| Message ID | 20231016-vv-kmem_memmap-v6-2-078f0d3c0371@intel.com (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | mm: use memmap_on_memory semantics for dax/kmem | expand |
Vishal Verma <vishal.l.verma@intel.com> writes: > The MHP_MEMMAP_ON_MEMORY flag for hotplugged memory is restricted to > 'memblock_size' chunks of memory being added. Adding a larger span of > memory precludes memmap_on_memory semantics. > > For users of hotplug such as kmem, large amounts of memory might get > added from the CXL subsystem. In some cases, this amount may exceed the > available 'main memory' to store the memmap for the memory being added. > In this case, it is useful to have a way to place the memmap on the > memory being added, even if it means splitting the addition into > memblock-sized chunks. > > Change add_memory_resource() to loop over memblock-sized chunks of > memory if caller requested memmap_on_memory, and if other conditions for > it are met. Teach try_remove_memory() to also expect that a memory > range being removed might have been split up into memblock sized chunks, > and to loop through those as needed. > > This does preclude being able to use PUD mappings in the direct map; a > proposal to how this could be optimized in the future is laid out > here[1]. > > [1]: https://lore.kernel.org/linux-mm/b6753402-2de9-25b2-36e9-eacd49752b19@redhat.com/ > > Cc: Andrew Morton <akpm@linux-foundation.org> > Cc: David Hildenbrand <david@redhat.com> > Cc: Michal Hocko <mhocko@suse.com> > Cc: Oscar Salvador <osalvador@suse.de> > Cc: Dan Williams <dan.j.williams@intel.com> > Cc: Dave Jiang <dave.jiang@intel.com> > Cc: Dave Hansen <dave.hansen@linux.intel.com> > Cc: Huang Ying <ying.huang@intel.com> > Suggested-by: David Hildenbrand <david@redhat.com> > Reviewed-by: Dan Williams <dan.j.williams@intel.com> > Signed-off-by: Vishal Verma <vishal.l.verma@intel.com> > --- > mm/memory_hotplug.c | 214 ++++++++++++++++++++++++++++++++++++---------------- > 1 file changed, 148 insertions(+), 66 deletions(-) > > diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c > index 6be7de9efa55..83e5ec377aad 100644 > --- a/mm/memory_hotplug.c > +++ b/mm/memory_hotplug.c > @@ -1380,6 +1380,43 @@ static bool mhp_supports_memmap_on_memory(unsigned long size) > return arch_supports_memmap_on_memory(vmemmap_size); > } > > +static int add_memory_create_devices(int nid, struct memory_group *group, > + u64 start, u64 size, mhp_t mhp_flags) > +{ > + struct mhp_params params = { .pgprot = pgprot_mhp(PAGE_KERNEL) }; > + struct vmem_altmap mhp_altmap = { > + .base_pfn = PHYS_PFN(start), > + .end_pfn = PHYS_PFN(start + size - 1), > + }; > + int ret; > + > + if ((mhp_flags & MHP_MEMMAP_ON_MEMORY)) { > + mhp_altmap.free = memory_block_memmap_on_memory_pages(); > + params.altmap = kmemdup(&mhp_altmap, sizeof(struct vmem_altmap), > + GFP_KERNEL); > + if (!params.altmap) > + return -ENOMEM; > + } > + > + /* call arch's memory hotadd */ > + ret = arch_add_memory(nid, start, size, ¶ms); > + if (ret < 0) > + goto error; > + > + /* create memory block devices after memory was added */ > + ret = create_memory_block_devices(start, size, params.altmap, group); > + if (ret) > + goto err_bdev; > + > + return 0; > + > +err_bdev: > + arch_remove_memory(start, size, NULL); > +error: > + kfree(params.altmap); > + return ret; > +} > + > /* > * NOTE: The caller must call lock_device_hotplug() to serialize hotplug > * and online/offline operations (triggered e.g. by sysfs). > @@ -1388,14 +1425,10 @@ static bool mhp_supports_memmap_on_memory(unsigned long size) > */ > int __ref add_memory_resource(int nid, struct resource *res, mhp_t mhp_flags) > { > - struct mhp_params