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([185.215.60.153]) by smtp.gmail.com with ESMTPSA id y3-20020a056512044300b0044a9bda3242sm1057573lfk.90.2022.03.30.14.29.39 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 30 Mar 2022 14:29:39 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=openvz-org.20210112.gappssmtp.com; s=20210112; h=from:to:cc:subject:date:message-id:in-reply-to:references :mime-version:content-transfer-encoding; bh=yxA16/0vHXnE0IYduXZZfLFZVO67I7ey+Qd97nmcKzs=; b=8ShyqqI+F118OYSRuIRF4jBftfAMmK32ogDXd3xbtzufEzyNYIeJB8/cwyWPb0G2ia 4HEx2j4lnGjpBR2YvlYCaJAba4xb59VC8cqy3UJxVilZA767PS4/v1KrBLbJUZT9FTrt P8anHmfhOOUqrObK7q4uNWO+bFUkzBZvAwln2uyMdkJgeqWovKjDm1e9ec0a64W9ZTxm vxMfsHzqosJHwAIQl6UPFHbuzG/R73OEjlRnFBWQDGVwKZUuirrfF18OrXIcLUY7vq6m Qk2dW3DwxmO0XCASePTAj0T5zBO//ImbUFjvMgdc2o0Nax23iUiddUhRlaw1eZ2MHJyK 55PA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:from:to:cc:subject:date:message-id:in-reply-to :references:mime-version:content-transfer-encoding; bh=yxA16/0vHXnE0IYduXZZfLFZVO67I7ey+Qd97nmcKzs=; b=LwYvfyhYwiBA+ejA9M7ZvxnPKdgK+9GE+xVKWb2F5qnKNSZRa2ddz9LPfKzRquzp0P TSr3oUAs2yj6wlh2jmnug0CLV7rm/0IuevNkTq08uO9uikI830CED/Me+n3FZ7dKk3Qb B/jZW3uY148pHAdQzraK9pgeVgYQVLW2Iv0vs0VVWSPQrcnwLTCW9huLe+w+Y8VuCl6q TcG5YZkgKvLBliaA4Eiw8hDzBYERr587Gj36NISBoVhrg/YSHz6AVhlL+Mnq7isf4nrn OxPOlSyqYo34aK+WwaicmU66MYXiJNLSOuFdXj/jGP2HIhFkgSIVlp5DSMpEk6gdVkUt 3RqQ== X-Gm-Message-State: AOAM530mpmsjQt0zPAFtqfQVGzO36GonodchSFio+IAlBjDHKNt3F/x2 LVvrAnwgpEWN/XSlj816Mjs1cE6Rq9rvPA== X-Google-Smtp-Source: ABdhPJyBCgCLkiGaBXqm8LhVIJbakMV4Qb+qy6LLCihdM6mD0kiDtubvzBR0x32kbsuyunmhz7JslA== X-Received: by 2002:a05:651c:1a27:b0:249:8dd8:6ceb with SMTP id by39-20020a05651c1a2700b002498dd86cebmr8080458ljb.8.1648675779478; Wed, 30 Mar 2022 14:29:39 -0700 (PDT) From: Vladimir Sementsov-Ogievskiy X-Google-Original-From: Vladimir Sementsov-Ogievskiy To: qemu-block@nongnu.org Subject: [PATCH v5 13/45] block: Manipulate bs->file / bs->backing pointers in .attach/.detach Date: Thu, 31 Mar 2022 00:28:30 +0300 Message-Id: <20220330212902.590099-14-vsementsov@openvz.org> X-Mailer: git-send-email 2.35.1 In-Reply-To: <20220330212902.590099-1-vsementsov@openvz.org> References: <20220330212902.590099-1-vsementsov@openvz.org> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-Host-Lookup-Failed: Reverse DNS lookup failed for 2a00:1450:4864:20::22b (failed) 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=2a00:1450:4864:20::22b; envelope-from=vladimir.sementsov-ogievskiy@openvz.org; helo=mail-lj1-x22b.google.com X-Spam_score_int: -4 X-Spam_score: -0.5 X-Spam_bar: / X-Spam_report: (-0.5 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, PDS_HP_HELO_NORDNS=0.659, RCVD_IN_DNSWL_NONE=-0.0001, RDNS_NONE=0.793, SPF_HELO_NONE=0.001, SPF_PASS=-0.001, T_SCC_BODY_TEXT_LINE=-0.01 autolearn=no autolearn_force=no X-Spam_action: no action X-Mailman-Approved-At: Wed, 30 Mar 2022 19:17:23 -0400 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: , Cc: kwolf@redhat.com, hreitz@redhat.com, vsementsov@openvz.org, v.sementsov-og@mail.ru, qemu-devel@nongnu.org