From: David Sterba <dsterba@suse.cz>
To: Josef Bacik <josef@toxicpanda.com>
Cc: kernel-team@fb.com, linux-btrfs@vger.kernel.org
Subject: Re: [PATCH 6/7] btrfs: hold a ref on the root->reloc_root
Date: Tue, 3 Mar 2020 16:51:50 +0100 [thread overview]
Message-ID: <20200303155150.GG2902@twin.jikos.cz> (raw)
In-Reply-To: <20200302184757.44176-7-josef@toxicpanda.com>
On Mon, Mar 02, 2020 at 01:47:56PM -0500, Josef Bacik wrote:
> We previously were relying on root->reloc_root to be cleaned up by the
> drop snapshot, or the error handling. However if btrfs_drop_snapshot()
> failed it wouldn't drop the ref for the root. Also we sort of depend on
> the right thing to happen with moving reloc roots between lists and the
> fs root they belong to, which makes it hard to figure out who owns the
> reference.
>
> Fix this by explicitly holding a reference on the reloc root for
> roo->reloc_root. This means that we hold two references on reloc roots,
> one for whichever reloc_roots list it's attached to, and the
> root->reloc_root we're on.
>
> This makes it easier to reason out who owns a reference on the root, and
> when it needs to be dropped.
I think the functions that add a reference should say that in it's
comment, so it can be easily pairred with btrfs_put_root.
Otherwise yes the explicit references make it easier to see the owner.
next prev parent reply other threads:[~2020-03-03 15:52 UTC|newest]
Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-03-02 18:47 [PATCH 0/7] relocation error handling fixes Josef Bacik
2020-03-02 18:47 ` [PATCH 1/7] btrfs: drop block from cache on error in relocation Josef Bacik
2020-03-03 0:59 ` Qu Wenruo
2020-03-03 14:59 ` David Sterba
2020-03-03 20:27 ` Josef Bacik
2020-03-02 18:47 ` [PATCH 2/7] btrfs: unset reloc control if we fail to recover Josef Bacik
2020-03-03 0:58 ` Qu Wenruo
2020-03-03 1:03 ` Josef Bacik
2020-03-03 1:18 ` Qu Wenruo
2020-03-03 15:21 ` David Sterba
2020-03-02 18:47 ` [PATCH 3/7] btrfs: splice rc->reloc_roots onto reloc roots in recover Josef Bacik
2020-03-03 1:02 ` Qu Wenruo
2020-03-02 18:47 ` [PATCH 4/7] btrfs: run clean_dirty_subvols if we fail to start a trans Josef Bacik
2020-03-03 1:04 ` Qu Wenruo
2020-03-03 15:32 ` David Sterba
2020-03-02 18:47 ` [PATCH 5/7] btrfs: clear BTRFS_ROOT_DEAD_RELOC_TREE before dropping the reloc root Josef Bacik
2020-03-02 19:31 ` David Sterba
2020-03-02 19:51 ` Josef Bacik
2020-03-03 15:34 ` David Sterba
2020-03-03 0:31 ` Qu Wenruo
2020-03-02 18:47 ` [PATCH 6/7] btrfs: hold a ref on the root->reloc_root Josef Bacik
2020-03-03 1:12 ` Qu Wenruo
2020-03-03 1:14 ` Josef Bacik
2020-03-03 15:51 ` David Sterba [this message]
2020-03-02 18:47 ` [PATCH 7/7] btrfs: remove a BUG_ON() from merge_reloc_roots() Josef Bacik
2020-03-03 1:17 ` Qu Wenruo
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