qemu-kvm/kvm-blockdev-reduce-aio_context-locked-sections-in-bitma.patch

From 107ad619739795199df98c56d0ad4db14fec3722 Mon Sep 17 00:00:00 2001
From: John Snow <jsnow@redhat.com>
Date: Fri, 27 Sep 2019 20:18:44 +0100
Subject: [PATCH 1/6] blockdev: reduce aio_context locked sections in bitmap
 add/remove

RH-Author: John Snow <jsnow@redhat.com>
Message-id: <20190927201846.6823-2-jsnow@redhat.com>
Patchwork-id: 90908
O-Subject: [RHEL-AV-8.1.0 qemu-kvm PATCH 1/3] blockdev: reduce aio_context locked sections in bitmap add/remove
Bugzilla: 1756413
RH-Acked-by: Maxim Levitsky <mlevitsk@redhat.com>
RH-Acked-by: Max Reitz <mreitz@redhat.com>
RH-Acked-by: Stefano Garzarella <sgarzare@redhat.com>

From: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>

Commit 0a6c86d024c52 returned these locks back to add/remove
functionality, to protect from intersection of persistent bitmap
related IO with other IO. But other bitmap-related functions called
here are unrelated to the problem, and there are no needs to keep these
calls inside critical sections.

Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Reviewed-by: John Snow <jsnow@redhat.com>
Signed-off-by: John Snow <jsnow@redhat.com>
Reviewed-by: Max Reitz <mreitz@redhat.com>
Message-id: 20190708220502.12977-2-jsnow@redhat.com
Signed-off-by: John Snow <jsnow@redhat.com>
(cherry picked from commit 2899f41eef2806cf8eb119811c9d6fcf15ce80f6)
Signed-off-by: John Snow <jsnow@redhat.com>
Signed-off-by: Danilo C. L. de Paula <ddepaula@redhat.com>
---
 blockdev.c | 30 +++++++++++++-----------------
 1 file changed, 13 insertions(+), 17 deletions(-)

diff --git a/blockdev.c b/blockdev.c
index 4d141e9..0124825 100644
--- a/blockdev.c
+++ b/blockdev.c
@@ -2811,7 +2811,6 @@ void qmp_block_dirty_bitmap_add(const char *node, const char *name,
 {
     BlockDriverState *bs;
     BdrvDirtyBitmap *bitmap;
-    AioContext *aio_context = NULL;
 
     if (!name || name[0] == '\0') {
         error_setg(errp, "Bitmap name cannot be empty");
@@ -2847,16 +2846,20 @@ void qmp_block_dirty_bitmap_add(const char *node, const char *name,
     }
 
     if (persistent) {
-        aio_context = bdrv_get_aio_context(bs);
+        AioContext *aio_context = bdrv_get_aio_context(bs);
+        bool ok;
+
         aio_context_acquire(aio_context);
-        if (!bdrv_can_store_new_dirty_bitmap(bs, name, granularity, errp)) {
-            goto out;
+        ok = bdrv_can_store_new_dirty_bitmap(bs, name, granularity, errp);
+        aio_context_release(aio_context);
+        if (!ok) {
+            return;
         }
     }
 
     bitmap = bdrv_create_dirty_bitmap(bs, granularity, name, errp);
     if (bitmap == NULL) {
-        goto out;
+        return;
     }
 
     if (disabled) {
@@ -2864,10 +2867,6 @@ void qmp_block_dirty_bitmap_add(const char *node, const char *name,
     }
 
     bdrv_dirty_bitmap_set_persistence(bitmap, persistent);
- out:
-    if (aio_context) {
-        aio_context_release(aio_context);
-    }
 }
 
 void qmp_block_dirty_bitmap_remove(const char *node, const char *name,
@@ -2875,8 +2874,6 @@ void qmp_block_dirty_bitmap_remove(const char *node, const char *name,
 {
     BlockDriverState *bs;
     BdrvDirtyBitmap *bitmap;
-    Error *local_err = NULL;
-    AioContext *aio_context = NULL;
 
     bitmap = block_dirty_bitmap_lookup(node, name, &bs, errp);
     if (!bitmap || !bs) {
@@ -2889,20 +2886,19 @@ void qmp_block_dirty_bitmap_remove(const char *node, const char *name,
     }
 
     if (bdrv_dirty_bitmap_get_persistence(bitmap)) {
-        aio_context = bdrv_get_aio_context(bs);
+        AioContext *aio_context = bdrv_get_aio_context(bs);
+        Error *local_err = NULL;
+
         aio_context_acquire(aio_context);
         bdrv_remove_persistent_dirty_bitmap(bs, name, &local_err);
+        aio_context_release(aio_context);
         if (local_err != NULL) {
             error_propagate(errp, local_err);
-            goto out;
+            return;
         }
     }
 
     bdrv_release_dirty_bitmap(bs, bitmap);
- out:
-    if (aio_context) {
-        aio_context_release(aio_context);
-    }
 }
 
 /**
-- 
1.8.3.1