From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id C70A7200BBC for ; Tue, 4 Mar 2025 13:05:37 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1741093537; cv=none; b=B+p/3eUvuvSTB7WK34aGKcGt2d4y1jPrM0FK0XumKY3xTZ1WnKe0mgOGNR/2pVLGVu+iGWZDbsLWJ136PpAMcyQX0rJkwOgiv+1ohoPN4yDiKShQFuT98PRqp8QT6E/ecJrhdv1K4VOqFt12jvRLk0TfYEhpo5dU19yGyQHyWik= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1741093537; c=relaxed/simple; bh=TBoYwdmhVU3A7bZEtzR43pdugSQUMpT+SDJo1xqadbs=; h=Message-ID:Subject:From:To:Cc:Date:In-Reply-To:References: Content-Type:MIME-Version; b=MhcUlYIlJnjhJf0zwzGsDtZAqierOMCqnQQKxSMB62RwE9pKTfOe4joUpZKH2ALUxQd1tJwEDZRx/dCpgeRUcPfD0kfHNHYE3kDBW32Puq3L5M+5Rldv4iW6wa+oskdSfeEJZ7Fas6aHFvUsx9nFAamEnxXXjYMzDNujtdKdHYM= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=msKcv5gH; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="msKcv5gH" Received: by smtp.kernel.org (Postfix) with ESMTPSA id A0D2AC4CEE7; Tue, 4 Mar 2025 13:05:36 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1741093537; bh=TBoYwdmhVU3A7bZEtzR43pdugSQUMpT+SDJo1xqadbs=; h=Subject:From:To:Cc:Date:In-Reply-To:References:From; b=msKcv5gHkX3M3kEwWqwu150mMDzRZLvM2vb2CJ/vnzfTVzokax0eJG2L+yCCu4Y8t AJvpJBoNv0V0AOhkEzOyLr5Iv/S/vON+FSkf0Zzhz8y75H0F/G9P0/zb4IT/EVz4DE wgHPAqhboY6LJidAk8NaeydzFWk3V/LZ0tZf3Vz6SWVw5DGmRZ3zjpm/h3c4ggemIq SEKLQxz5N5xMxVdEyUK2RcPj3SW88bqihQF7wVeZFlhOgOpbWWhl6tjZfs9dzPkGzS m7rd89Kd8nYBzeEf24tE+JZLmQVjVwp13oDjiqVNjjvQii5IW10tM001CqED7me8yp 2T93v7G+d8GVQ== Message-ID: <800082efb3b2537e80427eb9d3b0e20b10ac866c.camel@kernel.org> Subject: Re: [PATCH v2 05/15] pidfs: record exit code and cgroupid at exit From: Jeff Layton To: Christian Brauner , Oleg Nesterov Cc: linux-fsdevel@vger.kernel.org, Lennart Poettering , Daan De Meyer , Mike Yuan Date: Tue, 04 Mar 2025 08:05:35 -0500 In-Reply-To: <20250304-work-pidfs-kill_on_last_close-v2-5-44fdacfaa7b7@kernel.org> References: <20250304-work-pidfs-kill_on_last_close-v2-0-44fdacfaa7b7@kernel.org> <20250304-work-pidfs-kill_on_last_close-v2-5-44fdacfaa7b7@kernel.org> Autocrypt: addr=jlayton@kernel.org; prefer-encrypt=mutual; keydata=mQINBE6V0TwBEADXhJg7s8wFDwBMEvn0qyhAnzFLTOCHooMZyx7XO7dAiIhDSi7G1NPxw n8jdFUQMCR/GlpozMFlSFiZXiObE7sef9rTtM68ukUyZM4pJ9l0KjQNgDJ6Fr342Htkjxu/kFV1Wv egyjnSsFt7EGoDjdKqr1TS9syJYFjagYtvWk/UfHlW09X+jOh4vYtfX7iYSx/NfqV3W1D7EDi0PqV T2h6v8i8YqsATFPwO4nuiTmL6I40ZofxVd+9wdRI4Db8yUNA4ZSP2nqLcLtFjClYRBoJvRWvsv4lm 0OX6MYPtv76hka8lW4mnRmZqqx3UtfHX/hF/zH24Gj7A6sYKYLCU3YrI2Ogiu7/ksKcl7goQjpvtV YrOOI5VGLHge0awt7bhMCTM9KAfPc+xL/ZxAMVWd3NCk5SamL2cE99UWgtvNOIYU8m6EjTLhsj8sn