The patch titled
Subject: kernel/resource: make release_mem_region_adjustable() never fail
has been added to the -mm tree. Its filename is
kernel-resource-make-release_mem_region_adjustable-never-fail.patch
This patch should soon appear at
https://ozlabs.org/~akpm/mmots/broken-out/kernel-resource-make-release_mem_region_adjustable-never-fail.patch
and later at
https://ozlabs.org/~akpm/mmotm/broken-out/kernel-resource-make-release_mem_region_adjustable-never-fail.patch
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*** Remember to use Documentation/process/submit-checklist.rst when testing your code ***
The -mm tree is included into linux-next and is updated
there every 3-4 working days
------------------------------------------------------
From: David Hildenbrand <david@xxxxxxxxxx>
Subject: kernel/resource: make release_mem_region_adjustable() never fail
Patch series "selective merging of system ram resources", v4.
Some add_memory*() users add memory in small, contiguous memory blocks.
Examples include virtio-mem, hyper-v balloon, and the XEN balloon.
This can quickly result in a lot of memory resources, whereby the actual
resource boundaries are not of interest (e.g., it might be relevant for
DIMMs, exposed via /proc/iomem to user space). We really want to merge
added resources in this scenario where possible.
Resources are effectively stored in a list-based tree. Having a lot of
resources not only wastes memory, it also makes traversing that tree more
expensive, and makes /proc/iomem explode in size (e.g., requiring
kexec-tools to manually merge resources when creating a kdump header. The
current kexec-tools resource count limit does not allow for more than
~100GB of memory with a memory block size of 128MB on x86-64).
Let's allow to selectively merge system ram resources by specifying a new
flag for add_memory*(). Patch #5 contains a /proc/iomem example. Only
tested with virtio-mem.
This patch (of 8):
Let's make sure splitting a resource on memory hotunplug will never fail.
This will become more relevant once we merge selected System RAM resources
- then, we'll trigger that case more often on memory hotunplug.
In general, this function is already unlikely to fail. When we remove
memory, we free up quite a lot of metadata (memmap, page tables, memory
block device, etc.). The only reason it could really fail would be when
injecting allocation errors.
All other error cases inside release_mem_region_adjustable() seem to be
sanity checks if the function would be abused in different context - let's
add WARN_ON_ONCE() in these cases so we can catch them.
Link: https://lkml.kernel.org/r/20200911103459.10306-2-david@xxxxxxxxxx
Signed-off-by: David Hildenbrand <david@xxxxxxxxxx>
Cc: Michal Hocko <mhocko@xxxxxxxx>
Cc: Dan Williams <dan.j.williams@xxxxxxxxx>
Cc: Jason Gunthorpe <jgg@xxxxxxxx>
Cc: Kees Cook <keescook@xxxxxxxxxxxx>
Cc: Ard Biesheuvel <ardb@xxxxxxxxxx>
Cc: Pankaj Gupta <pankaj.gupta.linux@xxxxxxxxx>
Cc: Baoquan He <bhe@xxxxxxxxxx>
Cc: Wei Yang <richardw.yang@xxxxxxxxxxxxxxx>
Cc: Anton Blanchard <anton@xxxxxxxxxx>
Cc: Benjamin Herrenschmidt <benh@xxxxxxxxxxxxxxxxxxx>
Cc: Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>
Cc: Christian Borntraeger <borntraeger@xxxxxxxxxx>
Cc: Dave Jiang <dave.jiang@xxxxxxxxx>
