[PATCH v2 2/2] PM: hibernate: add check of preallocate mem for image size pages

[TGSP <tgsp002@gmail.com>]

From: xiongxin <xiongxin@kylinos.cn>

Added a check on the return value of preallocate_image_highmem(). If
memory preallocate is insufficient, S4 cannot be done;

I am playing 4K video on a machine with AMD or other graphics card and
only 8GiB memory, and the kernel is not configured with CONFIG_HIGHMEM.
When doing the S4 test, the analysis found that when the pages get from
minimum_image_size() is large enough, The preallocate_image_memory() and
preallocate_image_highmem() calls failed to obtain enough memory. Add
the judgment that memory preallocate is insufficient;

The detailed debugging data is as follows:

image_size: 3225923584, totalram_pages: 1968948 in
hibernate_reserved_size_init();

in hibernate_preallocate_memory():
code pages = minimum_image_size(saveable) = 717992, at this time(line):
count: 2030858
avail_normal: 2053753
highmem: 0
totalreserve_pages: 22895
max_size: 1013336
size: 787579
saveable: 1819905

When the code executes to:
pages = preallocate_image_memory(alloc, avail_normal), at that
time(line):
pages_highmem: 0
avail_normal: 1335761
alloc: 1017522
pages: 1017522

So enter the else branch judged by (pages < alloc), When executed to
size = preallocate_image_memory(alloc, avail_normal):
alloc = max_size - size = 225757;
size = preallocate_image_memory(alloc, avail_normal) = 168671, That is,
preallocate_image_memory() does not apply for all alloc memory pages,
because highmem is not enabled, and size_highmem will return 0 here, so
there is a memory page that has not been preallocated, so I think a
judgment needs to be added here.

But what I can't understand is that although pages are not preallocated
enough, "pages -= free_unnecessary_pages()" in the code below can also
discard some pages that have been preallocated, so I am not sure whether
it is appropriate to add a judgment here.

Cc: stable@vger.kernel.org
Signed-off-by: xiongxin <xiongxin@kylinos.cn>
Signed-off-by: huanglei <huanglei@kylinos.cn>
---
 kernel/power/snapshot.c | 11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

diff --git a/kernel/power/snapshot.c b/kernel/power/snapshot.c
index c20ca5fb9adc..546d544cf7de 100644
--- a/kernel/power/snapshot.c
+++ b/kernel/power/snapshot.c
@@ -1854,6 +1854,8 @@ int hibernate_preallocate_memory(void)
 		alloc = (count - pages) - size;
 		pages += preallocate_image_highmem(alloc);
 	} else {
+		unsigned long size_highmem = 0;
+
 		/*
 		 * There are approximately max_size saveable pages at this point
 		 * and we want to reduce this number down to size.
@@ -1863,8 +1865,13 @@ int hibernate_preallocate_memory(void)
 		pages_highmem += size;
 		alloc -= size;
 		size = preallocate_image_memory(alloc, avail_normal);
-		pages_highmem += preallocate_image_highmem(alloc - size);
-		pages += pages_highmem + size;
+		size_highmem = preallocate_image_highmem(alloc - size);
+		if (size_highmem < (alloc - size)) {
+			pr_err("Image allocation is %lu pages short, exit\n",
+				alloc - size - pages_highmem);
+			goto err_out;
+		}
+		pages += pages_highmem + size_highmem + size;
 	}
 
 	/*
-- 
2.25.1