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Sat, 18 May 2024 00:51:16 +0200 Message-ID: Date: Sat, 18 May 2024 08:21:12 +0930 Precedence: bulk X-Mailing-List: linux-btrfs@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 1/3] btrfs: always set an inode's delayed_inode with WRITE_ONCE() To: fdmanana@kernel.org, linux-btrfs@vger.kernel.org References: <3ebdf6919047ce1eb6ad4f4058e4084047fe1d6d.1715951291.git.fdmanana@suse.com> Content-Language: en-US From: Qu Wenruo Autocrypt: addr=quwenruo.btrfs@gmx.com; keydata= xsBNBFnVga8BCACyhFP3ExcTIuB73jDIBA/vSoYcTyysFQzPvez64TUSCv1SgXEByR7fju3o 8RfaWuHCnkkea5luuTZMqfgTXrun2dqNVYDNOV6RIVrc4YuG20yhC1epnV55fJCThqij0MRL 1NxPKXIlEdHvN0Kov3CtWA+R1iNN0RCeVun7rmOrrjBK573aWC5sgP7YsBOLK79H3tmUtz6b 9Imuj0ZyEsa76Xg9PX9Hn2myKj1hfWGS+5og9Va4hrwQC8ipjXik6NKR5GDV+hOZkktU81G5 gkQtGB9jOAYRs86QG/b7PtIlbd3+pppT0gaS+wvwMs8cuNG+Pu6KO1oC4jgdseFLu7NpABEB AAHNIlF1IFdlbnJ1byA8cXV3ZW5ydW8uYnRyZnNAZ214LmNvbT7CwJQEEwEIAD4CGwMFCwkI BwIGFQgJCgsCBBYCAwECHgECF4AWIQQt33LlpaVbqJ2qQuHCPZHzoSX+qAUCY00iVQUJDToH pgAKCRDCPZHzoSX+qNKACACkjDLzCvcFuDlgqCiS4ajHAo6twGra3uGgY2klo3S4JespWifr BLPPak74oOShqNZ8yWzB1Bkz1u93Ifx3c3H0r2vLWrImoP5eQdymVqMWmDAq+sV1Koyt8gXQ XPD2jQCrfR9nUuV1F3Z4Lgo+6I5LjuXBVEayFdz/VYK63+YLEAlSowCF72Lkz06TmaI0XMyj jgRNGM2MRgfxbprCcsgUypaDfmhY2nrhIzPUICURfp9t/65+/PLlV4nYs+DtSwPyNjkPX72+ LdyIdY+BqS8cZbPG5spCyJIlZonADojLDYQq4QnufARU51zyVjzTXMg5gAttDZwTH+8LbNI4 mm2YzsBNBFnVga8BCACqU+th4Esy/c8BnvliFAjAfpzhI1wH76FD1MJPmAhA3DnX5JDORcga CbPEwhLj1xlwTgpeT+QfDmGJ5B5BlrrQFZVE1fChEjiJvyiSAO4yQPkrPVYTI7Xj34FnscPj /IrRUUka68MlHxPtFnAHr25VIuOS41lmYKYNwPNLRz9Ik6DmeTG3WJO2BQRNvXA0pXrJH1fN GSsRb+pKEKHKtL1803x71zQxCwLh+zLP1iXHVM5j8gX9zqupigQR/Cel2XPS44zWcDW8r7B0 q1eW4Jrv0x19p4P923voqn+joIAostyNTUjCeSrUdKth9jcdlam9X2DziA/DHDFfS5eq4fEv ABEBAAHCwHwEGAEIACYCGwwWIQQt33LlpaVbqJ2qQuHCPZHzoSX+qAUCY00ibgUJDToHvwAK CRDCPZHzoSX+qK6vB/9yyZlsS+ijtsvwYDjGA2WhVhN07Xa5SBBvGCAycyGGzSMkOJcOtUUf tD+ADyrLbLuVSfRN1ke738UojphwkSFj4t9scG5A+U8GgOZtrlYOsY2+cG3R5vjoXUgXMP37 INfWh0KbJodf0G48xouesn08cbfUdlphSMXujCA8y5TcNyRuNv2q5Nizl8sKhUZzh4BascoK DChBuznBsucCTAGrwPgG4/ul6HnWE8DipMKvkV9ob1xJS2W4WJRPp6QdVrBWJ9cCdtpR6GbL iQi22uZXoSPv/0oUrGU+U5X4IvdnvT+8viPzszL5wXswJZfqfy8tmHM85yjObVdIG6AlnrrD In-Reply-To: <3ebdf6919047ce1eb6ad4f4058e4084047fe1d6d.1715951291.git.fdmanana@suse.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: quoted-printable X-Provags-ID: V03:K1:jpoF69fe8aOowfJfXmqBrlhMmiWr0baSQ2DQQOWx18RX3/N6oyN jtOTLUdxxZKbY7ejyyrBZGYHiAaOUxDLkjaSeZ2ddDmhOW6g/C1bDrUYx9/qRqsSe2SFD9F FU4SsM99+3aZWsUvvXiLSkafIlTkJKUKOFrH0+jzgj+NwxgFrxL8rMzwL2HCvfpyAQCBkoh d+9jXi/lxMgRbH12mwmdw== X-Spam-Flag: NO UI-OutboundReport: notjunk:1;M01:P0:9dYG6XPR8ng=;CcbGeGmkMosdUB+pcEyBX42MWTO