From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:57415) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1bDs2x-0008Dz-5Q for qemu-devel@nongnu.org; Fri, 17 Jun 2016 07:34:48 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1bDs2v-00008k-1F for qemu-devel@nongnu.org; Fri, 17 Jun 2016 07:34:46 -0400 Date: Fri, 17 Jun 2016 13:34:35 +0200 From: Kevin Wolf Message-ID: <20160617113435.GF5431@noname.redhat.com> References: <1464943756-14143-1-git-send-email-famz@redhat.com> <1464943756-14143-5-git-send-email-famz@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1464943756-14143-5-git-send-email-famz@redhat.com> Subject: Re: [Qemu-devel] [PATCH v6 04/22] block: Introduce image file locking List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Fam Zheng Cc: qemu-devel@nongnu.org, Max Reitz , Jeff Cody , Markus Armbruster , Eric Blake , qemu-block@nongnu.org, rjones@redhat.com, stefanha@redhat.com, pbonzini@redhat.com, John Snow , berrange@redhat.com, den@openvz.org Am 03.06.2016 um 10:48 hat Fam Zheng geschrieben: > Block drivers can implement this new operation .bdrv_lockf to actually lock the > image in the protocol specific way. > > Signed-off-by: Fam Zheng > --- > block.c | 57 +++++++++++++++++++++++++++++++++++++++++++++++ > include/block/block.h | 11 ++++++++- > include/block/block_int.h | 5 +++++ > 3 files changed, 72 insertions(+), 1 deletion(-) > > diff --git a/block.c b/block.c > index 736432f..4c2a3ff 100644 > --- a/block.c > +++ b/block.c > @@ -854,6 +854,50 @@ out: > g_free(gen_node_name); > } > > +BdrvLockfCmd bdrv_get_locking_cmd(int flags) > +{ > + if (flags & BDRV_O_NO_LOCK) { > + return BDRV_LOCKF_UNLOCK; > + } else if (flags & BDRV_O_SHARED_LOCK) { > + return BDRV_LOCKF_SHARED; > + } else if (flags & BDRV_O_RDWR) { > + return BDRV_LOCKF_EXCLUSIVE; > + } else { > + return BDRV_LOCKF_SHARED; > + } > +} It feels a bit counterintuitive to use the very same operation for "start of critical section, but don't actually lock" and "end of critical section". Is there a specific reason why you chose this instead of separate .bdrv_lock/bdrv_unlock callbacks? > +static int bdrv_lock_unlock_image_do(BlockDriverState *bs, BdrvLockfCmd cmd) > +{ > + int ret; > + > + if (bs->cur_lock == cmd) { > + return 0; > + } else if (!bs->drv) { > + return -ENOMEDIUM; > + } else if (!bs->drv->bdrv_lockf) { > + return 0; > + } > + ret = bs->drv->bdrv_lockf(bs, cmd); > + if (ret == -ENOTSUP) { > + /* Handle it the same way as !bs->drv->bdrv_lockf */ > + ret = 0; > + } else if (ret == 0) { > + bs->cur_lock = cmd; > + } > + return ret; > +} Okay, so the callback is supposed to support going from exclusive to shared and vice versa? Noted for the next patches. > +static int bdrv_lock_image(BlockDriverState *bs) > +{ > + return bdrv_lock_unlock_image_do(bs, bdrv_get_locking_cmd(bs->open_flags)); > +} > + > +static int bdrv_unlock_image(BlockDriverState *bs) > +{ > + return bdrv_lock_unlock_image_do(bs, BDRV_LOCKF_UNLOCK); > +} > + > static QemuOptsList bdrv_runtime_opts = { > .name = "bdrv_common", > .head = QTAILQ_HEAD_INITIALIZER(bdrv_runtime_opts.head), > @@ -1003,6 +1047,14 @@ static int bdrv_open_common(BlockDriverState *bs, BdrvChild *file, > goto free_and_fail; > } > > + if (!(open_flags & (BDRV_O_NO_LOCK | BDRV_O_INACTIVE))) { > + ret = bdrv_lock_image(bs); > + if (ret) { > + error_setg(errp, "Failed to lock image"); > + goto free_and_fail; > + } > + } > + > ret = refresh_total_sectors(bs, bs->total_sectors); > if (ret < 0) { > error_setg_errno(errp, -ret, "Could not refresh total sector count"); > @@ -2164,6 +2216,7 @@ static void bdrv_close(BlockDriverState *bs) > if (bs->drv) { > BdrvChild *child, *next; > > + bdrv_unlock_image(bs); > bs->drv->bdrv_close(bs); > bs->drv = NULL; > > @@ -3187,6 +3240,9 @@ void bdrv_invalidate_cache(BlockDriverState *bs, Error **errp) > error_setg_errno(errp, -ret, "Could not refresh total sector count"); > return; > } > + if (!(bs->open_flags & BDRV_O_NO_LOCK)) { > + bdrv_lock_image(bs); > + } > } I think the if is unnecessary, bdrv_lock_image() already looks at BDRV_O_NO_LOCK. > void bdrv_invalidate_cache_all(Error **errp) > @@ -3229,6 +3285,7 @@ static int bdrv_inactivate_recurse(BlockDriverState *bs, > } > > if (setting_flag) { > + ret = bdrv_unlock_image(bs); > bs->open_flags |= BDRV_O_INACTIVE; > } > return 0; Kevin