Cc: Eric Biederman <ebiederm@xxxxxxxxxxxx>
Cc: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
Cc: Haiyang Zhang <haiyangz@xxxxxxxxxxxxx>
Cc: Heiko Carstens <hca@xxxxxxxxxxxxx>
Cc: Jason Wang <jasowang@xxxxxxxxxx>
Cc: Juergen Gross <jgross@xxxxxxxx>
Cc: Julien Grall <julien@xxxxxxx>
Cc: "K. Y. Srinivasan" <kys@xxxxxxxxxxxxx>
Cc: Len Brown <lenb@xxxxxxxxxx>
Cc: Leonardo Bras <leobras.c@xxxxxxxxx>
Cc: Libor Pechacek <lpechacek@xxxxxxx>
Cc: Michael Ellerman <mpe@xxxxxxxxxxxxxx>
Cc: "Michael S. Tsirkin" <mst@xxxxxxxxxx>
Cc: Nathan Lynch <nathanl@xxxxxxxxxxxxx>
Cc: "Oliver O'Halloran" <oohall@xxxxxxxxx>
Cc: Paul Mackerras <paulus@xxxxxxxxx>
Cc: Pingfan Liu <kernelfans@xxxxxxxxx>
Cc: "Rafael J. Wysocki" <rjw@xxxxxxxxxxxxx>
Cc: Roger Pau Monn <roger.pau@xxxxxxxxxx>
Cc: Stefano Stabellini <sstabellini@xxxxxxxxxx>
Cc: Stephen Hemminger <sthemmin@xxxxxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Vasily Gorbik <gor@xxxxxxxxxxxxx>
Cc: Vishal Verma <vishal.l.verma@xxxxxxxxx>
Cc: Wei Liu <wei.liu@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
include/linux/ioport.h | 4 +--
kernel/resource.c | 49 ++++++++++++++++++++++-----------------
mm/memory_hotplug.c | 22 -----------------
3 files changed, 31 insertions(+), 44 deletions(-)
--- a/include/linux/ioport.h~kernel-resource-make-release_mem_region_adjustable-never-fail
+++ a/include/linux/ioport.h
@@ -248,8 +248,8 @@ extern struct resource * __request_regio
extern void __release_region(struct resource *, resource_size_t,
resource_size_t);
#ifdef CONFIG_MEMORY_HOTREMOVE
-extern int release_mem_region_adjustable(struct resource *, resource_size_t,
- resource_size_t);
+extern void release_mem_region_adjustable(struct resource *, resource_size_t,
+ resource_size_t);
#endif
/* Wrappers for managed devices */
--- a/kernel/resource.c~kernel-resource-make-release_mem_region_adjustable-never-fail
+++ a/kernel/resource.c
@@ -1258,21 +1258,28 @@ EXPORT_SYMBOL(__release_region);
* assumes that all children remain in the lower address entry for
* simplicity. Enhance this logic when necessary.
*/
-int release_mem_region_adjustable(struct resource *parent,
- resource_size_t start, resource_size_t size)
+void release_mem_region_adjustable(struct resource *parent,
+ resource_size_t start, resource_size_t size)
{
+ struct resource *new_res = NULL;
+ bool alloc_nofail = false;
struct resource **p;
struct resource *res;
- struct resource *new_res;
resource_size_t end;
- int ret = -EINVAL;
end = start + size - 1;
- if ((start < parent->start) || (end > parent->end))
- return ret;
+ if (WARN_ON_ONCE((start < parent->start) || (end > parent->end)))
+ return;
- /* The alloc_resource() result gets checked later */
- new_res = alloc_resource(GFP_KERNEL);
+ /*
+ * We free up quite a lot of memory on memory hotunplug (esp., memap),
+ * just before releasing the region. This is highly unlikely to
+ * fail - let's play save and make it never fail as the caller cannot
+ * perform any error handling (e.g., trying to re-add memory will fail
+ * similarly).
+ */
+retry:
+ new_res = alloc_resource(GFP_KERNEL | alloc_nofail ? __GFP_NOFAIL : 0);
p = &parent->child;
write_lock(&resource_lock);
@@ -1298,7 +1305,6 @@ int release_mem_region_adjustable(struct
* so if we are dealing with them, let us just back off here.
