From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 7D9F0EE3F3F for ; Wed, 13 Sep 2023 00:16:09 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S237938AbjIMAQM (ORCPT ); Tue, 12 Sep 2023 20:16:12 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:52210 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S237936AbjIMAQL (ORCPT ); Tue, 12 Sep 2023 20:16:11 -0400 Received: from wout4-smtp.messagingengine.com (wout4-smtp.messagingengine.com [64.147.123.20]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 1022E10F2 for ; Tue, 12 Sep 2023 17:16:08 -0700 (PDT) Received: from compute6.internal (compute6.nyi.internal [10.202.2.47]) by mailout.west.internal (Postfix) with ESMTP id 3EE5132004E7; Tue, 12 Sep 2023 20:16:07 -0400 (EDT) Received: from mailfrontend2 ([10.202.2.163]) by compute6.internal (MEProxy); Tue, 12 Sep 2023 20:16:07 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=bur.io; h=cc:cc :content-type:content-type:date:date:from:from:in-reply-to :in-reply-to:message-id:mime-version:references:reply-to:sender :subject:subject:to:to; s=fm2; t=1694564166; x=1694650566; bh=ea fn9znU0+gPi+Q9pJXOvX6ZNQE7Gfom9l8d44isyes=; b=c58y83voBG1sCbeDss PNzLlLCcL4Tobd62XsQcFioCQE7mBE1QJ0YgzIHRKEf2GkweIg34zaEk1gPdaZ+E um9fSnUAIb/sCl+7vEK4BXzGkW6GzSDB/I4rw980lXMckn5jN6Nage1QnPmaj7YC KSzofqhRu2EkvS2Agj89/xcYGVEn2vPhoHwo5mOT+JxY+Z6+s09b3syHOP0DEhpe 9W5CJ7Tmct+mWEFU3Y6+CwpT/Wp+p1AZUGy50ApEy9onxQT2o4LdmY6H/J3EbAXo PeI4r5mJt/NZG1pGJzWp/e48sTeOm0zQ7YKYjtXmuhVQyhg3AynkFqrt69ZWbCeC zJsA== DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d= messagingengine.com; h=cc:cc:content-type:content-type:date:date :feedback-id:feedback-id:from:from:in-reply-to:in-reply-to :message-id:mime-version:references:reply-to:sender:subject :subject:to:to:x-me-proxy:x-me-proxy:x-me-sender:x-me-sender :x-sasl-enc; s=fm1; t=1694564166; x=1694650566; bh=eafn9znU0+gPi +Q9pJXOvX6ZNQE7Gfom9l8d44isyes=; b=Il4Lpmo7m0W+VTdjKHrb58esadHHS /shXPgBwqb2h6/3zAgCkpWyKksrzvg2HqXmny36LWDpQx7v9lAN0CLcUDZScaBlO P64uPHaBkx4/qGi1QW0T9e9Z5ypw836zi60Bhsct+CxvqZVSQcJkOBAnPd64jMet j8lEubAFx2ccCrUpP7yG+kG/9l7t5FoEk2K9JjrdPjuSpcpgsOdW0yIejUyy9L1F 51K0oDbU9qk7aFkLI2b2915lweez/PU8RSAiIlYst7ihbHtykLs/3jPRLq2kwYPg T9mrcUsWK6IswB382eL5dgqQllCjbclbj7SY9wcPFaMsZiTEbYhtdoO0A== X-ME-Sender: X-ME-Received: X-ME-Proxy-Cause: gggruggvucftvghtrhhoucdtuddrgedviedrudeijedgfeefucetufdoteggodetrfdotf fvucfrrhhofhhilhgvmecuhfgrshhtofgrihhlpdfqfgfvpdfurfetoffkrfgpnffqhgen uceurghilhhouhhtmecufedttdenucesvcftvggtihhpihgvnhhtshculddquddttddmne cujfgurhepfffhvfevuffkfhggtggujgesthdtredttddtvdenucfhrhhomhepuehorhhi shcuuehurhhkohhvuceosghorhhishessghurhdrihhoqeenucggtffrrghtthgvrhhnpe ekvdekffejleelhfevhedvjeduhfejtdfhvdevieeiiedugfeugfdtjefgfeeljeenucev lhhushhtvghrufhiiigvpedtnecurfgrrhgrmhepmhgrihhlfhhrohhmpegsohhrihhsse gsuhhrrdhioh X-ME-Proxy: Feedback-ID: i083147f8:Fastmail Received: by mail.messagingengine.com (Postfix) with ESMTPA; Tue, 12 Sep 2023 20:16:06 -0400 (EDT) Date: Tue, 12 Sep 2023 17:17:02 -0700 From: Boris Burkov To: David Sterba Cc: linux-btrfs@vger.kernel.org, kernel-team@fb.com Subject: Re: [PATCH v5 15/18] btrfs: check generation when recording simple quota delta Message-ID: <20230913001702.GA224634@zen> References: <04ffbfcc145951c2f570312901b2c03c3c74e48e.1690495785.git.boris@bur.io> <20230907122449.GL3159@twin.jikos.cz> <20230908214146.GA172348@zen> <20230911180020.GF3159@twin.jikos.