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From 52cc1d1cd2f695c5761d65baec961d14552a79ed Mon Sep 17 00:00:00 2001
From: Kevin Wolf <kwolf@redhat.com>
Date: Wed, 8 Apr 2020 17:29:16 +0100
Subject: [PATCH 5/6] block: Increase BB.in_flight for coroutine and sync
 interfaces

RH-Author: Kevin Wolf <kwolf@redhat.com>
Message-id: <20200408172917.18712-6-kwolf@redhat.com>
Patchwork-id: 94600
O-Subject: [RHEL-AV-8.2.0 qemu-kvm PATCH 5/6] block: Increase BB.in_flight for coroutine and sync interfaces
Bugzilla: 1817621
RH-Acked-by: Eric Blake <eblake@redhat.com>
RH-Acked-by: Danilo de Paula <ddepaula@redhat.com>
RH-Acked-by: Max Reitz <mreitz@redhat.com>

External callers of blk_co_*() and of the synchronous blk_*() functions
don't currently increase the BlockBackend.in_flight counter, but calls
from blk_aio_*() do, so there is an inconsistency whether the counter
has been increased or not.

This patch moves the actual operations to static functions that can
later know they will always be called with in_flight increased exactly
once, even for external callers using the blk_co_*() coroutine
interfaces.

If the public blk_co_*() interface is unused, remove it.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Message-Id: <20200407121259.21350-3-kwolf@redhat.com>
Reviewed-by: Max Reitz <mreitz@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
(cherry picked from commit fbb92b6798894d3bf62fe3578d99fa62c720b242)
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Signed-off-by: Danilo C. L. de Paula <ddepaula@redhat.com>
---
 block/block-backend.c          | 103 ++++++++++++++++++++++++++++++++---------
 include/sysemu/block-backend.h |   1 -
 2 files changed, 80 insertions(+), 24 deletions(-)

diff --git a/block/block-backend.c b/block/block-backend.c
index 17b2e87..610dbfa 100644
--- a/block/block-backend.c
+++ b/block/block-backend.c
@@ -1147,9 +1147,10 @@ static void coroutine_fn blk_wait_while_drained(BlockBackend *blk)
     }
 }
 
-int coroutine_fn blk_co_preadv(BlockBackend *blk, int64_t offset,
-                               unsigned int bytes, QEMUIOVector *qiov,
-                               BdrvRequestFlags flags)
+/* To be called between exactly one pair of blk_inc/dec_in_flight() */
+static int coroutine_fn
+blk_do_preadv(BlockBackend *blk, int64_t offset, unsigned int bytes,
+              QEMUIOVector *qiov, BdrvRequestFlags flags)
 {
     int ret;
     BlockDriverState *bs;
@@ -1178,10 +1179,24 @@ int coroutine_fn blk_co_preadv(BlockBackend *blk, int64_t offset,
     return ret;
 }
 
-int coroutine_fn blk_co_pwritev_part(BlockBackend *blk, int64_t offset,
-                                     unsigned int bytes,
-                                     QEMUIOVector *qiov, size_t qiov_offset,
-                                     BdrvRequestFlags flags)
+int coroutine_fn blk_co_preadv(BlockBackend *blk, int64_t offset,
+                               unsigned int bytes, QEMUIOVector *qiov,
+                               BdrvRequestFlags flags)
+{
+    int ret;
+
+    blk_inc_in_flight(blk);
+    ret = blk_do_preadv(blk, offset, bytes, qiov, flags);
+    blk_dec_in_flight(blk);
+
+    return ret;
+}
+
+/* To be called between exactly one pair of blk_inc/dec_in_flight() */
+static int coroutine_fn
+blk_do_pwritev_part(BlockBackend *blk, int64_t offset, unsigned int bytes,
+                    QEMUIOVector *qiov, size_t qiov_offset,
+                    BdrvRequestFlags flags)
 {
     int ret;
     BlockDriverState *bs;
@@ -1214,6 +1229,20 @@ int coroutine_fn blk_co_pwritev_part(BlockBackend *blk, int64_t offset,
     return ret;
 }
 
