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V" , Nghia Le , Andrew Morton Subject: Re: [PATCH v4 1/5] hugetlb: add demote hugetlb page sysfs interfaces Message-ID: References: <20211007181918.136982-1-mike.kravetz@oracle.com> <20211007181918.136982-2-mike.kravetz@oracle.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20211007181918.136982-2-mike.kravetz@oracle.com> Authentication-Results: imf26.hostedemail.com; dkim=pass header.d=suse.de header.s=susede2_rsa header.b=imGUG8Sq; dkim=pass header.d=suse.de header.s=susede2_ed25519 header.b=UZ0Qkix4; spf=pass (imf26.hostedemail.com: domain of osalvador@suse.de designates 195.135.220.28 as permitted sender) smtp.mailfrom=osalvador@suse.de; dmarc=pass (policy=none) header.from=suse.de X-Rspamd-Server: rspam04 X-Rspamd-Queue-Id: 10850200FC89 X-Stat-Signature: i4bzhcnpkh7y45t3n9caga73ptjwxt98 X-HE-Tag: 1633679463-207752 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: On Thu, Oct 07, 2021 at 11:19:14AM -0700, Mike Kravetz wrote: > +static ssize_t demote_store(struct kobject *kobj, > + struct kobj_attribute *attr, const char *buf, size_t len) > +{ > + unsigned long nr_demote; > + unsigned long nr_available; > + nodemask_t nodes_allowed, *n_mask; > + struct hstate *h; > + int err = 0; > + int nid; > + > + err = kstrtoul(buf, 10, &nr_demote); > + if (err) > + return err; > + h = kobj_to_hstate(kobj, &nid); > + > + /* Synchronize with other sysfs operations modifying huge pages */ > + mutex_lock(&h->resize_lock); > + > + if (nid != NUMA_NO_NODE) { > + init_nodemask_of_node(&nodes_allowed, nid); > + n_mask = &nodes_allowed; > + } else { > + n_mask = &node_states[N_MEMORY]; > + } Why this needs to be protected by the resize_lock? I do not understand what are we really protecting here and from what. Besides that, I did not spot anything wrong. -- Oscar Salvador SUSE Labs