From nobody Tue Feb 10 09:28:22 2026 Delivered-To: importer@patchew.org Authentication-Results: mx.zohomail.com; dkim=pass; spf=pass (zohomail.com: domain of gnu.org designates 209.51.188.17 as permitted sender) smtp.mailfrom=qemu-devel-bounces+importer=patchew.org@nongnu.org; dmarc=pass(p=none dis=none) header.from=yandex-team.ru Return-Path: Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) by mx.zohomail.com with SMTPS id 1656106782965529.4035152735607; Fri, 24 Jun 2022 14:39:42 -0700 (PDT) Received: from localhost ([::1]:41340 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1o4r1g-00009k-VG for importer@patchew.org; Fri, 24 Jun 2022 17:39:41 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:60842) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1o4qrx-0000B7-K8; Fri, 24 Jun 2022 17:29:37 -0400 Received: from forwardcorp1o.mail.yandex.net ([95.108.205.193]:44506) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1o4qrv-0004SJ-BC; Fri, 24 Jun 2022 17:29:37 -0400 Received: from myt5-4c5921969858.qloud-c.yandex.net (myt5-4c5921969858.qloud-c.yandex.net [IPv6:2a02:6b8:c12:3b1a:0:640:4c59:2196]) by forwardcorp1o.mail.yandex.net (Yandex) with ESMTP id 5BCF12E1FC3; Sat, 25 Jun 2022 00:29:28 +0300 (MSK) Received: from myt6-81d8ab6a9f9d.qloud-c.yandex.net (myt6-81d8ab6a9f9d.qloud-c.yandex.net [2a02:6b8:c12:520a:0:640:81d8:ab6a]) by myt5-4c5921969858.qloud-c.yandex.net (mxbackcorp/Yandex) with ESMTP id jH780FLLL6-TSJGIj67; Sat, 25 Jun 2022 00:29:28 +0300 Received: from vsementsov-win.yandex-team.ru (unknown [2a02:6b8:b081:b64c::1:2c]) by myt6-81d8ab6a9f9d.qloud-c.yandex.net (smtpcorp/Yandex) with ESMTPSA id KXs24KJ458-TRMSB7Br; Sat, 25 Jun 2022 00:29:28 +0300 (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits)) (Client certificate not present) X-Yandex-Fwd: 2 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=yandex-team.ru; s=default; t=1656106168; bh=9X5Fe1QY16kEGnu9KH1+5gWtYizaZXNzjbSv3OFtbwY=; h=Message-Id:References:Date:Subject:In-Reply-To:Cc:To:From; b=aWN+aKlK4JPhzJny0pfJ6o0g0o9Qer3GfrWy5fgaosU3cqZYB0hTIsYGtoBKvWwf8 ++IT980udjXiWz1wpoxwuRO5IE4KZiuJPLiXs+Qxi9hDpmUJgM6SBCk6JwprjJbYzP lSZAPl6g74afmzQ9hKt3tBGM7cBO+XCUKEcXyV/o= Authentication-Results: myt5-4c5921969858.qloud-c.yandex.net; dkim=pass header.i=@yandex-team.ru From: Vladimir Sementsov-Ogievskiy To: qemu-block@nongnu.org Cc: qemu-devel@nongnu.org, kwolf@redhat.com, hreitz@redhat.com, vsementsov@yandex-team.ru Subject: [PATCH v6 09/15] Revert "block: Let replace_child_noperm free children" Date: Sat, 25 Jun 2022 00:28:24 +0300 Message-Id: <20220624212830.316919-10-vsementsov@yandex-team.ru> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20220624212830.316919-1-vsementsov@yandex-team.ru> References: <20220624212830.316919-1-vsementsov@yandex-team.ru> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Received-SPF: pass (zohomail.com: domain of gnu.org designates 209.51.188.17 as permitted sender) client-ip=209.51.188.17; envelope-from=qemu-devel-bounces+importer=patchew.org@nongnu.org; helo=lists.gnu.org; Received-SPF: pass client-ip=95.108.205.193; envelope-from=vsementsov@yandex-team.ru; helo=forwardcorp1o.mail.yandex.net X-Spam_score_int: -27 X-Spam_score: -2.8 X-Spam_bar: -- X-Spam_report: (-2.8 