| Message ID | 20190507183804.5512-8-david@redhat.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | [v2,1/8] mm/memory_hotplug: Simplify and fix check_hotplug_memory_range() | expand |
On Tue, May 7, 2019 at 11:39 AM David Hildenbrand <david@redhat.com> 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. > > 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 <chris@chris-wilson.co.uk> > Cc: David Hildenbrand <david@redhat.com> > 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 <david@redhat.com> > --- > 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). Given this comment can bitrot relative to the implementation lets instead add an explicit: lockdep_assert_held(&mem_sysfs_mutex); With that you can add: Reviewed-by: Dan Williams <dan.j.williams@intel.com>
>> 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). > > Given this comment can bitrot relative to the implementation lets > instead add an explicit: > > lockdep_assert_held(&mem_sysfs_mutex); That would require to make the mutex non-static. Is that what you suggest, or any other alternative? Thanks Dan! > > With that you can add: > > Reviewed-by: Dan Williams <dan.j.williams@intel.com> >
On Wed, May 8, 2019 at 12:22 AM David Hildenbrand <david@redhat.com> wrote: > > > >> 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). > > > > Given this comment can bitrot relative to the implementation lets > > instead add an explicit: > > > > lockdep_assert_held(&mem_sysfs_mutex); > > That would require to make the mutex non-static. Is that what you > suggest, or any other alternative? If the concern is other code paths taking the lock when they shouldn't then you could make a public "lockdep_assert_mem_sysfs_held()" to do the same, but I otherwise think the benefit of inline lock validation is worth the price of adding a new non-static symbol.
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,
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. 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 <chris@chris-wilson.co.uk> Cc: David Hildenbrand <david@redhat.com> 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 <david@redhat.com> --- drivers/base/node.c | 18 +++++------------- include/linux/node.h | 5 ++--- 2 files changed, 7 insertions(+), 16 deletions(-)