Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
Subject: Re: [V2] btrfs: drop inode reference count on error path
To:     Josef Bacik <josef@toxicpanda.com>
Cc:     Pan Bian <bianpan2016@163.com>, Chris Mason <clm@fb.com>,
        David Sterba <dsterba@suse.com>, linux-btrfs@vger.kernel.org,
        linux-kernel@vger.kernel.org
References: <1555585576-31045-1-git-send-email-bianpan2016@163.com>
 <ac36d111-547e-a76a-149e-a7ad603d7dfd@suse.com>
 <20190418140749.h57y5kqz4s47sbuo@macbook-pro-91.dhcp.thefacebook.com>
From:   Nikolay Borisov <nborisov@suse.com>
Openpgp: preference=signencrypt
Autocrypt: addr=nborisov@suse.com; prefer-encrypt=mutual; keydata=
 mQINBFiKBz4BEADNHZmqwhuN6EAzXj9SpPpH/nSSP8YgfwoOqwrP+JR4pIqRK0AWWeWCSwmZ
 T7g+RbfPFlmQp+EwFWOtABXlKC54zgSf+uulGwx5JAUFVUIRBmnHOYi/lUiE0yhpnb1KCA7f
 u/W+DkwGerXqhhe9TvQoGwgCKNfzFPZoM+gZrm+kWv03QLUCr210n4cwaCPJ0Nr9Z3c582xc
 bCUVbsjt7BN0CFa2BByulrx5xD9sDAYIqfLCcZetAqsTRGxM7LD0kh5WlKzOeAXj5r8DOrU2
 GdZS33uKZI/kZJZVytSmZpswDsKhnGzRN1BANGP8sC+WD4eRXajOmNh2HL4P+meO1TlM3GLl
 EQd2shHFY0qjEo7wxKZI1RyZZ5AgJnSmehrPCyuIyVY210CbMaIKHUIsTqRgY5GaNME24w7h
 TyyVCy2qAM8fLJ4Vw5bycM/u5xfWm7gyTb9V1TkZ3o1MTrEsrcqFiRrBY94Rs0oQkZvunqia
 c+NprYSaOG1Cta14o94eMH271Kka/reEwSZkC7T+o9hZ4zi2CcLcY0DXj0qdId7vUKSJjEep
 c++s8ncFekh1MPhkOgNj8pk17OAESanmDwksmzh1j12lgA5lTFPrJeRNu6/isC2zyZhTwMWs
 k3LkcTa8ZXxh0RfWAqgx/ogKPk4ZxOXQEZetkEyTFghbRH2BIwARAQABtCNOaWtvbGF5IEJv
 cmlzb3YgPG5ib3Jpc292QHN1c2UuY29tPokCOAQTAQIAIgUCWIo48QIbAwYLCQgHAwIGFQgC
 CQoLBBYCAwECHgECF4AACgkQcb6CRuU/KFc0eg/9GLD3wTQz9iZHMFbjiqTCitD7B6dTLV1C
 ddZVlC8Hm/TophPts1bWZORAmYIihHHI1EIF19+bfIr46pvfTu0yFrJDLOADMDH+Ufzsfy2v
 HSqqWV/nOSWGXzh8bgg/ncLwrIdEwBQBN9SDS6aqsglagvwFD91UCg/TshLlRxD5BOnuzfzI
 Leyx2c6YmH7Oa1R4MX9Jo79SaKwdHt2yRN3SochVtxCyafDlZsE/efp21pMiaK1HoCOZTBp5
 VzrIP85GATh18pN7YR9CuPxxN0V6IzT7IlhS4Jgj0NXh6vi1DlmKspr+FOevu4RVXqqcNTSS
 E2rycB2v6cttH21UUdu/0FtMBKh+rv8+yD49FxMYnTi1jwVzr208vDdRU2v7Ij/TxYt/v4O8
 V+jNRKy5Fevca/1xroQBICXsNoFLr10X5IjmhAhqIH8Atpz/89ItS3+HWuE4BHB6RRLM0gy8
 T7rN6ja+KegOGikp/VTwBlszhvfLhyoyjXI44Tf3oLSFM+8+qG3B7MNBHOt60CQlMkq0fGXd
 mm4xENl/SSeHsiomdveeq7cNGpHi6i6ntZK33XJLwvyf00PD7tip/GUj0Dic/ZUsoPSTF/mG
 EpuQiUZs8X2xjK/AS/l3wa4Kz2tlcOKSKpIpna7V1+CMNkNzaCOlbv7QwprAerKYywPCoOSC
 7P25Ag0EWIoHPgEQAMiUqvRBZNvPvki34O/dcTodvLSyOmK/MMBDrzN8Cnk302XfnGlW/YAQ
