| Message ID | 20221108184357.55614-3-shy828301@gmail.com (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | [mm-unstable,v3,1/3] Revert "mm: don't warn if the node is offlined" | expand |
On Tue 08-11-22 10:43:57, Yang Shi wrote: > Syzbot reported the below splat: > > WARNING: CPU: 1 PID: 3646 at include/linux/gfp.h:221 __alloc_pages_node > include/linux/gfp.h:221 [inline] > WARNING: CPU: 1 PID: 3646 at include/linux/gfp.h:221 > hpage_collapse_alloc_page mm/khugepaged.c:807 [inline] > WARNING: CPU: 1 PID: 3646 at include/linux/gfp.h:221 > alloc_charge_hpage+0x802/0xaa0 mm/khugepaged.c:963 > Modules linked in: > CPU: 1 PID: 3646 Comm: syz-executor210 Not tainted > 6.1.0-rc1-syzkaller-00454-ga70385240892 #0 > Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS > Google 10/11/2022 > RIP: 0010:__alloc_pages_node include/linux/gfp.h:221 [inline] > RIP: 0010:hpage_collapse_alloc_page mm/khugepaged.c:807 [inline] > RIP: 0010:alloc_charge_hpage+0x802/0xaa0 mm/khugepaged.c:963 > Code: e5 01 4c 89 ee e8 6e f9 ae ff 4d 85 ed 0f 84 28 fc ff ff e8 70 fc > ae ff 48 8d 6b ff 4c 8d 63 07 e9 16 fc ff ff e8 5e fc ae ff <0f> 0b e9 > 96 fa ff ff 41 bc 1a 00 00 00 e9 86 fd ff ff e8 47 fc ae > RSP: 0018:ffffc90003fdf7d8 EFLAGS: 00010293 > RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000000000000000 > RDX: ffff888077f457c0 RSI: ffffffff81cd8f42 RDI: 0000000000000001 > RBP: ffff888079388c0c R08: 0000000000000001 R09: 0000000000000000 > R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000 > R13: dffffc0000000000 R14: 0000000000000000 R15: 0000000000000000 > FS: 00007f6b48ccf700(0000) GS:ffff8880b9b00000(0000) > knlGS:0000000000000000 > CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 > CR2: 00007f6b48a819f0 CR3: 00000000171e7000 CR4: 00000000003506e0 > DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 > DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 > Call Trace: > <TASK> > collapse_file+0x1ca/0x5780 mm/khugepaged.c:1715 > hpage_collapse_scan_file+0xd6c/0x17a0 mm/khugepaged.c:2156 > madvise_collapse+0x53a/0xb40 mm/khugepaged.c:2611 > madvise_vma_behavior+0xd0a/0x1cc0 mm/madvise.c:1066 > madvise_walk_vmas+0x1c7/0x2b0 mm/madvise.c:1240 > do_madvise.part.0+0x24a/0x340 mm/madvise.c:1419 > do_madvise mm/madvise.c:1432 [inline] > __do_sys_madvise mm/madvise.c:1432 [inline] > __se_sys_madvise mm/madvise.c:1430 [inline] > __x64_sys_madvise+0x113/0x150 mm/madvise.c:1430 > do_syscall_x64 arch/x86/entry/common.c:50 [inline] > do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80 > entry_SYSCALL_64_after_hwframe+0x63/0xcd > RIP: 0033:0x7f6b48a4eef9 > Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 b1 15 00 00 90 48 89 f8 48 89 > f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 > f0 ff ff 73 01 c3 48 c7 c1 b8 ff ff ff f7 d8 64 89 01 48 > RSP: 002b:00007f6b48ccf318 EFLAGS: 00000246 ORIG_RAX: 000000000000001c > RAX: ffffffffffffffda RBX: 00007f6b48af0048 RCX: 00007f6b48a4eef9 > RDX: 0000000000000019 RSI: 0000000000600003 RDI: 0000000020000000 > RBP: 00007f6b48af0040 R08: 0000000000000000 R09: 0000000000000000 > R10: 0000000000000000 R11: 0000000000000246 R12: 00007f6b48aa53a4 > R13: 00007f6b48bffcbf R14: 00007f6b48ccf400 R15: 0000000000022000 > </TASK> > > It is because khugepaged allocates pages with __GFP_THISNODE, but the > preferred node is bogus. The previous patch fixed the khugepaged > code to avoid allocating page from non-existing node. But it is still > racy against memory hotremove. There is no synchronization with the > memory hotplug so it is possible