[PATCH v4 1/8] kernel/resource: make release_mem_region_adjustable() never fail

[PATCH v4 1/8] kernel/resource: make release_mem_region_adjustable() never fail

[David Hildenbrand]

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.

Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Jason Gunthorpe <jgg@ziepe.ca>
Cc: Kees Cook <keescook@chromium.org>
Cc: Ard Biesheuvel <ardb@kernel.org>
Cc: Pankaj Gupta <pankaj.gupta.linux@gmail.com>
Cc: Baoquan He <bhe@redhat.com>
Cc: Wei Yang <richardw.yang@linux.intel.com>
Signed-off-by: David Hildenbrand <david@redhat.com>
---
 include/linux/ioport.h |  4 ++--
 kernel/resource.c      | 49 ++++++++++++++++++++++++------------------
 mm/memory_hotplug.c    | 22 +------------------
 3 files changed, 31 insertions(+), 44 deletions(-)

diff --git a/include/linux/ioport.h b/include/linux/ioport.h
index 6c2b06fe8beb7..52a91f5fa1a36 100644
--- a/include/linux/ioport.h
+++ b/include/linux/ioport.h
@@ -248,8 +248,8 @@ extern struct resource * __request_region(struct resource *,
 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 */
diff --git a/kernel/resource.c b/kernel/resource.c
index f1175ce93a1d5..36b3552210120 100644
--- a/kernel/resource.c
+++ b/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 resource *parent,
 		 * 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 resource *parent,
 			/* 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 resource *parent,
 			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 resource *parent,
 
 	write_unlock(&resource_lock);
 	free_resource(new_res);
-	return ret;
 }
 #endif	/* CONFIG_MEMORY_HOTREMOVE */
 
diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
index baded53b9ff92..4c47b68a9f4b5 100644
--- a/mm/memory_hotplug.c
+++ b/mm/memory_hotplug.c
@@ -1724,26 +1724,6 @@ 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;
@@ -1777,7 +1757,7 @@ static int __ref try_remove_memory(int nid, u64 start, u64 size)
 		memblock_remove(start, size);
 	}
 
-	__release_memory_resource(start, size);
+	release_mem_region_adjustable(&iomem_resource, start, size);
 
 	try_offline_node(nid);
 
-- 
2.26.2

[PATCH] kernel/resource: Fix use of ternary condition in release_mem_region_adjustable

[Nathan Chancellor]

Clang warns:

kernel/resource.c:1281:53: warning: operator '?:' has lower precedence
than '|'; '|' will be evaluated first
[-Wbitwise-conditional-parentheses]
        new_res = alloc_resource(GFP_KERNEL | alloc_nofail ? __GFP_NOFAIL : 0);
                                 ~~~~~~~~~~~~~~~~~~~~~~~~~ ^
kernel/resource.c:1281:53: note: place parentheses around the '|'
expression to silence this warning
        new_res = alloc_resource(GFP_KERNEL | alloc_nofail ? __GFP_NOFAIL : 0);
                                 ~~~~~~~~~~~~~~~~~~~~~~~~~ ^
kernel/resource.c:1281:53: note: place parentheses around the '?:'
expression to evaluate it first
        new_res = alloc_resource(GFP_KERNEL | alloc_nofail ? __GFP_NOFAIL : 0);
                                                           ^
                                              (                              )
1 warning generated.

Add the parentheses as it was clearly intended for the ternary condition
to be evaluated first.

Fixes: 5fd23bd0d739 ("kernel/resource: make release_mem_region_adjustable() never fail")
Link: https://github.com/ClangBuiltLinux/linux/issues/1159
Signed-off-by: Nathan Chancellor <natechancellor@gmail.com>
---

Presumably, this will be squashed but I included a fixes tag
nonetheless. Apologies if this has already been noticed and fixed
already, I did not find anything on LKML.

 kernel/resource.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/resource.c b/kernel/resource.c
index ca2a666e4317..3ae2f56cc79d 100644
--- a/kernel/resource.c
+++ b/kernel/resource.c
@@ -1278,7 +1278,7 @@ void release_mem_region_adjustable(resource_size_t start, resource_size_t size)
 	 * similarly).
 	 */
 retry:
-	new_res = alloc_resource(GFP_KERNEL | alloc_nofail ? __GFP_NOFAIL : 0);
+	new_res = alloc_resource(GFP_KERNEL | (alloc_nofail ? __GFP_NOFAIL : 0));
 
 	p = &parent->child;
 	write_lock(&resource_lock);

base-commit: 40ee82f47bf297e31d0c47547cd8f24ede52415a
-- 
2.28.0

Re: [PATCH] kernel/resource: Fix use of ternary condition in release_mem_region_adjustable

[David Hildenbrand]

On 22.09.20 08:07, Nathan Chancellor wrote:
> Clang warns:
> 
> kernel/resource.c:1281:53: warning: operator '?:' has lower precedence
> than '|'; '|' will be evaluated first
> [-Wbitwise-conditional-parentheses]
>         new_res = alloc_resource(GFP_KERNEL | alloc_nofail ? __GFP_NOFAIL : 0);
>                                  ~~~~~~~~~~~~~~~~~~~~~~~~~ ^
> kernel/resource.c:1281:53: note: place parentheses around the '|'
> expression to silence this warning
>         new_res = alloc_resource(GFP_KERNEL | alloc_nofail ? __GFP_NOFAIL : 0);
>                                  ~~~~~~~~~~~~~~~~~~~~~~~~~ ^
> kernel/resource.c:1281:53: note: place parentheses around the '?:'
> expression to evaluate it first
>         new_res = alloc_resource(GFP_KERNEL | alloc_nofail ? __GFP_NOFAIL : 0);
>                                                            ^
>                                               (                              )
> 1 warning generated.
> 
> Add the parentheses as it was clearly intended for the ternary condition
> to be evaluated first.
> 
> Fixes: 5fd23bd0d739 ("kernel/resource: make release_mem_region_adjustable() never fail")
> Link: https://github.com/ClangBuiltLinux/linux/issues/1159
> Signed-off-by: Nathan Chancellor <natechancellor@gmail.com>
> ---
> 
> Presumably, this will be squashed but I included a fixes tag
> nonetheless. Apologies if this has already been noticed and fixed
> already, I did not find anything on LKML.

Hasn't been noticed before (I guess most people build with GCC, which
does not warn in this instance, at least for me) thanks!

Commit ids are not stable yet, so Andrew will most probably squash it.

Reviewed-by: David Hildenbrand <david@redhat.com>

> 
>  kernel/resource.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/kernel/resource.c b/kernel/resource.c
> index ca2a666e4317..3ae2f56cc79d 100644
> --- a/kernel/resource.c
> +++ b/kernel/resource.c
> @@ -1278,7 +1278,7 @@ void release_mem_region_adjustable(resource_size_t start, resource_size_t size)
>  	 * similarly).
>  	 */
>  retry:
> -	new_res = alloc_resource(GFP_KERNEL | alloc_nofail ? __GFP_NOFAIL : 0);
> +	new_res = alloc_resource(GFP_KERNEL | (alloc_nofail ? __GFP_NOFAIL : 0));
>  
>  	p = &parent->child;
>  	write_lock(&resource_lock);
> 
> base-commit: 40ee82f47bf297e31d0c47547cd8f24ede52415a
> 


-- 
Thanks,

David / dhildenb

Re: [PATCH] kernel/resource: Fix use of ternary condition in release_mem_region_adjustable

[Wei Yang]

On Mon, Sep 21, 2020 at 11:07:48PM -0700, Nathan Chancellor wrote:
>Clang warns:
>
>kernel/resource.c:1281:53: warning: operator '?:' has lower precedence
>than '|'; '|' will be evaluated first
>[-Wbitwise-conditional-parentheses]
>        new_res = alloc_resource(GFP_KERNEL | alloc_nofail ? __GFP_NOFAIL : 0);
>                                 ~~~~~~~~~~~~~~~~~~~~~~~~~ ^
>kernel/resource.c:1281:53: note: place parentheses around the '|'
>expression to silence this warning
>        new_res = alloc_resource(GFP_KERNEL | alloc_nofail ? __GFP_NOFAIL : 0);
>                                 ~~~~~~~~~~~~~~~~~~~~~~~~~ ^
>kernel/resource.c:1281:53: note: place parentheses around the '?:'
>expression to evaluate it first
>        new_res = alloc_resource(GFP_KERNEL | alloc_nofail ? __GFP_NOFAIL : 0);
>                                                           ^
>                                              (                              )
>1 warning generated.
>
>Add the parentheses as it was clearly intended for the ternary condition
>to be evaluated first.
>
>Fixes: 5fd23bd0d739 ("kernel/resource: make release_mem_region_adjustable() never fail")
>Link: https://github.com/ClangBuiltLinux/linux/issues/1159
>Signed-off-by: Nathan Chancellor <natechancellor@gmail.com>