+int coroutine_fn blk_co_pwritev_part(BlockBackend *blk, int64_t offset,
+                                     unsigned int bytes,
+                                     QEMUIOVector *qiov, size_t qiov_offset,
+                                     BdrvRequestFlags flags)
+{
+    int ret;
+
+    blk_inc_in_flight(blk);
+    ret = blk_do_pwritev_part(blk, offset, bytes, qiov, qiov_offset, flags);
+    blk_dec_in_flight(blk);
+
+    return ret;
+}
+
 int coroutine_fn blk_co_pwritev(BlockBackend *blk, int64_t offset,
                                 unsigned int bytes, QEMUIOVector *qiov,
                                 BdrvRequestFlags flags)
@@ -1234,7 +1263,7 @@ static void blk_read_entry(void *opaque)
     BlkRwCo *rwco = opaque;
     QEMUIOVector *qiov = rwco->iobuf;
 
-    rwco->ret = blk_co_preadv(rwco->blk, rwco->offset, qiov->size,
+    rwco->ret = blk_do_preadv(rwco->blk, rwco->offset, qiov->size,
                               qiov, rwco->flags);
     aio_wait_kick();
 }
@@ -1244,8 +1273,8 @@ static void blk_write_entry(void *opaque)
     BlkRwCo *rwco = opaque;
     QEMUIOVector *qiov = rwco->iobuf;
 
-    rwco->ret = blk_co_pwritev(rwco->blk, rwco->offset, qiov->size,
-                               qiov, rwco->flags);
+    rwco->ret = blk_do_pwritev_part(rwco->blk, rwco->offset, qiov->size,
+                                    qiov, 0, rwco->flags);
     aio_wait_kick();
 }
 
@@ -1262,6 +1291,7 @@ static int blk_prw(BlockBackend *blk, int64_t offset, uint8_t *buf,
         .ret    = NOT_DONE,
     };
 
+    blk_inc_in_flight(blk);
     if (qemu_in_coroutine()) {
         /* Fast-path if already in coroutine context */
         co_entry(&rwco);
@@ -1270,6 +1300,7 @@ static int blk_prw(BlockBackend *blk, int64_t offset, uint8_t *buf,
         bdrv_coroutine_enter(blk_bs(blk), co);
         BDRV_POLL_WHILE(blk_bs(blk), rwco.ret == NOT_DONE);
     }
+    blk_dec_in_flight(blk);
 
     return rwco.ret;
 }
@@ -1394,7 +1425,7 @@ static void blk_aio_read_entry(void *opaque)
     }
 
     assert(qiov->size == acb->bytes);
-    rwco->ret = blk_co_preadv(rwco->blk, rwco->offset, acb->bytes,
+    rwco->ret = blk_do_preadv(rwco->blk, rwco->offset, acb->bytes,
                               qiov, rwco->flags);
     blk_aio_complete(acb);
 }
@@ -1412,8 +1443,8 @@ static void blk_aio_write_entry(void *opaque)
     }
 
     assert(!qiov || qiov->size == acb->bytes);
-    rwco->ret = blk_co_pwritev(rwco->blk, rwco->offset, acb->bytes,
-                               qiov, rwco->flags);
+    rwco->ret = blk_do_pwritev_part(rwco->blk, rwco->offset, acb->bytes,
+                                    qiov, 0, rwco->flags);
     blk_aio_complete(acb);
 }
 
@@ -1498,7 +1529,9 @@ void blk_aio_cancel_async(BlockAIOCB *acb)
     bdrv_aio_cancel_async(acb);
 }
 
-int blk_co_ioctl(BlockBackend *blk, unsigned long int req, void *buf)
+/* To be called between exactly one pair of blk_inc/dec_in_flight() */
+static int coroutine_fn
+blk_do_ioctl(BlockBackend *blk, unsigned long int req, void *buf)
 {
     blk_wait_while_drained(blk);
 
@@ -1514,8 +1547,7 @@ static void blk_ioctl_entry(void *opaque)
     BlkRwCo *rwco = opaque;
     QEMUIOVector *qiov = rwco->iobuf;
 
-    rwco->ret = blk_co_ioctl(rwco->blk, rwco->offset,
-                             qiov->iov[0].iov_base);
+    rwco->ret = blk_do_ioctl(rwco->blk, rwco->offset, qiov->iov[0].iov_base);
     aio_wait_kick();
 }
 
@@ -1529,7 +1561,7 @@ static void blk_aio_ioctl_entry(void *opaque)
     BlkAioEmAIOCB *acb = opaque;
     BlkRwCo *rwco = &acb->rwco;
 
-    rwco->ret = blk_co_ioctl(rwco->blk, rwco->offset, rwco->iobuf);
+    rwco->ret = blk_do_ioctl(rwco->blk, rwco->offset, rwco->iobuf);
 
     blk_aio_complete(acb);
 }
@@ -1540,7 +1572,9 @@ BlockAIOCB *blk_aio_ioctl(BlockBackend *blk, unsigned long int req, void *buf,
     return blk_aio_prwv(blk, req, 0, buf, blk_aio_ioctl_entry, 0, cb, opaque);
 }
 