VluJH0/RcxEeFbnSaswVChNSGa7mXJrTR22lRL6ZPjdMgS2Km90haWPRc8Wolcz07Y2se0xpGVLEQ cDEsvv5IMmeMe1/qLZ6NaVkNuL3WOXvxaVT9USW1+/SGipO2IpKJjeDZfehlB/kpfF24+RrK+seQf CBYyUE8QJpvTZyfUHNYldXlrjO6n5MdOempLqWpfOmcGkwnyNRBR46g/jf8KnPRwXs509yAqDB6sE LZH+yWr9LQZEwARAQABtCVKZWZmIExheXRvbiA8amxheXRvbkBwb29jaGllcmVkcy5uZXQ+iQI7BB MBAgAlAhsDBgsJCAcDAgYVCAIJCgsEFgIDAQIeAQIXgAUCTpXWPAIZAQAKCRAADmhBGVaCFc65D/4 gBLNMHopQYgG/9RIM3kgFCCQV0pLv0hcg1cjr+bPI5f1PzJoOVi9s0wBDHwp8+vtHgYhM54yt43uI 7Htij0RHFL5eFqoVT4TSfAg2qlvNemJEOY0e4daljjmZM7UtmpGs9NN0r9r50W82eb5Kw5bc/r0km R/arUS2st+ecRsCnwAOj6HiURwIgfDMHGPtSkoPpu3DDp/cjcYUg3HaOJuTjtGHFH963B+f+hyQ2B rQZBBE76ErgTDJ2Db9Ey0kw7VEZ4I2nnVUY9B5dE2pJFVO5HJBMp30fUGKvwaKqYCU2iAKxdmJXRI ONb7dSde8LqZahuunPDMZyMA5+mkQl7kpIpR6kVDIiqmxzRuPeiMP7O2FCUlS2DnJnRVrHmCljLkZ Wf7ZUA22wJpepBligemtSRSbqCyZ3B48zJ8g5B8xLEntPo/NknSJaYRvfEQqGxgk5kkNWMIMDkfQO lDSXZvoxqU9wFH/9jTv1/6p8dHeGM0BsbBLMqQaqnWiVt5mG92E1zkOW69LnoozE6Le+12DsNW7Rj iR5K+27MObjXEYIW7FIvNN/TQ6U1EOsdxwB8o//Yfc3p2QqPr5uS93SDDan5ehH59BnHpguTc27Xi QQZ9EGiieCUx6Zh2ze3X2UW9YNzE15uKwkkuEIj60NvQRmEDfweYfOfPVOueC+iFifbQgSmVmZiBM YXl0b24gPGpsYXl0b25AcmVkaGF0LmNvbT6JAjgEEwECACIFAk6V0q0CGwMGCwkIBwMCBhUIAgkKC wQWAgMBAh4BAheAAAoJEAAOaEEZVoIViKUQALpvsacTMWWOd7SlPFzIYy2/fjvKlfB/Xs4YdNcf9q LqF+lk2RBUHdR/dGwZpvw/OLmnZ8TryDo2zXVJNWEEUFNc7wQpl3i78r6UU/GUY/RQmOgPhs3epQC 3PMJj4xFx+VuVcf/MXgDDdBUHaCTT793hyBeDbQuciARDJAW24Q1RCmjcwWIV/pgrlFa4lAXsmhoa c8UPc82Ijrs6ivlTweFf16VBc4nSLX5FB3ls7S5noRhm5/Zsd4PGPgIHgCZcPgkAnU1S/A/rSqf3F LpU+CbVBDvlVAnOq9gfNF+QiTlOHdZVIe4gEYAU3CUjbleywQqV02BKxPVM0C5/oVjMVx3bri75n1 TkBYGmqAXy9usCkHIsG5CBHmphv9MHmqMZQVsxvCzfnI5IO1+7MoloeeW/lxuyd0pU88dZsV/riHw 87i2GJUJtVlMl5IGBNFpqoNUoqmvRfEMeXhy/kUX4Xc03I1coZIgmwLmCSXwx9MaCPFzV/dOOrju2 xjO+2sYyB5BNtxRqUEyXglpujFZqJxxau7E0eXoYgoY9gtFGsspzFkVNntamVXEWVVgzJJr/EWW0y +jNd54MfPRqH+eCGuqlnNLktSAVz1MvVRY1dxUltSlDZT7P2bUoMorIPu8p7ZCg9dyX1+9T6Muc5d Hxf/BBP/ir+3e8JTFQBFOiLNdFtB9KZWZmIExheXRvbiA8amxheXRvbkBzYW1iYS5vcmc+iQI4BBM BAgAiBQJOldK9AhsDBgsJCAcDAgYVCAIJCgsEFgIDAQIeAQIXgAAKCRAADmhBGVaCFWgWD/0ZRi4h N9FK2BdQs9RwNnFZUr7JidAWfCrs37XrA/56olQl3ojn0fQtrP4DbTmCuh0SfMijB24psy1GnkPep naQ6VRf7Dxg/Y8muZELSOtsv2CKt3/02J1BBitrkkqmHyni5fLLYYg6fub0T/8Kwo1qGPdu1hx2BQ RERYtQ/S5d/T0cACdlzi6w8rs5f09hU9Tu4qV1JLKmBTgUWKN969HPRkxiojLQziHVyM/weR5Reu6 FZVNuVBGqBD+sfk/c98VJHjsQhYJijcsmgMb1NohAzwrBKcSGKOWJToGEO/1RkIN8tqGnYNp2G+aR 685D0chgTl1WzPRM6mFG1+n2b2RR95DxumKVpwBwdLPoCkI24JkeDJ7lXSe3uFWISstFGt0HL8Eew P8RuGC8s5h7Ct91HMNQTbjgA+Vi1foWUVXpEintAKgoywaIDlJfTZIl6Ew8ETN/7DLy8bXYgq0Xzh