Reviewed-by: Wei Yang <richard.weiyang@linux.alibaba.com>

>---
>
>Presumably, this will be squashed but I included a fixes tag
>nonetheless. Apologies if this has already been noticed and fixed
>already, I did not find anything on LKML.
>
> kernel/resource.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
>diff --git a/kernel/resource.c b/kernel/resource.c
>index ca2a666e4317..3ae2f56cc79d 100644
>--- a/kernel/resource.c
>+++ b/kernel/resource.c
>@@ -1278,7 +1278,7 @@ void release_mem_region_adjustable(resource_size_t start, resource_size_t size)
> 	 * similarly).
> 	 */
> retry:
>-	new_res = alloc_resource(GFP_KERNEL | alloc_nofail ? __GFP_NOFAIL : 0);
>+	new_res = alloc_resource(GFP_KERNEL | (alloc_nofail ? __GFP_NOFAIL : 0));
> 
> 	p = &parent->child;
> 	write_lock(&resource_lock);
>
>base-commit: 40ee82f47bf297e31d0c47547cd8f24ede52415a
>-- 
>2.28.0

-- 
Wei Yang
Help you, Help me

[PATCH v4 2/8] kernel/resource: move and rename IORESOURCE_MEM_DRIVER_MANAGED

[David Hildenbrand]

IORESOURCE_MEM_DRIVER_MANAGED currently uses an unused PnP bit, which is
always set to 0 by hardware. This is far from beautiful (and confusing),
and the bit only applies to SYSRAM. So let's move it out of the
bus-specific (PnP) defined bits.

We'll add another SYSRAM specific bit soon. If we ever need more bits for
other purposes, we can steal some from "desc", or reshuffle/regroup what we
have.

Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Jason Gunthorpe <jgg@ziepe.ca>
Cc: Kees Cook <keescook@chromium.org>
Cc: Ard Biesheuvel <ardb@kernel.org>
Cc: Pankaj Gupta <pankaj.gupta.linux@gmail.com>
Cc: Baoquan He <bhe@redhat.com>
Cc: Wei Yang <richardw.yang@linux.intel.com>
Cc: Eric Biederman <ebiederm@xmission.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: kexec@lists.infradead.org
Signed-off-by: David Hildenbrand <david@redhat.com>
---
 include/linux/ioport.h | 4 +++-
 kernel/kexec_file.c    | 2 +-
 mm/memory_hotplug.c    | 4 ++--
 3 files changed, 6 insertions(+), 4 deletions(-)

diff --git a/include/linux/ioport.h b/include/linux/ioport.h
index 52a91f5fa1a36..d7620d7c941a0 100644
--- a/include/linux/ioport.h
+++ b/include/linux/ioport.h
@@ -58,6 +58,9 @@ struct resource {
 #define IORESOURCE_EXT_TYPE_BITS 0x01000000	/* Resource extended types */
 #define IORESOURCE_SYSRAM	0x01000000	/* System RAM (modifier) */
 
+/* IORESOURCE_SYSRAM specific bits. */
+#define IORESOURCE_SYSRAM_DRIVER_MANAGED	0x02000000 /* Always detected via a driver. */
+
 #define IORESOURCE_EXCLUSIVE	0x08000000	/* Userland may not map this resource */
 
 #define IORESOURCE_DISABLED	0x10000000
@@ -103,7 +106,6 @@ struct resource {
 #define IORESOURCE_MEM_32BIT		(3<<3)
 #define IORESOURCE_MEM_SHADOWABLE	(1<<5)	/* dup: IORESOURCE_SHADOWABLE */
 #define IORESOURCE_MEM_EXPANSIONROM	(1<<6)
-#define IORESOURCE_MEM_DRIVER_MANAGED	(1<<7)
 
 /* PnP I/O specific bits (IORESOURCE_BITS) */
 #define IORESOURCE_IO_16BIT_ADDR	(1<<0)
diff --git a/kernel/kexec_file.c b/kernel/kexec_file.c
index ca40bef75a616..dfeeed1aed084 100644
--- a/kernel/kexec_file.c
+++ b/kernel/kexec_file.c
@@ -520,7 +520,7 @@ static int locate_mem_hole_callback(struct resource *res, void *arg)
 	/* Returning 0 will take to next memory range */
 
 	/* Don't use memory that will be detected and handled by a driver. */
-	if (res->flags & IORESOURCE_MEM_DRIVER_MANAGED)
+	if (res->flags & IORESOURCE_SYSRAM_DRIVER_MANAGED)
 		return 0;
 
 	if (sz < kbuf->memsz)
diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
index 4c47b68a9f4b5..8e1cd18b5cf14 100644
--- a/mm/memory_hotplug.c
+++ b/mm/memory_hotplug.c
@@ -105,7 +105,7 @@ static struct resource *register_memory_resource(u64 start, u64 size,
 	unsigned long flags =  IORESOURCE_SYSTEM_RAM | IORESOURCE_BUSY;
 
 	if (strcmp(resource_name, "System RAM"))
-		flags |= IORESOURCE_MEM_DRIVER_MANAGED;
+		flags |= IORESOURCE_SYSRAM_DRIVER_MANAGED;
 
 	/*
 	 * Make sure value parsed from 'mem=' only restricts memory adding
@@ -1160,7 +1160,7 @@ EXPORT_SYMBOL_GPL(add_memory);
  *
  * For this memory, no entries in /sys/firmware/memmap ("raw firmware-provided
  * memory map") are created. Also, the created memory resource is flagged
- * with IORESOURCE_MEM_DRIVER_MANAGED, so in-kernel users can special-case
+ * with IORESOURCE_SYSRAM_DRIVER_MANAGED, so in-kernel users can special-case
  * this memory as well (esp., not place kexec images onto it).
  *
  * The resource_name (visible via /proc/iomem) has to have the format
-- 
2.26.2

[PATCH v4 3/8] mm/memory_hotplug: guard more declarations by CONFIG_MEMORY_HOTPLUG

[David Hildenbrand]

We soon want to pass flags via a new type to add_memory() and friends.
That revealed that we currently don't guard some declarations by
CONFIG_MEMORY_HOTPLUG.

While some definitions could be moved to different places, let's keep it
minimal for now and use CONFIG_MEMORY_HOTPLUG for all functions only
compiled with CONFIG_MEMORY_HOTPLUG.

Wrap sparse_decode_mem_map() into CONFIG_MEMORY_HOTPLUG, it's only
called from CONFIG_MEMORY_HOTPLUG code.

While at it, remove allow_online_pfn_range(), which is no longer around,
and mhp_notimplemented(), which is unused.

Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Pankaj Gupta <pankaj.gupta.linux@gmail.com>
Cc: Baoquan He <bhe@redhat.com>
Cc: Wei Yang <richardw.yang@linux.intel.com>
Signed-off-by: David Hildenbrand <david@redhat.com>
---
 include/linux/memory_hotplug.h | 12 +++---------
 mm/sparse.c                    |  2 ++
 2 files changed, 5 insertions(+), 9 deletions(-)

diff --git a/include/linux/memory_hotplug.h b/include/linux/memory_hotplug.h
index 51a877fec8da8..1504b4d5ae6ce 100644
--- a/include/linux/memory_hotplug.h
+++ b/include/linux/memory_hotplug.h
@@ -247,13 +247,6 @@ static inline void zone_span_writelock(struct zone *zone) {}
 static inline void zone_span_writeunlock(struct zone *zone) {}
 static inline void zone_seqlock_init(struct zone *zone) {}
 
-static inline int mhp_notimplemented(const char *func)
-{
-	printk(KERN_WARNING "%s() called, with CONFIG_MEMORY_HOTPLUG disabled\n", func);
-	dump_stack();
-	return -ENOSYS;
-}
-
 static inline void register_page_bootmem_info_node(struct pglist_data *pgdat)
 {
 }
@@ -344,6 +337,7 @@ static inline void __remove_memory(int nid, u64 start, u64 size) {}
 extern void set_zone_contiguous(struct zone *zone);
 extern void clear_zone_contiguous(struct zone *zone);
 
+#ifdef CONFIG_MEMORY_HOTPLUG
 extern void __ref free_area_init_core_hotplug(int nid);
 extern int __add_memory(int nid, u64 start, u64 size);
 extern int add_memory(int nid, u64 start, u64 size);
@@ -364,8 +358,8 @@ extern void sparse_remove_section(struct mem_section *ms,
 		unsigned long map_offset, struct vmem_altmap *altmap);
 extern struct page *sparse_decode_mem_map(unsigned long coded_mem_map,
 					  unsigned long pnum);
-extern bool allow_online_pfn_range(int nid, unsigned long pfn, unsigned long nr_pages,
-		int online_type);
 extern struct zone *zone_for_pfn_range(int online_type, int nid, unsigned start_pfn,
 		unsigned long nr_pages);
+#endif /* CONFIG_MEMORY_HOTPLUG */
+
 #endif /* __LINUX_MEMORY_HOTPLUG_H */
diff --git a/mm/sparse.c b/mm/sparse.c
index b25ad8e648392..7bd23f9d6cef6 100644
--- a/mm/sparse.c
+++ b/mm/sparse.c
@@ -312,6 +312,7 @@ static unsigned long sparse_encode_mem_map(struct page *mem_map, unsigned long p
 	return coded_mem_map;
 }
 
+#ifdef CONFIG_MEMORY_HOTPLUG
 /*
  * Decode mem_map from the coded memmap
  */
@@ -321,6 +322,7 @@ struct page *sparse_decode_mem_map(unsigned long coded_mem_map, unsigned long pn
 	coded_mem_map &= SECTION_MAP_MASK;
 	return ((struct page *)coded_mem_map) + section_nr_to_pfn(pnum);
 }
+#endif /* CONFIG_MEMORY_HOTPLUG */
 
 static void __meminit sparse_init_one_section(struct mem_section *ms,
 		unsigned long pnum, struct page *mem_map,
-- 
2.26.2

[PATCH v4 4/8] mm/memory_hotplug: prepare passing flags to add_memory() and friends

[David Hildenbrand]

We soon want to pass flags, e.g., to mark added System RAM resources.
mergeable. Prepare for that.