that memory gets offline during a > longer taking scanning. > > So this warning still seems not quite helpful because: > * There is no guarantee the node is online for __GFP_THISNODE context > for all the callsites. > * Kernel just fails the allocation regardless the warning, and it looks > all callsites handle the allocation failure gracefully. > > Although while the warning has helped to identify a buggy code, it is not > safe in general and this warning could panic the system with panic-on-warn > configuration which tends to be used surprisingly often. So replace > VM_WARN_ON to pr_warn(). And the warning will be triggered if > __GFP_NOWARN is set since the allocator would print out warning for such > case if __GFP_NOWARN is not set. > > Reported-by: syzbot+0044b22d177870ee974f@syzkaller.appspotmail.com > Signed-off-by: Yang Shi <shy828301@gmail.com> > Suggested-by: Michal Hocko <mhocko@suse.com> > Cc: Zach O'Keefe <zokeefe@google.com> Acked-by: Michal Hocko <mhocko@suse.com> minor nit > --- > v3: * Reverted the old commit from mm-unstable which remove the VM_WARN > (patch 1/3). > * Incorporated the suggestion from Michal to use pr_warn. > > v2: * Added patch 1/2. > * Reworded the commit log per Michal. > > include/linux/gfp.h | 14 ++++++++++++-- > 1 file changed, 12 insertions(+), 2 deletions(-) > > diff --git a/include/linux/gfp.h b/include/linux/gfp.h > index ef4aea3b356e..60a1c70ec85c 100644 > --- a/include/linux/gfp.h > +++ b/include/linux/gfp.h > @@ -210,6 +210,16 @@ alloc_pages_bulk_array_node(gfp_t gfp, int nid, unsigned long nr_pages, struct p > return __alloc_pages_bulk(gfp, nid, NULL, nr_pages, NULL, page_array); > } > > +static inline void warn_if_node_offline(int nid, gfp_t gfp_mask) > +{ > + gfp_t gfp = gfp_mask & (__GFP_THISNODE|__GFP_NOWARN); I would use rather this_node or similarly descriptive name. gfp sounds like a pasm but this is only a subset of it. If you really want to improve the readability then you can restructure the condition a bit if (gfp_mask & (__GFP_THISNODE|__GFP_NOWARN)) != (__GFP_THISNODE|__GFP_NOWARN)) return; if (node_online(nid)) return; pr_warn("%pGg allocation from offline node %d\n", &gfp, nid); dump_stack(); > + > + if ((gfp == (__GFP_THISNODE|__GFP_NOWARN)) && !node_online(nid)) { > + pr_warn("%pGg allocation from offline node %d\n", &gfp, nid); > + dump_stack(); > + } > +} > +
On Tue, Nov 8, 2022 at 2:15 PM Michal Hocko <mhocko@suse.com> wrote: > > On Tue 08-11-22 10:43:57, Yang Shi wrote: > > Syzbot reported the below splat: > > > > WARNING: CPU: 1 PID: 3646 at include/linux/gfp.h:221 __alloc_pages_node > > include/linux/gfp.h:221 [inline] > > WARNING: CPU: 1 PID: 3646 at include/linux/gfp.h:221 > > hpage_collapse_alloc_page mm/khugepaged.c:807 [inline] > > WARNING: CPU: 1 PID: 3646 at include/linux/gfp.h:221 > > alloc_charge_hpage+0x802/0xaa0 mm/khugepaged.c:963 > > Modules linked in: > > CPU: 1 PID: 3646 Comm: syz-executor210 Not tainted > > 6.1.0-rc1-syzkaller-00454-ga70385240892 #0 > > Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS > > Google 10/11/2022 > > RIP: 0010:__alloc_pages_node include/linux/gfp.h:221 [inline] > > RIP: 0010:hpage_collapse_alloc_page mm/khugepaged.c:807 [inline] > > RIP: 0010:alloc_charge_hpage+0x802/0xaa0 mm/khugepaged.c:963 > > Code: e5 01 4c 89 ee e8 6e f9 ae ff 4d 85 ed 0f 84 28 fc ff ff e8 70 fc > > ae ff 48 8d 6b ff 4c 8d 63 07 e9 16 fc ff ff e8 5e fc ae ff <0f> 0b e9 > > 96 fa ff ff 41 bc 1a 00 00 00 e9 86 fd ff ff e8 47 fc ae > > RSP: 0018:ffffc90003fdf7d8 EFLAGS: 00010293 > > RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000000000000000 > > RDX: ffff888077f457c0 RSI: ffffffff81cd8f42 RDI: 0000000000000001 > > RBP: ffff888079388c0c R08: 0000000000000001 R09: 0000000000000000 > > R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000 > > R13: dffffc0000000000 R14: 0000000000000000 R15: 0000000000000000 > > FS: 00007f6b48ccf700(0000) GS:ffff8880b9b00000(0000) > > knlGS:0000000000000000 > > CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 > > CR2: 00007f6b48a819f0 CR3: 00000000171e7000 CR4: 00000000003506e0 > > DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 > > DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 > > Call Trace: > > <TASK> > > collapse_file+0x1ca/0x5780 mm/khugepaged.c:1715 > > hpage_collapse_scan_file+0xd6c/0x17a0 mm/khugepaged.c:2156 > > madvise_collapse+0x53a/0xb40 mm/khugepaged.c:2611 > > madvise_vma_behavior+0xd0a/0x1cc0 mm/madvise.c:1066 > > madvise_walk_vmas+0x1c7/0x2b0 mm/madvise.c:1240 > > do_madvise.part.0+0x24a/0x340 mm/madvise.c:1419 > > do_madvise mm/madvise.c:1432 [inline] > > __do_sys_madvise mm/madvise.c:1432 [inline] > > __se_sys_madvise mm/madvise.c:1430 [inline] > > __x64_sys_madvise+0x113/0x150 mm/madvise.c:1430 > > do_syscall_x64 arch/x86/entry/common.c:50 [inline] > > do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80 > > entry_SYSCALL_64_after_hwframe+0x63/0xcd > > RIP: 0033:0x7f6b48a4eef9 > > Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 b1 15 00 00 90 48 89 f8 48 89 > > f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 > > f0 ff ff 73 01 c3 48 c7 c1 b8 ff ff ff f7 d8 64 89 01 48 > > RSP: 002b:00007f6b48ccf318 EFLAGS: 00000246 ORIG_RAX: 000000000000001c > > RAX: ffffffffffffffda RBX: 00007f6b48af0048 RCX: 00007f6b48a4eef9 > > RDX: 0000000000000019 RSI: 0000000000600003 RDI: 0000000020000000 > > RBP: 00007f6b48af0040 R08: 0000000000000000 R09: 0000000000000000 > > R10: 0000000000000000 R11: 0000000000000246 R12: 00007f6b48aa53a4 > > R13: 00007f6b48bffcbf R14: 00007f6b48ccf400 R15: 0000000000022000 > > </TASK> > > > > It is because khugepaged allocates pages with __GFP_THISNODE, but the > > preferred node is bogus. The previous patch fixed the khugepaged > > code to avoid allocating page from non-existing node. But it is still > > racy against memory hotremove. There is no synchronization with the > > memory hotplug so it is possible that memory gets offline during a > > longer taking scanning. > > > > So this warning still seems not quite helpful because: > > * There is no guarantee the node is online for __GFP_THISNODE context > > for all the callsites. > > * Kernel just fails the allocation regardless the warning, and it looks > > all callsites handle the allocation failure gracefully. > > > > Although while the warning has helped to identify a buggy code, it is not > > safe in general and this warning could panic the system with panic-on-warn > > configuration which tends to be used surprisingly often. So replace > > VM_WARN_ON to pr_warn(). And the warning will be triggered if > > __GFP_NOWARN is set since the allocator would print out warning for such > > case if __GFP_NOWARN is not set. > > > > Reported-by: syzbot+0044b22d177870ee974f@syzkaller.appspotmail.com > > Signed-off-by: Yang Shi <shy828301@gmail.com> > > Suggested-by: Michal Hocko <mhocko@suse.com> > > Cc: Zach O'Keefe <zokeefe@google.com> > > Acked-by: Michal Hocko <mhocko@suse.com> > > minor nit > > > --- > > v3: * Reverted the old commit from mm-unstable which remove the VM_WARN > > (patch 1/3). > > * Incorporated the