params = { .pgprot = pgprot_mhp(PAGE_KERNEL) }; > + unsigned long memblock_size = memory_block_size_bytes(); > enum memblock_flags memblock_flags = MEMBLOCK_NONE; > - struct vmem_altmap mhp_altmap = { > - .base_pfn = PHYS_PFN(res->start), > - .end_pfn = PHYS_PFN(res->end), > - }; > struct memory_group *group = NULL; > - u64 start, size; > + u64 start, size, cur_start; > bool new_node = false; > int ret; > > @@ -1436,28 +1469,21 @@ int __ref add_memory_resource(int nid, struct resource *res, mhp_t mhp_flags) > /* > * Self hosted memmap array > */ > - if (mhp_flags & MHP_MEMMAP_ON_MEMORY) { > - if (mhp_supports_memmap_on_memory(size)) { > - mhp_altmap.free = memory_block_memmap_on_memory_pages(); > - params.altmap = kmemdup(&mhp_altmap, > - sizeof(struct vmem_altmap), > - GFP_KERNEL); > - if (!params.altmap) > + if ((mhp_flags & MHP_MEMMAP_ON_MEMORY) && > + mhp_supports_memmap_on_memory(memblock_size)) { > + for (cur_start = start; cur_start < start + size; > + cur_start += memblock_size) { > + ret = add_memory_create_devices(nid, group, cur_start, > + memblock_size, > + mhp_flags); > + if (ret) > goto error; > } > - /* fallback to not using altmap */ > - } > - > - /* call arch's memory hotadd */ > - ret = arch_add_memory(nid, start, size, ¶ms); > - if (ret < 0) > - goto error_free; > - > - /* create memory block devices after memory was added */ > - ret = create_memory_block_devices(start, size, params.altmap, group); > - if (ret) { > - arch_remove_memory(start, size, NULL); > - goto error_free; > + } else { > + ret = add_memory_create_devices(nid, group, start, size, > + mhp_flags); IIUC, if (mhp_flags & MHP_MEMMAP_ON_MEMORY) == true and mhp_supports_memmap_on_memory(memblock_size) == false, we will go here and allocate params.altmap in add_memory_create_devices(). If so, it seems better to pass whether to create altmap instead of mhp_flags to add_memory_create_devices(). -- Best Regards, Huang, Ying > + if (ret) > + goto error; > } > > if (new_node) { [snip]
On 17.10.23 07:44, Vishal Verma wrote: > The MHP_MEMMAP_ON_MEMORY flag for hotplugged memory is restricted to > 'memblock_size' chunks of memory being added. Adding a larger span of > memory precludes memmap_on_memory semantics. > > For users of hotplug such as kmem, large amounts of memory might get > added from the CXL subsystem. In some cases, this amount may exceed the > available 'main memory' to store the memmap for the memory being added. > In this case, it is useful to have a way to place the memmap on the > memory being added, even if it means splitting the addition into > memblock-sized chunks. > > Change add_memory_resource() to loop over memblock-sized chunks of > memory if caller requested memmap_on_memory, and if other conditions for > it are met. Teach try_remove_memory() to also expect that a memory > range being removed might have been split up into memblock sized chunks, > and to loop through those as needed. > > This does preclude being able to use PUD mappings in the direct map; a > proposal to how this could be optimized in the future is laid out > here[1]. > > [1]: https://lore.kernel.org/linux-mm/b6753402-2de9-25b2-36e9-eacd49752b19@redhat.com/ > > Cc: Andrew Morton <akpm@linux-foundation.org> > Cc: David Hildenbrand <david@redhat.com> > Cc: Michal Hocko <mhocko@suse.com> > Cc: Oscar Salvador <osalvador@suse.de> > Cc: Dan Williams <dan.j.williams@intel.com> > Cc: Dave Jiang <dave.jiang@intel.com> > Cc: Dave Hansen <dave.hansen@linux.intel.com> > Cc: Huang Ying <ying.huang@intel.com> > Suggested-by: David Hildenbrand <david@redhat.com> > Reviewed-by: Dan Williams <dan.j.williams@intel.com> > Signed-off-by: Vishal Verma <vishal.l.verma@intel.com> > --- > mm/memory_hotplug.c | 214 ++++++++++++++++++++++++++++++++++++---------------- > 1 file changed, 148 insertions(+), 66 deletions(-) > > diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c > index 6be7de9efa55..83e5ec377aad 100644 > --- a/mm/memory_hotplug.c > +++ b/mm/memory_hotplug.c > @@ -1380,6 +1380,43 @@ static bool mhp_supports_memmap_on_memory(unsigned long size) > return arch_supports_memmap_on_memory(vmemmap_size); > } > > +static int add_memory_create_devices(int nid, struct memory_group *group, > + u64 start, u64 size, mhp_t mhp_flags) > +{ > + struct mhp_params params = { .pgprot = pgprot_mhp(PAGE_KERNEL) }; > + struct vmem_altmap mhp_altmap = { > + .base_pfn = PHYS_PFN(start), > + .end_pfn = PHYS_PFN(start + size - 1), > + }; > + int ret; > + > + if ((mhp_flags & MHP_MEMMAP_ON_MEMORY)) { > + mhp_altmap.free = memory_block_memmap_on_memory_pages(); > + params.altmap = kmemdup(&mhp_altmap, sizeof(struct vmem_altmap), > + GFP_KERNEL); > + if (!params.altmap) > + return -ENOMEM; > + } > + > + /* call arch's memory hotadd */ > + ret = arch_add_memory(nid, start, size, ¶ms); > + if (ret < 0) > + goto error; > + > + /* create memory block devices after memory was added */ > + ret = create_memory_block_devices(start, size, params.altmap, group); > + if (ret) > + goto err_bdev; > + > + return 0; > + > +err_bdev: > + arch_remove_memory(start, size, NULL); > +error: > + kfree(params.altmap); > + return ret; > +} > + > /* > * NOTE: The caller must call lock_device_hotplug() to serialize hotplug > * and online/offline operations (triggered e.g. by sysfs). > @@ -1388,14 +1425,10 @@ static bool mhp_supports_memmap_on_memory(unsigned long size) > */ > int __ref add_memory_resource(int nid, struct resource *res, mhp_t mhp_flags) > { > - struct mhp_params params = { .pgprot = pgprot_mhp(PAGE_KERNEL) }; > + unsigned long memblock_size = memory_block_size_bytes(); > enum memblock_flags memblock_flags = MEMBLOCK_NONE; > - struct vmem_altmap mhp_altmap = { > - .base_pfn = PHYS_PFN(res->start), > - .end_pfn = PHYS_PFN(res->end), > - }; > struct memory_group *group = NULL; > - u64 start, size; > + u64 start, size, cur_start; > bool new_node = false; > int ret; > > @@ -1436,28 +1469,21 @@ int __ref add_memory_resource(int nid, struct resource *res, mhp_t mhp_flags) > /* > * Self hosted memmap array > */ > - if (mhp_flags & MHP_MEMMAP_ON_MEMORY) { > - if (mhp_supports_memmap_on_memory(size)) { > - mhp_altmap.free = memory_block_memmap_on_memory_pages(); > - params.altmap = kmemdup(&mhp_altmap, > - sizeof(struct vmem_altmap), > - GFP_KERNEL); > - if (!params.altmap) > + if ((mhp_flags & MHP_MEMMAP_ON_MEMORY) && > + mhp_supports_memmap_on_memory(memblock_size)) { > + for (cur_start = start; cur_start < start + size; > + cur_start += memblock_size) { > + ret = add_memory_create_devices(nid, group, cur_start, > + memblock_size, > + mhp_flags); Just like on the removal part, that function doesn't make any sense to be called with altmap and a bigger range. Maybe better also move that loop into a function called "create_altmap_and_memory_blocks()" , to be the opposite of "remove_memory_blocks_and_altmaps()". Then you can keep the existing !altmap code here in the "else" case. Again, similar to the removal code below. > + if (ret) > goto error; > } > - /* fallback to not using altmap */ > - } > - > - /* call arch's memory hotadd */ > - ret = arch_add_memory(nid, start, size, ¶ms); > - if (ret < 0) > - goto error_free; > - > - /* create memory block devices after memory was added */ > - ret = create_memory_block_devices(start, size, params.altmap, group); > - if (ret) { > - arch_remove_memory(start, size, NULL); > - goto