aKg3CnOUuGQV5/nl4OAX/3jocT5Cz/OtAiNYj5mLPeL5z2ZszjoCAH6caqsF2oLyAnLqRgDgR+wTQ T6gMhr2IRsl+cp8gPHBwQ4uZMb+X00c/Amm9VfviT+BI7B66cnC7Zv6Gvmtu2rEjWDGWPqUgccB7h dMKnKDthkA227/82tYoFiFMb/NwtgGrn5n2vwJyKN6SEoygGrNt0SI84y6hEVbQlSmVmZiBMYXl0b 24gPGpsYXl0b25AcHJpbWFyeWRhdGEuY29tPokCOQQTAQIAIwUCU4xmKQIbAwcLCQgHAwIBBhUIAg kKCwQWAgMBAh4BAheAAAoJEAAOaEEZVoIV1H0P/j4OUTwFd7BBbpoSp695qb6HqCzWMuExsp8nZjr uymMaeZbGr3OWMNEXRI1FWNHMtcMHWLP/RaDqCJil28proO+PQ/yPhsr2QqJcW4nr91tBrv/MqItu AXLYlsgXqp4BxLP67bzRJ1Bd2x0bWXurpEXY//VBOLnODqThGEcL7jouwjmnRh9FTKZfBDpFRaEfD FOXIfAkMKBa/c9TQwRpx2DPsl3eFWVCNuNGKeGsirLqCxUg5kWTxEorROppz9oU4HPicL6rRH22Ce 6nOAON2vHvhkUuO3GbffhrcsPD4DaYup4ic+DxWm+DaSSRJ+e1yJvwi6NmQ9P9UAuLG93S2MdNNbo sZ9P8k2mTOVKMc+GooI9Ve/vH8unwitwo7ORMVXhJeU6Q0X7zf3SjwDq2lBhn1DSuTsn2DbsNTiDv qrAaCvbsTsw+SZRwF85eG67eAwouYk+dnKmp1q57LDKMyzysij2oDKbcBlwB/TeX16p8+LxECv51a sjS9TInnipssssUDrHIvoTTXWcz7Y5wIngxDFwT8rPY3EggzLGfK5Zx2Q5S/N0FfmADmKknG/D8qG IcJE574D956tiUDKN4I+/g125ORR1v7bP+OIaayAvq17RP+qcAqkxc0x8iCYVCYDouDyNvWPGRhbL UO7mlBpjW9jK9e2fvZY9iw3QzIPGKtClKZWZmIExheXRvbiA8amVmZi5sYXl0b25AcHJpbWFyeWRh dGEuY29tPokCOQQTAQIAIwUCU4xmUAIbAwcLCQgHAwIBBhUIAgkKCwQWAgMBAh4BAheAAAoJEAAOa EEZVoIVzJoQALFCS6n/FHQS+hIzHIb56JbokhK0AFqoLVzLKzrnaeXhE5isWcVg0eoV2oTScIwUSU apy94if69tnUo4Q7YNt8/6yFM6hwZAxFjOXR0ciGE3Q+Z1zi49Ox51yjGMQGxlakV9ep4sV/d5a50 M+LFTmYSAFp6HY23JN9PkjVJC4PUv5DYRbOZ6Y1+TfXKBAewMVqtwT1Y+LPlfmI8dbbbuUX/kKZ5d dhV2736fgyfpslvJKYl0YifUOVy4D1G/oSycyHkJG78OvX4JKcf2kKzVvg7/Rnv+AueCfFQ6nGwPn 0P91I7TEOC4XfZ6a1K3uTp4fPPs1Wn75X7K8lzJP/p8lme40uqwAyBjk+IA5VGd+CVRiyJTpGZwA0 jwSYLyXboX+Dqm9pSYzmC9+/AE7lIgpWj+3iNisp1SWtHc4pdtQ5EU2SEz8yKvDbD0lNDbv4ljI7e flPsvN6vOrxz24mCliEco5DwhpaaSnzWnbAPXhQDWb/lUgs/JNk8dtwmvWnqCwRqElMLVisAbJmC0 BhZ/Ab4sph3EaiZfdXKhiQqSGdK4La3OTJOJYZphPdGgnkvDV9Pl1QZ0ijXQrVIy3zd6VCNaKYq7B AKidn5g/2Q8oio9Tf4XfdZ9dtwcB+bwDJFgvvDYaZ5bI3ln4V3EyW5i2NfXazz/GA/I/ZtbsigCFc 8ftCBKZWZmIExheXRvbiA8amxheXRvbkBrZXJuZWwub3JnPokCOAQTAQIAIgUCWe8u6AIbAwYLCQg HAwIGFQgCCQoLBBYCAwECHgECF4AACgkQAA5oQRlWghUuCg/+Lb/xGxZD2Q1oJVAE37uW308UpVSD 2tAMJUvFTdDbfe3zKlPDTuVsyNsALBGclPLagJ5ZTP+Vp2irAN9uwBuacBOTtmOdz4ZN2tdvNgozz uxp4CHBDVzAslUi2idy+xpsp47DWPxYFIRP3M8QG/aNW052LaPc0cedYxp8+9eiVUNpxF4SiU4i9J DfX/sn9XcfoVZIxMpCRE750zvJvcCUz9HojsrMQ1NFc7MFT1z3MOW2/RlzPcog7xvR5ENPH19ojRD CHqumUHRry+RF0lH00clzX/W8OrQJZtoBPXv9ahka/Vp7kEulcBJr1cH5Wz/WprhsIM7U9pse1f1g Yy9YbXtWctUz8uvDR7shsQxAhX3qO7DilMtuGo1v97I/Kx4gXQ52syh/w6EBny71CZrOgD6kJwPVV AaM1LRC28muq91WCFhs/nzHozpbzcheyGtMUI2Ao4K6mnY+3zIuXPygZMFr9KXE6fF7HzKxKuZMJO aEZCiDOq0anx6FmOzs5E6Jqdpo/mtI8beK+BE7Va6ni7YrQlnT0i3vaTVMTiCThbqsB20VrbMjlhp