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imf17.hostedemail.com; dkim=none; dmarc=none; spf=pass (imf17.hostedemail.com: domain of rakie.kim@sk.com designates 166.125.252.92 as permitted sender) smtp.mailfrom=rakie.kim@sk.com ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1744356102; a=rsa-sha256; cv=none; b=HIm7GWc/zc0MKovg5XcBSC13VGS5yrdMNPQYR7ZB3KfX1vsUpJR6tddQT9dYaskCpMHdOW DCMFD0qlHboCunAhaoOXWjnoAvIP/9gBqxFdXx5gYLCMkxe7Vyo+gr4IXBjsCZXTWF4Z9O m7WH+uJptBFsTcut98Qg9u17IYjQ2xY= X-AuditID: a67dfc5b-669ff7000002311f-57-67f8c302739f From: Rakie Kim To: Dan Williams Cc: gourry@gourry.net, linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-cxl@vger.kernel.org, joshua.hahnjy@gmail.com, ying.huang@linux.alibaba.com, david@redhat.com, Jonathan.Cameron@huawei.com, osalvador@suse.de, kernel_team@skhynix.com, honggyu.kim@sk.com, yunjeong.mun@sk.com, rakie.kim@sk.com, akpm@linux-foundation.org Subject: Re: [PATCH v7 2/3] mm/mempolicy: Prepare weighted interleave sysfs for memory hotplug Date: Fri, 11 Apr 2025 16:21:28 +0900 Message-ID: <20250411072135.588-1-rakie.kim@sk.com> X-Mailer: git-send-email 2.48.1.windows.1 In-Reply-To: <67f5ef882b674_72052946a@dwillia2-xfh.jf.intel.com.notmuch> References: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Brightmail-Tracker: H4sIAAAAAAAAA+NgFnrBLMWRmVeSWpSXmKPExsXC9ZZnoS7T4R/pBm8PWVjMWb+GzWL61AuM Fl/X/2K2+Hn3OLvFqoXX2CyOb53HbnF+1ikWi8u75rBZ3Fvzn9XizLQii9VrMhy4PXbOusvu 0d12md2j5chbVo/Fe14yeWz6NInd48SM3yweOx9aerzfd5XNY/Ppao/Pm+QCuKK4bFJSczLL Uov07RK4Mia/amIvmKFV8WP9RbYGxpkKXYycHBICJhIt3zYww9ibJ/SzdDFycLAJKEkc2xsD EhYR0JaYOOcgUAkXB7PAEyaJuUeWsoEkhAXiJPb93sgGUs8ioCrxcpIESJhXwFji4v4HTBAj NSUaLt0DszkFPCT2XzvDCGILCfBIvNqwnxGiXlDi5MwnLCA2s4C8RPPW2WC7JAS+s0l8PLgZ 6jZJiYMrbrBMYOSfhaRnFpKeBYxMqxiFMvPKchMzc0z0MirzMiv0kvNzNzECw39Z7Z/oHYyf LgQfYhTgYFTi4d2x+nu6EGtiWXFl7iFGCQ5mJRHe9uAf6UK8KYmVValF+fFFpTmpxYcYpTlY lMR5jb6VpwgJpCeWpGanphakFsFkmTg4pRoYezZe+LI8c/P9xR2np7+/au/hKbT6TnnuK7VN 3pN1pip9frNru3vsqQ4BD7+F95w+HtjyxWuPhU1R+cqlm1vc13r31jddMz7xMqG+rWu56hPf aQImxpNFWsy0ag9Edqq9PlkvsdfdtyFl4lPRLcb9C3NXz5x08KqMyL0Pd9JeZpcxhsX3lJ2p UmIpzkg01GIuKk4EAExPmnd7AgAA X-Brightmail-Tracker: H4sIAAAAAAAAA+NgFnrELMWRmVeSWpSXmKPExsXCNUNNS5fp8I90g59ftC3mrF/DZjF96gVG i6/rfzFb/Lx7nN3i87PXzBarFl5jszi+dR67xeG5J1ktzs86xWJxedccNot7a/6zWpyZVmRx 6NpzVovVazIsfm9bwebA77Fz1l12j+62y+weLUfesnos3vOSyWPTp0nsHidm/Gbx2PnQ0uP9 vqtsHt9ue3gsfvGByWPz6WqPz5vkAniiuGxSUnMyy1KL9O0SuDImv2piL5ihVfFj/UW2BsaZ Cl2MnBwSAiYSmyf0s3QxcnCwCShJHNsbAxIWEdCWmDjnIHMXIxcHs8ATJom5R5aygSSEBeIk 9v3eyAZSzyKgKvFykgRImFfAWOLi/gdMECM1JRou3QOzOQU8JPZfO8MIYgsJ8Ei82rCfEaJe UOLkzCcsIDazgLxE89bZzBMYeWYhSc1CklrAyLSKUSQzryw3MTPHVK84O6MyL7NCLzk/dxMj MOSX1f6ZuIPxy2X3Q4wCHIxKPLw7Vn9PF2JNLCuuzD3EKMHBrCTC2x78I12INyWxsiq1KD++ qDQntfgQozQHi5I4r1d4aoKQQHpiSWp2ampBahFMlomDU6qB0cdejNMgoXzTufW17V1fWqQ/ 7gi3sl/K33wsYZomz7Q7pWGNrWab5a45+ehe7ov3zFD9JnFG0fylzH3fFPbQ1lnilx4e0i3v EJE7Kxzv37jq0CXNLMPa+pzcH3dj9Lvn5rI0m397XPVYQjMv2qzv9mwzBfNis2Cr7mr7K6ck Vy2dpanNUKPEUpyRaKjFXFScCADh+s2ydQIAAA== X-CFilter-Loop: Reflected X-Rspamd-Queue-Id: 613CE40006 X-Rspamd-Server: rspam05 X-Rspam-User: X-Stat-Signature: uc4feikqkb51izw666d47fxbgedfw84t X-HE-Tag: 1744356101-887532 X-HE-Meta: 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 ZF8NSHve 9WDtkSsfsbD1aZRO+bTAtdfoP6HmXto77B11x+KNIdAJy2hXlIcSaMH2pfwMyh/HbVDkK X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Tue, 8 Apr 2025 20:54:48 -0700 Dan Williams wrote: > Dan Williams wrote: > > > > > > +struct sysfs_wi_group { > > > + struct kobject wi_kobj; > > > + struct iw_node_attr *nattrs[]; > > > +}; > > > + > > > +static struct sysfs_wi_group *wi_group; > > > + > > > static ssize_t node_show(struct kobject *kobj, struct kobj_attribute *attr, > > > char *buf) > > > { > > > @@ -3461,27 +3468,24 @@ static ssize_t node_store(struct kobject *kobj, struct kobj_attribute *attr, > > > return count; > > > } > > > > > > -static struct iw_node_attr **node_attrs; > > > - > > > -static void sysfs_wi_node_release(struct iw_node_attr *node_attr, > > > - struct kobject *parent) > > > +static void sysfs_wi_node_delete(int nid) > > > { > > > - if (!node_attr) > > > + if (!wi_group->nattrs[nid]) > > > return; > > > - sysfs_remove_file(parent, &node_attr->kobj_attr.attr); > > > - kfree(node_attr->kobj_attr.attr.name); > > > - kfree(node_attr); > > > + > > > + sysfs_remove_file(&wi_group->wi_kobj, > > > + &wi_group->nattrs[nid]->kobj_attr.attr); > > > > This still looks broken to me, but I think this is more a problem that > > was present in the original code. > > > > At this point @wi_group's reference count is zero because > > sysfs_wi_release() has been called. However, it can only be zero if it has > > properly transitioned through kobject_del() and final kobject_put(). It > > follows that kobject_del() arranges for kobj->sd to be NULL. That means > > that this *should* be hitting the WARN() in kernfs_remove_by_name_ns() > > for the !parent case. > > > > So, either you are not triggering that path, or testing that path, but > > sys_remove_file() of the child attributes should be happening *before* > > sysfs_wi_release(). > > > > Did I miss something? > > I think the missing change is that sysfs_wi_node_add() failures need to > be done with a sysfs_wi_node_delete() of the added attrs *before* the > kobject_del() of @wi_group. Hi Dan, Thank you for pointing out this issue. As you suggested, I believe the most appropriate way to handle this is to incorporate