mm/memory_hotplug: make __remove_section() never fail

Let's just warn in case a section is not valid instead of failing to
remove somewhere in the middle of the process, returning an error that
will be mostly ignored by callers.

Link: http://lkml.kernel.org/r/20190409100148.24703-4-david@redhat.comSigned-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: Qian Cai <cai@lca.pw>
Cc: Wei Yang <richard.weiyang@gmail.com>
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>

mm/memory_hotplug.c

@@ -516,15 +516,15 @@ static void __remove_zone(struct zone *zone, unsigned long start_pfn)
 	pgdat_resize_unlock(zone->zone_pgdat, &flags);
 }
 
-static int __remove_section(struct zone *zone, struct mem_section *ms,
-		unsigned long map_offset, struct vmem_altmap *altmap)
+static void __remove_section(struct zone *zone, struct mem_section *ms,
+			     unsigned long map_offset,
+			     struct vmem_altmap *altmap)
 {
 	unsigned long start_pfn;
 	int scn_nr;
-	int ret = -EINVAL;
 
-	if (!valid_section(ms))
-		return ret;
+	if (WARN_ON_ONCE(!valid_section(ms)))
+		return;
 
 	unregister_memory_section(ms);
 
@@ -533,7 +533,6 @@ static int __remove_section(struct zone *zone, struct mem_section *ms,
 	__remove_zone(zone, start_pfn);
 
 	sparse_remove_one_section(zone, ms, map_offset, altmap);
-	return 0;
 }
 
 /**
@@ -553,7 +552,7 @@ int __remove_pages(struct zone *zone, unsigned long phys_start_pfn,
 {
 	unsigned long i;
 	unsigned long map_offset = 0;
-	int sections_to_remove, ret = 0;
+	int sections_to_remove;
 
 	/* In the ZONE_DEVICE case device driver owns the memory region */
 	if (is_dev_zone(zone)) {
@@ -574,16 +573,13 @@ int __remove_pages(struct zone *zone, unsigned long phys_start_pfn,
 		unsigned long pfn = phys_start_pfn + i*PAGES_PER_SECTION;
 
 		cond_resched();
-		ret = __remove_section(zone, __pfn_to_section(pfn), map_offset,
-				altmap);
+		__remove_section(zone, __pfn_to_section(pfn), map_offset,
+				 altmap);
 		map_offset = 0;
-		if (ret)
-			break;
 	}
 
 	set_zone_contiguous(zone);
-
-	return ret;
+	return 0;
 }
 #endif /* CONFIG_MEMORY_HOTREMOVE */