From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([209.51.188.92]:35590) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1gte5D-00041n-Ds for qemu-devel@nongnu.org; Tue, 12 Feb 2019 14:51:08 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1gtdxz-00021B-Gw for qemu-devel@nongnu.org; Tue, 12 Feb 2019 14:43:41 -0500 References: <20190206170205.13061-1-jsnow@redhat.com> From: John Snow Message-ID: Date: Tue, 12 Feb 2019 14:43:35 -0500 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] [PATCH] blockdev: acquire aio_context for bitmap add/remove List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Eric Blake , qemu-devel@nongnu.org, qemu-block@nongnu.org Cc: Max Reitz , Kevin Wolf , Markus Armbruster , vsementsov@virtuozzo.com On 2/12/19 2:36 PM, Eric Blake wrote: > On 2/6/19 11:02 AM, John Snow wrote: >> When bitmaps are persistent, they may incur a disk read or write when bitmaps >> are added or removed. For configurations like virtio-dataplane, failing to >> acquire this lock will abort QEMU when disk IO occurs. >> >> We used to acquire aio_context as part of the bitmap lookup, so re-introduce >> the lock for just the cases that have an IO penalty. >> >> Fixes: https://bugzilla.redhat.com/show_bug.cgi?id=1672010 >> Reported-By: Aihua Liang >> Signed-off-by: John Snow >> --- >> blockdev.c | 24 +++++++++++++++++++----- >> 1 file changed, 19 insertions(+), 5 deletions(-) >> >> diff --git a/blockdev.c b/blockdev.c >> index fb18e9c975..ce458de037 100644 >> --- a/blockdev.c >> +++ b/blockdev.c >> @@ -2820,6 +2820,7 @@ 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"); >> @@ -2854,10 +2855,12 @@ void qmp_block_dirty_bitmap_add(const char *node, const char *name, >> disabled = false; >> } >> >> - if (persistent && >> - !bdrv_can_store_new_dirty_bitmap(bs, name, granularity, errp)) >> - { >> - return; >> + if (persistent) { >> + aio_context = bdrv_get_aio_context(bs); >> + aio_context_acquire(aio_context); >> + if (!bdrv_can_store_new_dirty_bitmap(bs, name, granularity, errp)) { >> + goto out; >> + } >> } >> >> bitmap = bdrv_create_dirty_bitmap(bs, granularity, name, errp); > if (bitmap == NULL) { > return; > } > > Oops - this early return fails to release the aio context. Good spot, thanks! This would be awful to diagnose later.