your feedback into Patch 1 (mm/mempolicy: Fix memory leaks in weighted interleave sysfs). To ensure that sysfs_remove_file() is called before kobject_del(), I have restructured the code as follows: static void sysfs_wi_release(struct kobject *wi_kobj) { int nid; for (nid = 0; nid < nr_node_ids; nid++) sysfs_wi_node_delete(node_attrs[nid], wi_kobj); -> ERROR: sysfs_remove_file called here kfree(node_attrs); kfree(wi_kobj); } static void sysfs_wi_node_delete_all(struct kobject *wi_kobj) { int nid; for (nid = 0; nid < nr_node_ids; nid++) sysfs_wi_node_delete(node_attrs[nid], wi_kobj); -> sysfs_remove_file called here } static void sysfs_wi_release(struct kobject *wi_kobj) { kfree(node_attrs); kfree(wi_kobj); } In addition, I call sysfs_wi_node_delete_all() before kobject_del() during error handling: +err_cleanup_kobj: + sysfs_wi_node_delete_all(wi_kobj); kobject_del(wi_kobj); I believe this resolves the issue you raised. That said, I have a follow-up question. With this structure, when the system is shutting down, sysfs_remove_file() will not be called. Based on my review of other kernel subsystems, it seems that sysfs_remove_file() is only called during module_exit() in driver code, and not in other built-in subsystems. Is this an acceptable practice? If you happen to know the expected behavior in such cases, I would appreciate your insights. Below is the full content of the updated Patch 1. @@ -3463,8 +3463,8 @@ static ssize_t node_store(struct kobject *kobj, struct kobj_attribute *attr, static struct iw_node_attr **node_attrs; -static void sysfs_wi_node_release(struct iw_node_attr *node_attr, - struct kobject *parent) +static void sysfs_wi_node_delete(struct iw_node_attr *node_attr, + struct kobject *parent) { if (!node_attr) return; @@ -3473,13 +3473,16 @@ static void sysfs_wi_node_release(struct iw_node_attr *node_attr, kfree(node_attr); } -static void sysfs_wi_release(struct kobject *wi_kobj) +static void sysfs_wi_node_delete_all(struct kobject *wi_kobj) { - int i; + int nid; - for (i = 0; i < nr_node_ids; i++) - sysfs_wi_node_release(node_attrs[i], wi_kobj); + for (nid = 0; nid < nr_node_ids; nid++) + sysfs_wi_node_delete(node_attrs[nid], wi_kobj); +} +static void sysfs_wi_release(struct kobject *wi_kobj) +{ kfree(node_attrs); kfree(wi_kobj); } @@ -3547,13 +3550,14 @@ static int add_weighted_interleave_group(struct kobject *root_kobj) err = add_weight_node(nid, wi_kobj); if (err) { pr_err("failed to add sysfs [node%d]\n", nid); - goto err_del_kobj; + goto err_cleanup_kobj; } } return 0; -err_del_kobj: +err_cleanup_kobj: + sysfs_wi_node_delete_all(wi_kobj); kobject_del(wi_kobj); err_put_kobj: kobject_put(wi_kobj); Thank you again for your helpful feedback. Rakie