*/
if (!(res->flags & IORESOURCE_SYSRAM)) {
- ret = 0;
break;
}
@@ -1315,20 +1321,23 @@ int release_mem_region_adjustable(struct
/* free the whole entry */
*p = res->sibling;
free_resource(res);
- ret = 0;
} else if (res->start == start && res->end != end) {
/* adjust the start */
- ret = __adjust_resource(res, end + 1,
- res->end - end);
+ WARN_ON_ONCE(__adjust_resource(res, end + 1,
+ res->end - end));
} else if (res->start != start && res->end == end) {
/* adjust the end */
- ret = __adjust_resource(res, res->start,
- start - res->start);
+ WARN_ON_ONCE(__adjust_resource(res, res->start,
+ start - res->start));
} else {
- /* split into two entries */
+ /* split into two entries - we need a new resource */
if (!new_res) {
- ret = -ENOMEM;
- break;
+ new_res = alloc_resource(GFP_ATOMIC);
+ if (!new_res) {
+ alloc_nofail = true;
+ write_unlock(&resource_lock);
+ goto retry;
+ }
}
new_res->name = res->name;
new_res->start = end + 1;
@@ -1339,9 +1348,8 @@ int release_mem_region_adjustable(struct
new_res->sibling = res->sibling;
new_res->child = NULL;
- ret = __adjust_resource(res, res->start,
- start - res->start);
- if (ret)
+ if (WARN_ON_ONCE(__adjust_resource(res, res->start,
+ start - res->start)))
break;
res->sibling = new_res;
new_res = NULL;
@@ -1352,7 +1360,6 @@ int release_mem_region_adjustable(struct
write_unlock(&resource_lock);
free_resource(new_res);
- return ret;
}
#endif /* CONFIG_MEMORY_HOTREMOVE */
--- a/mm/memory_hotplug.c~kernel-resource-make-release_mem_region_adjustable-never-fail
+++ a/mm/memory_hotplug.c
@@ -1726,26 +1726,6 @@ void try_offline_node(int nid)
}
EXPORT_SYMBOL(try_offline_node);
-static void __release_memory_resource(resource_size_t start,
- resource_size_t size)
-{
- int ret;
-
- /*
- * When removing memory in the same granularity as it was added,
- * this function never fails. It might only fail if resources
- * have to be adjusted or split. We'll ignore the error, as
- * removing of memory cannot fail.
- */
- ret = release_mem_region_adjustable(&iomem_resource, start, size);
- if (ret) {
- resource_size_t endres = start + size - 1;
-
- pr_warn("Unable to release resource <%pa-%pa> (%d)\n",
- &start, &endres, ret);
- }
-}
-
static int __ref try_remove_memory(int nid, u64 start, u64 size)
{
int rc = 0;
@@ -1779,7 +1759,7 @@ static int __ref try_remove_memory(int n
memblock_remove(start, size);
}
- __release_memory_resource(start, size);
+ release_mem_region_adjustable(&iomem_resource, start, size);
try_offline_node(nid);
_
Patches currently in -mm which might be from david@xxxxxxxxxx are
mm-page_alloc-tweak-comments-in-has_unmovable_pages.patch
mm-page_isolation-exit-early-when-pageblock-is-isolated-in-set_migratetype_isolate.patch
mm-page_isolation-drop-warn_on_once-in-set_migratetype_isolate.patch
mm-page_isolation-cleanup-set_migratetype_isolate.patch
virtio-mem-dont-special-case-zone_movable.patch
mm-document-semantics-of-zone_movable.patch
mm-memory_hotplug-inline-__offline_pages-into-offline_pages.patch
mm-memory_hotplug-enforce-section-granularity-when-onlining-offlining.patch
mm-memory_hotplug-simplify-page-offlining.patch
mm-page_alloc-simplify-__offline_isolated_pages.patch
mm-memory_hotplug-drop-nr_isolate_pageblock-in-offline_pages.patch
mm-page_isolation-simplify-return-value-of-start_isolate_page_range.patch
mm-memory_hotplug-simplify-page-onlining.patch
mm-page_alloc-drop-stale-pageblock-comment-in-memmap_init_zone.patch
mm-pass-migratetype-into-memmap_init_zone-and-move_pfn_range_to_zone.patch
mm-memory_hotplug-mark-pageblocks-migrate_isolate-while-onlining-memory.patch
kernel-resource-make-release_mem_region_adjustable-never-fail.patch
kernel-resource-move-and-rename-ioresource_mem_driver_managed.patch
mm-memory_hotplug-guard-more-declarations-by-config_memory_hotplug.patch
mm-memory_hotplug-prepare-passing-flags-to-add_memory-and-friends.patch
mm-memory_hotplug-memhp_merge_resource-to-specify-merging-of-system-ram-resources.patch
virtio-mem-try-to-merge-system-ram-resources.patch
xen-balloon-try-to-merge-system-ram-resources.patch
hv_balloon-try-to-merge-system-ram-resources.patch