Errors-To: qemu-devel-bounces+importer=patchew.org@nongnu.org Sender: "Qemu-devel" X-ZohoMail-DKIM: fail (Header signature does not verify) X-ZM-MESSAGEID: 1648682821439100001 Content-Type: text/plain; charset="utf-8" bs->file and bs->backing are a kind of duplication of part of bs->children. But very useful diplication, so let's not drop them at all:) We should manage bs->file and bs->backing in same place, where we manage bs->children, to keep them in sync. Moreover, generic io paths are unprepared to BdrvChild without a bs, so it's double good to clear bs->file / bs->backing when we detach the child. Detach is simple: if we detach bs->file or bs->backing child, just set corresponding field to NULL. Attach is a bit more complicated. But we still can precisely detect should we set one of bs->file / bs->backing or not: - if role is BDRV_CHILD_COW, we definitely deal with bs->backing - else, if role is BDRV_CHILD_FILTERED (it must be also BDRV_CHILD_PRIMARY), it's a filtered child. Use bs->drv->filtered_child_is_backing to chose the pointer field to modify. - else, if role is BDRV_CHILD_PRIMARY, we deal with bs->file - in all other cases, it's neither bs->backing nor bs->file. It's some other child and we shouldn't care OK. This change brings one more good thing: we can (and should) get rid of all indirect pointers in the block-graph-change transactions: bdrv_attach_child_common() stores BdrvChild** into transaction to clear it on abort. bdrv_attach_child_common() has two callers: bdrv_attach_child_noperm() just pass-through this feature, bdrv_root_attach_child() doesn't need the feature. Look at bdrv_attach_child_noperm() callers: - bdrv_attach_child() doesn't need the feature - bdrv_set_file_or_backing_noperm() uses the feature to manage bs->file and bs->backing, we don't want it anymore - bdrv_append() uses the feature to manage bs->backing, again we don't want it anymore So, we should drop this stuff! Great! We still keep BdrvChild** argument to return the child and int return value, and not move to simply returning BdrvChild*, as we don't want to lose int return values. However we don't require *@child to be NULL anymore, and even allow @child to be NULL, if caller don't need the new child pointer. Finally, we now set .file / .backing automatically in generic code and want to restring setting them by hand outside of .attach/.detach. So, this patch cleanups all remaining places where they were set. To find such places I use: git grep '\->file =3D' git grep '\->backing =3D' git grep '&.*\' git grep '&.*\' Signed-off-by: Vladimir Sementsov-Ogievskiy --- block.c | 156 ++++++++++++++----------------- block/raw-format.c | 4 +- block/snapshot.c | 1 - include/block/block_int-common.h | 15 ++- tests/unit/test-bdrv-drain.c | 10 +- 5 files changed, 89 insertions(+), 97 deletions(-) diff --git a/block.c b/block.c index 8e8ed639fe..6b43e101a1 100644 --- a/block.c +++ b/block.c @@ -1438,9 +1438,33 @@ static void bdrv_child_cb_attach(BdrvChild *child) =20 assert_bdrv_graph_writable(bs); QLIST_INSERT_HEAD(&bs->children, child, next); - - if (child->role & BDRV_CHILD_COW) { + if (bs->drv->is_filter | (child->role & BDRV_CHILD_FILTERED)) { + /* + * Here we handle filters and block/raw-format.c when it behave li= ke + * filter. + */ + assert(!