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20230911180020.GF3159@twin.jikos.cz> Precedence: bulk List-ID: X-Mailing-List: linux-btrfs@vger.kernel.org On Mon, Sep 11, 2023 at 08:00:20PM +0200, David Sterba wrote: > On Fri, Sep 08, 2023 at 02:41:46PM -0700, Boris Burkov wrote: > > On Thu, Sep 07, 2023 at 02:24:49PM +0200, David Sterba wrote: > > > On Thu, Jul 27, 2023 at 03:13:02PM -0700, Boris Burkov wrote: > > > > Simple quotas count extents only from the moment the feature is enabled. > > > > Therefore, if we do something like: > > > > 1. create subvol S > > > > 2. write F in S > > > > 3. enable quotas > > > > 4. remove F > > > > 5. write G in S > > > > > > > > then after 3. and 4. we would expect the simple quota usage of S to be 0 > > > > (putting aside some metadata extents that might be written) and after > > > > 5., it should be the size of G plus metadata. Therefore, we need to be > > > > able to determine whether a particular quota delta we are processing > > > > predates simple quota enablement. > > > > > > > > To do this, store the transaction id when quotas were enabled. In > > > > fs_info for immediate use and in the quota status item to make it > > > > recoverable on mount. When we see a delta, check if the generation of > > > > the extent item is less than that of quota enablement. If so, we should > > > > ignore the delta from this extent. > > > > > > > > Signed-off-by: Boris Burkov > > > > --- > > > > fs/btrfs/accessors.h | 2 ++ > > > > fs/btrfs/extent-tree.c | 4 ++++ > > > > fs/btrfs/fs.h | 2 ++ > > > > fs/btrfs/qgroup.c | 14 ++++++++++++-- > > > > fs/btrfs/qgroup.h | 1 + > > > > include/uapi/linux/btrfs_tree.h | 7 +++++++ > > > > 6 files changed, 28 insertions(+), 2 deletions(-) > > > > > > > > diff --git a/fs/btrfs/accessors.h b/fs/btrfs/accessors.h > > > > index a23045c05937..513f8edbd98e 100644 > > > > --- a/fs/btrfs/accessors.h > > > > +++ b/fs/btrfs/accessors.h > > > > @@ -970,6 +970,8 @@ BTRFS_SETGET_FUNCS(qgroup_status_flags, struct btrfs_qgroup_status_item, > > > > flags, 64); > > > > BTRFS_SETGET_FUNCS(qgroup_status_rescan, struct btrfs_qgroup_status_item, > > > > rescan, 64); > > > > +BTRFS_SETGET_FUNCS(qgroup_status_enable_gen, struct btrfs_qgroup_status_item, > > > > + enable_gen, 64); > > > > > > > > /* btrfs_qgroup_info_item */ > > > > BTRFS_SETGET_FUNCS(qgroup_info_generation, struct btrfs_qgroup_info_item, > > > > diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c > > > > index 1b5efd03ef83..395ab46e520b 100644 > > > > --- a/fs/btrfs/extent-tree.c > > > > +++ b/fs/btrfs/extent-tree.c > > > > @@ -1513,6 +1513,7 @@ static int run_delayed_data_ref(struct btrfs_trans_handle *trans, > > > > .rsv_bytes = href->reserved_bytes, > > > > .is_data = true, > > > > .is_inc = true, > > > > + .generation = trans->transid, > > > > }; > > > > > > > > if (extent_op) > > > > @@ -1676,6 +1677,7 @@ static int run_delayed_tree_ref(struct btrfs_trans_handle *trans, > > > > .rsv_bytes = 0, > > > > .is_data = false, > > > > .is_inc = true, > > > > + .generation = trans->transid, > > > > }; > > > > > > > > BUG_ON(!extent_op || !extent_op->update_flags); > > > > @@ -3217,6 +3219,7 @@ static int __btrfs_free_extent(struct btrfs_trans_handle *trans, > > > > .rsv_bytes = 0, > > > > .is_data = is_data, > > > > .is_inc = false, > > > > + .generation = btrfs_extent_generation(leaf, ei), > > > > }; > > > > > > > > /* In this