-int blk_co_pdiscard(BlockBackend *blk, int64_t offset, int bytes)
+/* To be called between exactly one pair of blk_inc/dec_in_flight() */
+static int coroutine_fn
+blk_do_pdiscard(BlockBackend *blk, int64_t offset, int bytes)
 {
     int ret;
 
@@ -1559,7 +1593,7 @@ static void blk_aio_pdiscard_entry(void *opaque)
     BlkAioEmAIOCB *acb = opaque;
     BlkRwCo *rwco = &acb->rwco;
 
-    rwco->ret = blk_co_pdiscard(rwco->blk, rwco->offset, acb->bytes);
+    rwco->ret = blk_do_pdiscard(rwco->blk, rwco->offset, acb->bytes);
     blk_aio_complete(acb);
 }
 
@@ -1571,12 +1605,23 @@ BlockAIOCB *blk_aio_pdiscard(BlockBackend *blk,
                         cb, opaque);
 }
 
+int coroutine_fn blk_co_pdiscard(BlockBackend *blk, int64_t offset, int bytes)
+{
+    int ret;
+
+    blk_inc_in_flight(blk);
+    ret = blk_do_pdiscard(blk, offset, bytes);
+    blk_dec_in_flight(blk);
+
+    return ret;
+}
+
 static void blk_pdiscard_entry(void *opaque)
 {
     BlkRwCo *rwco = opaque;
     QEMUIOVector *qiov = rwco->iobuf;
 
-    rwco->ret = blk_co_pdiscard(rwco->blk, rwco->offset, qiov->size);
+    rwco->ret = blk_do_pdiscard(rwco->blk, rwco->offset, qiov->size);
     aio_wait_kick();
 }
 
@@ -1585,7 +1630,8 @@ int blk_pdiscard(BlockBackend *blk, int64_t offset, int bytes)
     return blk_prw(blk, offset, NULL, bytes, blk_pdiscard_entry, 0);
 }
 
-int blk_co_flush(BlockBackend *blk)
+/* To be called between exactly one pair of blk_inc/dec_in_flight() */
+static int coroutine_fn blk_do_flush(BlockBackend *blk)
 {
     blk_wait_while_drained(blk);
 
@@ -1601,7 +1647,7 @@ static void blk_aio_flush_entry(void *opaque)
     BlkAioEmAIOCB *acb = opaque;
     BlkRwCo *rwco = &acb->rwco;
 
-    rwco->ret = blk_co_flush(rwco->blk);
+    rwco->ret = blk_do_flush(rwco->blk);
     blk_aio_complete(acb);
 }
 
@@ -1611,10 +1657,21 @@ BlockAIOCB *blk_aio_flush(BlockBackend *blk,
     return blk_aio_prwv(blk, 0, 0, NULL, blk_aio_flush_entry, 0, cb, opaque);
 }
 
+int coroutine_fn blk_co_flush(BlockBackend *blk)
+{
+    int ret;
+
+    blk_inc_in_flight(blk);
+    ret = blk_do_flush(blk);
+    blk_dec_in_flight(blk);
+
+    return ret;
+}
+
 static void blk_flush_entry(void *opaque)
 {
     BlkRwCo *rwco = opaque;
-    rwco->ret = blk_co_flush(rwco->blk);
+    rwco->ret = blk_do_flush(rwco->blk);
     aio_wait_kick();
 }
 
diff --git a/include/sysemu/block-backend.h b/include/sysemu/block-backend.h
index b198dec..9bbdbd6 100644
--- a/include/sysemu/block-backend.h
+++ b/include/sysemu/block-backend.h
@@ -171,7 +171,6 @@ BlockAIOCB *blk_aio_pdiscard(BlockBackend *blk, int64_t offset, int bytes,
                              BlockCompletionFunc *cb, void *opaque);
 void blk_aio_cancel(BlockAIOCB *acb);
 void blk_aio_cancel_async(BlockAIOCB *acb);
-int blk_co_ioctl(BlockBackend *blk, unsigned long int req, void *buf);
 int blk_ioctl(BlockBackend *blk, unsigned long int req, void *buf);
 BlockAIOCB *blk_aio_ioctl(BlockBackend *blk, unsigned long int req, void *buf,
                           BlockCompletionFunc *cb, void *opaque);
-- 
1.8.3.1