[PATCH 10/14] block: Convert bdrv_is_inserted() to co_wrapper

[Kevin Wolf <kwolf@redhat.com>]

From: Emanuele Giuseppe Esposito <eesposit@redhat.com>

bdrv_is_inserted() is categorized as an I/O function, and it currently
doesn't run in a coroutine. We should let it take a graph rdlock since
it traverses the block nodes graph, which however is only possible in a
coroutine.

Therefore turn it into a co_wrapper to move the actual function into a
coroutine where the lock can be taken.

At the same time, add also blk_is_inserted as co_wrapper_mixed, since it
is called in both coroutine and non-coroutine contexts.

Because now this function creates a new coroutine and polls, we need to
take the AioContext lock where it is missing, for the only reason that
internally c_w_mixed_bdrv_rdlock calls AIO_WAIT_WHILE and it expects to
release the AioContext lock. Once the rwlock is ultimated and placed in
every place it needs to be, we will poll using AIO_WAIT_WHILE_UNLOCKED
and remove the AioContext lock.

Signed-off-by: Emanuele Giuseppe Esposito <eesposit@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
---
 include/block/block-io.h          |  5 ++++-
 include/block/block_int-common.h  |  2 +-
 include/sysemu/block-backend-io.h |  5 ++++-
 block.c                           |  4 ++--
 block/block-backend.c             |  4 ++--
 block/io.c                        | 12 ++++++------
 blockdev.c                        |  8 +++++++-
 7 files changed, 26 insertions(+), 14 deletions(-)

diff --git a/include/block/block-io.h b/include/block/block-io.h
index 1d6748463c..e27dc9787b 100644
--- a/include/block/block-io.h
+++ b/include/block/block-io.h
@@ -139,7 +139,10 @@ bool bdrv_is_read_only(BlockDriverState *bs);
 bool bdrv_is_writable(BlockDriverState *bs);
 bool bdrv_is_sg(BlockDriverState *bs);
 int bdrv_get_flags(BlockDriverState *bs);
-bool bdrv_is_inserted(BlockDriverState *bs);
+
+bool coroutine_fn bdrv_co_is_inserted(BlockDriverState *bs);
+bool co_wrapper bdrv_is_inserted(BlockDriverState *bs);
+
 void bdrv_lock_medium(BlockDriverState *bs, bool locked);
 void bdrv_eject(BlockDriverState *bs, bool eject_flag);
 const char *bdrv_get_format_name(BlockDriverState *bs);
diff --git a/include/block/block_int-common.h b/include/block/block_int-common.h
index 2c190c6d75..b954b3cb36 100644
--- a/include/block/block_int-common.h
+++ b/include/block/block_int-common.h
@@ -710,7 +710,7 @@ struct BlockDriver {
         BlockDriverState *bs, QEMUIOVector *qiov, int64_t pos);
 
     /* removable device specific */
-    bool (*bdrv_is_inserted)(BlockDriverState *bs);
+    bool coroutine_fn (*bdrv_is_inserted)(BlockDriverState *bs);
     void (*bdrv_eject)(BlockDriverState *bs, bool eject_flag);
     void (*bdrv_lock_medium)(BlockDriverState *bs, bool locked);
 
diff --git a/include/sysemu/block-backend-io.h b/include/sysemu/block-backend-io.h
index 8ad8854ecb..a1eac6c00a 100644
--- a/include/sysemu/block-backend-io.h
+++ b/include/sysemu/block-backend-io.h
@@ -53,7 +53,10 @@ BlockAIOCB *blk_aio_ioctl(BlockBackend *blk, unsigned long int req, void *buf,
 
 void blk_inc_in_flight(BlockBackend *blk);
 void blk_dec_in_flight(BlockBackend *blk);
-bool blk_is_inserted(BlockBackend *blk);
+
+bool coroutine_fn blk_co_is_inserted(BlockBackend *blk);
+bool co_wrapper_mixed blk_is_inserted(BlockBackend *blk);
+
 bool blk_is_available(BlockBackend *blk);
 void blk_lock_medium(BlockBackend *blk, bool locked);
 void blk_eject(BlockBackend *blk, bool eject_flag);
diff --git a/block.c b/block.c
index 7694879a54..a7b9da6a7e 100644
--- a/block.c
+++ b/block.c
@@ -6797,7 +6797,7 @@ out:
 /**
  * Return TRUE if the media is present
  */
-bool bdrv_is_inserted(BlockDriverState *bs)
+bool coroutine_fn bdrv_co_is_inserted(BlockDriverState *bs)
 {
     BlockDriver *drv = bs->drv;
     BdrvChild *child;
@@ -6810,7 +6810,7 @@ bool bdrv_is_inserted(BlockDriverState *bs)
         return drv->bdrv_is_inserted(bs);
     }
     QLIST_FOREACH(child, &bs->children, next) {
-        if (!bdrv_is_inserted(child->bs)) {
+        if (!bdrv_co_is_inserted(child->bs)) {
             return false;
         }
     }
diff --git a/block/block-backend.c b/block/block-backend.c
index 5f6b269a79..e4b54f7b0c 100644
--- a/block/block-backend.c
+++ b/block/block-backend.c
@@ -1985,12 +1985,12 @@ void blk_activate(BlockBackend *blk, Error **errp)
     bdrv_activate(bs, errp);
 }
 
