From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([209.51.188.92]:49548) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1gtIHq-0001y9-Sf for qemu-devel@nongnu.org; Mon, 11 Feb 2019 15:34:43 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1gtIHg-0004bY-Ej for qemu-devel@nongnu.org; Mon, 11 Feb 2019 15:34:35 -0500 References: <20190206170205.13061-1-jsnow@redhat.com> From: John Snow Message-ID: <649b8765-bf1d-aeae-eef5-4c4a4ebc875a@redhat.com> Date: Mon, 11 Feb 2019 15:25:39 -0500 MIME-Version: 1.0 In-Reply-To: <20190206170205.13061-1-jsnow@redhat.com> 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: qemu-devel@nongnu.org, qemu-block@nongnu.org, Kevin Wolf Cc: vsementsov@virtuozzo.com, Markus Armbruster , Max Reitz On 2/6/19 12:02 PM, 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); > @@ -2870,6 +2873,10 @@ void qmp_block_dirty_bitmap_add(const char *node, const char *name, > } > > bdrv_dirty_bitmap_set_persistance(bitmap, persistent); > + out: > + if (aio_context) { > + aio_context_release(aio_context); > + } > } > > void qmp_block_dirty_bitmap_remove(const char *node, const char *name, > @@ -2878,6 +2885,7 @@ 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) { > @@ -2892,14 +2900,20 @@ void qmp_block_dirty_bitmap_remove(const char *node, const char *name, > } > > if (bdrv_dirty_bitmap_get_persistance(bitmap)) { > + aio_context = bdrv_get_aio_context(bs); > + aio_context_acquire(aio_context); > bdrv_remove_persistent_dirty_bitmap(bs, name, &local_err); > if (local_err != NULL) { > error_propagate(errp, local_err); > - return; > + goto out; > } > } > > bdrv_release_dirty_bitmap(bs, bitmap); > + out: > + if (aio_context) { > + aio_context_release(aio_context); > + } > } > > /** > If this looks noncontroversial to everyone (Paolo said he agreed with Kevin's advice on the general approach here) I'm keen to merge it this week. May I take it through my tree, or should I be patient and wait for you, Kevin?