| Message ID | 20190517215438.6487-3-pasha.tatashin@soleen.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | "Hotremove" persistent memory | expand |
On Fri 17-05-19 17:54:37, Pavel Tatashin wrote: > As of right now remove_memory() interface is inherently broken. It tries > to remove memory but panics if some memory is not offline. The problem > is that it is impossible to ensure that all memory blocks are offline as > this function also takes lock_device_hotplug that is required to > change memory state via sysfs. > > So, between calling this function and offlining all memory blocks there > is always a window when lock_device_hotplug is released, and therefore, > there is always a chance for a panic during this window. > > Make this interface to return an error if memory removal fails. This way > it is safe to call this function without panicking machine, and also > makes it symmetric to add_memory() which already returns an error. I was about to object because of the acpi hotremove but looking closer acpi_memory_remove_memory and few others already do use __remove_memory instead of remove_memory so this is good to go. I really hate how we had to BUG in remove_memory as well so this is definitely a good change. > Signed-off-by: Pavel Tatashin <pasha.tatashin@soleen.com> > Reviewed-by: David Hildenbrand <david@redhat.com> Acked-by: Michal Hocko <mhocko@suse.com> > --- > include/linux/memory_hotplug.h | 8 +++-- > mm/memory_hotplug.c | 64 +++++++++++++++++++++++----------- > 2 files changed, 49 insertions(+), 23 deletions(-) > > diff --git a/include/linux/memory_hotplug.h b/include/linux/memory_hotplug.h > index ae892eef8b82..988fde33cd7f 100644 > --- a/include/linux/memory_hotplug.h > +++ b/include/linux/memory_hotplug.h > @@ -324,7 +324,7 @@ static inline void pgdat_resize_init(struct pglist_data *pgdat) {} > extern bool is_mem_section_removable(unsigned long pfn, unsigned long nr_pages); > extern void try_offline_node(int nid); > extern int offline_pages(unsigned long start_pfn, unsigned long nr_pages); > -extern void remove_memory(int nid, u64 start, u64 size); > +extern int remove_memory(int nid, u64 start, u64 size); > extern void __remove_memory(int nid, u64 start, u64 size); > > #else > @@ -341,7 +341,11 @@ static inline int offline_pages(unsigned long start_pfn, unsigned long nr_pages) > return -EINVAL; > } > > -static inline void remove_memory(int nid, u64 start, u64 size) {} > +static inline int remove_memory(int nid, u64 start, u64 size) > +{ > + return -EBUSY; > +} > + > static inline void __remove_memory(int nid, u64 start, u64 size) {} > #endif /* CONFIG_MEMORY_HOTREMOVE */ > > diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c > index 328878b6799d..ace2cc614da4 100644 > --- a/mm/memory_hotplug.c > +++ b/mm/memory_hotplug.c > @@ -1735,9 +1735,10 @@ static int check_memblock_offlined_cb(struct memory_block *mem, void *arg) > endpa = PFN_PHYS(section_nr_to_pfn(mem->end_section_nr + 1))-1; > pr_warn("removing memory fails, because memory [%pa-%pa] is onlined\n", > &beginpa, &endpa); > - } > > - return ret; > + return -EBUSY; > + } > + return 0; > } > > static int check_cpu_on_node(pg_data_t *pgdat) > @@ -1820,19 +1821,9 @@ static void __release_memory_resource(resource_size_t start, > } > } > > -/** > - * remove_memory > - * @nid: the node ID > - * @start: physical address of the region to remove > - * @size: size of the region to remove > - * > - * NOTE: The caller must call lock_device_hotplug() to serialize hotplug > - * and online/offline operations before this call, as required by > - * try_offline_node(). > - */ > -void __ref __remove_memory(int nid, u64 start, u64 size) > +static int __ref try_remove_memory(int nid, u64 start, u64 size) > { > - int ret; > + int rc = 0; > > BUG_ON(check_hotplug_memory_range(start, size)); > > @@ -1840,13 +1831,13 @@ void __ref __remove_memory(int nid, u64 start, u64 size) > > /* > * All memory blocks must be offlined before removing memory. Check > - * whether all memory blocks in question are offline and trigger a BUG() > + * whether all memory blocks in question are offline and return error > * if this is not the case. > */ > - ret = walk_memory_range(PFN_DOWN(start), PFN_UP(start + size - 1), NULL, > - check_memblock_offlined_cb); > - if (ret) > - BUG(); > + rc = walk_memory_range(PFN_DOWN(start), PFN_UP(start + size - 1), NULL, > + check_memblock_offlined_cb); > + if (rc) > + goto done; > > /* remove memmap entry */ > firmware_map_remove(start, start + size, "System RAM"); > @@ -1858,14 +1849,45 @@ void __ref __remove_memory(int nid, u64 start, u64 size) > > try_offline_node(nid); > > +done: > mem_hotplug_done(); > + return rc; > } > > -void remove_memory(int nid, u64 start, u64 size) > +/** > + * remove_memory > + * @nid: the node ID > + * @start: physical address of the