| Message ID | 1567503958-25831-2-git-send-email-anshuman.khandual@arm.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | arm64/mm: Enable memory hot remove | expand |
On 03.09.19 11:45, Anshuman Khandual wrote: > Memory hot remove uses get_nid_for_pfn() while tearing down linked sysfs > entries between memory block and node. It first checks pfn validity with > pfn_valid_within() before fetching nid. With CONFIG_HOLES_IN_ZONE config > (arm64 has this enabled) pfn_valid_within() calls pfn_valid(). > > pfn_valid() is an arch implementation on arm64 (CONFIG_HAVE_ARCH_PFN_VALID) > which scans all mapped memblock regions with memblock_is_map_memory(). This > creates a problem in memory hot remove path which has already removed given > memory range from memory block with memblock_[remove|free] before arriving > at unregister_mem_sect_under_nodes(). Hence get_nid_for_pfn() returns -1 > skipping subsequent sysfs_remove_link() calls leaving node <-> memory block > sysfs entries as is. Subsequent memory add operation hits BUG_ON() because > of existing sysfs entries. Since commit 60bb462fc7adb06ebee3beb5a4af6c7e6182e248 Author: David Hildenbrand <david@redhat.com> Date: Wed Aug 28 13:57:15 2019 +1000 drivers/base/node.c: simplify unregister_memory_block_under_nodes() that problem should be gone. There is no get_nid_for_pfn() call anymore. So this patch should no longer be necessary - but as I said during earlier versions of this patch, the re-ordering might still make sense for consistency (removing stuff in the reverse order they were added). You'll have to rephrase the description then. > > [ 62.007176] NUMA: Unknown node for memory at 0x680000000, assuming node 0 > [ 62.052517] ------------[ cut here ]------------ > [ 62.053211] kernel BUG at mm/memory_hotplug.c:1143! > [ 62.053868] Internal error: Oops - BUG: 0 [#1] PREEMPT SMP > [ 62.054589] Modules linked in: > [ 62.054999] CPU: 19 PID: 3275 Comm: bash Not tainted 5.1.0-rc2-00004-g28cea40b2683 #41 > [ 62.056274] Hardware name: linux,dummy-virt (DT) > [ 62.057166] pstate: 40400005 (nZcv daif +PAN -UAO) > [ 62.058083] pc : add_memory_resource+0x1cc/0x1d8 > [ 62.058961] lr : add_memory_resource+0x10c/0x1d8 > [ 62.059842] sp : ffff0000168b3ce0 > [ 62.060477] x29: ffff0000168b3ce0 x28: ffff8005db546c00 > [ 62.061501] x27: 0000000000000000 x26: 0000000000000000 > [ 62.062509] x25: ffff0000111ef000 x24: ffff0000111ef5d0 > [ 62.063520] x23: 0000000000000000 x22: 00000006bfffffff > [ 62.064540] x21: 00000000ffffffef x20: 00000000006c0000 > [ 62.065558] x19: 0000000000680000 x18: 0000000000000024 > [ 62.066566] x17: 0000000000000000 x16: 0000000000000000 > [ 62.067579] x15: ffffffffffffffff x14: ffff8005e412e890 > [ 62.068588] x13: ffff8005d6b105d8 x12: 0000000000000000 > [ 62.069610] x11: ffff8005d6b10490 x10: 0000000000000040 > [ 62.070615] x9 : ffff8005e412e898 x8 : ffff8005e412e890 > [ 62.071631] x7 : ffff8005d6b105d8 x6 : ffff8005db546c00 > [ 62.072640] x5 : 0000000000000001 x4 : 0000000000000002 > [ 62.073654] x3 : ffff8005d7049480 x2 : 0000000000000002 > [ 62.074666] x1 : 0000000000000003 x0 : 00000000ffffffef > [ 62.075685] Process bash (pid: 3275, stack limit = 0x00000000d754280f) > [ 62.076930] Call trace: > [ 62.077411] add_memory_resource+0x1cc/0x1d8 > [ 62.078227] __add_memory+0x70/0xa8 > [ 62.078901] probe_store+0xa4/0xc8 > [ 62.079561] dev_attr_store+0x18/0x28 > [ 62.080270] sysfs_kf_write+0x40/0x58 > [ 62.080992] kernfs_fop_write+0xcc/0x1d8 > [ 62.081744] __vfs_write+0x18/0x40 > [ 62.082400] vfs_write+0xa4/0x1b0 > [ 