f8lfK1XVNbRq/R7GZ9zHESlsa35ha60yd/j3pu5hT2xyy8krV8vGhHvnJ1XRMJBAB/UYb6FyC7S+m QZIQXVeAA+smfTT0tDrisj1U5x6ZB9b3nBg65kc= Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable User-Agent: Evolution 3.54.3 (3.54.3-1.fc41) Precedence: bulk X-Mailing-List: linux-fsdevel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 On Tue, 2025-03-04 at 10:41 +0100, Christian Brauner wrote: > Record the exit code and cgroupid in do_exit() and stash in struct > pidfs_exit_info so it can be retrieved even after the task has been > reaped. >=20 > Signed-off-by: Christian Brauner > --- > fs/internal.h | 1 + > fs/libfs.c | 4 ++-- > fs/pidfs.c | 41 ++++++++++++++++++++++++++++++++++++++++- > include/linux/pidfs.h | 1 + > kernel/exit.c | 2 ++ > 5 files changed, 46 insertions(+), 3 deletions(-) >=20 > diff --git a/fs/internal.h b/fs/internal.h > index e7f02ae1e098..c1e6d8b294cb 100644 > --- a/fs/internal.h > +++ b/fs/internal.h > @@ -325,6 +325,7 @@ struct stashed_operations { > int path_from_stashed(struct dentry **stashed, struct vfsmount *mnt, voi= d *data, > struct path *path); > void stashed_dentry_prune(struct dentry *dentry); > +struct dentry *stashed_dentry_get(struct dentry **stashed); > /** > * path_mounted - check whether path is mounted > * @path: path to check > diff --git a/fs/libfs.c b/fs/libfs.c > index 8444f5cc4064..cf5a267aafe4 100644 > --- a/fs/libfs.c > +++ b/fs/libfs.c > @@ -2113,7 +2113,7 @@ struct timespec64 simple_inode_init_ts(struct inode= *inode) > } > EXPORT_SYMBOL(simple_inode_init_ts); > =20 > -static inline struct dentry *get_stashed_dentry(struct dentry **stashed) > +struct dentry *stashed_dentry_get(struct dentry **stashed) > { > struct dentry *dentry; > =20 > @@ -2215,7 +2215,7 @@ int path_from_stashed(struct dentry **stashed, stru= ct vfsmount *mnt, void *data, > const struct stashed_operations *sops =3D mnt->mnt_sb->s_fs_info; > =20 > /* See if dentry can be reused. */ > - path->dentry =3D get_stashed_dentry(stashed); > + path->dentry =3D stashed_dentry_get(stashed); > if (path->dentry) { > sops->put_data(data); > goto out_path; > diff --git a/fs/pidfs.c b/fs/pidfs.c > index eaecb0a947f0..258e1c13ee56 100644 > --- a/fs/pidfs.c > +++ b/fs/pidfs.c > @@ -32,7 +32,7 @@ static struct kmem_cache *pidfs_cachep __ro_after_init; > */ > struct pidfs_exit_info { > __u64 cgroupid; > - __u64 exit_code; > + __s32 exit_code; ^^^ The above delta should be folded into the previous patch. > }; > =20 > struct pidfs_inode { > @@ -458,6 +458,45 @@ struct pid *pidfd_pid(const struct file *file) > return file_inode(file)->i_private; > } > =20 > +/* > + * We're called from release_task(). We know there's at least one > + * reference to struct pid being held that won't be released until the > + * task has been reaped which cannot happen until we're out of > + * release_task(). > + * > + * If this struct pid is refered to by a pidfd then stashed_dentry_get() > + * will return the dentry and inode for that struct pid. Since we've > + * taken a reference on it there's now an additional reference from the > + * exit path on it. Which is fine. We're going to put it again in a > + * second and we know that the pid is kept alive anyway. > + * > + * Worst case is that we've filled in the info and immediately free the > + * dentry and inode afterwards since the pidfd has been closed. Since > + * pidfs_exit() currently is placed after exit_task_work() we know that > + * it cannot be us aka the exiting task holding a pidfd to ourselves. > + */ That is a subtle interaction. Thanks for the comment! > +void pidfs_exit(struct task_struct *tsk) > +{ > + struct dentry *dentry; > + > + dentry =3D stashed_dentry_get(&task_pid(tsk)->stashed); > + if (dentry) { > + struct inode *inode =3D d_inode(dentry); > + struct pidfs_exit_info *exit_info =3D &pidfs_i(inode)->exit_info; > +#ifdef CONFIG_CGROUPS > + struct cgroup *cgrp; > + > + rcu_read_lock(); > + cgrp =3D task_dfl_cgroup(tsk); > + exit_info->cgroupid =3D cgroup_id(cgrp); > + rcu_read_unlock(); > +#endif > + exit_info->exit_code =3D tsk->exit_code; > + > + dput(dentry); > + } > +} > + > static struct vfsmount *pidfs_mnt __ro_after_init; > =20 > /* > diff --git a/include/linux/pidfs.h b/include/linux/pidfs.h > index 7c830d0dec9a..05e6f8f4a026 100644 > --- a/include/linux/pidfs.h > +++ b/include/linux/pidfs.h > @@ -6,6 +6,7 @@ struct file *pidfs_alloc_file(struct pid *pid, unsigned i= nt flags); > void __init pidfs_init(void); > void pidfs_add_pid(struct pid *pid); > void pidfs_remove_pid(struct pid *pid); > +void pidfs_exit(struct task_struct *tsk); > extern const struct dentry_operations pidfs_dentry_operations; > =20 > #endif /* _LINUX_PID_FS_H */ > diff --git a/kernel/exit.c b/kernel/exit.c > index 3485e5fc499e..98d292120296 100644 > --- a/kernel/exit.c > +++ b/kernel/exit.c > @@ -69,6 +69,7 @@ > #include > #include > #include > +#include > =20 > #include > =20 > @@ -254,6 +255,7 @@ void release_task(struct task_struct *p) > write_lock_irq(&tasklist_lock); > ptrace_release_task(p); > thread_pid =3D get_pid(p->thread_pid); > + pidfs_exit(p); > __exit_signal(p); > =20 > /* >=20 Reviewed-by: Jeff Layton