block: drop BlockDriverState::read_only

This variable is just a cache for !(bs->open_flags & BDRV_O_RDWR),
which we have to synchronize everywhere. Let's just drop it and
consistently use bdrv_is_read_only().

Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Message-Id: <20210527154056.70294-3-vsementsov@virtuozzo.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>

block.c

@@ -265,7 +265,7 @@ void bdrv_parse_filename_strip_prefix(const char *filename, const char *prefix,
  * image is inactivated. */
 bool bdrv_is_read_only(BlockDriverState *bs)
 {
-    return bs->read_only;
+    return !(bs->open_flags & BDRV_O_RDWR);
 }
 
 int bdrv_can_set_read_only(BlockDriverState *bs, bool read_only,
@@ -317,7 +317,6 @@ int bdrv_apply_auto_read_only(BlockDriverState *bs, const char *errmsg,
         goto fail;
     }
 
-    bs->read_only = true;
     bs->open_flags &= ~BDRV_O_RDWR;
 
     return 0;
@@ -1549,7 +1548,6 @@ static int bdrv_open_driver(BlockDriverState *bs, BlockDriver *drv,
     }
 
     bs->drv = drv;
-    bs->read_only = !(bs->open_flags & BDRV_O_RDWR);
     bs->opaque = g_malloc0(drv->instance_size);
 
     if (drv->bdrv_file_open) {
@@ -1771,8 +1769,6 @@ static int bdrv_open_common(BlockDriverState *bs, BlockBackend *file,
     trace_bdrv_open_common(bs, filename ?: "", bs->open_flags,
                            drv->format_name);
 
-    bs->read_only = !(bs->open_flags & BDRV_O_RDWR);
-
     ro = bdrv_is_read_only(bs);
 
     if (use_bdrv_whitelist && !bdrv_is_whitelisted(drv, ro)) {
@@ -4548,7 +4544,6 @@ static void bdrv_reopen_commit(BDRVReopenState *reopen_state)
     bs->explicit_options   = reopen_state->explicit_options;
     bs->options            = reopen_state->options;
     bs->open_flags         = reopen_state->flags;
-    bs->read_only = !(reopen_state->flags & BDRV_O_RDWR);
     bs->detect_zeroes      = reopen_state->detect_zeroes;
 
     if (reopen_state->replace_backing_bs) {

include/block/block_int.h

@@ -843,7 +843,6 @@ struct BlockDriverState {
      * locking needed during I/O...
      */
     int open_flags; /* flags used to open the file, re-used for re-open */
-    bool read_only; /* if true, the media is read only */
     bool encrypted; /* if true, the media is encrypted */
     bool sg;        /* if true, the device is a /dev/sg* */
     bool probed;    /* if true, format was probed rather than specified */

tests/unit/test-block-iothread.c

@@ -194,13 +194,11 @@ static void test_sync_op_truncate(BdrvChild *c)
     g_assert_cmpint(ret, ==, -EINVAL);
 
     /* Error: Read-only image */
-    c->bs->read_only = true;
     c->bs->open_flags &= ~BDRV_O_RDWR;
 
     ret = bdrv_truncate(c, 65536, false, PREALLOC_MODE_OFF, 0, NULL);
     g_assert_cmpint(ret, ==, -EACCES);
 
-    c->bs->read_only = false;
     c->bs->open_flags |= BDRV_O_RDWR;
 }
 
@@ -236,13 +234,11 @@ static void test_sync_op_flush(BdrvChild *c)
     g_assert_cmpint(ret, ==, 0);
 
     /* Early success: Read-only image */
-    c->bs->read_only = true;
     c->bs->open_flags &= ~BDRV_O_RDWR;
 
     ret = bdrv_flush(c->bs);
     g_assert_cmpint(ret, ==, 0);
 
-    c->bs->read_only = false;
     c->bs->open_flags |= BDRV_O_RDWR;
 }
 
@@ -256,13 +252,11 @@ static void test_sync_op_blk_flush(BlockBackend *blk)
     g_assert_cmpint(ret, ==, 0);
 
     /* Early success: Read-only image */
-    bs->read_only = true;
     bs->open_flags &= ~BDRV_O_RDWR;
 
     ret = blk_flush(blk);
     g_assert_cmpint(ret, ==, 0);
 
-    bs->read_only = false;
     bs->open_flags |= BDRV_O_RDWR;
 }