error_free; > + } else { > + ret = add_memory_create_devices(nid, group, start, size, > + mhp_flags); > + if (ret) > + goto error; > } > > if (new_node) { > @@ -1494,8 +1520,6 @@ int __ref add_memory_resource(int nid, struct resource *res, mhp_t mhp_flags) > walk_memory_blocks(start, size, NULL, online_memory_block); > > return ret; > -error_free: > - kfree(params.altmap); > error: > if (IS_ENABLED(CONFIG_ARCH_KEEP_MEMBLOCK)) > memblock_remove(start, size); > @@ -2076,6 +2100,23 @@ static int test_has_altmap_cb(struct memory_block *mem, void *arg) > return 0; > } [...] > + > +static int memblocks_have_altmaps(u64 start, u64 size) > +{ > + struct memory_range_altmap_info altmap_info = { > + .num_memblocks = 0, > + .num_altmaps = 0 > + }; You can get the number of memblocks simply by "size / memory_block_size_bytes()". So you can avoid the "struct" and just pass an int. > + > + if (!mhp_memmap_on_memory()) > + return 0; > + > + walk_memory_blocks(start, size, &altmap_info, > + count_memory_range_altmaps_cb); > + > + if (!altmap_info.num_altmaps) > + return 0; > + > + if (altmap_info.num_memblocks != altmap_info.num_altmaps) { > + WARN_ONCE(1, "Not all memblocks in range have altmaps"); > + return -EINVAL; > + } > + > + return 1; > +} > + > +static int __ref try_remove_memory(u64 start, u64 size) > +{ > + int rc, nid = NUMA_NO_NODE; > > BUG_ON(check_hotplug_memory_range(start, size)); > > @@ -2167,45 +2272,21 @@ static int __ref try_remove_memory(u64 start, u64 size) > if (rc) > return rc; > > - /* > - * We only support removing memory added with MHP_MEMMAP_ON_MEMORY in > - * the same granularity it was added - a single memory block. > - */ > - if (mhp_memmap_on_memory()) { > - rc = walk_memory_blocks(start, size, &mem, test_has_altmap_cb); > - if (rc) { > - if (size != memory_block_size_bytes()) { > - pr_warn("Refuse to remove %#llx - %#llx," > - "wrong granularity\n", > - start, start + size); > - return -EINVAL; > - } > - altmap = mem->altmap; > - /* > - * Mark altmap NULL so that we can add a debug > - * check on memblock free. > - */ > - mem->altmap = NULL; > - } > - } > - > /* remove memmap entry */ > firmware_map_remove(start, start + size, "System RAM"); > > - /* > - * Memory block device removal under the device_hotplug_lock is > - * a barrier against racing online attempts. > - */ Maybe move that comment into the else branch and not into remove_memory_blocks_and_altmaps > - remove_memory_block_devices(start, size); > - > mem_hotplug_begin(); > > - arch_remove_memory(start, size, altmap); > - > - /* Verify that all vmemmap pages have actually been freed. */ > - if (altmap) { > - WARN(altmap->alloc, "Altmap not fully unmapped"); > - kfree(altmap); > + rc = memblocks_have_altmaps(start, size); Don't use the term memblocks here, to not confuse it with the memblock allocator. "memory blocks" or "memory block devices". it's complicated. > + if (rc < 0) { > + goto err; > + } else if (rc == 0) { > + /* no altmaps, do the removal directly */ > + remove_memory_block_devices(start, size); > + arch_remove_memory(start, size, NULL); > + } else { > + /* all memblocks in the range have altmaps */ > + remove_memory_blocks_and_altmaps(start, size); > } > > if (IS_ENABLED(CONFIG_ARCH_KEEP_MEMBLOCK)) { > @@ -2218,8 +2299,9 @@ static int __ref try_remove_memory(u64 start, u64 size) > if (nid != NUMA_NO_NODE) > try_offline_node(nid); > > +err: > mem_hotplug_done(); > - return 0; > + return (rc < 0 ? rc : 0); > } > > /** >
diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c index 6be7de9efa55..83e5ec377aad 100644 --- a/mm/memory_hotplug.c +++ b/mm/memory_hotplug.c @@ -1380,6 +1380,43 @@ static bool mhp_supports_memmap_on_memory(unsigned long size) return arch_supports_memmap_on_memory(vmemmap_size); } +static int add_memory_create_devices(int nid, struct memory_group *group, + u64 start, u64 size, mhp_t mhp_flags) +{ + struct mhp_params params = { .pgprot = pgprot_mhp(PAGE_KERNEL) }; + struct vmem_altmap mhp_altmap = { + .base_pfn = PHYS_PFN(start), + .end_pfn = PHYS_PFN(start + size - 1), + }; + int ret; + + if ((mhp_flags & MHP_MEMMAP_ON_MEMORY)) { + mhp_altmap.free = memory_block_memmap_on_memory_pages(); + params.altmap = kmemdup(&mhp_altmap, sizeof(struct vmem_altmap), + GFP_KERNEL); + if (!params.altmap) + return -ENOMEM; + } + + /* call arch's memory hotadd */ + ret = arch_add_memory(nid, start, size, ¶ms); + if (ret < 0) + goto error; + + /* create memory block devices after memory was added */ + ret = create_memory_block_devices(start, size, params.altmap, group); + if (ret) + goto err_bdev; + + return 0; + +err_bdev: + arch_remove_memory(start, size, NULL); +error: + kfree(params.altmap); + return ret; +} + /* * NOTE: The caller must call lock_device_hotplug() to serialize hotplug * and online/offline operations (triggered e.g. by sysfs). @@ -1388,14 +1425,10 @@ static bool mhp_supports_memmap_on_memory(unsigned long size) */ int __ref add_memory_resource(int nid, struct resource *res, mhp_t mhp_flags) { - struct mhp_params params = { .pgprot = pgprot_mhp(PAGE_KERNEL) }; + unsigned long memblock_size = memory_block_size_bytes(); enum memblock_flags memblock_flags = MEMBLOCK_NONE; - struct vmem_altmap mhp_altmap = { - .base_pfn = PHYS_PFN(res->start), - .end_pfn = PHYS_PFN(res->end), - }; struct memory_group *group = NULL; - u64 start, size; + u64 start, size, cur_start; bool new_node = false; int ret; @@ -1436,28 +1469,21 @@ int __ref add_memory_resource(int nid, struct resource *res, mhp_t mhp_flags) /* * Self hosted memmap array */ - if (mhp_flags & MHP_MEMMAP_ON_MEMORY) { - if (mhp_supports_memmap_on_memory(size)) { - mhp_altmap.free = memory_block_memmap_on_memory_pages(); - params.altmap = kmemdup(&mhp_altmap, - sizeof(struct vmem_altmap), - GFP_KERNEL); - if (!params.altmap) + if ((mhp_flags & MHP_MEMMAP_ON_MEMORY) && + mhp_supports_memmap_on_memory(memblock_size)) { + for (cur_start = start; cur_start < start + size; + cur_start += memblock_size) { + ret = add_memory_create_devices(nid, group, cur_start, + memblock_size, + mhp_flags); + if (ret) goto error; } - /* fallback to not using altmap */ - } - - /* call arch's memory hotadd */ - ret = arch_add_memory(nid, start, size, ¶ms); - if (ret < 0) - goto error_free; - - /* create memory block devices after memory was added */ - ret = create_memory_block_devices(start, size, params.altmap, group); - if (ret) { - arch_remove_memory(start, size, NULL); - goto error_free; + } else { + ret = add_memory_create_devices(nid, group, start, size, + mhp_flags); + if (ret) + goto error; } if (new_node) { @@ -1494,8 +1520,6 @@ int __ref add_memory_resource(int nid, struct resource *res, mhp_t mhp_flags) walk_memory_blocks(start, size, NULL, online_memory_block); return ret; -error_free: - kfree(params.altmap); error: if (IS_ENABLED(CONFIG_ARCH_KEEP_MEMBLOCK)) memblock_remove(start, size); @@ -2076,6 +2100,23 @@ static int test_has_altmap_cb(struct memory_block *mem, void *arg) return 0; } +struct memory_range_altmap_info { + u64 num_memblocks; + u64 num_altmaps; +}; + +static int count_memory_range_altmaps_cb(struct memory_block *mem, void *arg) +{ + struct memory_range_altmap_info *altmap_info = + (struct memory_range_altmap_info *)arg; + + altmap_info->num_memblocks += 1; + if (mem->altmap) + altmap_info->num_altmaps += 1; + + return 0; +} + static int check_cpu_on_node(int