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Date: Wed, 6 May 2020 17:41:45 -0700 From: Anthony Yznaga <anthony.yznaga@...cle.com> To: linux-mm@...ck.org, linux-kernel@...r.kernel.org Cc: willy@...radead.org, corbet@....net, tglx@...utronix.de, mingo@...hat.com, bp@...en8.de, x86@...nel.org, hpa@...or.com, dave.hansen@...ux.intel.com, luto@...nel.org, peterz@...radead.org, rppt@...ux.ibm.com, akpm@...ux-foundation.org, hughd@...gle.com, ebiederm@...ssion.com, masahiroy@...nel.org, ardb@...nel.org, ndesaulniers@...gle.com, dima@...ovin.in, daniel.kiper@...cle.com, nivedita@...m.mit.edu, rafael.j.wysocki@...el.com, dan.j.williams@...el.com, zhenzhong.duan@...cle.com, jroedel@...e.de, bhe@...hat.com, guro@...com, Thomas.Lendacky@....com, andriy.shevchenko@...ux.intel.com, keescook@...omium.org, hannes@...xchg.org, minchan@...nel.org, mhocko@...nel.org, ying.huang@...el.com, yang.shi@...ux.alibaba.com, gustavo@...eddedor.com, ziqian.lzq@...fin.com, vdavydov.dev@...il.com, jason.zeng@...el.com, kevin.tian@...el.com, zhiyuan.lv@...el.com, lei.l.li@...el.com, paul.c.lai@...el.com, ashok.raj@...el.com, linux-fsdevel@...r.kernel.org, linux-doc@...r.kernel.org, kexec@...ts.infradead.org Subject: [RFC 19/43] mm: PKRAM: allow preserved memory to be freed from userspace To free all space utilized for preserved memory, one can write 0 to /sys/kernel/pkram. This will destroy all PKRAM nodes that are not currently being read or written. Originally-by: Vladimir Davydov <vdavydov.dev@...il.com> Signed-off-by: Anthony Yznaga <anthony.yznaga@...cle.com> --- mm/pkram.c | 39 ++++++++++++++++++++++++++++++++++++++- 1 file changed, 38 insertions(+), 1 deletion(-) diff --git a/mm/pkram.c b/mm/pkram.c index 0aaaf9b79682..95e691382721 100644 --- a/mm/pkram.c +++ b/mm/pkram.c @@ -509,6 +509,32 @@ static void pkram_truncate_node(struct pkram_node *node) node->obj_pfn = 0; } +/* + * Free all nodes that are not under operation. + */ +static void pkram_truncate(void) +{ + struct page *page, *tmp; + struct pkram_node *node; + LIST_HEAD(dispose); + + mutex_lock(&pkram_mutex); + list_for_each_entry_safe(page, tmp, &pkram_nodes, lru) { + node = page_address(page); + if (!(node->flags & PKRAM_ACCMODE_MASK)) + list_move(&page->lru, &dispose); + } + mutex_unlock(&pkram_mutex); + + while (!list_empty(&dispose)) { + page = list_first_entry(&dispose, struct page, lru); + list_del(&page->lru); + node = page_address(page); + pkram_truncate_node(node); + pkram_free_page(node); + } +} + static void pkram_add_link(struct pkram_link *link, struct pkram_obj *obj) { link->link_pfn = obj->link_pfn; @@ -1141,8 +1167,19 @@ static ssize_t show_pkram_sb_pfn(struct kobject *kobj, return sprintf(buf, "%lx\n", pfn); } +static ssize_t store_pkram_sb_pfn(struct kobject *kobj, + struct kobj_attribute *attr, const char *buf, size_t count) +{ + int val; + + if (kstrtoint(buf, 0, &val) || val) + return -EINVAL; + pkram_truncate(); + return count; +} + static struct kobj_attribute pkram_sb_pfn_attr = - __ATTR(pkram, 0444, show_pkram_sb_pfn, NULL); + __ATTR(pkram, 0644, show_pkram_sb_pfn, store_pkram_sb_pfn); static struct attribute *pkram_attrs[] = { &pkram_sb_pfn_attr.attr, -- 2.13.3
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