62.083037] ksys_write+0x5c/0xc0 > [ 62.083681] __arm64_sys_write+0x18/0x20 > [ 62.084432] el0_svc_handler+0x88/0x100 > [ 62.085177] el0_svc+0x8/0xc > > Re-ordering memblock_[free|remove]() with arch_remove_memory() solves the > problem on arm64 as pfn_valid() behaves correctly and returns positive > as memblock for the address range still exists. arch_remove_memory() > removes applicable memory sections from zone with __remove_pages() and > tears down kernel linear mapping. Removing memblock regions afterwards > is safe because there is no other memblock (bootmem) allocator user that > late. So nobody is going to allocate from the removed range just to blow > up later. Also nobody should be using the bootmem allocated range else > we wouldn't allow to remove it. So reordering is indeed safe. > > Reviewed-by: David Hildenbrand <david@redhat.com> > Reviewed-by: Oscar Salvador <osalvador@suse.de> > Acked-by: Mark Rutland <mark.rutland@arm.com> > Acked-by: Michal Hocko <mhocko@suse.com> > Signed-off-by: Anshuman Khandual <anshuman.khandual@arm.com> > --- > mm/memory_hotplug.c | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) > > diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c > index c73f09913165..355c466e0621 100644 > --- a/mm/memory_hotplug.c > +++ b/mm/memory_hotplug.c > @@ -1770,13 +1770,13 @@ static int __ref try_remove_memory(int nid, u64 start, u64 size) > > /* remove memmap entry */ > firmware_map_remove(start, start + size, "System RAM"); > - memblock_free(start, size); > - memblock_remove(start, size); > > /* remove memory block devices before removing memory */ > remove_memory_block_devices(start, size); > > arch_remove_memory(nid, start, size, NULL); > + memblock_free(start, size); > + memblock_remove(start, size); > __release_memory_resource(start, size); > > try_offline_node(nid); >
On 09/04/2019 01:46 PM, David Hildenbrand wrote: > On 03.09.19 11:45, Anshuman Khandual wrote: >> Memory hot remove uses get_nid_for_pfn() while tearing down linked sysfs >> entries between memory block and node. It first checks pfn validity with >> pfn_valid_within() before fetching nid. With CONFIG_HOLES_IN_ZONE config >> (arm64 has this enabled) pfn_valid_within() calls pfn_valid(). >> >> pfn_valid() is an arch implementation on arm64 (CONFIG_HAVE_ARCH_PFN_VALID) >> which scans all mapped memblock regions with memblock_is_map_memory(). This >> creates a problem in memory hot remove path which has already removed given >> memory range from memory block with memblock_[remove|free] before arriving >> at unregister_mem_sect_under_nodes(). Hence get_nid_for_pfn() returns -1 >> skipping subsequent sysfs_remove_link() calls leaving node <-> memory block >> sysfs entries as is. Subsequent memory add operation hits BUG_ON() because >> of existing sysfs entries. > Since > > commit 60bb462fc7adb06ebee3beb5a4af6c7e6182e248 > Author: David Hildenbrand <david@redhat.com> > Date: Wed Aug 28 13:57:15 2019 +1000 > > drivers/base/node.c: simplify unregister_memory_block_under_nodes() > > that problem should be gone. There is no get_nid_for_pfn() call anymore. Yes, the problem is gone. The above commit is still not present on arm64 tree against which this series was rebased and tested while posting. > > So this patch should no longer be necessary - but as I said during > earlier versions of this patch, the re-ordering might still make sense > for consistency (removing stuff in the reverse order they were added). > You'll have to rephrase the description then. Sure will reword the commit message on these lines.