nid) { int cpu; @@ -2146,11 +2187,75 @@ void try_offline_node(int nid) } EXPORT_SYMBOL(try_offline_node); -static int __ref try_remove_memory(u64 start, u64 size) +static void __ref remove_memory_blocks_and_altmaps(u64 start, u64 size) { - struct memory_block *mem; - int rc = 0, nid = NUMA_NO_NODE; + unsigned long memblock_size = memory_block_size_bytes(); struct vmem_altmap *altmap = NULL; + struct memory_block *mem; + u64 cur_start; + int rc; + + /* + * For memmap_on_memory, the altmaps could have been added on + * a per-memblock basis. Loop through the entire range if so, + * and remove each memblock and its altmap. + */ + for (cur_start = start; cur_start < start + size; + cur_start += memblock_size) { + rc = walk_memory_blocks(cur_start, memblock_size, &mem, + test_has_altmap_cb); + if (rc) { + altmap = mem->altmap; + /* + * Mark altmap NULL so that we can add a debug + * check on memblock free. + */ + mem->altmap = NULL; + } + + /* + * Memory block device removal under the device_hotplug_lock is + * a barrier against racing online attempts. + */ + remove_memory_block_devices(cur_start, memblock_size); + + arch_remove_memory(cur_start, memblock_size, altmap); + + /* Verify that all vmemmap pages have actually been freed. */ + if (altmap) { + WARN(altmap->alloc, "Altmap not fully unmapped"); + kfree(altmap); + } + } +} + +static int memblocks_have_altmaps(u64 start, u64 size) +{ + struct memory_range_altmap_info altmap_info = { + .num_memblocks = 0, + .num_altmaps = 0 + }; + + if (!mhp_memmap_on_memory()) + return 0; + + walk_memory_blocks(start, size, &altmap_info, + count_memory_range_altmaps_cb); + + if (!altmap_info.num_altmaps) + return 0; + + if (altmap_info.num_memblocks != altmap_info.num_altmaps) { + WARN_ONCE(1, "Not all memblocks in range have altmaps"); + return -EINVAL; + } + + return 1; +} + +static int __ref try_remove_memory(u64 start, u64 size) +{ + int rc, nid = NUMA_NO_NODE; BUG_ON(check_hotplug_memory_range(start, size)); @@ -2167,45 +2272,21 @@ static int __ref try_remove_memory(u64 start, u64 size) if (rc) return rc; - /* - * We only support removing memory added with MHP_MEMMAP_ON_MEMORY in - * the same granularity it was added - a single memory block. - */ - if (mhp_memmap_on_memory()) { - rc = walk_memory_blocks(start, size, &mem, test_has_altmap_cb); - if (rc) { - if (size != memory_block_size_bytes()) { - pr_warn("Refuse to remove %#llx - %#llx," - "wrong granularity\n", - start, start + size); - return -EINVAL; - } - altmap = mem->altmap; - /* - * Mark altmap NULL so that we can add a debug - * check on memblock free. - */ - mem->altmap = NULL; - } - } - /* remove memmap entry */ firmware_map_remove(start, start + size, "System RAM"); - /* - * Memory block device removal under the device_hotplug_lock is - * a barrier against racing online attempts. - */ - remove_memory_block_devices(start, size); - mem_hotplug_begin(); - arch_remove_memory(start, size, altmap); - - /* Verify that all vmemmap pages have actually been freed. */ - if (altmap) { - WARN(altmap->alloc, "Altmap not fully unmapped"); - kfree(altmap); + rc = memblocks_have_altmaps(start, size); + if (rc < 0) { + goto err; + } else if (rc == 0) { + /* no altmaps, do the removal directly */ + remove_memory_block_devices(start, size); + arch_remove_memory(start, size, NULL); + } else { + /* all memblocks in the range have altmaps */ + remove_memory_blocks_and_altmaps(start, size); } if (IS_ENABLED(CONFIG_ARCH_KEEP_MEMBLOCK)) { @@ -2218,8 +2299,9 @@ static int __ref try_remove_memory(u64 start, u64 size) if (nid != NUMA_NO_NODE) try_offline_node(nid); +err: mem_hotplug_done(); - return 0; + return (rc < 0 ? rc : 0); } /**