This patch is based on a similar patch by Oscar Salvador:

https://lkml.kernel.org/r/20190625075227.15193-3-osalvador@suse.de

Acked-by: Wei Liu <wei.liu@kernel.org>
Reviewed-by: Juergen Gross <jgross@suse.com> # Xen related part
Reviewed-by: Pankaj Gupta <pankaj.gupta.linux@gmail.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Jason Gunthorpe <jgg@ziepe.ca>
Cc: Pankaj Gupta <pankaj.gupta.linux@gmail.com>
Cc: Baoquan He <bhe@redhat.com>
Cc: Wei Yang <richardw.yang@linux.intel.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: "Rafael J. Wysocki" <rjw@rjwysocki.net>
Cc: Len Brown <lenb@kernel.org>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Vishal Verma <vishal.l.verma@intel.com>
Cc: Dave Jiang <dave.jiang@intel.com>
Cc: "K. Y. Srinivasan" <kys@microsoft.com>
Cc: Haiyang Zhang <haiyangz@microsoft.com>
Cc: Stephen Hemminger <sthemmin@microsoft.com>
Cc: Wei Liu <wei.liu@kernel.org>
Cc: Heiko Carstens <hca@linux.ibm.com>
Cc: Vasily Gorbik <gor@linux.ibm.com>
Cc: Christian Borntraeger <borntraeger@de.ibm.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: "Michael S. Tsirkin" <mst@redhat.com>
Cc: Jason Wang <jasowang@redhat.com>
Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Cc: Juergen Gross <jgross@suse.com>
Cc: Stefano Stabellini <sstabellini@kernel.org>
Cc: "Oliver O'Halloran" <oohall@gmail.com>
Cc: Pingfan Liu <kernelfans@gmail.com>
Cc: Nathan Lynch <nathanl@linux.ibm.com>
Cc: Libor Pechacek <lpechacek@suse.cz>
Cc: Anton Blanchard <anton@ozlabs.org>
Cc: Leonardo Bras <leobras.c@gmail.com>
Cc: linuxppc-dev@lists.ozlabs.org
Cc: linux-acpi@vger.kernel.org
Cc: linux-nvdimm@lists.01.org
Cc: linux-hyperv@vger.kernel.org
Cc: linux-s390@vger.kernel.org
Cc: virtualization@lists.linux-foundation.org
Cc: xen-devel@lists.xenproject.org
Signed-off-by: David Hildenbrand <david@redhat.com>
---
 arch/powerpc/platforms/powernv/memtrace.c       |  2 +-
 arch/powerpc/platforms/pseries/hotplug-memory.c |  2 +-
 drivers/acpi/acpi_memhotplug.c                  |  3 ++-
 drivers/base/memory.c                           |  3 ++-
 drivers/dax/kmem.c                              |  2 +-
 drivers/hv/hv_balloon.c                         |  2 +-
 drivers/s390/char/sclp_cmd.c                    |  2 +-
 drivers/virtio/virtio_mem.c                     |  2 +-
 drivers/xen/balloon.c                           |  2 +-
 include/linux/memory_hotplug.h                  | 16 ++++++++++++----
 mm/memory_hotplug.c                             | 14 +++++++-------
 11 files changed, 30 insertions(+), 20 deletions(-)

diff --git a/arch/powerpc/platforms/powernv/memtrace.c b/arch/powerpc/platforms/powernv/memtrace.c
index 13b369d2cc454..6828108486f83 100644
--- a/arch/powerpc/platforms/powernv/memtrace.c
+++ b/arch/powerpc/platforms/powernv/memtrace.c
@@ -224,7 +224,7 @@ static int memtrace_online(void)
 			ent->mem = 0;
 		}
 
-		if (add_memory(ent->nid, ent->start, ent->size)) {
+		if (add_memory(ent->nid, ent->start, ent->size, MHP_NONE)) {
 			pr_err("Failed to add trace memory to node %d\n",
 				ent->nid);
 			ret += 1;
diff --git a/arch/powerpc/platforms/pseries/hotplug-memory.c b/arch/powerpc/platforms/pseries/hotplug-memory.c
index 0ea976d1cac47..e1c9fa0d730f5 100644
--- a/arch/powerpc/platforms/pseries/hotplug-memory.c
+++ b/arch/powerpc/platforms/pseries/hotplug-memory.c
@@ -615,7 +615,7 @@ static int dlpar_add_lmb(struct drmem_lmb *lmb)
 	nid = memory_add_physaddr_to_nid(lmb->base_addr);
 
 	/* Add the memory */
-	rc = __add_memory(nid, lmb->base_addr, block_sz);
+	rc = __add_memory(nid, lmb->base_addr, block_sz, MHP_NONE);
 	if (rc) {
 		invalidate_lmb_associativity_index(lmb);
 		return rc;
diff --git a/drivers/acpi/acpi_memhotplug.c b/drivers/acpi/acpi_memhotplug.c
index e294f44a78504..2067c3bc55763 100644
--- a/drivers/acpi/acpi_memhotplug.c
+++ b/drivers/acpi/acpi_memhotplug.c
@@ -207,7 +207,8 @@ static int acpi_memory_enable_device(struct acpi_memory_device *mem_device)
 		if (node < 0)
 			node = memory_add_physaddr_to_nid(info->start_addr);
 
-		result = __add_memory(node, info->start_addr, info->length);
+		result = __add_memory(node, info->start_addr, info->length,
+				      MHP_NONE);
 
 		/*
 		 * If the memory block has been used by the kernel, add_memory()
diff --git a/drivers/base/memory.c b/drivers/base/memory.c
index 4db3c660de831..b4c297dd04755 100644
--- a/drivers/base/memory.c
+++ b/drivers/base/memory.c
@@ -432,7 +432,8 @@ static ssize_t probe_store(struct device *dev, struct device_attribute *attr,
 
 	nid = memory_add_physaddr_to_nid(phys_addr);
 	ret = __add_memory(nid, phys_addr,
-			   MIN_MEMORY_BLOCK_SIZE * sections_per_block);
+			   MIN_MEMORY_BLOCK_SIZE * sections_per_block,
+			   MHP_NONE);
 
 	if (ret)
 		goto out;
diff --git a/drivers/dax/kmem.c b/drivers/dax/kmem.c
index 7dcb2902e9b1b..896cb9444e727 100644
--- a/drivers/dax/kmem.c
+++ b/drivers/dax/kmem.c
@@ -95,7 +95,7 @@ int dev_dax_kmem_probe(struct dev_dax *dev_dax)
 		 * this as RAM automatically.
 		 */
 		rc = add_memory_driver_managed(numa_node, range.start,
-				range_len(&range), kmem_name);
+				range_len(&range), kmem_name, MHP_NONE);
 
 		res->flags |= IORESOURCE_BUSY;
 		if (rc) {
diff --git a/drivers/hv/hv_balloon.c b/drivers/hv/hv_balloon.c
index 32e3bc0aa665a..3c0d52e244520 100644
--- a/drivers/hv/hv_balloon.c
+++ b/drivers/hv/hv_balloon.c
@@ -726,7 +726,7 @@ static void hv_mem_hot_add(unsigned long start, unsigned long size,
 
 		nid = memory_add_physaddr_to_nid(PFN_PHYS(start_pfn));
 		ret = add_memory(nid, PFN_PHYS((start_pfn)),
-				(HA_CHUNK << PAGE_SHIFT));
+				(HA_CHUNK << PAGE_SHIFT), MHP_NONE);
 
 		if (ret) {
 			pr_err("hot_add memory failed error is %d\n", ret);
diff --git a/drivers/s390/char/sclp_cmd.c b/drivers/s390/char/sclp_cmd.c
index a864b21af602a..f6e97f0830f64 100644
--- a/drivers/s390/char/sclp_cmd.c
+++ b/drivers/s390/char/sclp_cmd.c
@@ -406,7 +406,7 @@ static void __init add_memory_merged(u16 rn)
 	if (!size)
 		goto skip_add;
 	for (addr = start; addr < start + size; addr += block_size)
-		add_memory(0, addr, block_size);
+		add_memory(0, addr, block_size, MHP_NONE);
 skip_add:
 	first_rn = rn;
 	num = 1;
diff --git a/drivers/virtio/virtio_mem.c b/drivers/virtio/virtio_mem.c
index 834b7c13ef3dc..ed99e43354010 100644
--- a/drivers/virtio/virtio_mem.c
+++ b/drivers/virtio/virtio_mem.c
@@ -424,7 +424,7 @@ static int virtio_mem_mb_add(struct virtio_mem *vm, unsigned long mb_id)
 
 	dev_dbg(&vm->vdev->dev, "adding memory block: %lu\n", mb_id);
 	return add_memory_driver_managed(nid, addr, memory_block_size_bytes(),
-					 vm->resource_name);
+					 vm->resource_name, MHP_NONE);
 }
 