On 3/9/19 7:45 pm, Anshuman Khandual wrote: > Memory hot remove uses get_nid_for_pfn() while tearing down linked sysfs I could not find this path in the code, the only called for get_nid_for_pfn() was register_mem_sect_under_node() when the system is under boot. > entries between memory block and node. It first checks pfn validity with > pfn_valid_within() before fetching nid. With CONFIG_HOLES_IN_ZONE config > (arm64 has this enabled) pfn_valid_within() calls pfn_valid(). > > pfn_valid() is an arch implementation on arm64 (CONFIG_HAVE_ARCH_PFN_VALID) > which scans all mapped memblock regions with memblock_is_map_memory(). This > creates a problem in memory hot remove path which has already removed given > memory range from memory block with memblock_[remove|free] before arriving > at unregister_mem_sect_under_nodes(). Hence get_nid_for_pfn() returns -1 > skipping subsequent sysfs_remove_link() calls leaving node <-> memory block > sysfs entries as is. Subsequent memory add operation hits BUG_ON() because > of existing sysfs entries. > > [ 62.007176] NUMA: Unknown node for memory at 0x680000000, assuming node 0 > [ 62.052517] ------------[ cut here ]------------ This seems like arm64 is not ready for probe_store() via drivers/base/memory.c/ode.c > [ 62.053211] kernel BUG at mm/memory_hotplug.c:1143! > [ 62.053868] Internal error: Oops - BUG: 0 [#1] PREEMPT SMP > [ 62.054589] Modules linked in: > [ 62.054999] CPU: 19 PID: 3275 Comm: bash Not tainted 5.1.0-rc2-00004-g28cea40b2683 #41 > [ 62.056274] Hardware name: linux,dummy-virt (DT) > [ 62.057166] pstate: 40400005 (nZcv daif +PAN -UAO) > [ 62.058083] pc : add_memory_resource+0x1cc/0x1d8 > [ 62.058961] lr : add_memory_resource+0x10c/0x1d8 > [ 62.059842] sp : ffff0000168b3ce0 > [ 62.060477] x29: ffff0000168b3ce0 x28: ffff8005db546c00 > [ 62.061501] x27: 0000000000000000 x26: 0000000000000000 > [ 62.062509] x25: ffff0000111ef000 x24: ffff0000111ef5d0 > [ 62.063520] x23: 0000000000000000 x22: 00000006bfffffff > [ 62.064540] x21: 00000000ffffffef x20: 00000000006c0000 > [ 62.065558] x19: 0000000000680000 x18: 0000000000000024 > [ 62.066566] x17: 0000000000000000 x16: 0000000000000000 > [ 62.067579] x15: ffffffffffffffff x14: ffff8005e412e890 > [ 62.068588] x13: ffff8005d6b105d8 x12: 0000000000000000 > [ 62.069610] x11: ffff8005d6b10490 x10: 0000000000000040 > [ 62.070615] x9 : ffff8005e412e898 x8 : ffff8005e412e890 > [ 62.071631] x7 : ffff8005d6b105d8 x6 : ffff8005db546c00 > [ 62.072640] x5 : 0000000000000001 x4 : 0000000000000002 > [ 62.073654] x3 : ffff8005d7049480 x2 : 0000000000000002 > [ 62.074666] x1 : 0000000000000003 x0 : 00000000ffffffef > [ 62.075685] Process bash (pid: 3275, stack limit = 0x00000000d754280f) > [ 62.076930] Call trace: > [ 62.077411] add_memory_resource+0x1cc/0x1d8 > [ 62.078227] __add_memory+0x70/0xa8 > [ 62.078901] probe_store+0xa4/0xc8 > [ 62.079561] dev_attr_store+0x18/0x28 > [ 62.080270] sysfs_kf_write+0x40/0x58 > [ 62.080992] kernfs_fop_write+0xcc/0x1d8 > [ 62.081744] __vfs_write+0x18/0x40 > [ 62.082400] vfs_write+0xa4/0x1b0 > [ 62.083037] ksys_write+0x5c/0xc0 > [ 62.083681] __arm64_sys_write+0x18/0x20 > [ 62.084432] el0_svc_handler+0x88/0x100 > [ 62.085177] el0_svc+0x8/0xc > > Re-ordering memblock_[free|remove]() with arch_remove_memory() solves the > problem on arm64 as pfn_valid() behaves correctly and returns positive > as memblock for the address range still exists. arch_remove_memory() > removes applicable memory sections from zone with __remove_pages() and > tears down kernel linear mapping. Removing memblock regions afterwards > is safe because there is no other memblock (bootmem) allocator user that > late. So nobody is going to allocate from the removed range just to blow > up later. Also nobody should be using the bootmem