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_LOW=-0.7, SPF_HELO_NONE=0.001, SPF_PASS=-0.001, T_SCC_BODY_TEXT_LINE=-0.01 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+importer=patchew.org@nongnu.org Sender: "Qemu-devel" X-ZohoMail-DKIM: pass (identity @yandex-team.ru) X-ZM-MESSAGEID: 1656106783987100001 Content-Type: text/plain; charset="utf-8" We are going to reimplement this behavior (clear bs->file / bs->backing pointers automatically when child->bs is cleared) in a nicer way, see further commit "block: Manipulate bs->file / bs->backing pointers in .attach/.detach". With this revert we bring back a problem that was fixed by b0a9f6fed3d8. Still the problem was mostly theoretical, we don't have concrete bugs fixed by b0a9f6fed3d8, we don't have a specific test. Probably some accidental failures of iotests are related. Alternatively, we may merge this and following three reverts into final "block: Manipulate ..." to avoid any kind of regression. But seems that in this case having separate clear revert commits is better. This reverts commit b0a9f6fed3d80de610dcd04a7e66f9f30a04174f. Signed-off-by: Vladimir Sementsov-Ogievskiy --- block.c | 102 +++++++++++++------------------------------------------- 1 file changed, 23 insertions(+), 79 deletions(-) diff --git a/block.c b/block.c index 883b1bb242..34ca046470 100644 --- a/block.c +++ b/block.c @@ -90,10 +90,8 @@ static BlockDriverState *bdrv_open_inherit(const char *f= ilename, static bool bdrv_recurse_has_child(BlockDriverState *bs, BlockDriverState *child); =20 -static void bdrv_child_free(BdrvChild *child); static void bdrv_replace_child_noperm(BdrvChild **child, - BlockDriverState *new_bs, - bool free_empty_child); + BlockDriverState *new_bs); static void bdrv_remove_file_or_backing_child(BlockDriverState *bs, BdrvChild *child, Transaction *tran); @@ -2338,7 +2336,6 @@ typedef struct BdrvReplaceChildState { BdrvChild *child; BdrvChild **childp; BlockDriverState *old_bs; - bool free_empty_child; } BdrvReplaceChildState; =20 static void bdrv_replace_child_commit(void *opaque) @@ -2346,9 +2343,6 @@ static void bdrv_replace_child_commit(void *opaque) BdrvReplaceChildState *s =3D opaque; GLOBAL_STATE_CODE(); =20 - if (s->free_empty_child && !s->child->bs) { - bdrv_child_free(s->child); - } bdrv_unref(s->old_bs); } =20 @@ -2366,26 +2360,22 @@ static void bdrv_replace_child_abort(void *opaque) * modify the BdrvChild * pointer we indirectly pass to it, i.e. it * will not modify s->child. From that perspective, it does not m= atter * whether we pass s->childp or &s->child. + * (TODO: Right now, bdrv_replace_child_noperm() never modifies th= at + * pointer anyway (though it will in the future), so at this point= it + * absolutely does not matter whether we pass s->childp or &s->chi= ld.) * (2) If new_bs is not NULL, s->childp will be NULL. We then cannot = use * it here. * (3) If new_bs is NULL, *s->childp will have been NULLed by * bdrv_replace_child_tran()'s bdrv_replace_child_noperm() call, a= nd we * must not pass a NULL *s->childp here. + * (TODO: In its current state, bdrv_replace_child_noperm() will n= ot + * have NULLed *s->childp, so this does not apply yet. It will in= the + * future.) * * So whether new_bs was NULL or not, we cannot pass s->childp here; a= nd in * any case, there is no reason to pass it anyway. */ - bdrv_replace_child_noperm(&s->child, s->old_bs, true); - /* - * The child was pre-existing, so s->old_bs must be non-NULL, and - * s->child thus must not have been freed - */ - assert(s->child !