branch refs == 1 */ > > > > @@ -4850,6 +4853,7 @@ int btrfs_alloc_logged_file_extent(struct btrfs_trans_handle *trans, > > > > struct btrfs_simple_quota_delta delta = { > > > > .root = root_objectid, > > > > .num_bytes = ins->offset, > > > > + .generation = trans->transid, > > > > .rsv_bytes = 0, > > > > .is_data = true, > > > > .is_inc = true, > > > > diff --git a/fs/btrfs/fs.h b/fs/btrfs/fs.h > > > > index f76f450c2abf..da7b623ff15f 100644 > > > > --- a/fs/btrfs/fs.h > > > > +++ b/fs/btrfs/fs.h > > > > @@ -802,6 +802,8 @@ struct btrfs_fs_info { > > > > spinlock_t eb_leak_lock; > > > > struct list_head allocated_ebs; > > > > #endif > > > > + > > > > + u64 quota_enable_gen; > > > > > > Please move it to the other quota/qgroup related members, at the end of > > > fs_info there's only debugging stuff. > > > > > > > }; > > > > > > > > static inline void btrfs_set_last_root_drop_gen(struct btrfs_fs_info *fs_info, > > > > diff --git a/fs/btrfs/qgroup.c b/fs/btrfs/qgroup.c > > > > index 58e9ed0deedd..a8a603242431 100644 > > > > --- a/fs/btrfs/qgroup.c > > > > +++ b/fs/btrfs/qgroup.c > > > > @@ -454,6 +454,8 @@ int btrfs_read_qgroup_config(struct btrfs_fs_info *fs_info) > > > > } > > > > fs_info->qgroup_flags = btrfs_qgroup_status_flags(l, ptr); > > > > simple = fs_info->qgroup_flags & BTRFS_QGROUP_STATUS_FLAG_SIMPLE; > > > > + if (simple) > > > > + fs_info->quota_enable_gen = btrfs_qgroup_status_enable_gen(l, ptr); > > > > if (btrfs_qgroup_status_generation(l, ptr) != > > > > fs_info->generation && !simple) { > > > > qgroup_mark_inconsistent(fs_info); > > > > @@ -1107,10 +1109,12 @@ int btrfs_quota_enable(struct btrfs_fs_info *fs_info, > > > > btrfs_set_qgroup_status_generation(leaf, ptr, trans->transid); > > > > btrfs_set_qgroup_status_version(leaf, ptr, BTRFS_QGROUP_STATUS_VERSION); > > > > fs_info->qgroup_flags = BTRFS_QGROUP_STATUS_FLAG_ON; > > > > - if (simple) > > > > + if (simple) { > > > > fs_info->qgroup_flags |= BTRFS_QGROUP_STATUS_FLAG_SIMPLE; > > > > - else > > > > + btrfs_set_qgroup_status_enable_gen(leaf, ptr, trans->transid); > > > > + } else { > > > > fs_info->qgroup_flags |= BTRFS_QGROUP_STATUS_FLAG_INCONSISTENT; > > > > + } > > > > btrfs_set_qgroup_status_flags(leaf, ptr, fs_info->qgroup_flags & > > > > BTRFS_QGROUP_STATUS_FLAGS_MASK); > > > > btrfs_set_qgroup_status_rescan(leaf, ptr, 0); > > > > @@ -1202,6 +1206,8 @@ int btrfs_quota_enable(struct btrfs_fs_info *fs_info, > > > > goto out_free_path; > > > > } > > > > > > > > + fs_info->quota_enable_gen = trans->transid; > > > > + > > > > mutex_unlock(&fs_info->qgroup_ioctl_lock); > > > > /* > > > > * Commit the transaction while not holding qgroup_ioctl_lock, to avoid > > > > @@ -4622,6 +4628,10 @@ int btrfs_record_simple_quota_delta(struct btrfs_fs_info *fs_info, > > > > if (!is_fstree(root)) > > > > return 0; > > > > > > > > + /* If the extent predates enabling quotas, don't count it. */ > > > > + if (delta->generation < fs_info->quota_enable_gen) > > > > + return 0; > > > > + > > > > spin_lock(&fs_info->qgroup_lock); > > > > qgroup = find_qgroup_rb(fs_info, root); > > > > if (!qgroup) { > > > > diff --git a/fs/btrfs/qgroup.h b/fs/btrfs/qgroup.h > > > > index ce6fa8694ca7..ae1ce14b365c 100644 > > > > --- a/fs/btrfs/qgroup.h > > > > +++ b/fs/btrfs/qgroup.h > > > > @@ -241,6 +241,7 @@ struct btrfs_simple_quota_delta { > > > > u64 rsv_bytes; /* The number of bytes reserved for