(child->role & BDRV_CHILD_COW)); + if (child->role & (BDRV_CHILD_PRIMARY | BDRV_CHILD_FILTERED)) { + assert(child->role & BDRV_CHILD_PRIMARY); + assert(child->role & BDRV_CHILD_FILTERED); + assert(!bs->backing); + assert(!bs->file); + + if (bs->drv->filtered_child_is_backing) { + bs->backing =3D child; + } else { + bs->file =3D child; + } + } + } else if (child->role & BDRV_CHILD_COW) { + assert(bs->drv->supports_backing); + assert(!(child->role & BDRV_CHILD_PRIMARY)); + assert(!bs->backing); + bs->backing =3D child; bdrv_backing_attach(child); + } else if (child->role & BDRV_CHILD_PRIMARY) { + assert(!bs->file); + bs->file =3D child; } =20 bdrv_apply_subtree_drain(child, bs); @@ -1458,6 +1482,12 @@ static void bdrv_child_cb_detach(BdrvChild *child) =20 assert_bdrv_graph_writable(bs); QLIST_REMOVE(child, next); + if (child =3D=3D bs->backing) { + assert(child !=3D bs->file); + bs->backing =3D NULL; + } else if (child =3D=3D bs->file) { + bs->file =3D NULL; + } } =20 static int bdrv_child_cb_update_filename(BdrvChild *c, BlockDriverState *b= ase, @@ -1663,7 +1693,7 @@ open_failed: bs->drv =3D NULL; if (bs->file !=3D NULL) { bdrv_unref_child(bs, bs->file); - bs->file =3D NULL; + assert(!bs->file); } g_free(bs->opaque); bs->opaque =3D NULL; @@ -2852,7 +2882,7 @@ static void bdrv_child_free(BdrvChild *child) } =20 typedef struct BdrvAttachChildCommonState { - BdrvChild **child; + BdrvChild *child; AioContext *old_parent_ctx; AioContext *old_child_ctx; } BdrvAttachChildCommonState; @@ -2860,33 +2890,31 @@ typedef struct BdrvAttachChildCommonState { static void bdrv_attach_child_common_abort(void *opaque) { BdrvAttachChildCommonState *s =3D opaque; - BdrvChild *child =3D *s->child; - BlockDriverState *bs =3D child->bs; + BlockDriverState *bs =3D s->child->bs; =20 GLOBAL_STATE_CODE(); - bdrv_replace_child_noperm(child, NULL); + 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); } =20 - if (bdrv_child_get_parent_aio_context(child) !=3D s->old_parent_ctx) { + if (bdrv_child_get_parent_aio_context(s->child) !=3D s->old_parent_ctx= ) { GSList *ignore; =20 /* No need to ignore `child`, because it has been detached already= */ ignore =3D NULL; - child->klass->can_set_aio_ctx(child, s->old_parent_ctx, &ignore, - &error_abort); + s->child->klass->can_set_aio_ctx(s->child, s->old_parent_ctx, &ign= ore, + &error_abort); g_slist_free(ignore); =20 ignore =3D NULL; - child->klass->set_aio_ctx(child, s->old_parent_ctx, &ignore); + s->child->klass->set_aio_ctx(s->child, s->old_parent_ctx, &ignore); g_slist_free(ignore); } =20 bdrv_unref(bs); - bdrv_child_free(child); - *s->child =3D NULL; + bdrv_child_free(s->child); } =20 static TransactionActionDrv bdrv_attach_child_common_drv =3D { @@ -2897,11 +2925,11 @@ static TransactionActionDrv bdrv_attach_child_commo= n_drv =3D { /* * Common part of attaching bdrv child to bs or to blk or to job * - * Resulting new child is returned through @child. - * At start *@child must be NULL. - * @child is saved to a new entry of @tran, so that *@child could be rever= ted to - * NULL on abort(). So referenced variable must live at least until transa= ction - * end. + * If @child is not NULL, it's set to new created child. Note, that @child + * pointer is stored in the transaction and therefore not cleared on abort. + * Consider @child as part of return value: we may change the return value= of + * the function to BdrvChild* and return child directly, but this way we l= ose + * different return codes. * * Function doesn't update permissions, caller is responsible for this. */ @@ -2917,8 +2945,6 @@ static int bdrv_attach_child_common(BlockDriverState = *child_bs, AioContext *parent_ctx; AioContext *child_ctx =3D bdrv_get_aio_context(child_bs); =20 - assert(child); - assert(*child =3D=3D NULL); assert(child_class->get_parent_desc); GLOBAL_STATE_CODE(); =20 @@ -2967,22 +2993,25 @@ static int bdrv_attach_child_common(BlockDriverStat= e *child_bs, bdrv_ref(child_bs); bdrv_replace_child_noperm(new_child, child_bs); =20 - *child =3D new_child; - BdrvAttachChildCommonState *s =3D g_new(BdrvAttachChildCommonState, 1); *s =3D (BdrvAttachChildCommonState) { - .child =3D child, + .child =3D new_child, .old_parent_ctx =3D parent_ctx, .old_child_ctx =3D child_ctx, }; tran_add(tran, &bdrv_attach_child_common_drv, s); =20 + if (child) { + *child =3D new_child; + } + return 0; } =20 /* - * Variable referenced by @child must live at least until transaction end. - * (see bdrv_attach_child_common() doc for details) + * If @child is not NULL, it's set to new created child. @child is a part = of + * return value, not a part of transaction (see bdrv_attach_child_common()= doc + * for details). * * Function doesn't update permissions, caller is responsible for this. */ @@ -3063,7 +3092,7 @@ BdrvChild *bdrv_root_attach_child(BlockDriverState *c= hild_bs, void *opaque, Error **errp) { int ret; - BdrvChild *child =3D NULL; + BdrvChild *child; Transaction *tran =3D tran_new(); =20 GLOBAL_STATE_CODE(); @@ -3079,11 +3108,10 @@ BdrvChild *bdrv_root_attach_child(BlockDriverState = *child_bs, =20 out: tran_finalize(tran, ret); - /* child is unset on failure by bdrv_attach_child_common_abort() */ - assert((ret < 0) =3D=3D !child); =20 bdrv_unref(child_bs); - return child; + + return ret < 0 ? NULL : child; } =20 /* @@ -3105,7 +3133,7 @@ BdrvChild *bdrv_attach_child(BlockDriverState *parent= _bs, Error **errp) { int ret; - BdrvChild *child =3D NULL; + BdrvChild *child; Transaction *tran =3D tran_new(); =20 GLOBAL_STATE_CODE(); @@ -3123,12 +3151,10 @@ BdrvChild *bdrv_attach_child(BlockDriverState *pare= nt_bs, =20 out: tran_finalize(tran, ret); - /* child is unset on failure by bdrv_attach_child_common_abort() */ - assert((ret < 0) =3D=3D !child); =20 bdrv_unref(child_bs); =20 - return child; + return ret < 0 ? NULL : child; } =20 /* Callers must ensure that child->frozen is false. */ @@ -3331,9 +3357,7 @@ static int bdrv_set_file_or_backing_noperm(BlockDrive= rState *parent_bs, ret =3D bdrv_attach_child_noperm(parent_bs, child_bs, is_backing ? "backing" : "file", &child_of_bds, role, - is_backing ? &parent_bs->backing : - &parent_bs->file, - tran, errp); + NULL, tran, errp); if (ret < 0) { return ret; } @@ -3591,14 +3615,16 @@ int bdrv_open_file_child(const char *filename, =20 /* commit_top and mirror_top don't use this function */ assert(!parent->drv->filtered_child_is_backing); - role =3D parent->drv->is_filter ? (BDRV_CHILD_FILTERED | BDRV_CHILD_PRIMARY) : BDRV_CHILD_IMAGE; =20 - parent->file =3D bdrv_open_child(filename, options, bdref_key, parent, - &child_of_bds, role, false, errp); + if (!bdrv_open_child(filename, options, bdref_key, parent, + &child_of_bds, role, false, errp)) + { + return -EINVAL; + } =20 - return parent->file ? 0 : -EINVAL; + return 0; } =20 /* @@ -4873,8 +4899,8 @@ static void bdrv_close(BlockDriverState *bs) bdrv_unref_child(bs, child); } =20 - bs->backing =3D NULL; - bs->file =3D NULL; + assert(!bs->backing); + assert(!bs->file); g_free(bs->opaque); bs->opaque =3D NULL; qatomic_set(&bs->copy_on_read, 0); @@ -5005,41 +5031,14 @@ static bool should_update_child(BdrvChild *c, Block= DriverState *to) return ret; } =20 -typedef struct BdrvRemoveFilterOrCowChild { - BdrvChild *child; - bool is_backing; -} BdrvRemoveFilterOrCowChild; - -static void bdrv_remove_filter_or_cow_child_abort(void *opaque) -{ - BdrvRemoveFilterOrCowChild *s =3D opaque; - BlockDriverState *parent_bs =3D s->child->opaque; - - if (s->is_backing) { - parent_bs->backing =3D s->child; - } else { - parent_bs->file =3D s->child; - } - - /* - * We don't have to restore child->bs here to undo bdrv_replace_child_= tran() - * because that function is transactionable and it registered own comp= letion - * entries in @tran, so .abort() for bdrv_replace_child_safe() will be - * called automatically. - */ -} - static void bdrv_remove_filter_or_cow_child_commit(void *opaque) { - BdrvRemoveFilterOrCowChild *s =3D opaque; GLOBAL_STATE_CODE(); - bdrv_child_free(s->child); + bdrv_child_free(opaque); } =20 static TransactionActionDrv bdrv_remove_filter_or_cow_child_drv =3D { - .abort =3D bdrv_remove_filter_or_cow_child_abort, .commit =3D bdrv_remove_filter_or_cow_child_commit, - .clean =3D g_free, }; =20 /* @@ -5050,8 +5049,6 @@ static void bdrv_remove_file_or_backing_child(BlockDr= iverState *bs, BdrvChild *child, Transaction *tran) { - BdrvRemoveFilterOrCowChild *s; - assert(child =3D=3D bs->backing || child =3D=3D bs->file); =20 if (!child) { @@ -5062,18 +5059,7 @@ static void bdrv_remove_file_or_backing_child(BlockD= riverState *bs, bdrv_replace_child_tran(child, NULL, tran); } =20 - s =3D g_new(BdrvRemoveFilterOrCowChild, 1); - *s =3D (BdrvRemoveFilterOrCowChild) { - .child =3D child, - .is_backing =3D (child =3D=3D bs->backing), - }; - tran_add(tran, &bdrv_remove_filter_or_cow_child_drv, s); - - if (s->is_backing) { - bs->backing =3D NULL; - } else { - bs->file =3D NULL; - } + tran_add(tran, &bdrv_remove_filter_or_cow_child_drv, child); } =20 /* @@ -5235,7 +5221,7 @@ int bdrv_append(BlockDriverState *bs_new, BlockDriver= State *bs_top, =20 ret =3D