allocated range else > we wouldn't allow to remove it. So reordering is indeed safe. > > Reviewed-by: David Hildenbrand <david@redhat.com> > Reviewed-by: Oscar Salvador <osalvador@suse.de> > Acked-by: Mark Rutland <mark.rutland@arm.com> > Acked-by: Michal Hocko <mhocko@suse.com> > Signed-off-by: Anshuman Khandual <anshuman.khandual@arm.com> > --- Honestly, the issue is not clear from the changelog, largely because I can't find the use of get_nid_for_pfn() being used in memory hotunplug. I can see why using pfn_valid() after memblock_free/remove is bad on the architecture. I think the checks to pfn_valid() can be avoided from the remove paths if we did the following memblock_isolate_regions() for each isolate_region { memblock_free memblock_remove arch_memory_remove # ensure that __remove_memory can avoid calling pfn_valid } Having said that, your patch is easier and if your assumption about not using the memblocks is valid (after arch_memory_remove()) then might be the least resistant way forward Balbir Singh. > mm/memory_hotplug.c | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) > > diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c > index c73f09913165..355c466e0621 100644 > --- a/mm/memory_hotplug.c > +++ b/mm/memory_hotplug.c > @@ -1770,13 +1770,13 @@ static int __ref try_remove_memory(int nid, u64 start, u64 size) > > /* remove memmap entry */ > firmware_map_remove(start, start + size, "System RAM"); > - memblock_free(start, size); > - memblock_remove(start, size); > > /* remove memory block devices before removing memory */ > remove_memory_block_devices(start, size); > > arch_remove_memory(nid, start, size, NULL); > + memblock_free(start, size); > + memblock_remove(start, size); > __release_memory_resource(start, size); > > try_offline_node(nid); >
On 09/16/2019 07:14 AM, Balbir Singh wrote: > > > On 3/9/19 7:45 pm, Anshuman Khandual wrote: >> Memory hot remove uses get_nid_for_pfn() while tearing down linked sysfs > > I could not find this path in the code, the only called for get_nid_for_pfn() > was register_mem_sect_under_node() when the system is under boot. > >> entries between memory block and node. It first checks pfn validity with >> pfn_valid_within() before fetching nid. With CONFIG_HOLES_IN_ZONE config >> (arm64 has this enabled) pfn_valid_within() calls pfn_valid(). >> >> pfn_valid() is an arch implementation on arm64 (CONFIG_HAVE_ARCH_PFN_VALID) >> which scans all mapped memblock regions with memblock_is_map_memory(). This >> creates a problem in memory hot remove path which has already removed given >> memory range from memory block with memblock_[remove|free] before arriving >> at unregister_mem_sect_under_nodes(). Hence get_nid_for_pfn() returns -1 >> skipping subsequent sysfs_remove_link() calls leaving node <-> memory block >> sysfs entries as is. Subsequent memory add operation hits BUG_ON() because >> of existing sysfs entries. >> >> [ 62.007176] NUMA: Unknown node for memory at 0x680000000, assuming node 0 >> [ 62.052517] ------------[ cut here ]------------ > > This seems like arm64 is not ready for probe_store() via drivers/base/memory.c/ode.c > >> [ 62.053211] kernel BUG at mm/memory_hotplug.c:1143! > > > >> [ 62.053868] Internal error: Oops - BUG: 0 [#1] PREEMPT SMP >> [ 62.054589] Modules linked in: >> [ 62.054999] CPU: 19 PID: 3275 Comm: bash Not tainted 5.1.0-rc2-00004-g28cea40b2683 #41 >> [ 62.056274] Hardware name: linux,dummy-virt (DT) >> [ 62.057166] pstate: 40400005 (nZcv daif +PAN -UAO) >> [ 62.058083] pc : add_memory_resource+0x1cc/0x1d8 >> [ 62.058961] lr : add_memory_resource+0x10c/0x1d8 >> [ 62.059842] sp : ffff0000168b3ce0 >> [ 62.060477] x29: ffff0000168b3ce0 x28: ffff8005db546c00 >> [ 62.061501] x27: 0000000000000000 x26: 0000000000000000 >> [ 