B3PYMZ6613KWj+PI8eMXSA7KFGGrW0Ncz8zO2pG5yM/aB2TXTMCBlLPGFmTXjZ4spVyyFhYvr 9P3SIA1AdH8/0ZK7f81Zjin7yeOY+jdB3do73wYCe/1qLcCsxlSjNpnjOKFuzm0wiDkY8y9l9 2/1SHH3DFFCrVZLYxtS36lK71u+qDszJ108gkBai/kwgx2tLZlrdU6vOtNKcuGx5M3rTBynrs iCGVm9dUOzhcKM56MRqrR7TZ1s4y4ZweZT3lQwBmTcUyXw5B3iZde76hiNYh2QNfOXlMFelZM PW8YRSoPoXldf5INMWZToV9Wlswsyxy7TwB95/BVPe2DCHj+7ERYDktqd7vvupZ5hNOZZqTRH kuFM1eFA4shvriL+b1N/5gxF6uXdWzJdda5SdGWiepmAuW+7XBSP9xeRSPXI5+gBRTGVbNmQW 7JZfaLD1w9NprFUMy9RUJWmkTxbrH1RSkygSrmzPudB+NWMkDGOWhR1PUg06eFqq0ICPNPAi0 N48OsyVNEZBEDAMoVseN+BiwtzXsizvKrIYMYHGSzs+gbprsDz5XlC1lpNWO0COehnPJbFrXf luTj6F6gQtcF/0i/KDafu4faMruThoVQZgdrOmhNW/LdeKF6YiAlwvEXdyIXlgaTnPrXRxAoR GQ8n4pzMQBhCg2CyHQ8HlQxyAFQvtrXMOJuvh0KIdfA0F4nZFkPj1Jih3YCwgJg5lERqwtbyJ fRR1tu5ctjDClFJyHDjvp4QIdHxOXhtP+841iqz1phXqev4QgUPSjIqBCFEFdmXJc8lqyI9Zt uR8we5Xx65uaWJPpz7Mc6cUtAwl3vT2dEl4uBwjbXt2+8= =E5=9C=A8 2024/5/17 22:43, fdmanana@kernel.org =E5=86=99=E9=81=93: > From: Filipe Manana > > Currently we have a couple places using READ_ONCE() to access an inode's > delayed_inode without taking the lock that protects the xarray for delay= ed > inodes, while all the other places access it while holding the lock. > > However we never update the delayed_inode pointer of an inode with > WRITE_ONCE(), making the use of READ_ONCE() pointless since it should > always be paired with a WRITE_ONCE() in order to protect against issues > such as write tearing for example. > > So change all the places that update struct btrfs_inode::delayed_inode t= o > use WRITE_ONCE() instead of simple assignments. > > Signed-off-by: Filipe Manana Reviewed-by: Qu Wenruo Thanks, Qu > --- > fs/btrfs/delayed-inode.c | 6 +++--- > 1 file changed, 3 insertions(+), 3 deletions(-) > > diff --git a/fs/btrfs/delayed-inode.c b/fs/btrfs/delayed-inode.c > index 483c141dc488..6df7e44d9d31 100644 > --- a/fs/btrfs/delayed-inode.c > +++ b/fs/btrfs/delayed-inode.c > @@ -106,7 +106,7 @@ static struct btrfs_delayed_node *btrfs_get_delayed_= node( > */ > if (refcount_inc_not_zero(&node->refs)) { > refcount_inc(&node->refs); > - btrfs_inode->delayed_node =3D node; > + WRITE_ONCE(btrfs_inode->delayed_node, node); > } else { > node =3D NULL; > } > @@ -161,7 +161,7 @@ static struct btrfs_delayed_node *btrfs_get_or_creat= e_delayed_node( > ASSERT(xa_err(ptr) !=3D -EINVAL); > ASSERT(xa_err(ptr) !=3D -ENOMEM); > ASSERT(ptr =3D=3D NULL); > - btrfs_inode->delayed_node =3D node; > + WRITE_ONCE(btrfs_inode->delayed_node, node); > xa_unlock(&root->delayed_nodes); > > return node; > @@ -1312,7 +1312,7 @@ void btrfs_remove_delayed_node(struct btrfs_inode = *inode) > if (!delayed_node) > return; > > - inode->delayed_node =3D NULL; > + WRITE_ONCE(inode->delayed_node, NULL); > btrfs_release_delayed_node(delayed_node); > } >