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From: Josef Bacik <josef@toxicpanda.com>
To: Nikolay Borisov <nborisov@suse.com>,
	linux-btrfs@vger.kernel.org, kernel-team@fb.com
Subject: Re: [PATCH 3/8] btrfs: move the root freeing stuff into btrfs_put_root
Date: Thu, 20 Feb 2020 10:48:24 -0500
Message-ID: <842ad5d0-fada-40da-2d20-bf255a36691f@toxicpanda.com> (raw)
In-Reply-To: <058f94f8-7fb6-9dfb-61e0-21dc989e22bc@suse.com>

On 2/19/20 10:10 AM, Nikolay Borisov wrote:
> 
> 
> On 14.02.20 г. 23:11 ч., Josef Bacik wrote:
>> There are a few different ways to free roots, either you allocated them
>> yourself and you just do
>>
>> free_extent_buffer(root->node);
>> free_extent_buffer(root->commit_node);
>> btrfs_put_root(root);
>>
>> Which is the pattern for log roots.  Or for snapshots/subvolumes that
>> are being dropped you simply call btrfs_free_fs_root() which does all
>> the cleanup for you.
>>
>> Unify this all into btrfs_put_root(), so that we don't free up things
>> associated with the root until the last reference is dropped.  This
>> makes the root freeing code much more significant.
>>
>> The only caveat is at close_ctree() time we have to free the extent
>> buffers for all of our main roots (extent_root, chunk_root, etc) because
>> we have to drop the btree_inode and we'll run into issues if we hold
>> onto those nodes until ->kill_sb() time.  This will be addressed in the
>> future when we kill the btree_inode.
>>
>> Signed-off-by: Josef Bacik <josef@toxicpanda.com>
> 
> Nit: This patch obsoleted the last comment in btrfs_init_fs_root, namely:
> 
> /* The caller is responsible to call btrfs_free_fs_root */
> 
>> ---
>>   fs/btrfs/disk-io.c           | 64 ++++++++++++++++++------------------
>>   fs/btrfs/disk-io.h           | 16 +--------
>>   fs/btrfs/extent-tree.c       |  7 ++--
>>   fs/btrfs/extent_io.c         | 16 +++++++--
>>   fs/btrfs/free-space-tree.c   |  2 --
>>   fs/btrfs/qgroup.c            |  7 +---
>>   fs/btrfs/relocation.c        |  4 ---
>>   fs/btrfs/tests/btrfs-tests.c |  5 +--
>>   fs/btrfs/tree-log.c          |  6 ----
>>   9 files changed, 50 insertions(+), 77 deletions(-)
>>
> 
> <snip>
> 
>> @@ -4795,7 +4803,6 @@ int extent_fiemap(struct inode *inode, struct fiemap_extent_info *fieinfo,
>>   
>>   static void __free_extent_buffer(struct extent_buffer *eb)
>>   {
>> -	btrfs_leak_debug_del(&eb->fs_info->eb_leak_lock, &eb->leak_list);
>>   	kmem_cache_free(extent_buffer_cache, eb);
>>   }
> 
> This function becomes a trivial wrapper so should be eliminated altogether.
> 
> <snip>
> 
>> diff --git a/fs/btrfs/relocation.c b/fs/btrfs/relocation.c
>> index 034f5f151a74..4fb7e3cc2aca 100644
>> --- a/fs/btrfs/relocation.c
>> +++ b/fs/btrfs/relocation.c
>> @@ -2549,10 +2549,6 @@ void free_reloc_roots(struct list_head *list)
>>   		reloc_root = list_entry(list->next, struct btrfs_root,
>>   					root_list);
>>   		__del_reloc_root(reloc_root);
>> -		free_extent_buffer(reloc_root->node);
>> -		free_extent_buffer(reloc_root->commit_root);
>> -		reloc_root->node = NULL;
>> -		reloc_root->commit_root = NULL;
> 
> Shouldn't you do btrfs_put_root(reloc_root) here ?

No, but I can see how this is confusing.  The reloc root is actually cleaned up 
in clean_dirty_subvols(), so it's final put happens there.  Thanks,

Josef

  reply index

Thread overview: 15+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-02-14 21:11 [PATCH 0/8][v4] Cleanup how we handle root refs, part 2 Josef Bacik
2020-02-14 21:11 ` [PATCH 1/8] btrfs: make the extent buffer leak check per fs info Josef Bacik
2020-02-19 13:59   ` Nikolay Borisov
2020-02-20 15:49     ` Josef Bacik
2020-02-14 21:11 ` [PATCH 2/8] btrfs: move ino_cache_inode dropping Josef Bacik
2020-02-14 21:11 ` [PATCH 3/8] btrfs: move the root freeing stuff into btrfs_put_root Josef Bacik
2020-02-19 15:10   ` Nikolay Borisov
2020-02-20 15:48     ` Josef Bacik [this message]
2020-02-14 21:11 ` [PATCH 4/8] btrfs: make inodes hold a ref on their roots Josef Bacik
2020-02-14 21:11 ` [PATCH 5/8] btrfs: hold a ref on the root on the dead roots list Josef Bacik
2020-02-14 21:11 ` [PATCH 6/8] btrfs: don't take an extra root ref at allocation time Josef Bacik
2020-02-14 21:11 ` [PATCH 7/8] btrfs: make btrfs_cleanup_fs_roots use the fs_roots_radix_lock Josef Bacik
2020-02-14 21:11 ` [PATCH 8/8] btrfs: kill the subvol_srcu Josef Bacik
2020-03-13 21:19 ` [PATCH 0/8][v4] Cleanup how we handle root refs, part 2 David Sterba
  -- strict thread matches above, loose matches on Subject: below --
2020-01-17 13:52 [PATCH 0/8][v2] " Josef Bacik
2020-01-17 13:52 ` [PATCH 3/8] btrfs: move the root freeing stuff into btrfs_put_root Josef Bacik

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