region to remove > + * @size: size of the region to remove > + * > + * NOTE: The caller must call lock_device_hotplug() to serialize hotplug > + * and online/offline operations before this call, as required by > + * try_offline_node(). > + */ > +void __remove_memory(int nid, u64 start, u64 size) > +{ > + > + /* > + * trigger BUG() is some memory is not offlined prior to calling this > + * function > + */ > + if (try_remove_memory(nid, start, size)) > + BUG(); > +} > + > +/* > + * Remove memory if every memory block is offline, otherwise return -EBUSY is > + * some memory is not offline > + */ > +int remove_memory(int nid, u64 start, u64 size) > { > + int rc; > + > lock_device_hotplug(); > - __remove_memory(nid, start, size); > + rc = try_remove_memory(nid, start, size); > unlock_device_hotplug(); > + > + return rc; > } > EXPORT_SYMBOL_GPL(remove_memory); > #endif /* CONFIG_MEMORY_HOTREMOVE */ > -- > 2.21.0 >
diff --git a/include/linux/memory_hotplug.h b/include/linux/memory_hotplug.h index ae892eef8b82..988fde33cd7f 100644 --- a/include/linux/memory_hotplug.h +++ b/include/linux/memory_hotplug.h @@ -324,7 +324,7 @@ static inline void pgdat_resize_init(struct pglist_data *pgdat) {} extern bool is_mem_section_removable(unsigned long pfn, unsigned long nr_pages); extern void try_offline_node(int nid); extern int offline_pages(unsigned long start_pfn, unsigned long nr_pages); -extern void remove_memory(int nid, u64 start, u64 size); +extern int remove_memory(int nid, u64 start, u64 size); extern void __remove_memory(int nid, u64 start, u64 size); #else @@ -341,7 +341,11 @@ static inline int offline_pages(unsigned long start_pfn, unsigned long nr_pages) return -EINVAL; } -static inline void remove_memory(int nid, u64 start, u64 size) {} +static inline int remove_memory(int nid, u64 start, u64 size) +{ + return -EBUSY; +} + static inline void __remove_memory(int nid, u64 start, u64 size) {} #endif /* CONFIG_MEMORY_HOTREMOVE */ diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c index 328878b6799d..ace2cc614da4 100644 --- a/mm/memory_hotplug.c +++ b/mm/memory_hotplug.c @@ -1735,9 +1735,10 @@ static int check_memblock_offlined_cb(struct memory_block *mem, void *arg) endpa = PFN_PHYS(section_nr_to_pfn(mem->end_section_nr + 1))-1; pr_warn("removing memory fails, because memory [%pa-%pa] is onlined\n", &beginpa, &endpa); - } - return ret; + return -EBUSY; + } + return 0; } static int check_cpu_on_node(pg_data_t *pgdat) @@ -1820,19 +1821,9 @@ static void __release_memory_resource(resource_size_t start, } } -/** - * remove_memory - * @nid: the node ID - * @start: physical address of the region to remove - * @size: size of the region to remove - * - * NOTE: The caller must call lock_device_hotplug() to serialize hotplug - * and online/offline operations before this call, as required by - * try_offline_node(). - */ -void __ref __remove_memory(int nid, u64 start, u64 size) +static int __ref try_remove_memory(int nid, u64 start, u64 size) { - int ret; + int rc = 0; BUG_ON(check_hotplug_memory_range(start, size)); @@ -1840,13 +1831,13 @@ void __ref __remove_memory(int nid, u64 start, u64 size) /* * All memory blocks must be offlined before removing memory. Check - * whether all memory blocks in question are offline and trigger a BUG() + * whether all memory blocks in question are offline and return error * if this is not the case. */ - ret = walk_memory_range(PFN_DOWN(start), PFN_UP(start + size - 1), NULL, - check_memblock_offlined_cb); - if (ret) - BUG(); + rc = walk_memory_range(PFN_DOWN(start), PFN_UP(start + size - 1), NULL, + check_memblock_offlined_cb); + if (rc) + goto done; /* remove memmap entry */ firmware_map_remove(start, start + size, "System RAM"); @@ -1858,14 +1849,45 @@ void __ref __remove_memory(int nid, u64 start, u64 size) try_offline_node(nid); +done: mem_hotplug_done(); + return rc; } -void remove_memory(int nid, u64 start, u64 size) +/** + * remove_memory + * @nid: the node ID + * @start: physical address of the region to remove + * @size: size of the region to remove + * + * NOTE: The caller must call lock_device_hotplug() to serialize hotplug + * and online/offline operations before this call, as required by + * try_offline_node(). + */ +void __remove_memory(int nid, u64 start, u64 size) +{ + + /* + * trigger BUG() is some memory is not offlined prior to calling this + * function + */ + if (try_remove_memory(nid, start, size)) + BUG(); +} + +/* + * Remove memory if every memory block is offline, otherwise return -EBUSY is + * some memory is not offline + */ +int remove_memory(int nid, u64 start, u64 size) { + int rc; + lock_device_hotplug(); - __remove_memory(nid, start, size); + rc = try_remove_memory(nid, start, size); unlock_device_hotplug(); + + return rc; } EXPORT_SYMBOL_GPL(remove_memory); #endif /* CONFIG_MEMORY_HOTREMOVE */