 /*
diff --git a/drivers/xen/balloon.c b/drivers/xen/balloon.c
index 51427c752b37b..9f40a294d398d 100644
--- a/drivers/xen/balloon.c
+++ b/drivers/xen/balloon.c
@@ -331,7 +331,7 @@ static enum bp_state reserve_additional_memory(void)
 	mutex_unlock(&balloon_mutex);
 	/* add_memory_resource() requires the device_hotplug lock */
 	lock_device_hotplug();
-	rc = add_memory_resource(nid, resource);
+	rc = add_memory_resource(nid, resource, MHP_NONE);
 	unlock_device_hotplug();
 	mutex_lock(&balloon_mutex);
 
diff --git a/include/linux/memory_hotplug.h b/include/linux/memory_hotplug.h
index 1504b4d5ae6ce..33eb80fdba22f 100644
--- a/include/linux/memory_hotplug.h
+++ b/include/linux/memory_hotplug.h
@@ -57,6 +57,12 @@ enum {
 	MMOP_ONLINE_MOVABLE,
 };
 
+/* Flags for add_memory() and friends to specify memory hotplug details. */
+typedef int __bitwise mhp_t;
+
+/* No special request */
+#define MHP_NONE		((__force mhp_t)0)
+
 /*
  * Extended parameters for memory hotplug:
  * altmap: alternative allocator for memmap array (optional)
@@ -339,11 +345,13 @@ extern void clear_zone_contiguous(struct zone *zone);
 
 #ifdef CONFIG_MEMORY_HOTPLUG
 extern void __ref free_area_init_core_hotplug(int nid);
-extern int __add_memory(int nid, u64 start, u64 size);
-extern int add_memory(int nid, u64 start, u64 size);
-extern int add_memory_resource(int nid, struct resource *resource);
+extern int __add_memory(int nid, u64 start, u64 size, mhp_t mhp_flags);
+extern int add_memory(int nid, u64 start, u64 size, mhp_t mhp_flags);
+extern int add_memory_resource(int nid, struct resource *resource,
+			       mhp_t mhp_flags);
 extern int add_memory_driver_managed(int nid, u64 start, u64 size,
-				     const char *resource_name);
+				     const char *resource_name,
+				     mhp_t mhp_flags);
 extern void move_pfn_range_to_zone(struct zone *zone, unsigned long start_pfn,
 				   unsigned long nr_pages,
 				   struct vmem_altmap *altmap, int migratetype);
diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
index 8e1cd18b5cf14..8f0bd7c9a63a5 100644
--- a/mm/memory_hotplug.c
+++ b/mm/memory_hotplug.c
@@ -1039,7 +1039,7 @@ static int online_memory_block(struct memory_block *mem, void *arg)
  *
  * we are OK calling __meminit stuff here - we have CONFIG_MEMORY_HOTPLUG
  */
-int __ref add_memory_resource(int nid, struct resource *res)
+int __ref add_memory_resource(int nid, struct resource *res, mhp_t mhp_flags)
 {
 	struct mhp_params params = { .pgprot = PAGE_KERNEL };
 	u64 start, size;
@@ -1118,7 +1118,7 @@ int __ref add_memory_resource(int nid, struct resource *res)
 }
 
 /* requires device_hotplug_lock, see add_memory_resource() */
-int __ref __add_memory(int nid, u64 start, u64 size)
+int __ref __add_memory(int nid, u64 start, u64 size, mhp_t mhp_flags)
 {
 	struct resource *res;
 	int ret;
@@ -1127,18 +1127,18 @@ int __ref __add_memory(int nid, u64 start, u64 size)
 	if (IS_ERR(res))
 		return PTR_ERR(res);
 
-	ret = add_memory_resource(nid, res);
+	ret = add_memory_resource(nid, res, mhp_flags);
 	if (ret < 0)
 		release_memory_resource(res);
 	return ret;
 }
 
-int add_memory(int nid, u64 start, u64 size)
+int add_memory(int nid, u64 start, u64 size, mhp_t mhp_flags)
 {
 	int rc;
 
 	lock_device_hotplug();
-	rc = __add_memory(nid, start, size);
+	rc = __add_memory(nid, start, size, mhp_flags);
 	unlock_device_hotplug();
 
 	return rc;
@@ -1167,7 +1167,7 @@ EXPORT_SYMBOL_GPL(add_memory);
  * "System RAM ($DRIVER)".
  */
 int add_memory_driver_managed(int nid, u64 start, u64 size,
-			      const char *resource_name)
+			      const char *resource_name, mhp_t mhp_flags)
 {
 	struct resource *res;
 	int rc;
@@ -1185,7 +1185,7 @@ int add_memory_driver_managed(int nid, u64 start, u64 size,
 		goto out_unlock;
 	}
 
-	rc = add_memory_resource(nid, res);
+	rc = add_memory_resource(nid, res, mhp_flags);
 	if (rc < 0)
 		release_memory_resource(res);
 
-- 
2.26.2

[PATCH v4 5/8] mm/memory_hotplug: MEMHP_MERGE_RESOURCE to specify merging of System RAM resources

[David Hildenbrand]

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.

Let's provide a flag (MEMHP_MERGE_RESOURCE) to specify that a resource
either created within add_memory*() or passed via add_memory_resource()
shall be marked mergeable and merged with applicable siblings.

To implement that, we need a kernel/resource interface to mark selected
System RAM resources mergeable (IORESOURCE_SYSRAM_MERGEABLE) and trigger
merging.

Note: We really want to merge after the whole operation succeeded, not
directly when adding a resource to the resource tree (it would break
add_memory_resource() and require splitting resources again when the
operation failed - e.g., due to -ENOMEM).

Reviewed-by: Pankaj Gupta <pankaj.gupta.linux@gmail.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Jason Gunthorpe <jgg@ziepe.ca>
Cc: Kees Cook <keescook@chromium.org>
Cc: Ard Biesheuvel <ardb@kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: "K. Y. Srinivasan" <kys@microsoft.com>
Cc: Haiyang Zhang <haiyangz@microsoft.com>
Cc: Stephen Hemminger <sthemmin@microsoft.com>
Cc: Wei Liu <wei.liu@kernel.org>
Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Cc: Juergen Gross <jgross@suse.com>
Cc: Stefano Stabellini <sstabellini@kernel.org>
Cc: Roger Pau Monné <roger.pau@citrix.com>
Cc: Julien Grall <julien@xen.org>
Cc: Pankaj Gupta <pankaj.gupta.linux@gmail.com>
Cc: Baoquan He <bhe@redhat.com>
Cc: Wei Yang <richardw.yang@linux.intel.com>
Signed-off-by: David Hildenbrand <david@redhat.com>
---
 include/linux/ioport.h         |  4 +++
 include/linux/memory_hotplug.h |  7 ++++
 kernel/resource.c              | 60 ++++++++++++++++++++++++++++++++++
 mm/memory_hotplug.c            |  7 ++++
 4 files changed, 78 insertions(+)

diff --git a/include/linux/ioport.h b/include/linux/ioport.h
index d7620d7c941a0..7e61389dcb017 100644
--- a/include/linux/ioport.h
+++ b/include/linux/ioport.h
@@ -60,6 +60,7 @@ struct resource {
 
 /* IORESOURCE_SYSRAM specific bits. */
 #define IORESOURCE_SYSRAM_DRIVER_MANAGED	0x02000000 /* Always detected via a driver. */
+#define IORESOURCE_SYSRAM_MERGEABLE		0x04000000 /* Resource can be merged. */
 
