The patch titled Subject: mm, pcp: allow restoring percpu_pagelist_fraction default has been removed from the -mm tree. Its filename was mm-pcp-allow-restoring-percpu_pagelist_fraction-default.patch This patch was dropped because it was merged into mainline or a subsystem tree ------------------------------------------------------ From: David Rientjes <rientjes@xxxxxxxxxx> Subject: mm, pcp: allow restoring percpu_pagelist_fraction default Oleg reports a division by zero error on zero-length write() to the percpu_pagelist_fraction sysctl: divide error: 0000 [#1] SMP DEBUG_PAGEALLOC CPU: 1 PID: 9142 Comm: badarea_io Not tainted 3.15.0-rc2-vm-nfs+ #19 Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011 task: ffff8800d5aeb6e0 ti: ffff8800d87a2000 task.ti: ffff8800d87a2000 RIP: 0010:[<ffffffff81152664>] [<ffffffff81152664>] percpu_pagelist_fraction_sysctl_handler+0x84/0x120 RSP: 0018:ffff8800d87a3e78 EFLAGS: 00010246 RAX: 0000000000000f89 RBX: ffff88011f7fd000 RCX: 0000000000000000 RDX: 0000000000000000 RSI: 0000000000000001 RDI: 0000000000000010 RBP: ffff8800d87a3e98 R08: ffffffff81d002c8 R09: ffff8800d87a3f50 R10: 000000000000000b R11: 0000000000000246 R12: 0000000000000060 R13: ffffffff81c3c3e0 R14: ffffffff81cfddf8 R15: ffff8801193b0800 FS: 00007f614f1e9740(0000) GS:ffff88011f440000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 000000008005003b CR2: 00007f614f1fa000 CR3: 00000000d9291000 CR4: 00000000000006e0 Stack: 0000000000000001 ffffffffffffffea ffffffff81c3c3e0 0000000000000000 ffff8800d87a3ee8 ffffffff8122b163 ffff8800d87a3f50 00007fff1564969c 0000000000000000 ffff8800d8098f00 00007fff1564969c ffff8800d87a3f50 Call Trace: [<ffffffff8122b163>] proc_sys_call_handler+0xb3/0xc0 [<ffffffff8122b184>] proc_sys_write+0x14/0x20 [<ffffffff811ba93a>] vfs_write+0xba/0x1e0 [<ffffffff811bb486>] SyS_write+0x46/0xb0 [<ffffffff816db7ff>] tracesys+0xe1/0xe6 However, if the percpu_pagelist_fraction sysctl is set by the user, it is also impossible to restore it to the kernel default since the user cannot write 0 to the sysctl. This patch allows the user to write 0 to restore the default behavior. It still requires a fraction equal to or larger than 8, however, as stated by the documentation for sanity. If a value in the range [1, 7] is written, the sysctl will return EINVAL. This successfully solves the divide by zero issue at the same time. Signed-off-by: David Rientjes <rientjes@xxxxxxxxxx> Reported-by: Oleg Drokin <green@xxxxxxxxxxxxxx> Cc: <stable@xxxxxxxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- Documentation/sysctl/vm.txt | 3 +- kernel/sysctl.c | 3 -- mm/page_alloc.c | 40 +++++++++++++++++++++++----------- 3 files changed, 31 insertions(+), 15 deletions(-) diff -puN Documentation/sysctl/vm.txt~mm-pcp-allow-restoring-percpu_pagelist_fraction-default Documentation/sysctl/vm.txt --- a/Documentation/sysctl/vm.txt~mm-pcp-allow-restoring-percpu_pagelist_fraction-default +++ a/Documentation/sysctl/vm.txt @@ -702,7 +702,8 @@ The batch value of each per cpu pagelist set to pcp->high/4. The upper limit of batch is (PAGE_SHIFT * 8) The initial value is zero. Kernel does not use this value at boot time to set -the high water marks for each per cpu page list. +the high water marks for each per cpu page list. If the user writes '0' to this +sysctl, it will revert to this default behavior. ============================================================== diff -puN kernel/sysctl.c~mm-pcp-allow-restoring-percpu_pagelist_fraction-default kernel/sysctl.c --- a/kernel/sysctl.c~mm-pcp-allow-restoring-percpu_pagelist_fraction-default +++ a/kernel/sysctl.c @@ -136,7 +136,6 @@ static unsigned long dirty_bytes_min = 2 /* this is needed for the proc_dointvec_minmax for [fs_]overflow UID and GID */ static int maxolduid = 65535; static int minolduid; -static int min_percpu_pagelist_fract = 8; static int ngroups_max = NGROUPS_MAX; static const int cap_last_cap = CAP_LAST_CAP; @@ -1317,7 +1316,7 @@ static struct ctl_table vm_table[] = { .maxlen = sizeof(percpu_pagelist_fraction), .mode = 0644, .proc_handler = percpu_pagelist_fraction_sysctl_handler, - .extra1 = &min_percpu_pagelist_fract, + .extra1 = &zero, }, #ifdef CONFIG_MMU { diff -puN