From: Jiaqi Yan <jiaqiyan@google.com> mainline inclusion from mainline-v6.11-rc1 commit 56374430c5dfcf6d4f1df79514f797b45fbd0485 category: feature bugzilla: https://gitee.com/openeuler/kernel/issues/ID6J4B Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?i... -------------------------------- Correctable memory errors are very common on servers with large amount of memory, and are corrected by ECC. Soft offline is kernel's additional recovery handling for memory pages having (excessive) corrected memory errors. Impacted page is migrated to a healthy page if inuse; the original page is discarded for any future use. The actual policy on whether (and when) to soft offline should be maintained by userspace, especially in case of an 1G HugeTLB page. Soft-offline dissolves the HugeTLB page, either in-use or free, into chunks of 4K pages, reducing HugeTLB pool capacity by 1 hugepage. If userspace has not acknowledged such behavior, it may be surprised when later failed to mmap hugepages due to lack of hugepages. In case of a transparent hugepage, it will be split into 4K pages as well; userspace will stop enjoying the transparent performance. In addition, discarding the entire 1G HugeTLB page only because of corrected memory errors sounds very costly and kernel better not doing under the hood. But today there are at least 2 such cases doing so: 1. when GHES driver sees both GHES_SEV_CORRECTED and CPER_SEC_ERROR_THRESHOLD_EXCEEDED after parsing CPER. 2. RAS Correctable Errors Collector counts correctable errors per PFN and when the counter for a PFN reaches threshold In both cases, userspace has no control of the soft offline performed by kernel's memory failure recovery. This commit gives userspace the control of softofflining any page: kernel only soft offlines raw page / transparent hugepage / HugeTLB hugepage if userspace has agreed to. The interface to userspace is a new sysctl at /proc/sys/vm/enable_soft_offline. By default its value is set to 1 to preserve existing behavior in kernel. When set to 0, soft-offline (e.g. MADV_SOFT_OFFLINE) will fail with EOPNOTSUPP. [jiaqiyan@google.com: v7] Link: https://lkml.kernel.org/r/20240628205958.2845610-3-jiaqiyan@google.com Link: https://lkml.kernel.org/r/20240626050818.2277273-3-jiaqiyan@google.com Signed-off-by: Jiaqi Yan <jiaqiyan@google.com> Acked-by: Miaohe Lin <linmiaohe@huawei.com> Acked-by: David Rientjes <rientjes@google.com> Cc: Frank van der Linden <fvdl@google.com> Cc: Jane Chu <jane.chu@oracle.com> Cc: Jonathan Corbet <corbet@lwn.net> Cc: Lance Yang <ioworker0@gmail.com> Cc: Muchun Song <muchun.song@linux.dev> Cc: Naoya Horiguchi <nao.horiguchi@gmail.com> Cc: Oscar Salvador <osalvador@suse.de> Cc: Randy Dunlap <rdunlap@infradead.org> Cc: Shuah Khan <shuah@kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Wupeng Ma <mawupeng1@huawei.com> --- include/linux/mm.h | 1 + kernel/sysctl.c | 9 +++++++++ mm/memory-failure.c | 13 ++++++++++++- 3 files changed, 22 insertions(+), 1 deletion(-) diff --git a/include/linux/mm.h b/include/linux/mm.h index 67e299374ac8..0274a82144e4 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -2873,6 +2873,7 @@ extern int get_hwpoison_page(struct page *page); #define put_hwpoison_page(page) put_page(page) extern int sysctl_memory_failure_early_kill; extern int sysctl_memory_failure_recovery; +extern int sysctl_enable_soft_offline; extern void shake_page(struct page *p, int access); extern atomic_long_t num_poisoned_pages __read_mostly; extern int soft_offline_page(struct page *page, int flags); diff --git a/kernel/sysctl.c b/kernel/sysctl.c index 0d1f07dc7b44..f35a1990456e 100644 --- a/kernel/sysctl.c +++ b/kernel/sysctl.c @@ -1824,6 +1824,15 @@ static struct ctl_table vm_table[] = { .extra1 = &zero, .extra2 = &one, }, + { + .procname = "enable_soft_offline", + .data = &sysctl_enable_soft_offline, + .maxlen = sizeof(sysctl_enable_soft_offline), + .mode = 0644, + .proc_handler = proc_dointvec_minmax, + .extra1 = &zero, + .extra2 = &one, + }, #endif { .procname = "user_reserve_kbytes", diff --git a/mm/memory-failure.c b/mm/memory-failure.c index 28bd5d6ed1bf..ad416016d1e9 100644 --- a/mm/memory-failure.c +++ b/mm/memory-failure.c @@ -67,6 +67,8 @@ int sysctl_memory_failure_early_kill __read_mostly = 0; int sysctl_memory_failure_recovery __read_mostly = 1; +int sysctl_enable_soft_offline __read_mostly = 1; + atomic_long_t num_poisoned_pages __read_mostly = ATOMIC_LONG_INIT(0); static bool page_handle_poison(struct page *page, bool hugepage_or_freepage, bool release) @@ -1996,7 +1998,9 @@ static int soft_offline_free_page(struct page *page) * @page: page to offline * @flags: flags. Same as memory_failure(). * - * Returns 0 on success, otherwise negated errno. + * Returns 0 on success, + * -EOPNOTSUPP for disabled by /proc/sys/vm/enable_soft_offline, + * < 0 otherwise negated errno. * * Soft offline a page, by migration or invalidation, * without killing anything. This is for the case when @@ -2027,6 +2031,13 @@ int soft_offline_page(struct page *page, int flags) return -EIO; } + if (!sysctl_enable_soft_offline) { + pr_info_once("disabled by /proc/sys/vm/enable_soft_offline\n"); + if (flags & MF_COUNT_INCREASED) + put_page(page); + return -EOPNOTSUPP; + } + if (PageHWPoison(page)) { pr_info("soft offline: %#lx page already poisoned\n", pfn); if (flags & MF_COUNT_INCREASED) -- 2.43.0