 csMWISKKSpStc6tmD+2Y0z9WjyRqFr3EGfH1RXSv9Z1vmfPzU42jsdZn667UxrRcVQXUgoKg
 QYx055Q2FdUeaZSaivoIBD9WtJq/66UPXRRr4H/+Y5FaUZx+gWNGmBT6a0S/GQnHb9g3nonD
 jmDKGw+YO4P6aEMxyy3k9PstaoiyBXnzQASzdOi39BgWQuZfIQjN0aW+Dm8kOAfT5i/yk59h
 VV6v3NLHBjHVw9kHli3jwvsizIX9X2W8tb1SefaVxqvqO1132AO8V9CbE1DcVT8fzICvGi42
 FoV/k0QOGwq+LmLf0t04Q0csEl+h69ZcqeBSQcIMm/Ir+NorfCr6HjrB6lW7giBkQl6hhomn
 l1mtDP6MTdbyYzEiBFcwQD4terc7S/8ELRRybWQHQp7sxQM/Lnuhs77MgY/e6c5AVWnMKd/z
 MKm4ru7A8+8gdHeydrRQSWDaVbfy3Hup0Ia76J9FaolnjB8YLUOJPdhI2vbvNCQ2ipxw3Y3c
 KhVIpGYqwdvFIiz0Fej7wnJICIrpJs/+XLQHyqcmERn3s/iWwBpeogrx2Lf8AGezqnv9woq7
 OSoWlwXDJiUdaqPEB/HmGfqoRRN20jx+OOvuaBMPAPb+aKJyle8zABEBAAGJAh8EGAECAAkF
 AliKBz4CGwwACgkQcb6CRuU/KFdacg/+M3V3Ti9JYZEiIyVhqs+yHb6NMI1R0kkAmzsGQ1jU
 zSQUz9AVMR6T7v2fIETTT/f5Oout0+Hi9cY8uLpk8CWno9V9eR/B7Ifs2pAA8lh2nW43FFwp
 IDiSuDbH6oTLmiGCB206IvSuaQCp1fed8U6yuqGFcnf0ZpJm/sILG2ECdFK9RYnMIaeqlNQm
 iZicBY2lmlYFBEaMXHoy+K7nbOuizPWdUKoKHq+tmZ3iA+qL5s6Qlm4trH28/fPpFuOmgP8P
 K+7LpYLNSl1oQUr+WlqilPAuLcCo5Vdl7M7VFLMq4xxY/dY99aZx0ZJQYFx0w/6UkbDdFLzN
 upT7NIN68lZRucImffiWyN7CjH23X3Tni8bS9ubo7OON68NbPz1YIaYaHmnVQCjDyDXkQoKC
 R82Vf9mf5slj0Vlpf+/Wpsv/TH8X32ajva37oEQTkWNMsDxyw3aPSps6MaMafcN7k60y2Wk/
 TCiLsRHFfMHFY6/lq/c0ZdOsGjgpIK0G0z6et9YU6MaPuKwNY4kBdjPNBwHreucrQVUdqRRm
 RcxmGC6ohvpqVGfhT48ZPZKZEWM+tZky0mO7bhZYxMXyVjBn4EoNTsXy1et9Y1dU3HVJ8fod
 5UqrNrzIQFbdeM0/JqSLrtlTcXKJ7cYFa9ZM2AP7UIN9n1UWxq+OPY9YMOewVfYtL8M=
Message-ID: <bf1a23fa-d9e3-3fd4-8cf5-2ed53225fe11@suse.com>
Date:   Thu, 18 Apr 2019 17:09:44 +0300
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101
 Thunderbird/60.6.1
MIME-Version: 1.0
In-Reply-To: <20190418140749.h57y5kqz4s47sbuo@macbook-pro-91.dhcp.thefacebook.com>
Content-Type: text/plain; charset=utf-8
Content-Language: en-US
Content-Transfer-Encoding: 8bit
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk


On 18.04.19 г. 17:07 ч., Josef Bacik wrote:
> On Thu, Apr 18, 2019 at 03:50:00PM +0300, Nikolay Borisov wrote:
>>
>>
>> On 18.04.19 г. 14:06 ч., Pan Bian wrote:
>>> The reference count of inode is incremented by ihold. It should be
>>> dropped if not used. However, the reference count is not dropped if
>>> error occurs during updating the inode or deleting orphan items. This
>>> patch fixes the bug.
