file-posix: Fix aio=threads performance regression after enablign FUA

For aio=threads, we're currently not implementing REQ_FUA in any useful
way, but just do a separate raw_co_flush_to_disk() call. This changes
behaviour compared to the old state, which used bdrv_co_flush() with its
optimisations. As a quick fix, call bdrv_co_flush() again like before.
Eventually, we can use pwritev2() to make use of RWF_DSYNC if available,
but we'll still have to keep this code path as a fallback, so this fix
is required either way.

While the fix itself is a one-liner, some new graph locking annotations
are needed to convince TSA that the locking is correct.

Cc: [email protected]
Fixes: 984a32f ("file-posix: Support FUA writes")
Buglink: https://issues.redhat.com/browse/RHEL-96854
Reported-by: Tingting Mao <[email protected]>
Signed-off-by: Kevin Wolf <[email protected]>
Message-ID: <[email protected]>
Reviewed-by: Eric Blake <[email protected]>
Signed-off-by: Kevin Wolf <[email protected]>
(cherry picked from commit d402da1360c2240e81f0e5fc80ddbfc6238e0da8)
Signed-off-by: Michael Tokarev <[email protected]>

Author: kevmw

block/file-posix.c

@@ -2484,9 +2484,9 @@ static inline bool raw_check_linux_aio(BDRVRawState *s)
 }
 #endif
 
-static int coroutine_fn raw_co_prw(BlockDriverState *bs, int64_t *offset_ptr,
-                                   uint64_t bytes, QEMUIOVector *qiov, int type,
-                                   int flags)
+static int coroutine_fn GRAPH_RDLOCK
+raw_co_prw(BlockDriverState *bs, int64_t *offset_ptr, uint64_t bytes,
+           QEMUIOVector *qiov, int type, int flags)
 {
     BDRVRawState *s = bs->opaque;
     RawPosixAIOData acb;
@@ -2545,7 +2545,7 @@ static int coroutine_fn raw_co_prw(BlockDriverState *bs, int64_t *offset_ptr,
     ret = raw_thread_pool_submit(handle_aiocb_rw, &acb);
     if (ret == 0 && (flags & BDRV_REQ_FUA)) {
         /* TODO Use pwritev2() instead if it's available */
-        ret = raw_co_flush_to_disk(bs);
+        ret = bdrv_co_flush(bs);
     }
     goto out; /* Avoid the compiler err of unused label */
 
@@ -2580,16 +2580,16 @@ static int coroutine_fn raw_co_prw(BlockDriverState *bs, int64_t *offset_ptr,
     return ret;
 }
 
-static int coroutine_fn raw_co_preadv(BlockDriverState *bs, int64_t offset,
-                                      int64_t bytes, QEMUIOVector *qiov,
-                                      BdrvRequestFlags flags)
+static int coroutine_fn GRAPH_RDLOCK
+raw_co_preadv(BlockDriverState *bs, int64_t offset, int64_t bytes,
+              QEMUIOVector *qiov, BdrvRequestFlags flags)
 {
     return raw_co_prw(bs, &offset, bytes, qiov, QEMU_AIO_READ, flags);
 }
 
-static int coroutine_fn raw_co_pwritev(BlockDriverState *bs, int64_t offset,
-                                       int64_t bytes, QEMUIOVector *qiov,
-                                       BdrvRequestFlags flags)
+static int coroutine_fn GRAPH_RDLOCK
+raw_co_pwritev(BlockDriverState *bs, int64_t offset, int64_t bytes,
+               QEMUIOVector *qiov, BdrvRequestFlags flags)
 {
     return raw_co_prw(bs, &offset, bytes, qiov, QEMU_AIO_WRITE, flags);
 }
@@ -3525,10 +3525,11 @@ static int coroutine_fn raw_co_zone_mgmt(BlockDriverState *bs, BlockZoneOp op,
 #endif
 
 #if defined(CONFIG_BLKZONED)
-static int coroutine_fn raw_co_zone_append(BlockDriverState *bs,
-                                           int64_t *offset,
-                                           QEMUIOVector *qiov,
-                                           BdrvRequestFlags flags) {
+static int coroutine_fn GRAPH_RDLOCK
+raw_co_zone_append(BlockDriverState *bs,
+                   int64_t *offset,
+                   QEMUIOVector *qiov,
+                   BdrvRequestFlags flags) {
     assert(flags == 0);
     int64_t zone_size_mask = bs->bl.zone_size - 1;
     int64_t iov_len = 0;