linux-kernel - [PATCH v1 1/3] drivers/base/memory.c: drop section

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Message-Id: <20200127110424.5757-2-david@redhat.com>
Date:   Mon, 27 Jan 2020 12:04:22 +0100
From:   David Hildenbrand <david@...hat.com>
To:     linux-kernel@...r.kernel.org
Cc:     linux-mm@...ck.org, David Hildenbrand <david@...hat.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Michal Hocko <mhocko@...e.com>,
        Dan Williams <dan.j.williams@...el.com>,
        Pavel Tatashin <pasha.tatashin@...een.com>,
        Anshuman Khandual <anshuman.khandual@....com>
Subject: [PATCH v1 1/3] drivers/base/memory.c: drop section_count

Since commit c5e79ef561b0 ("mm/memory_hotplug.c: don't allow to
online/offline memory blocks with holes") we have a generic check in
offline_pages() that disallows offlining memory blocks with holes.

Memory blocks with missing sections are just another variant of these
type of blocks. We can stop checking (and especially storing) present
sections. A proper error message is now printed why offlining failed.

section_count was initially introduced in commit 07681215975e ("Driver
core: Add section count to memory_block struct") in order to detect
when it is okay to remove a memory block. It was used in commit
26bbe7ef6d5c ("drivers/base/memory.c: prohibit offlining of memory blocks
with missing sections") to disallow offlining memory blocks with missing
sections. As we refactored creation/removal of memory devices and have
a proper check for holes in place, we can drop the section_count.

This also removes a leftover comment regarding the mem_sysfs_mutex,
which was removed in commit 848e19ad3c33 ("drivers/base/memory.c: drop
the mem_sysfs_mutex").

Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc: "Rafael J. Wysocki" <rafael@...nel.org>
Cc: Andrew Morton <akpm@...ux-foundation.org>
Cc: Michal Hocko <mhocko@...e.com>
Cc: Dan Williams <dan.j.williams@...el.com>
Cc: Pavel Tatashin <pasha.tatashin@...een.com>
Cc: Anshuman Khandual <anshuman.khandual@....com>
Signed-off-by: David Hildenbrand <david@...hat.com>
---
 drivers/base/memory.c  | 17 +++--------------
 include/linux/memory.h |  1 -
 2 files changed, 3 insertions(+), 15 deletions(-)

diff --git a/drivers/base/memory.c b/drivers/base/memory.c
index 6503f5d0b749..852fece9be1d 100644
--- a/drivers/base/memory.c
+++ b/drivers/base/memory.c
@@ -292,10 +292,6 @@ static int memory_subsys_offline(struct device *dev)
 	if (mem->state == MEM_OFFLINE)
 		return 0;
 
-	/* Can't offline block with non-present sections */
-	if (mem->section_count != sections_per_block)
-		return -EINVAL;
-
 	return memory_block_change_state(mem, MEM_OFFLINE, MEM_ONLINE);
 }
 
@@ -660,7 +656,7 @@ static int init_memory_block(struct memory_block **memory,
 
 static int add_memory_block(unsigned long base_section_nr)
 {
-	int ret, section_count = 0;
+	int section_count = 0;
 	struct memory_block *mem;
 	unsigned long nr;
 
@@ -671,12 +667,8 @@ static int add_memory_block(unsigned long base_section_nr)
 
 	if (section_count == 0)
 		return 0;
-	ret = init_memory_block(&mem, base_memory_block_id(base_section_nr),
-				MEM_ONLINE);
-	if (ret)
-		return ret;
-	mem->section_count = section_count;
-	return 0;
+	return init_memory_block(&mem, base_memory_block_id(base_section_nr),
+				 MEM_ONLINE);
 }
 
 static void unregister_memory(struct memory_block *memory)
@@ -714,7 +706,6 @@ int create_memory_block_devices(unsigned long start, unsigned long size)
 		ret = init_memory_block(&mem, block_id, MEM_OFFLINE);
 		if (ret)
 			break;
-		mem->section_count = sections_per_block;
 	}
 	if (ret) {
 		end_block_id = block_id;
@@ -723,7 +714,6 @@ int create_memory_block_devices(unsigned long start, unsigned long size)
 			mem = find_memory_block_by_id(block_id);
 			if (WARN_ON_ONCE(!mem))
 				continue;
-			mem->section_count = 0;
 			unregister_memory(mem);
 		}
 	}
@@ -752,7 +742,6 @@ void remove_memory_block_devices(unsigned long start, unsigned long size)
 		mem = find_memory_block_by_id(block_id);
 		if (WARN_ON_ONCE(!mem))
 			continue;
-		mem->section_count = 0;
 		unregister_memory_block_under_nodes(mem);
 		unregister_memory(mem);
 	}
diff --git a/include/linux/memory.h b/include/linux/memory.h
index 0b8d791b6669..439a89e758d8 100644
--- a/include/linux/memory.h
+++ b/include/linux/memory.h
@@ -26,7 +26,6 @@
 struct memory_block {
 	unsigned long start_section_nr;
 	unsigned long state;		/* serialized by the dev->lock */
-	int section_count;		/* serialized by mem_sysfs_mutex */
 	int online_type;		/* for passing data to online routine */
 	int phys_device;		/* to which fru does this belong? */
 	struct device dev;
-- 
2.24.1