mm/page_alloc.c~mm-pcp-allow-restoring-percpu_pagelist_fraction-default mm/page_alloc.c --- a/mm/page_alloc.c~mm-pcp-allow-restoring-percpu_pagelist_fraction-default +++ a/mm/page_alloc.c @@ -69,6 +69,7 @@ /* prevent >1 _updater_ of zone percpu pageset ->high and ->batch fields */ static DEFINE_MUTEX(pcp_batch_high_lock); +#define MIN_PERCPU_PAGELIST_FRACTION (8) #ifdef CONFIG_USE_PERCPU_NUMA_NODE_ID DEFINE_PER_CPU(int, numa_node); @@ -4145,7 +4146,7 @@ static void __meminit zone_init_free_lis memmap_init_zone((size), (nid), (zone), (start_pfn), MEMMAP_EARLY) #endif -static int __meminit zone_batchsize(struct zone *zone) +static int zone_batchsize(struct zone *zone) { #ifdef CONFIG_MMU int batch; @@ -4261,8 +4262,8 @@ static void pageset_set_high(struct per_ pageset_update(&p->pcp, high, batch); } -static void __meminit pageset_set_high_and_batch(struct zone *zone, - struct per_cpu_pageset *pcp) +static void pageset_set_high_and_batch(struct zone *zone, + struct per_cpu_pageset *pcp) { if (percpu_pagelist_fraction) pageset_set_high(pcp, @@ -5881,23 +5882,38 @@ int percpu_pagelist_fraction_sysctl_hand void __user *buffer, size_t *length, loff_t *ppos) { struct zone *zone; - unsigned int cpu; + int old_percpu_pagelist_fraction; int ret; + mutex_lock(&pcp_batch_high_lock); + old_percpu_pagelist_fraction = percpu_pagelist_fraction; + ret = proc_dointvec_minmax(table, write, buffer, length, ppos); - if (!write || (ret < 0)) - return ret; + if (!write || ret < 0) + goto out; + + /* Sanity checking to avoid pcp imbalance */ + if (percpu_pagelist_fraction && + percpu_pagelist_fraction < MIN_PERCPU_PAGELIST_FRACTION) { + percpu_pagelist_fraction = old_percpu_pagelist_fraction; + ret = -EINVAL; + goto out; + } + + /* No change? */ + if (percpu_pagelist_fraction == old_percpu_pagelist_fraction) + goto out; - mutex_lock(&pcp_batch_high_lock); for_each_populated_zone(zone) { - unsigned long high; - high = zone->managed_pages / percpu_pagelist_fraction; + unsigned int cpu; + for_each_possible_cpu(cpu) - pageset_set_high(per_cpu_ptr(zone->pageset, cpu), - high); + pageset_set_high_and_batch(zone, + per_cpu_ptr(zone->pageset, cpu)); } +out: mutex_unlock(&pcp_batch_high_lock); - return 0; + return ret; } int hashdist = HASHDIST_DEFAULT; _ Patches currently in -mm which might be from rientjes@xxxxxxxxxx are origin.patch mm-slabc-add-__init-to-init_lock_keys.patch slab-common-add-functions-for-kmem_cache_node-access.patch slub-use-new-node-functions.patch slub-use-new-node-functions-fix.patch slab-use-get_node-and-kmem_cache_node-functions.patch slab-use-get_node-and-kmem_cache_node-functions-fix.patch slab-use-get_node-and-kmem_cache_node-functions-fix-2.patch mm-slabh-wrap-the-whole-file-with-guarding-macro.patch mm-slub-mark-resiliency_test-as-init-text.patch mm-slub-slub_debug=n-use-the-same-alloc-free-hooks-as-for-slub_debug=y.patch mm-readaheadc-remove-unused-file_ra_state-from-count_history_pages.patch mm-memory_hotplugc-add-__meminit-to-grow_zone_span-grow_pgdat_span.patch mm-page_allocc-unexport-alloc_pages_exact_nid.patch mm-page_alloc-simplify-drain_zone_pages-by-using-min.patch memcg-cleanup-memcg_cache_params-refcnt-usage.patch memcg-destroy-kmem-caches-when-last-slab-is-freed.patch memcg-mark-caches-that-belong-to-offline-memcgs-as-dead.patch slub-dont-fail-kmem_cache_shrink-if-slab-placement-optimization-fails.patch slub-make-slab_free-non-preemptable.patch memcg-wait-for-kfrees-to-finish-before-destroying-cache.patch slub-make-dead-memcg-caches-discard-free-slabs-immediately.patch slab-do-not-keep-free-objects-slabs-on-dead-memcg-caches.patch mm-mem-hotplug-replace-simple_strtoull-with-kstrtoull.patch include-kernelh-rewrite-min3-max3-and-clamp-using-min-and-max.patch mm-utilc-add-kstrimdup.patch lib-add-size-unit-t-p-e-to-memparse.patch fs-proc-kcorec-use-page_align-instead-of-alignpage_size.patch proc-stat-convert-to-single_open_size.patch fs-seq_file-fallback-to-vmalloc-allocation.patch fork-exec-cleanup-mm-initialization.patch fork-reset-mm-pinned_vm.patch fork-copy-mms-vm-usage-counters-under-mmap_sem.patch linux-next.patch -- To unsubscribe from this list: send the line "unsubscribe mm-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html