62.062509] x25: ffff0000111ef000 x24: ffff0000111ef5d0 >> [ 62.063520] x23: 0000000000000000 x22: 00000006bfffffff >> [ 62.064540] x21: 00000000ffffffef x20: 00000000006c0000 >> [ 62.065558] x19: 0000000000680000 x18: 0000000000000024 >> [ 62.066566] x17: 0000000000000000 x16: 0000000000000000 >> [ 62.067579] x15: ffffffffffffffff x14: ffff8005e412e890 >> [ 62.068588] x13: ffff8005d6b105d8 x12: 0000000000000000 >> [ 62.069610] x11: ffff8005d6b10490 x10: 0000000000000040 >> [ 62.070615] x9 : ffff8005e412e898 x8 : ffff8005e412e890 >> [ 62.071631] x7 : ffff8005d6b105d8 x6 : ffff8005db546c00 >> [ 62.072640] x5 : 0000000000000001 x4 : 0000000000000002 >> [ 62.073654] x3 : ffff8005d7049480 x2 : 0000000000000002 >> [ 62.074666] x1 : 0000000000000003 x0 : 00000000ffffffef >> [ 62.075685] Process bash (pid: 3275, stack limit = 0x00000000d754280f) >> [ 62.076930] Call trace: >> [ 62.077411] add_memory_resource+0x1cc/0x1d8 >> [ 62.078227] __add_memory+0x70/0xa8 >> [ 62.078901] probe_store+0xa4/0xc8 >> [ 62.079561] dev_attr_store+0x18/0x28 >> [ 62.080270] sysfs_kf_write+0x40/0x58 >> [ 62.080992] kernfs_fop_write+0xcc/0x1d8 >> [ 62.081744] __vfs_write+0x18/0x40 >> [ 62.082400] vfs_write+0xa4/0x1b0 >> [ 62.083037] ksys_write+0x5c/0xc0 >> [ 62.083681] __arm64_sys_write+0x18/0x20 >> [ 62.084432] el0_svc_handler+0x88/0x100 >> [ 62.085177] el0_svc+0x8/0xc >> >> Re-ordering memblock_[free|remove]() with arch_remove_memory() solves the >> problem on arm64 as pfn_valid() behaves correctly and returns positive >> as memblock for the address range still exists. arch_remove_memory() >> removes applicable memory sections from zone with __remove_pages() and >> tears down kernel linear mapping. Removing memblock regions afterwards >> is safe because there is no other memblock (bootmem) allocator user that >> late. So nobody is going to allocate from the removed range just to blow >> up later. Also nobody should be using the bootmem allocated range else >> we wouldn't allow to remove it. So reordering is indeed safe. >> >> Reviewed-by: David Hildenbrand <david@redhat.com> >> Reviewed-by: Oscar Salvador <osalvador@suse.de> >> Acked-by: Mark Rutland <mark.rutland@arm.com> >> Acked-by: Michal Hocko <mhocko@suse.com> >> Signed-off-by: Anshuman Khandual <anshuman.khandual@arm.com> >> --- > > Honestly, the issue is not clear from the changelog, largely > because I can't find the use of get_nid_for_pfn() being used > in memory hotunplug. I can see why using pfn_valid() after > memblock_free/remove is bad on the architecture. > > I think the checks to pfn_valid() can be avoided from the > remove paths if we did the following > > memblock_isolate_regions() > for each isolate_region { > memblock_free > memblock_remove > arch_memory_remove > > # ensure that __remove_memory can avoid calling pfn_valid > } > > Having said that, your patch is easier and if your assumption > about not using the memblocks is valid (after arch_memory_remove()) > then might be the least resistant way forward The context for this patch has changed a bit which now reflects in it's current posting (https://patchwork.kernel.org/patch/11146361/)
diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c index c73f09913165..355c466e0621 100644 --- a/mm/memory_hotplug.c +++ b/mm/memory_hotplug.c @@ -1770,13 +1770,13 @@ static int __ref try_remove_memory(int nid, u64 start, u64 size) /* remove memmap entry */ firmware_map_remove(start, start + size, "System RAM"); - memblock_free(start, size); - memblock_remove(start, size); /* remove memory block devices before removing memory */ remove_memory_block_devices(start, size); arch_remove_memory(nid, start, size, NULL); + memblock_free(start, size); + memblock_remove(start, size); __release_memory_resource(start, size); try_offline_node(nid);