suggestion from Michal to use pr_warn. > > > > v2: * Added patch 1/2. > > * Reworded the commit log per Michal. > > > > include/linux/gfp.h | 14 ++++++++++++-- > > 1 file changed, 12 insertions(+), 2 deletions(-) > > > > diff --git a/include/linux/gfp.h b/include/linux/gfp.h > > index ef4aea3b356e..60a1c70ec85c 100644 > > --- a/include/linux/gfp.h > > +++ b/include/linux/gfp.h > > @@ -210,6 +210,16 @@ alloc_pages_bulk_array_node(gfp_t gfp, int nid, unsigned long nr_pages, struct p > > return __alloc_pages_bulk(gfp, nid, NULL, nr_pages, NULL, page_array); > > } > > > > +static inline void warn_if_node_offline(int nid, gfp_t gfp_mask) > > +{ > > + gfp_t gfp = gfp_mask & (__GFP_THISNODE|__GFP_NOWARN); > > I would use rather this_node or similarly descriptive name. gfp sounds this_node sounds good to me. > like a pasm but this is only a subset of it. If you really want to > improve the readability then you can restructure the condition a bit Just because I thought "if (gfp_mask & (__GFP_THISNODE|__GFP_NOWARN)) != (__GFP_THISNODE|__GFP_NOWARN))" is too long, so I added gfp to store the intermediate result. > > if (gfp_mask & (__GFP_THISNODE|__GFP_NOWARN)) != (__GFP_THISNODE|__GFP_NOWARN)) > return; > > if (node_online(nid)) > return; > > pr_warn("%pGg allocation from offline node %d\n", &gfp, nid); > dump_stack(); > > > + > > + if ((gfp == (__GFP_THISNODE|__GFP_NOWARN)) && !node_online(nid)) { > > + pr_warn("%pGg allocation from offline node %d\n", &gfp, nid); > > + dump_stack(); > > + } > > +} > > + > -- > Michal Hocko > SUSE Labs
diff --git a/include/linux/gfp.h b/include/linux/gfp.h index ef4aea3b356e..60a1c70ec85c 100644 --- a/include/linux/gfp.h +++ b/include/linux/gfp.h @@ -210,6 +210,16 @@ alloc_pages_bulk_array_node(gfp_t gfp, int nid, unsigned long nr_pages, struct p return __alloc_pages_bulk(gfp, nid, NULL, nr_pages, NULL, page_array); } +static inline void warn_if_node_offline(int nid, gfp_t gfp_mask) +{ + gfp_t gfp = gfp_mask & (__GFP_THISNODE|__GFP_NOWARN); + + if ((gfp == (__GFP_THISNODE|__GFP_NOWARN)) && !node_online(nid)) { + pr_warn("%pGg allocation from offline node %d\n", &gfp, nid); + dump_stack(); + } +} + /* * Allocate pages, preferring the node given as nid. The node must be valid and * online. For more general interface, see alloc_pages_node(). @@ -218,7 +228,7 @@ static inline struct page * __alloc_pages_node(int nid, gfp_t gfp_mask, unsigned int order) { VM_BUG_ON(nid < 0 || nid >= MAX_NUMNODES); - VM_WARN_ON((gfp_mask & __GFP_THISNODE) && !node_online(nid)); + warn_if_node_offline(nid, gfp_mask); return __alloc_pages(gfp_mask, order, nid, NULL); } @@ -227,7 +237,7 @@ static inline struct folio *__folio_alloc_node(gfp_t gfp, unsigned int order, int nid) { VM_BUG_ON(nid < 0 || nid >= MAX_NUMNODES); - VM_WARN_ON((gfp & __GFP_THISNODE) && !node_online(nid)); + warn_if_node_offline(nid, gfp); return __folio_alloc(gfp, order, nid, NULL); }
Syzbot reported the below splat: WARNING: CPU: 1 PID: 3646 at include/linux/gfp.h:221 __alloc_pages_node include/linux/gfp.h:221 [inline] WARNING: CPU: 1 PID: 3646 at include/linux/gfp.h:221 hpage_collapse_alloc_page mm/khugepaged.c:807 [inline] WARNING: CPU: 1 PID: 3646 at include/linux/gfp.h:221 alloc_charge_hpage+0x802/0xaa0 mm/khugepaged.c:963 Modules linked in: CPU: 1 PID: 3646 Comm: syz-executor210 Not tainted 6.1.0-rc1-syzkaller-00454-ga70385240892 #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/11/2022 RIP: 0010:__alloc_pages_node include/linux/gfp.h:221 [inline] RIP: 0010:hpage_collapse_alloc_page mm/khugepaged.c:807 [inline] RIP: 0010:alloc_charge_hpage+0x802/0xaa0 mm/khugepaged.c:963 Code: e5 01 4c 89 ee e8 6e f9 ae ff 4d 85 ed 0f 84 28 fc ff ff e8 70 fc ae ff 48 8d 6b ff 4c 8d 63 07 e9 16 fc ff ff e8 5e fc ae ff <0f> 0b e9 96 fa ff ff 41 bc 1a 00 00 00 e9 86 fd ff ff e8 47 fc ae RSP: 0018:ffffc90003fdf7d8 EFLAGS: 00010293 RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000000000000000 RDX: ffff888077f457c0 RSI: ffffffff81cd8f42 RDI: 0000000000000001 RBP: ffff888079388c0c R08: 0000000000000001 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000 R13: dffffc0000000000 R14: 0000000000000000 R15: 0000000000000000 FS: 00007f6b48ccf700(0000) GS:ffff8880b9b00000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00007f6b48a819f0 CR3: 00000000171e7000 CR4: 00000000003506e0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 Call Trace: <TASK> collapse_file+0x1ca/0x5780 mm/khugepaged.c:1715 hpage_collapse_scan_file+0xd6c/0x17a0 mm/khugepaged.c:2156 madvise_collapse+0x53a/0xb40 mm/khugepaged.c:2611 madvise_vma_behavior+0xd0a/0x1cc0 mm/madvise.c:1066 madvise_walk_vmas+0x1c7/0x2b0 mm/madvise.c:1240 do_madvise.part.0+0x24a/0x340 mm/madvise.c:1419 do_madvise mm/madvise.c:1432 [inline] __do_sys_madvise mm/madvise.c:1432 [inline] __se_sys_madvise mm/madvise.c:1430 [inline] __x64_sys_madvise+0x113/0x150 mm/madvise.c:1430 do_syscall_x64 arch/x86/entry/common.c:50 [inline] do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80 entry_SYSCALL_64_after_hwframe+0x63/0xcd RIP: 0033:0x7f6b48a4eef9 Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 b1 15 00 00 90 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 b8 ff ff ff f7 d8 64 89 01 48 RSP: 002b:00007f6b48ccf318 EFLAGS: 00000246 ORIG_RAX: 000000000000001c RAX: ffffffffffffffda RBX: 00007f6b48af0048 RCX: 00007f6b48a4eef9 RDX: 0000000000000019 RSI: 0000000000600003 RDI: 0000000020000000 RBP: 00007f6b48af0040 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 00007f6b48aa53a4 R13: 00007f6b48bffcbf R14: 00007f6b48ccf400 R15: 0000000000022000 </TASK> It is because khugepaged allocates pages with __GFP_THISNODE, but the preferred node is bogus. The previous patch fixed the khugepaged code to avoid allocating page from non-existing node. But it is still racy against memory hotremove. There is no synchronization with the memory hotplug so it is possible that memory gets offline during a longer taking scanning. So this warning still seems not quite helpful because: * There is no guarantee the node is online for __GFP_THISNODE context for all the callsites. * Kernel just fails the allocation regardless the warning, and it looks all callsites handle the allocation failure gracefully. Although while the warning has helped to identify a buggy code, it is not safe in general and this warning could panic the system with panic-on-warn configuration which tends to be used surprisingly often. So replace VM_WARN_ON to pr_warn(). And the warning will be triggered if __GFP_NOWARN is set since the allocator would print out warning for such case if __GFP_NOWARN is not set. Reported-by: syzbot+0044b22d177870ee974f@syzkaller.appspotmail.com Signed-off-by: Yang Shi <shy828301@gmail.com> Suggested-by: Michal Hocko <mhocko@suse.com> Cc: Zach O'Keefe <zokeefe@google.com> --- v3: * Reverted the old commit from mm-unstable which remove the VM_WARN (patch 1/3). * Incorporated the suggestion from Michal to use pr_warn. v2: * Added patch 1/2. * Reworded the commit log per Michal. include/linux/gfp.h | 14 ++++++++++++-- 1 file changed, 12 insertions(+), 2 deletions(-)