this extent */ > > > > bool is_inc; /* Whether we are using or freeing the extent */ > > > > bool is_data; /* Whether the extent is data or metadata */ > > > > + u64 generation; /* The generation the extent was created in */ > > > > > > Please reorder it so it does not leave gaps between struct members. > > > > > > > }; > > > > > > > > static inline u64 btrfs_qgroup_subvolid(u64 qgroupid) > > > > diff --git a/include/uapi/linux/btrfs_tree.h b/include/uapi/linux/btrfs_tree.h > > > > index eacb26caf3c6..1120ce3dae42 100644 > > > > --- a/include/uapi/linux/btrfs_tree.h > > > > +++ b/include/uapi/linux/btrfs_tree.h > > > > @@ -1242,6 +1242,13 @@ struct btrfs_qgroup_status_item { > > > > * of the scan. It contains a logical address > > > > */ > > > > __le64 rescan; > > > > + > > > > + /* > > > > + * the generation when quotas are enabled. Used by simple quotas to > > > > + * avoid decrementing when freeing an extent that was written before > > > > + * enable. > > > > + */ > > > > + __le64 enable_gen; > > > > > > This is public interface and btrfs_qgroup_status_item is used in many > > > places in user space at least in btrfs-progs. This needs a lot of > > > sanity checks. > > > > Totally agreed in principle, but not exactly sure how to proceed in > > practice. I would definitely appreciate some tips/help! > > > > How we interact with the new field: > > - When enabling squota, set it, the incompat bit, and the status flag > > - When reading in the qgroup status_item, if the status flag is set, > > then read the enable_gen. > > > > I believe this prevents us from ever reading garbage while trying to > > read an old fs (status flag won't be set) and it prevents any > > btrfs-progs from getting confused by a wrong-sized status item, since > > it would choke on the incompat bit first. > > > > Am I missing some other case? I can try to make it more explicitly > > zeroed when we enable qgroups but not squotas? I can add an ASSERT that > > the incompat bit is set as expected when we read the status item with > > the flag on (that seems good no matter what)? > > > > I can also write a wrapper for getting it which does the incompat/status > > flag checking to make it more clear that it isn't safe to read in > > general. Or a comment on the struct saying it depends on the incompat > > bit? > > All of the above makes sense and I had something like that in mind when > writing the comment. The wrappers can make sure the bit is set when > reading the item. I think there's an example in existing code that > versions an item based on size, I can't find it now (probably something > from the send/receive time where several new struct members were added). > > I just noticed we have versioning for the qgoup status item, > BTRFS_QGROUP_STATUS_VERSION is now 1 and has backward compatibility > handling. We can probably use version 2 for squotas, in addition to the > helpers with sanity checks. I made the helper/validation changes in V6, but forgot to address the BTRFS_QGROUP_STATUS_VERSION idea. Right now, that field is for preventing forward compatibility as well as backward (for lack of a better term?) The check on it is a !=, so if you bump the version, you can no longer honor old fs-es qgroups, which is not the case with this change. Since the version has never been bumped, I believe we can safely change it to a backwards compatibility check and use it for squotas.