 #define IORESOURCE_EXCLUSIVE	0x08000000	/* Userland may not map this resource */
 
@@ -253,6 +254,9 @@ extern void __release_region(struct resource *, resource_size_t,
 extern void release_mem_region_adjustable(struct resource *, resource_size_t,
 					  resource_size_t);
 #endif
+#ifdef CONFIG_MEMORY_HOTPLUG
+extern void merge_system_ram_resource(struct resource *res);
+#endif
 
 /* Wrappers for managed devices */
 struct device;
diff --git a/include/linux/memory_hotplug.h b/include/linux/memory_hotplug.h
index 33eb80fdba22f..d65c6fdc5cfc3 100644
--- a/include/linux/memory_hotplug.h
+++ b/include/linux/memory_hotplug.h
@@ -62,6 +62,13 @@ typedef int __bitwise mhp_t;
 
 /* No special request */
 #define MHP_NONE		((__force mhp_t)0)
+/*
+ * Allow merging of the added System RAM resource with adjacent,
+ * mergeable resources. After a successful call to add_memory_resource()
+ * with this flag set, the resource pointer must no longer be used as it
+ * might be stale, or the resource might have changed.
+ */
+#define MEMHP_MERGE_RESOURCE	((__force mhp_t)BIT(0))
 
 /*
  * Extended parameters for memory hotplug:
diff --git a/kernel/resource.c b/kernel/resource.c
index 36b3552210120..7a91b935f4c20 100644
--- a/kernel/resource.c
+++ b/kernel/resource.c
@@ -1363,6 +1363,66 @@ void release_mem_region_adjustable(struct resource *parent,
 }
 #endif	/* CONFIG_MEMORY_HOTREMOVE */
 
+#ifdef CONFIG_MEMORY_HOTPLUG
+static bool system_ram_resources_mergeable(struct resource *r1,
+					   struct resource *r2)
+{
+	/* We assume either r1 or r2 is IORESOURCE_SYSRAM_MERGEABLE. */
+	return r1->flags == r2->flags && r1->end + 1 == r2->start &&
+	       r1->name == r2->name && r1->desc == r2->desc &&
+	       !r1->child && !r2->child;
+}
+
+/*
+ * merge_system_ram_resource - mark the System RAM resource mergeable and try to
+ * merge it with adjacent, mergeable resources
+ * @res: resource descriptor
+ *
+ * This interface is intended for memory hotplug, whereby lots of contiguous
+ * system ram resources are added (e.g., via add_memory*()) by a driver, and
+ * the actual resource boundaries are not of interest (e.g., it might be
+ * relevant for DIMMs). Only resources that are marked mergeable, that have the
+ * same parent, and that don't have any children are considered. All mergeable
+ * resources must be immutable during the request.
+ *
+ * Note:
+ * - The caller has to make sure that no pointers to resources that are
+ *   marked mergeable are used anymore after this call - the resource might
+ *   be freed and the pointer might be stale!
+ * - release_mem_region_adjustable() will split on demand on memory hotunplug
+ */
+void merge_system_ram_resource(struct resource *res)
+{
+	const unsigned long flags = IORESOURCE_SYSTEM_RAM | IORESOURCE_BUSY;
+	struct resource *cur;
+
+	if (WARN_ON_ONCE((res->flags & flags) != flags))
+		return;
+
+	write_lock(&resource_lock);
+	res->flags |= IORESOURCE_SYSRAM_MERGEABLE;
+
+	/* Try to merge with next item in the list. */
+	cur = res->sibling;
+	if (cur && system_ram_resources_mergeable(res, cur)) {
+		res->end = cur->end;
+		res->sibling = cur->sibling;
+		free_resource(cur);
+	}
+
+	/* Try to merge with previous item in the list. */
+	cur = res->parent->child;
+	while (cur && cur->sibling != res)
+		cur = cur->sibling;
+	if (cur && system_ram_resources_mergeable(cur, res)) {
+		cur->end = res->end;
+		cur->sibling = res->sibling;
+		free_resource(res);
+	}
+	write_unlock(&resource_lock);
+}
+#endif	/* CONFIG_MEMORY_HOTPLUG */
+
 /*
  * Managed region resource
  */
diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
index 8f0bd7c9a63a5..553c718226b3e 100644
--- a/mm/memory_hotplug.c
+++ b/mm/memory_hotplug.c
@@ -1102,6 +1102,13 @@ int __ref add_memory_resource(int nid, struct resource *res, mhp_t mhp_flags)
 	/* device_online() will take the lock when calling online_pages() */
 	mem_hotplug_done();
 
+	/*
+	 * In case we're allowed to merge the resource, flag it and trigger
+	 * merging now that adding succeeded.
+	 */
+	if (mhp_flags & MEMHP_MERGE_RESOURCE)
+		merge_system_ram_resource(res);
+
 	/* online pages if requested */
 	if (memhp_default_online_type != MMOP_OFFLINE)
 		walk_memory_blocks(start, size, NULL, online_memory_block);
-- 
2.26.2

Re: [PATCH v4 5/8] mm/memory_hotplug: MEMHP_MERGE_RESOURCE to specify merging of System RAM resources

[Wei Yang]

On Fri, Sep 11, 2020 at 12:34:56PM +0200, David Hildenbrand wrote:
>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.
>
>Let's provide a flag (MEMHP_MERGE_RESOURCE) to specify that a resource
>either created within add_memory*() or passed via add_memory_resource()
>shall be marked mergeable and merged with applicable siblings.
>
>To implement that, we need a kernel/resource interface to mark selected
>System RAM resources mergeable (IORESOURCE_SYSRAM_MERGEABLE) and trigger
>merging.
>
>Note: We really want to merge after the whole operation succeeded, not
>directly when adding a resource to the resource tree (it would break
>add_memory_resource() and require splitting resources again when the
>operation failed - e.g., due to -ENOMEM).

Oops, the latest version is here.

BTW, I don't see patch 4. Not sure it is junked by my mail system?