bdrv_attach_child_noperm(bs_new, bs_top, "backing", &child_of_bds, bdrv_backing_role(bs_new= ), - &bs_new->backing, tran, errp); + NULL, tran, errp); if (ret < 0) { goto out; } diff --git a/block/raw-format.c b/block/raw-format.c index 69fd650eaf..d8ca8ee3a9 100644 --- a/block/raw-format.c +++ b/block/raw-format.c @@ -457,8 +457,8 @@ static int raw_open(BlockDriverState *bs, QDict *option= s, int flags, file_role =3D BDRV_CHILD_FILTERED | BDRV_CHILD_PRIMARY; } =20 - bs->file =3D bdrv_open_child(NULL, options, "file", bs, &child_of_bds, - file_role, false, errp); + bdrv_open_child(NULL, options, "file", bs, &child_of_bds, + file_role, false, errp); if (!bs->file) { return -EINVAL; } diff --git a/block/snapshot.c b/block/snapshot.c index f4ec4f9ef3..02a880911f 100644 --- a/block/snapshot.c +++ b/block/snapshot.c @@ -288,7 +288,6 @@ int bdrv_snapshot_goto(BlockDriverState *bs, =20 /* .bdrv_open() will re-attach it */ bdrv_unref_child(bs, *fallback_ptr); - *fallback_ptr =3D NULL; =20 ret =3D bdrv_snapshot_goto(fallback_bs, snapshot_id, errp); open_ret =3D drv->bdrv_open(bs, options, bs->open_flags, &local_er= r); diff --git a/include/block/block_int-common.h b/include/block/block_int-com= mon.h index d68adc6ff3..c4d8b11dbb 100644 --- a/include/block/block_int-common.h +++ b/include/block/block_int-common.h @@ -1056,9 +1056,6 @@ struct BlockDriverState { QDict *full_open_options; char exact_filename[PATH_MAX]; =20 - BdrvChild *backing; - BdrvChild *file; - /* I/O Limits */ BlockLimits bl; =20 @@ -1117,7 +1114,19 @@ struct BlockDriverState { * parent node of this node. */ BlockDriverState *inherits_from; + + /* + * @backing and @file are some of @children or NULL. All these three f= ields + * (@file, @backing and @children) are modified only in + * bdrv_child_cb_attach() and bdrv_child_cb_detach(). + * + * See also comment in include/block/block.h, to learn how backing and= file + * are connected with BdrvChildRole. + */ QLIST_HEAD(, BdrvChild) children; + BdrvChild *backing; + BdrvChild *file; + QLIST_HEAD(, BdrvChild) parents; =20 QDict *options; diff --git a/tests/unit/test-bdrv-drain.c b/tests/unit/test-bdrv-drain.c index 23d425a494..4cf99edf5b 100644 --- a/tests/unit/test-bdrv-drain.c +++ b/tests/unit/test-bdrv-drain.c @@ -1808,9 +1808,8 @@ static void test_drop_intermediate_poll(void) for (i =3D 0; i < 3; i++) { if (i) { /* Takes the reference to chain[i - 1] */ - chain[i]->backing =3D bdrv_attach_child(chain[i], chain[i - 1], - "chain", &chain_child_cl= ass, - BDRV_CHILD_COW, &error_a= bort); + bdrv_attach_child(chain[i], chain[i - 1], "chain", + &chain_child_class, BDRV_CHILD_COW, &error_a= bort); } } =20 @@ -2028,9 +2027,8 @@ static void do_test_replace_child_mid_drain(int old_d= rain_count, new_child_bs->total_sectors =3D 1; =20 bdrv_ref(old_child_bs); - parent_bs->backing =3D bdrv_attach_child(parent_bs, old_child_bs, "chi= ld", - &child_of_bds, BDRV_CHILD_COW, - &error_abort); + bdrv_attach_child(parent_bs, old_child_bs, "child", &child_of_bds, + BDRV_CHILD_COW, &error_abort); =20 for (i =3D 0; i < old_drain_count; i++) { bdrv_drained_begin(old_child_bs); --=20 2.35.1