=3D NULL); - if (!new_bs) { - /* As described above, *s->childp was cleared, so restore it */ - assert(s->childp !=3D NULL); - *s->childp =3D s->child; - } + bdrv_replace_child_noperm(&s->child, s->old_bs); bdrv_unref(new_bs); } =20 @@ -2402,44 +2392,30 @@ static TransactionActionDrv bdrv_replace_child_drv = =3D { * * The function doesn't update permissions, caller is responsible for this. * - * (*childp)->bs must not be NULL. - * * Note that if new_bs =3D=3D NULL, @childp is stored in a state object at= tached * to @tran, so that the old child can be reinstated in the abort handler. * Therefore, if @new_bs can be NULL, @childp must stay valid until the * transaction is committed or aborted. * - * If @free_empty_child is true and @new_bs is NULL, the BdrvChild is - * freed (on commit). @free_empty_child should only be false if the - * caller will free the BDrvChild themselves (which may be important - * if this is in turn called in another transactional context). + * (TODO: The reinstating does not happen yet, but it will once + * bdrv_replace_child_noperm() NULLs *childp when new_bs is NULL.) */ static void bdrv_replace_child_tran(BdrvChild **childp, BlockDriverState *new_bs, - Transaction *tran, - bool free_empty_child) + Transaction *tran) { BdrvReplaceChildState *s =3D g_new(BdrvReplaceChildState, 1); *s =3D (BdrvReplaceChildState) { .child =3D *childp, .childp =3D new_bs =3D=3D NULL ? childp : NULL, .old_bs =3D (*childp)->bs, - .free_empty_child =3D free_empty_child, }; tran_add(tran, &bdrv_replace_child_drv, s); =20 - /* The abort handler relies on this */ - assert(s->old_bs !=3D NULL); - if (new_bs) { bdrv_ref(new_bs); } - /* - * Pass free_empty_child=3Dfalse, we will free the child (if - * necessary) in bdrv_replace_child_commit() (if our - * @free_empty_child parameter was true). - */ - bdrv_replace_child_noperm(childp, new_bs, false); + bdrv_replace_child_noperm(childp, new_bs); /* old_bs reference is transparently moved from *childp to @s */ } =20 @@ -2821,22 +2797,8 @@ uint64_t bdrv_qapi_perm_to_blk_perm(BlockPermission = qapi_perm) return permissions[qapi_perm]; } =20 -/** - * Replace (*childp)->bs by @new_bs. - * - * If @new_bs is NULL, *childp will be set to NULL, too: BDS parents - * generally cannot handle a BdrvChild with .bs =3D=3D NULL, so clearing - * BdrvChild.bs should generally immediately be followed by the - * BdrvChild pointer being cleared as well. - * - * If @free_empty_child is true and @new_bs is NULL, the BdrvChild is - * freed. @free_empty_child should only be false if the caller will - * free the BdrvChild themselves (this may be important in a - * transactional context, where it may only be freed on commit). - */ static void bdrv_replace_child_noperm(BdrvChild **childp, - BlockDriverState *new_bs, - bool free_empty_child) + BlockDriverState *new_bs) { BdrvChild *child =3D *childp; BlockDriverState *old_bs =3D child->bs; @@ -2875,9 +2837,6 @@ static void bdrv_replace_child_noperm(BdrvChild **chi= ldp, } =20 child->bs =3D new_bs; - if (!new_bs) { - *childp =3D NULL; - } =20 if (new_bs) { assert_bdrv_graph_writable(new_bs); @@ -2908,10 +2867,6 @@ static void bdrv_replace_child_noperm(BdrvChild **ch= ildp, bdrv_parent_drained_end_single(child); drain_saldo++; } - - if (free_empty_child && !child->bs) { - bdrv_child_free(child); - } } =20 /** @@ -2943,14 +2898,7 @@ static void bdrv_attach_child_common_abort(void *opa= que) BlockDriverState *bs =3D child->bs; =20 GLOBAL_STATE_CODE(); - /* - * Pass free_empty_child=3Dfalse, because we still need the child - * for the AioContext operations on the parent below; those - * BdrvChildClass methods all work on a BdrvChild object, so we - * need to keep it as an empty shell (after this function, it will - * not be attached to any parent, and it will not have a .bs). - */ - bdrv_replace_child_noperm(s->child, NULL, false); + bdrv_replace_child_noperm(s->child, NULL); =20 if (bdrv_get_aio_context(bs) !=3D s->old_child_ctx) { bdrv_try_set_aio_context(bs, s->old_child_ctx, &error_abort); @@ -2972,6 +2920,7 @@ static void bdrv_attach_child_common_abort(void *opaq= ue) =20 bdrv_unref(bs); bdrv_child_free(child); + *s->child =3D NULL; } =20 static TransactionActionDrv bdrv_attach_child_common_drv =3D { @@ -3050,9 +2999,7 @@ static int bdrv_attach_child_common(BlockDriverState = *child_bs, } =20 bdrv_ref(child_bs); - bdrv_replace_child_noperm(&new_child, child_bs, true); - /* child_bs was non-NULL, so new_child must not have been freed */ - assert(new_child !=3D NULL); + bdrv_replace_child_noperm(&new_child, child_bs); =20 *child =3D new_child; =20 @@ -3113,7 +3060,8 @@ static void bdrv_detach_child(BdrvChild **childp) BlockDriverState *old_bs =3D (*childp)->bs; =20 GLOBAL_STATE_CODE(); - bdrv_replace_child_noperm(childp, NULL, true); + bdrv_replace_child_noperm(childp, NULL); + bdrv_child_free(*childp); =20 if (old_bs) { /* @@ -5167,11 +5115,7 @@ static void bdrv_remove_file_or_backing_child(BlockD= riverState *bs, } =20 if (child->bs) { - /* - * Pass free_empty_child=3Dfalse, we will free the child in - * bdrv_remove_filter_or_cow_child_commit() - */ - bdrv_replace_child_tran(childp, NULL, tran, false); + bdrv_replace_child_tran(childp, NULL, tran); } =20 s =3D g_new(BdrvRemoveFilterOrCowChild, 1); @@ -5181,6 +5125,8 @@ static void bdrv_remove_file_or_backing_child(BlockDr= iverState *bs, .is_backing =3D (childp =3D=3D &bs->backing), }; tran_add(tran, &bdrv_remove_filter_or_cow_child_drv, s); + + *childp =3D NULL; } =20 /* @@ -5224,7 +5170,7 @@ static int bdrv_replace_node_noperm(BlockDriverState = *from, * Passing a pointer to the local variable @c is fine here, because * @to is not NULL, and so &c will not be attached to the transact= ion. */ - bdrv_replace_child_tran(&c, to, tran, true); + bdrv_replace_child_tran(&c, to, tran); } =20 return 0; @@ -5389,9 +5335,7 @@ int bdrv_replace_child_bs(BdrvChild *child, BlockDriv= erState *new_bs, bdrv_drained_begin(old_bs); bdrv_drained_begin(new_bs); =20 - bdrv_replace_child_tran(&child, new_bs, tran, true); - /* @new_bs must have been non-NULL, so @child must not have been freed= */ - assert(child !=3D NULL); + bdrv_replace_child_tran(&child, new_bs, tran); =20 found =3D g_hash_table_new(NULL, NULL); refresh_list =3D bdrv_topological_dfs(refresh_list, found, old_bs); --=20 2.25.1