>
>Reviewed-by: Pankaj Gupta <pankaj.gupta.linux@gmail.com>
>Cc: Andrew Morton <akpm@linux-foundation.org>
>Cc: Michal Hocko <mhocko@suse.com>
>Cc: Dan Williams <dan.j.williams@intel.com>
>Cc: Jason Gunthorpe <jgg@ziepe.ca>
>Cc: Kees Cook <keescook@chromium.org>
>Cc: Ard Biesheuvel <ardb@kernel.org>
>Cc: Thomas Gleixner <tglx@linutronix.de>
>Cc: "K. Y. Srinivasan" <kys@microsoft.com>
>Cc: Haiyang Zhang <haiyangz@microsoft.com>
>Cc: Stephen Hemminger <sthemmin@microsoft.com>
>Cc: Wei Liu <wei.liu@kernel.org>
>Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com>
>Cc: Juergen Gross <jgross@suse.com>
>Cc: Stefano Stabellini <sstabellini@kernel.org>
>Cc: Roger Pau Monné <roger.pau@citrix.com>
>Cc: Julien Grall <julien@xen.org>
>Cc: Pankaj Gupta <pankaj.gupta.linux@gmail.com>
>Cc: Baoquan He <bhe@redhat.com>
>Cc: Wei Yang <richardw.yang@linux.intel.com>
>Signed-off-by: David Hildenbrand <david@redhat.com>
>---
> include/linux/ioport.h         |  4 +++
> include/linux/memory_hotplug.h |  7 ++++
> kernel/resource.c              | 60 ++++++++++++++++++++++++++++++++++
> mm/memory_hotplug.c            |  7 ++++
> 4 files changed, 78 insertions(+)
>
>diff --git a/include/linux/ioport.h b/include/linux/ioport.h
>index d7620d7c941a0..7e61389dcb017 100644
>--- a/include/linux/ioport.h
>+++ b/include/linux/ioport.h
>@@ -60,6 +60,7 @@ struct resource {
> 
> /* IORESOURCE_SYSRAM specific bits. */
> #define IORESOURCE_SYSRAM_DRIVER_MANAGED	0x02000000 /* Always detected via a driver. */
>+#define IORESOURCE_SYSRAM_MERGEABLE		0x04000000 /* Resource can be merged. */
> 
> #define IORESOURCE_EXCLUSIVE	0x08000000	/* Userland may not map this resource */
> 
>@@ -253,6 +254,9 @@ extern void __release_region(struct resource *, resource_size_t,
> extern void release_mem_region_adjustable(struct resource *, resource_size_t,
> 					  resource_size_t);
> #endif
>+#ifdef CONFIG_MEMORY_HOTPLUG
>+extern void merge_system_ram_resource(struct resource *res);
>+#endif
> 
> /* Wrappers for managed devices */
> struct device;
>diff --git a/include/linux/memory_hotplug.h b/include/linux/memory_hotplug.h
>index 33eb80fdba22f..d65c6fdc5cfc3 100644
>--- a/include/linux/memory_hotplug.h
>+++ b/include/linux/memory_hotplug.h
>@@ -62,6 +62,13 @@ typedef int __bitwise mhp_t;
> 
> /* No special request */
> #define MHP_NONE		((__force mhp_t)0)
>+/*
>+ * Allow merging of the added System RAM resource with adjacent,
>+ * mergeable resources. After a successful call to add_memory_resource()
>+ * with this flag set, the resource pointer must no longer be used as it
>+ * might be stale, or the resource might have changed.
>+ */
>+#define MEMHP_MERGE_RESOURCE	((__force mhp_t)BIT(0))
> 
> /*
>  * Extended parameters for memory hotplug:
>diff --git a/kernel/resource.c b/kernel/resource.c
>index 36b3552210120..7a91b935f4c20 100644
>--- a/kernel/resource.c
>+++ b/kernel/resource.c
>@@ -1363,6 +1363,66 @@ void release_mem_region_adjustable(struct resource *parent,
> }
> #endif	/* CONFIG_MEMORY_HOTREMOVE */
> 
>+#ifdef CONFIG_MEMORY_HOTPLUG
>+static bool system_ram_resources_mergeable(struct resource *r1,
>+					   struct resource *r2)
>+{
>+	/* We assume either r1 or r2 is IORESOURCE_SYSRAM_MERGEABLE. */
>+	return r1->flags == r2->flags && r1->end + 1 == r2->start &&
>+	       r1->name == r2->name && r1->desc == r2->desc &&
>+	       !r1->child && !r2->child;
>+}
>+
>+/*
>+ * merge_system_ram_resource - mark the System RAM resource mergeable and try to
>+ * merge it with adjacent, mergeable resources
>+ * @res: resource descriptor
>+ *
>+ * This interface is intended for memory hotplug, whereby lots of contiguous
>+ * system ram resources are added (e.g., via add_memory*()) by a driver, and
>+ * the actual resource boundaries are not of interest (e.g., it might be
>+ * relevant for DIMMs). Only resources that are marked mergeable, that have the
>+ * same parent, and that don't have any children are considered. All mergeable
>+ * resources must be immutable during the request.
>+ *
>+ * Note:
>+ * - The caller has to make sure that no pointers to resources that are
>+ *   marked mergeable are used anymore after this call - the resource might
>+ *   be freed and the pointer might be stale!
>+ * - release_mem_region_adjustable() will split on demand on memory hotunplug
>+ */
>+void merge_system_ram_resource(struct resource *res)
>+{
>+	const unsigned long flags = IORESOURCE_SYSTEM_RAM | IORESOURCE_BUSY;
>+	struct resource *cur;
>+
>+	if (WARN_ON_ONCE((res->flags & flags) != flags))
>+		return;
>+
>+	write_lock(&resource_lock);
>+	res->flags |= IORESOURCE_SYSRAM_MERGEABLE;
>+
>+	/* Try to merge with next item in the list. */
>+	cur = res->sibling;
>+	if (cur && system_ram_resources_mergeable(res, cur)) {
>+		res->end = cur->end;
>+		res->sibling = cur->sibling;
>+		free_resource(cur);
>+	}
>+
>+	/* Try to merge with previous item in the list. */
>+	cur = res->parent->child;
>+	while (cur && cur->sibling != res)
>+		cur = cur->sibling;
>+	if (cur && system_ram_resources_mergeable(cur, res)) {
>+		cur->end = res->end;
>+		cur->sibling = res->sibling;
>+		free_resource(res);
>+	}
>+	write_unlock(&resource_lock);
>+}
>+#endif	/* CONFIG_MEMORY_HOTPLUG */
>+
> /*
>  * Managed region resource
>  */
>diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
>index 8f0bd7c9a63a5..553c718226b3e 100644
>--- a/mm/memory_hotplug.c
>+++ b/mm/memory_hotplug.c
>@@ -1102,6 +1102,13 @@ int __ref add_memory_resource(int nid, struct resource *res, mhp_t mhp_flags)
> 	/* device_online() will take the lock when calling online_pages() */
> 	mem_hotplug_done();
> 
>+	/*
>+	 * In case we're allowed to merge the resource, flag it and trigger
>+	 * merging now that adding succeeded.
>+	 */
>+	if (mhp_flags & MEMHP_MERGE_RESOURCE)
>+		merge_system_ram_resource(res);
>+
> 	/* online pages if requested */
> 	if (memhp_default_online_type != MMOP_OFFLINE)
> 		walk_memory_blocks(start, size, NULL, online_memory_block);
>-- 
>2.26.2

-- 
Wei Yang
Help you, Help me

Re: [PATCH v4 5/8] mm/memory_hotplug: MEMHP_MERGE_RESOURCE to specify merging of System RAM resources

[David Hildenbrand]

On 15.09.20 04:43, Wei Yang wrote:
> On Fri, Sep 11, 2020 at 12:34:56PM +0200, David Hildenbrand wrote:
>> 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.
>>
>> Let's provide a flag (MEMHP_MERGE_RESOURCE) to specify that a resource
>> either created within add_memory*() or passed via add_memory_resource()
>> shall be marked mergeable and merged with applicable siblings.
>>
>> To implement that, we need a kernel/resource interface to mark selected
>> System RAM resources mergeable (IORESOURCE_SYSRAM_MERGEABLE) and trigger
>> merging.
>>
>> Note: We really want to merge after the whole operation succeeded, not
>> directly when adding a resource to the resource tree (it would break
>> add_memory_resource() and require splitting resources again when the
>> operation failed - e.g., due to -ENOMEM).
> 
> Oops, the latest version is here.

Yeah, sorry, I dropped the "mm" prefix on the subject of the cover
letter by mistake.

> 
> BTW, I don't see patch 4. Not sure it is junked by my mail system?

At least you're in the CC list below with your old mail address (I
assume you monitor that).

I'll try to use your new address in the future.


-- 
Thanks,

David / dhildenb

[PATCH v4 6/8] virtio-mem: try to merge system ram resources

[David Hildenbrand]

virtio-mem adds memory in memory block granularity, to be able to
remove it in the same granularity again later, and to grow slowly on
demand. This, however, results in quite a lot of resources when
adding a lot of memory. 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 later
when e.g., trying to create a kdump header).

Before this patch, we get (/proc/iomem) when hotplugging 2G via virtio-mem
on x86-64:
        [...]
        100000000-13fffffff : System RAM
        140000000-33fffffff : virtio0
          140000000-147ffffff : System RAM (virtio_mem)
          148000000-14fffffff : System RAM (virtio_mem)
          150000000-157ffffff : System RAM (virtio_mem)
          158000000-15fffffff : System RAM (virtio_mem)
          160000000-167ffffff : System RAM (virtio_mem)
          168000000-16fffffff : System RAM (virtio_mem)
          170000000-177ffffff : System RAM (virtio_mem)
          178000000-17fffffff : System RAM (virtio_mem)
          180000000-187ffffff : System RAM (virtio_mem)
          188000000-18fffffff : System RAM (virtio_mem)
          190000000-197ffffff : System RAM (virtio_mem)
          198000000-19fffffff : System RAM (virtio_mem)
          1a0000000-1a7ffffff : System RAM (virtio_mem)
          1a8000000-1afffffff : System RAM (virtio_mem)
          1b0000000-1b7ffffff : System RAM (virtio_mem)
          1b8000000-1bfffffff : System RAM (virtio_mem)
        3280000000-32ffffffff : PCI Bus 0000:00

With this patch, we get (/proc/iomem):
        [...]
        fffc0000-ffffffff : Reserved
        100000000-13fffffff : System RAM
        140000000-33fffffff : virtio0
          140000000-1bfffffff : System RAM (virtio_mem)
        3280000000-32ffffffff : PCI Bus 0000:00

Of course, with more hotplugged memory, it gets worse. When unplugging
memory blocks again, try_remove_memory() (via
offline_and_remove_memory()) will properly split the resource up again.

Reviewed-by: Pankaj Gupta <pankaj.gupta.linux@gmail.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Michael S. Tsirkin <mst@redhat.com>
Cc: Jason Wang <jasowang@redhat.com>
Cc: Pankaj Gupta <pankaj.gupta.linux@gmail.com>
Cc: Baoquan He <bhe@redhat.com>
Cc: Wei Yang <richardw.yang@linux.intel.com>
Signed-off-by: David Hildenbrand <david@redhat.com>
---
 drivers/virtio/virtio_mem.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/virtio/virtio_mem.c b/drivers/virtio/virtio_mem.c
index ed99e43354010..ba4de598f6636 100644
--- a/drivers/virtio/virtio_mem.c
+++ b/drivers/virtio/virtio_mem.c
@@ -424,7 +424,8 @@ static int virtio_mem_mb_add(struct virtio_mem *vm, unsigned long mb_id)
 
 	dev_dbg(&vm->vdev->dev, "adding memory block: %lu\n", mb_id);
 	return add_memory_driver_managed(nid, addr, memory_block_size_bytes(),
-					 vm->resource_name, MHP_NONE);
+					 vm->resource_name,
+					 MEMHP_MERGE_RESOURCE);
 }
 
 /*
-- 
2.26.2

[PATCH v4 7/8] xen/balloon: try to merge system ram resources

[David Hildenbrand]

Let's try to merge system ram resources we add, to minimize the number
of resources in /proc/iomem. We don't care about the boundaries of
individual chunks we added.

