 }
 
@@ -178,6 +221,12 @@ static int coroutine_fn 
cor_co_pwritev_compressed(BlockDriverState *bs,
                                                   uint64_t bytes,
                                                   QEMUIOVector *qiov)
 {
+    int ret = node_above_base(bs, offset, bytes);
+
+    if (!ret || ret < 0) {
+        return ret;
+    }
+
     return bdrv_co_pwritev(bs->file, offset, bytes, qiov,
                            BDRV_REQ_WRITE_COMPRESSED);
 }
-- 
1.8.3.1