-bool blk_is_inserted(BlockBackend *blk)
+bool coroutine_fn blk_co_is_inserted(BlockBackend *blk)
 {
     BlockDriverState *bs = blk_bs(blk);
     IO_CODE();
 
-    return bs && bdrv_is_inserted(bs);
+    return bs && bdrv_co_is_inserted(bs);
 }
 
 bool blk_is_available(BlockBackend *blk)
diff --git a/block/io.c b/block/io.c
index f988e42f26..116d6cf10b 100644
--- a/block/io.c
+++ b/block/io.c
@@ -1612,7 +1612,7 @@ int coroutine_fn bdrv_co_preadv_part(BdrvChild *child,
 
     trace_bdrv_co_preadv_part(bs, offset, bytes, flags);
 
-    if (!bdrv_is_inserted(bs)) {
+    if (!bdrv_co_is_inserted(bs)) {
         return -ENOMEDIUM;
     }
 
@@ -2057,7 +2057,7 @@ int coroutine_fn bdrv_co_pwritev_part(BdrvChild *child,
 
     trace_bdrv_co_pwritev_part(child->bs, offset, bytes, flags);
 
-    if (!bdrv_is_inserted(bs)) {
+    if (!bdrv_co_is_inserted(bs)) {
         return -ENOMEDIUM;
     }
 
@@ -2825,7 +2825,7 @@ int coroutine_fn bdrv_co_flush(BlockDriverState *bs)
 
     bdrv_inc_in_flight(bs);
 
-    if (!bdrv_is_inserted(bs) || bdrv_is_read_only(bs) ||
+    if (!bdrv_co_is_inserted(bs) || bdrv_is_read_only(bs) ||
         bdrv_is_sg(bs)) {
         goto early_exit;
     }
@@ -2949,7 +2949,7 @@ int coroutine_fn bdrv_co_pdiscard(BdrvChild *child, int64_t offset,
     BlockDriverState *bs = child->bs;
     IO_CODE();
 
-    if (!bs || !bs->drv || !bdrv_is_inserted(bs)) {
+    if (!bs || !bs->drv || !bdrv_co_is_inserted(bs)) {
         return -ENOMEDIUM;
     }
 
@@ -3231,7 +3231,7 @@ static int coroutine_fn bdrv_co_copy_range_internal(
     assert(!(read_flags & BDRV_REQ_NO_WAIT));
     assert(!(write_flags & BDRV_REQ_NO_WAIT));
 
-    if (!dst || !dst->bs || !bdrv_is_inserted(dst->bs)) {
+    if (!dst || !dst->bs || !bdrv_co_is_inserted(dst->bs)) {
         return -ENOMEDIUM;
     }
     ret = bdrv_check_request32(dst_offset, bytes, NULL, 0);
@@ -3242,7 +3242,7 @@ static int coroutine_fn bdrv_co_copy_range_internal(
         return bdrv_co_pwrite_zeroes(dst, dst_offset, bytes, write_flags);
     }
 
-    if (!src || !src->bs || !bdrv_is_inserted(src->bs)) {
+    if (!src || !src->bs || !bdrv_co_is_inserted(src->bs)) {
         return -ENOMEDIUM;
     }
     ret = bdrv_check_request32(src_offset, bytes, NULL, 0);
diff --git a/blockdev.c b/blockdev.c
index 011e48df7b..cef3bc1215 100644
--- a/blockdev.c
+++ b/blockdev.c
@@ -1023,6 +1023,7 @@ fail:
 static BlockDriverState *qmp_get_root_bs(const char *name, Error **errp)
 {
     BlockDriverState *bs;
+    AioContext *aio_context;
 
     bs = bdrv_lookup_bs(name, name, errp);
     if (bs == NULL) {
@@ -1034,11 +1035,16 @@ static BlockDriverState *qmp_get_root_bs(const char *name, Error **errp)
         return NULL;
     }
 
+    aio_context = bdrv_get_aio_context(bs);
+    aio_context_acquire(aio_context);
+
     if (!bdrv_is_inserted(bs)) {
         error_setg(errp, "Device has no medium");
-        return NULL;
+        bs = NULL;
     }
 
+    aio_context_release(aio_context);
+
     return bs;
 }
 
-- 
2.38.1