Reviewed-by: Juergen Gross <jgross@suse.com>
Cc: Andrew Morton <akpmt@linux-foundation.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Cc: Juergen Gross <jgross@suse.com>
Cc: Stefano Stabellini <sstabellini@kernel.org>
Cc: Roger Pau Monné <roger.pau@citrix.com>
Cc: Julien Grall <julien@xen.org>
Cc: Pankaj Gupta <pankaj.gupta.linux@gmail.com>
Cc: Baoquan He <bhe@redhat.com>
Cc: Wei Yang <richardw.yang@linux.intel.com>
Signed-off-by: David Hildenbrand <david@redhat.com>
---
 drivers/xen/balloon.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/xen/balloon.c b/drivers/xen/balloon.c
index 9f40a294d398d..b57b2067ecbfb 100644
--- a/drivers/xen/balloon.c
+++ b/drivers/xen/balloon.c
@@ -331,7 +331,7 @@ static enum bp_state reserve_additional_memory(void)
 	mutex_unlock(&balloon_mutex);
 	/* add_memory_resource() requires the device_hotplug lock */
 	lock_device_hotplug();
-	rc = add_memory_resource(nid, resource, MHP_NONE);
+	rc = add_memory_resource(nid, resource, MEMHP_MERGE_RESOURCE);
 	unlock_device_hotplug();
 	mutex_lock(&balloon_mutex);
 
-- 
2.26.2

[PATCH v4 8/8] hv_balloon: try to merge system ram resources

[David Hildenbrand]

Let's try to merge system ram resources we add, to minimize the number
of resources in /proc/iomem. We don't care about the boundaries of
individual chunks we added.

Reviewed-by: Wei Liu <wei.liu@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: "K. Y. Srinivasan" <kys@microsoft.com>
Cc: Haiyang Zhang <haiyangz@microsoft.com>
Cc: Stephen Hemminger <sthemmin@microsoft.com>
Cc: Wei Liu <wei.liu@kernel.org>
Cc: Pankaj Gupta <pankaj.gupta.linux@gmail.com>
Cc: Baoquan He <bhe@redhat.com>
Cc: Wei Yang <richardw.yang@linux.intel.com>
Signed-off-by: David Hildenbrand <david@redhat.com>
---
 drivers/hv/hv_balloon.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/hv/hv_balloon.c b/drivers/hv/hv_balloon.c
index 3c0d52e244520..b64d2efbefe71 100644
--- a/drivers/hv/hv_balloon.c
+++ b/drivers/hv/hv_balloon.c
@@ -726,7 +726,7 @@ static void hv_mem_hot_add(unsigned long start, unsigned long size,
 
 		nid = memory_add_physaddr_to_nid(PFN_PHYS(start_pfn));
 		ret = add_memory(nid, PFN_PHYS((start_pfn)),
-				(HA_CHUNK << PAGE_SHIFT), MHP_NONE);
+				(HA_CHUNK << PAGE_SHIFT), MEMHP_MERGE_RESOURCE);
 
 		if (ret) {
 			pr_err("hot_add memory failed error is %d\n", ret);
-- 
2.26.2

[PATCH] kernel/resource: make iomem_resource implicit in release_mem_region_adjustable()

[David Hildenbrand]

"mem" in the name already indicates the root, similar to
release_mem_region() and devm_request_mem_region(). Make it implicit.
The only single caller always passes iomem_resource, other parents are
not applicable.

Suggested-by: Wei Yang <richard.weiyang@linux.alibaba.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Jason Gunthorpe <jgg@ziepe.ca>
Cc: Kees Cook <keescook@chromium.org>
Cc: Ard Biesheuvel <ardb@kernel.org>
Cc: Pankaj Gupta <pankaj.gupta.linux@gmail.com>
Cc: Baoquan He <bhe@redhat.com>
Cc: Wei Yang <richard.weiyang@linux.alibaba.com>
Signed-off-by: David Hildenbrand <david@redhat.com>
---

Based on next-20200915. Follow up on
	"[PATCH v4 0/8] selective merging of system ram resources" [1]
That's in next-20200915. As noted during review of v2 by Wei [2].

[1] https://lkml.kernel.org/r/20200911103459.10306-1-david@redhat.com
[2] https://lkml.kernel.org/r/20200915021012.GC2007@L-31X9LVDL-1304.local

---
 include/linux/ioport.h | 3 +--
 kernel/resource.c      | 5 ++---
 mm/memory_hotplug.c    | 2 +-
 3 files changed, 4 insertions(+), 6 deletions(-)

diff --git a/include/linux/ioport.h b/include/linux/ioport.h
index 7e61389dcb01..5135d4b86cd6 100644
--- a/include/linux/ioport.h
+++ b/include/linux/ioport.h
@@ -251,8 +251,7 @@ extern struct resource * __request_region(struct resource *,
 extern void __release_region(struct resource *, resource_size_t,
 				resource_size_t);
 #ifdef CONFIG_MEMORY_HOTREMOVE
-extern void release_mem_region_adjustable(struct resource *, resource_size_t,
-					  resource_size_t);
+extern void release_mem_region_adjustable(resource_size_t, resource_size_t);
 #endif
 #ifdef CONFIG_MEMORY_HOTPLUG
 extern void merge_system_ram_resource(struct resource *res);
diff --git a/kernel/resource.c b/kernel/resource.c
index 7a91b935f4c2..ca2a666e4317 100644
--- a/kernel/resource.c
+++ b/kernel/resource.c
@@ -1240,7 +1240,6 @@ EXPORT_SYMBOL(__release_region);
 #ifdef CONFIG_MEMORY_HOTREMOVE
 /**
  * release_mem_region_adjustable - release a previously reserved memory region
- * @parent: parent resource descriptor
  * @start: resource start address
  * @size: resource region size
  *
@@ -1258,9 +1257,9 @@ EXPORT_SYMBOL(__release_region);
  *   assumes that all children remain in the lower address entry for
  *   simplicity.  Enhance this logic when necessary.
  */
-void release_mem_region_adjustable(struct resource *parent,
-				   resource_size_t start, resource_size_t size)
+void release_mem_region_adjustable(resource_size_t start, resource_size_t size)
 {
+	struct resource *parent = &iomem_resource;
 	struct resource *new_res = NULL;
 	bool alloc_nofail = false;
 	struct resource **p;
diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
index 553c718226b3..7c5e4744ac51 100644
--- a/mm/memory_hotplug.c
+++ b/mm/memory_hotplug.c
@@ -1764,7 +1764,7 @@ static int __ref try_remove_memory(int nid, u64 start, u64 size)
 		memblock_remove(start, size);
 	}
 
-	release_mem_region_adjustable(&iomem_resource, start, size);
+	release_mem_region_adjustable(start, size);
 
 	try_offline_node(nid);
 
-- 
2.26.2

Re: [PATCH] kernel/resource: make iomem_resource implicit in release_mem_region_adjustable()

[Wei Yang]

On Wed, Sep 16, 2020 at 09:30:41AM +0200, David Hildenbrand wrote:
>"mem" in the name already indicates the root, similar to
>release_mem_region() and devm_request_mem_region(). Make it implicit.
>The only single caller always passes iomem_resource, other parents are
>not applicable.
>

Looks good to me.

