Re: [PATCH v3 10/11] mm/memory_hotplug: Make unregister_memory_block_under_nodes() never fail
From: Michal Hocko <mhocko@kernel.org>
Date: 2019-07-01 08:51:49
Also in:
linux-mm, linux-s390, linux-sh, linuxppc-dev, lkml
On Mon 27-05-19 13:11:51, David Hildenbrand wrote:
We really don't want anything during memory hotunplug to fail. We always pass a valid memory block device, that check can go. Avoid allocating memory and eventually failing. As we are always called under lock, we can use a static piece of memory. This avoids having to put the structure onto the stack, having to guess about the stack size of callers. Patch inspired by a patch from Oscar Salvador. In the future, there might be no need to iterate over nodes at all. mem->nid should tell us exactly what to remove. Memory block devices with mixed nodes (added during boot) should properly fenced off and never removed.
Yeah, we do not allow to offline multi zone (node) ranges so the current code seems to be over engineered. Anyway, I am wondering why do we have to strictly check for already removed nodes links. Is the sysfs code going to complain we we try to remove again?
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Cc: "Rafael J. Wysocki" <rafael@kernel.org> Cc: Alex Deucher <alexander.deucher@amd.com> Cc: "David S. Miller" <davem@davemloft.net> Cc: Mark Brown <broonie@kernel.org> Cc: Chris Wilson <redacted> Cc: David Hildenbrand <redacted> Cc: Oscar Salvador <osalvador@suse.de> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Jonathan Cameron <Jonathan.Cameron@huawei.com> Signed-off-by: David Hildenbrand <redacted>
Anyway Acked-by: Michal Hocko <mhocko@suse.com>
quoted hunk ↗ jump to hunk
--- drivers/base/node.c | 18 +++++------------- include/linux/node.h | 5 ++--- 2 files changed, 7 insertions(+), 16 deletions(-)diff --git a/drivers/base/node.c b/drivers/base/node.c index 04fdfa99b8bc..9be88fd05147 100644 --- a/drivers/base/node.c +++ b/drivers/base/node.c@@ -803,20 +803,14 @@ int register_mem_sect_under_node(struct memory_block *mem_blk, void *arg) /* * Unregister memory block device under all nodes that it spans. + * Has to be called with mem_sysfs_mutex held (due to unlinked_nodes). */ -int unregister_memory_block_under_nodes(struct memory_block *mem_blk) +void unregister_memory_block_under_nodes(struct memory_block *mem_blk) { - NODEMASK_ALLOC(nodemask_t, unlinked_nodes, GFP_KERNEL); unsigned long pfn, sect_start_pfn, sect_end_pfn; + static nodemask_t unlinked_nodes; - if (!mem_blk) { - NODEMASK_FREE(unlinked_nodes); - return -EFAULT; - } - if (!unlinked_nodes) - return -ENOMEM; - nodes_clear(*unlinked_nodes); - + nodes_clear(unlinked_nodes); sect_start_pfn = section_nr_to_pfn(mem_blk->start_section_nr); sect_end_pfn = section_nr_to_pfn(mem_blk->end_section_nr); for (pfn = sect_start_pfn; pfn <= sect_end_pfn; pfn++) {@@ -827,15 +821,13 @@ int unregister_memory_block_under_nodes(struct memory_block *mem_blk) continue; if (!node_online(nid)) continue; - if (node_test_and_set(nid, *unlinked_nodes)) + if (node_test_and_set(nid, unlinked_nodes)) continue; sysfs_remove_link(&node_devices[nid]->dev.kobj, kobject_name(&mem_blk->dev.kobj)); sysfs_remove_link(&mem_blk->dev.kobj, kobject_name(&node_devices[nid]->dev.kobj)); } - NODEMASK_FREE(unlinked_nodes); - return 0; } int link_mem_sections(int nid, unsigned long start_pfn, unsigned long end_pfn)diff --git a/include/linux/node.h b/include/linux/node.h index 02a29e71b175..548c226966a2 100644 --- a/include/linux/node.h +++ b/include/linux/node.h@@ -139,7 +139,7 @@ extern int register_cpu_under_node(unsigned int cpu, unsigned int nid); extern int unregister_cpu_under_node(unsigned int cpu, unsigned int nid); extern int register_mem_sect_under_node(struct memory_block *mem_blk, void *arg); -extern int unregister_memory_block_under_nodes(struct memory_block *mem_blk); +extern void unregister_memory_block_under_nodes(struct memory_block *mem_blk); extern int register_memory_node_under_compute_node(unsigned int mem_nid, unsigned int cpu_nid,@@ -175,9 +175,8 @@ static inline int register_mem_sect_under_node(struct memory_block *mem_blk, { return 0; } -static inline int unregister_memory_block_under_nodes(struct memory_block *mem_blk) +static inline void unregister_memory_block_under_nodes(struct memory_block *mem_blk) { - return 0; } static inline void register_hugetlbfs_with_node(node_registration_func_t reg,-- 2.20.1
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