>>>
>>> Signed-off-by: Pan Bian <bianpan2016@163.com>
>>> ---
>>> V2: move ihold just before device_initialize to make code clearer
>>> ---
>>>  fs/btrfs/inode.c | 54 +++++++++++++++++++++++++-----------------------------
>>>  1 file changed, 25 insertions(+), 29 deletions(-)
>>>
>>> diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
>>> index 82fdda8..d6630df 100644
>>> --- a/fs/btrfs/inode.c
>>> +++ b/fs/btrfs/inode.c
>>> @@ -6579,7 +6579,7 @@ static int btrfs_link(struct dentry *old_dentry, struct inode *dir,
>>>  	struct btrfs_fs_info *fs_info = btrfs_sb(inode->i_sb);
>>>  	u64 index;
>>>  	int err;
>>> -	int drop_inode = 0;
>>> +	int log_mode;
>>>  
>>>  	/* do not allow sys_link's with other subvols of the same device */
>>>  	if (root->root_key.objectid != BTRFS_I(inode)->root->root_key.objectid)
>>> @@ -6616,41 +6616,37 @@ static int btrfs_link(struct dentry *old_dentry, struct inode *dir,
>>>  	err = btrfs_add_nondir(trans, BTRFS_I(dir), dentry, BTRFS_I(inode),
>>>  			1, index);
>>>  
>>> -	if (err) {
>>> -		drop_inode = 1;
>>> -	} else {
>>> -		struct dentry *parent = dentry->d_parent;
>>> -		int ret;
>>> +	if (err)
>>> +		goto err_link;
>>>  
>>> -		err = btrfs_update_inode(trans, root, inode);
>>> +	err = btrfs_update_inode(trans, root, inode);
>>> +	if (err)
>>> +		goto err_link;
>>> +	if (inode->i_nlink == 1) {
>>> +		/*
>>> +		 * If new hard link count is 1, it's a file created
>>> +		 * with open(2) O_TMPFILE flag.
>>> +		 */
>>> +		err = btrfs_orphan_del(trans, BTRFS_I(inode));
>>>  		if (err)
>>> -			goto fail;
>>> -		if (inode->i_nlink == 1) {
>>> -			/*
>>> -			 * If new hard link count is 1, it's a file created
>>> -			 * with open(2) O_TMPFILE flag.
>>> -			 */
>>> -			err = btrfs_orphan_del(trans, BTRFS_I(inode));
>>> -			if (err)
>>> -				goto fail;
>>> -		}
>>> -		BTRFS_I(inode)->last_link_trans = trans->transid;
>>> -		d_instantiate(dentry, inode);
>>> -		ret = btrfs_log_new_name(trans, BTRFS_I(inode), NULL, parent,
>>> -					 true, NULL);
>>> -		if (ret == BTRFS_NEED_TRANS_COMMIT) {
>>> -			err = btrfs_commit_transaction(trans);
>>> -			trans = NULL;
>>> -		}
>>> +			goto err_link;
>>> +	}
>>> +	BTRFS_I(inode)->last_link_trans = trans->transid;
>>> +	ihold(inode);
> 
> Where is the iput for this ihold?

This ihold is sort of "given" to the d_instantiate. I.e the iput happens
when the respective dentry is unhashed/removed.

> 
> Josef
>