Reviewed-by: Wei Yang <richard.weiyang@linux.alibaba.com>

>Suggested-by: Wei Yang <richard.weiyang@linux.alibaba.com>
>Cc: Andrew Morton <akpm@linux-foundation.org>
>Cc: Michal Hocko <mhocko@suse.com>
>Cc: Dan Williams <dan.j.williams@intel.com>
>Cc: Jason Gunthorpe <jgg@ziepe.ca>
>Cc: Kees Cook <keescook@chromium.org>
>Cc: Ard Biesheuvel <ardb@kernel.org>
>Cc: Pankaj Gupta <pankaj.gupta.linux@gmail.com>
>Cc: Baoquan He <bhe@redhat.com>
>Cc: Wei Yang <richard.weiyang@linux.alibaba.com>
>Signed-off-by: David Hildenbrand <david@redhat.com>
>---
>
>Based on next-20200915. Follow up on
>	"[PATCH v4 0/8] selective merging of system ram resources" [1]
>That's in next-20200915. As noted during review of v2 by Wei [2].
>
>[1] https://lkml.kernel.org/r/20200911103459.10306-1-david@redhat.com
>[2] https://lkml.kernel.org/r/20200915021012.GC2007@L-31X9LVDL-1304.local
>
>---
> include/linux/ioport.h | 3 +--
> kernel/resource.c      | 5 ++---
> mm/memory_hotplug.c    | 2 +-
> 3 files changed, 4 insertions(+), 6 deletions(-)
>
>diff --git a/include/linux/ioport.h b/include/linux/ioport.h
>index 7e61389dcb01..5135d4b86cd6 100644
>--- a/include/linux/ioport.h
>+++ b/include/linux/ioport.h
>@@ -251,8 +251,7 @@ extern struct resource * __request_region(struct resource *,
> extern void __release_region(struct resource *, resource_size_t,
> 				resource_size_t);
> #ifdef CONFIG_MEMORY_HOTREMOVE
>-extern void release_mem_region_adjustable(struct resource *, resource_size_t,
>-					  resource_size_t);
>+extern void release_mem_region_adjustable(resource_size_t, resource_size_t);
> #endif
> #ifdef CONFIG_MEMORY_HOTPLUG
> extern void merge_system_ram_resource(struct resource *res);
>diff --git a/kernel/resource.c b/kernel/resource.c
>index 7a91b935f4c2..ca2a666e4317 100644
>--- a/kernel/resource.c
>+++ b/kernel/resource.c
>@@ -1240,7 +1240,6 @@ EXPORT_SYMBOL(__release_region);
> #ifdef CONFIG_MEMORY_HOTREMOVE
> /**
>  * release_mem_region_adjustable - release a previously reserved memory region
>- * @parent: parent resource descriptor
>  * @start: resource start address
>  * @size: resource region size
>  *
>@@ -1258,9 +1257,9 @@ EXPORT_SYMBOL(__release_region);
>  *   assumes that all children remain in the lower address entry for
>  *   simplicity.  Enhance this logic when necessary.
>  */
>-void release_mem_region_adjustable(struct resource *parent,
>-				   resource_size_t start, resource_size_t size)
>+void release_mem_region_adjustable(resource_size_t start, resource_size_t size)
> {
>+	struct resource *parent = &iomem_resource;
> 	struct resource *new_res = NULL;
> 	bool alloc_nofail = false;
> 	struct resource **p;
>diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
>index 553c718226b3..7c5e4744ac51 100644
>--- a/mm/memory_hotplug.c
>+++ b/mm/memory_hotplug.c
>@@ -1764,7 +1764,7 @@ static int __ref try_remove_memory(int nid, u64 start, u64 size)
> 		memblock_remove(start, size);
> 	}
> 
>-	release_mem_region_adjustable(&iomem_resource, start, size);
>+	release_mem_region_adjustable(start, size);
> 
> 	try_offline_node(nid);
> 
>-- 
>2.26.2

-- 
Wei Yang
Help you, Help me

Re: [PATCH] kernel/resource: make iomem_resource implicit in release_mem_region_adjustable()

[David Hildenbrand]

On 16.09.20 12:02, Wei Yang wrote:
> On Wed, Sep 16, 2020 at 09:30:41AM +0200, David Hildenbrand wrote:
>> "mem" in the name already indicates the root, similar to
>> release_mem_region() and devm_request_mem_region(). Make it implicit.
>> The only single caller always passes iomem_resource, other parents are
>> not applicable.
>>
> 
> Looks good to me.
> 
> Reviewed-by: Wei Yang <richard.weiyang@linux.alibaba.com>
>

Thanks for the review!

-- 
Thanks,

David / dhildenb

Re: [PATCH] kernel/resource: make iomem_resource implicit in release_mem_region_adjustable()

[David Hildenbrand]

On 16.09.20 14:10, Wei Yang wrote:
> On Wed, Sep 16, 2020 at 12:03:20PM +0200, David Hildenbrand wrote:
>> On 16.09.20 12:02, Wei Yang wrote:
>>> On Wed, Sep 16, 2020 at 09:30:41AM +0200, David Hildenbrand wrote:
>>>> "mem" in the name already indicates the root, similar to
>>>> release_mem_region() and devm_request_mem_region(). Make it implicit.
>>>> The only single caller always passes iomem_resource, other parents are
>>>> not applicable.
>>>>
>>>
>>> Looks good to me.
>>>
>>> Reviewed-by: Wei Yang <richard.weiyang@linux.alibaba.com>
>>>
>>
>> Thanks for the review!
>>
> 
> Would you send another version? I didn't take a look into the following
> patches, since the 4th is missed.

Not planning to send another one as long as there are no further
comments. Seems to be an issue on your side because all patches arrived
on linux-mm (see
https://lore.kernel.org/linux-mm/20200911103459.10306-1-david@redhat.com/)

You can find patch #4 at
https://lore.kernel.org/linux-mm/20200911103459.10306-5-david@redhat.com/

(which has CC "Wei Yang <richardw.yang@linux.intel.com>")

-- 
Thanks,

David / dhildenb

Re: [PATCH] kernel/resource: make iomem_resource implicit in release_mem_region_adjustable()

[Pankaj Gupta]

> "mem" in the name already indicates the root, similar to
> release_mem_region() and devm_request_mem_region(). Make it implicit.
> The only single caller always passes iomem_resource, other parents are
> not applicable.
>
> Suggested-by: Wei Yang <richard.weiyang@linux.alibaba.com>
> Cc: Andrew Morton <akpm@linux-foundation.org>
> Cc: Michal Hocko <mhocko@suse.com>
> Cc: Dan Williams <dan.j.williams@intel.com>
> Cc: Jason Gunthorpe <jgg@ziepe.ca>
> Cc: Kees Cook <keescook@chromium.org>
> Cc: Ard Biesheuvel <ardb@kernel.org>
> Cc: Pankaj Gupta <pankaj.gupta.linux@gmail.com>
> Cc: Baoquan He <bhe@redhat.com>
> Cc: Wei Yang <richard.weiyang@linux.alibaba.com>
> Signed-off-by: David Hildenbrand <david@redhat.com>
> ---
>
> Based on next-20200915. Follow up on
>         "[PATCH v4 0/8] selective merging of system ram resources" [1]
> That's in next-20200915. As noted during review of v2 by Wei [2].
>
> [1] https://lkml.kernel.org/r/20200911103459.10306-1-david@redhat.com
> [2] https://lkml.kernel.org/r/20200915021012.GC2007@L-31X9LVDL-1304.local
>
> ---
>  include/linux/ioport.h | 3 +--
>  kernel/resource.c      | 5 ++---
>  mm/memory_hotplug.c    | 2 +-
>  3 files changed, 4 insertions(+), 6 deletions(-)
>
> diff --git a/include/linux/ioport.h b/include/linux/ioport.h
> index 7e61389dcb01..5135d4b86cd6 100644
> --- a/include/linux/ioport.h
> +++ b/include/linux/ioport.h
> @@ -251,8 +251,7 @@ extern struct resource * __request_region(struct resource *,
>  extern void __release_region(struct resource *, resource_size_t,
>                                 resource_size_t);
>  #ifdef CONFIG_MEMORY_HOTREMOVE
> -extern void release_mem_region_adjustable(struct resource *, resource_size_t,
> -                                         resource_size_t);
> +extern void release_mem_region_adjustable(resource_size_t, resource_size_t);
>  #endif
>  #ifdef CONFIG_MEMORY_HOTPLUG
>  extern void merge_system_ram_resource(struct resource *res);
> diff --git a/kernel/resource.c b/kernel/resource.c
> index 7a91b935f4c2..ca2a666e4317 100644
> --- a/kernel/resource.c
> +++ b/kernel/resource.c
> @@ -1240,7 +1240,6 @@ EXPORT_SYMBOL(__release_region);
>  #ifdef CONFIG_MEMORY_HOTREMOVE
>  /**
>   * release_mem_region_adjustable - release a previously reserved memory region
> - * @parent: parent resource descriptor
>   * @start: resource start address
>   * @size: resource region size
>   *
> @@ -1258,9 +1257,9 @@ EXPORT_SYMBOL(__release_region);
>   *   assumes that all children remain in the lower address entry for
>   *   simplicity.  Enhance this logic when necessary.
>   */
> -void release_mem_region_adjustable(struct resource *parent,
> -                                  resource_size_t start, resource_size_t size)
> +void release_mem_region_adjustable(resource_size_t start, resource_size_t size)
>  {
> +       struct resource *parent = &iomem_resource;
>         struct resource *new_res = NULL;
>         bool alloc_nofail = false;
>         struct resource **p;
> diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
> index 553c718226b3..7c5e4744ac51 100644
> --- a/mm/memory_hotplug.c
> +++ b/mm/memory_hotplug.c
> @@ -1764,7 +1764,7 @@ static int __ref try_remove_memory(int nid, u64 start, u64 size)
>                 memblock_remove(start, size);
>         }
>
> -       release_mem_region_adjustable(&iomem_resource, start, size);
> +       release_mem_region_adjustable(start, size);
>
>         try_offline_node(nid);
>

Reviewed-by: Pankaj Gupta <pankaj.gupta.linux@gmail.com>