commit d9eb1417c77df7ce19abd2e41619e9dceccbdf2a upstream.
Patch series "mm/memory_hotplug: Better error handling when removing memory", v1.
Error handling when removing memory is somewhat messed up right now. Some errors result in warnings, others are completely ignored. Memory unplug code can essentially not deal with errors properly as of now. remove_memory() will never fail.
We have basically two choices: 1. Allow arch_remov_memory() and friends to fail, propagating errors via remove_memory(). Might be problematic (e.g. DIMMs consisting of multiple pieces added/removed separately). 2. Don't allow the functions to fail, handling errors in a nicer way.
It seems like most errors that can theoretically happen are really corner cases and mostly theoretical (e.g. "section not valid"). However e.g. aborting removal of sections while all callers simply continue in case of errors is not nice.
If we can gurantee that removal of memory always works (and WARN/skip in case of theoretical errors so we can figure out what is going on), we can go ahead and implement better error handling when adding memory.
E.g. via add_memory():
arch_add_memory() ret = do_stuff() if (ret) { arch_remove_memory(); goto error; }
Handling here that arch_remove_memory() might fail is basically impossible. So I suggest, let's avoid reporting errors while removing memory, warning on theoretical errors instead and continuing instead of aborting.
This patch (of 4):
__add_pages() doesn't add the memory resource, so __remove_pages() shouldn't remove it. Let's factor it out. Especially as it is a special case for memory used as system memory, added via add_memory() and friends.
We now remove the resource after removing the sections instead of doing it the other way around. I don't think this change is problematic.
add_memory() register memory resource arch_add_memory()
remove_memory arch_remove_memory() release memory resource
While at it, explain why we ignore errors and that it only happeny if we remove memory in a different granularity as we added it.
[david@redhat.com: fix printk warning] Link: http://lkml.kernel.org/r/20190417120204.6997-1-david@redhat.com Link: http://lkml.kernel.org/r/20190409100148.24703-2-david@redhat.com Signed-off-by: David Hildenbrand david@redhat.com Reviewed-by: Oscar Salvador osalvador@suse.de Cc: Michal Hocko mhocko@suse.com Cc: David Hildenbrand david@redhat.com Cc: Pavel Tatashin pasha.tatashin@soleen.com Cc: Wei Yang richard.weiyang@gmail.com Cc: Qian Cai cai@lca.pw Cc: Arun KS arunks@codeaurora.org Cc: Mathieu Malaterre malat@debian.org Cc: Andrew Banman andrew.banman@hpe.com Cc: Andy Lutomirski luto@kernel.org Cc: Benjamin Herrenschmidt benh@kernel.crashing.org Cc: Borislav Petkov bp@alien8.de Cc: Christophe Leroy christophe.leroy@c-s.fr Cc: Dave Hansen dave.hansen@linux.intel.com Cc: Fenghua Yu fenghua.yu@intel.com Cc: Geert Uytterhoeven geert@linux-m68k.org Cc: Greg Kroah-Hartman gregkh@linuxfoundation.org Cc: Heiko Carstens heiko.carstens@de.ibm.com Cc: "H. Peter Anvin" hpa@zytor.com Cc: Ingo Molnar mingo@kernel.org Cc: Ingo Molnar mingo@redhat.com Cc: Joonsoo Kim iamjoonsoo.kim@lge.com Cc: "Kirill A. Shutemov" kirill.shutemov@linux.intel.com Cc: Martin Schwidefsky schwidefsky@de.ibm.com Cc: Masahiro Yamada yamada.masahiro@socionext.com Cc: Michael Ellerman mpe@ellerman.id.au Cc: Mike Rapoport rppt@linux.ibm.com Cc: Mike Travis mike.travis@hpe.com Cc: Nicholas Piggin npiggin@gmail.com Cc: Oscar Salvador osalvador@suse.com Cc: Paul Mackerras paulus@samba.org Cc: Peter Zijlstra peterz@infradead.org Cc: "Rafael J. Wysocki" rafael@kernel.org Cc: Rich Felker dalias@libc.org Cc: Rob Herring robh@kernel.org Cc: Stefan Agner stefan@agner.ch Cc: Thomas Gleixner tglx@linutronix.de Cc: Tony Luck tony.luck@intel.com Cc: Vasily Gorbik gor@linux.ibm.com Cc: Yoshinori Sato ysato@users.sourceforge.jp Signed-off-by: Andrew Morton akpm@linux-foundation.org Signed-off-by: Linus Torvalds torvalds@linux-foundation.org Signed-off-by: David Hildenbrand david@redhat.com --- mm/memory_hotplug.c | 35 +++++++++++++++++++++-------------- 1 file changed, 21 insertions(+), 14 deletions(-)
diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c index a51e5ffdaa04..418d589552b3 100644 --- a/mm/memory_hotplug.c +++ b/mm/memory_hotplug.c @@ -523,20 +523,6 @@ int __remove_pages(struct zone *zone, unsigned long phys_start_pfn, if (is_dev_zone(zone)) { if (altmap) map_offset = vmem_altmap_offset(altmap); - } else { - resource_size_t start, size; - - start = phys_start_pfn << PAGE_SHIFT; - size = nr_pages * PAGE_SIZE; - - ret = release_mem_region_adjustable(&iomem_resource, start, - size); - if (ret) { - resource_size_t endres = start + size - 1; - - pr_warn("Unable to release resource <%pa-%pa> (%d)\n", - &start, &endres, ret); - } }
clear_zone_contiguous(zone); @@ -1883,6 +1869,26 @@ void try_offline_node(int nid) } EXPORT_SYMBOL(try_offline_node);
+static void __release_memory_resource(resource_size_t start, + resource_size_t size) +{ + int ret; + + /* + * When removing memory in the same granularity as it was added, + * this function never fails. It might only fail if resources + * have to be adjusted or split. We'll ignore the error, as + * removing of memory cannot fail. + */ + ret = release_mem_region_adjustable(&iomem_resource, start, size); + if (ret) { + resource_size_t endres = start + size - 1; + + pr_warn("Unable to release resource <%pa-%pa> (%d)\n", + &start, &endres, ret); + } +} + /** * remove_memory * @nid: the node ID @@ -1917,6 +1923,7 @@ void __ref __remove_memory(int nid, u64 start, u64 size) memblock_remove(start, size);
arch_remove_memory(nid, start, size, NULL); + __release_memory_resource(start, size);
try_offline_node(nid);