+ kexec-improve-the-readability-of-crash_shrink_memory.patch added to mm-nonmm-unstable branch

+ kexec-improve-the-readability-of-crash_shrink_memory.patch added to mm-nonmm-unstable branch

[Andrew Morton]

The patch titled
     Subject: kexec: improve the readability of crash_shrink_memory()
has been added to the -mm mm-nonmm-unstable branch.  Its filename is
     kexec-improve-the-readability-of-crash_shrink_memory.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/kexec-improve-the-readability-of-crash_shrink_memory.patch

This patch will later appear in the mm-nonmm-unstable branch at
    git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

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------------------------------------------------------
From: Zhen Lei <thunder.leizhen@huawei.com>
Subject: kexec: improve the readability of crash_shrink_memory()
Date: Sat, 27 May 2023 20:34:37 +0800

The major adjustments are:
1. end = start + new_size.
   The 'end' here is not an accurate representation, because it is not the
   new end of crashk_res, but the start of ram_res, difference 1. So
   eliminate it and replace it with ram_res->start.
2. Use 'ram_res->start' and 'ram_res->end' as arguments to
   crash_free_reserved_phys_range() to indicate that the memory covered by
   'ram_res' is released from the crashk. And keep it close to
   insert_resource().
3. Replace 'if (start == end)' with 'if (!new_size)', clear indication that
   all crashk memory will be shrunken.

No functional change.

Link: https://lkml.kernel.org/r/20230527123439.772-5-thunder.leizhen@huawei.com
Signed-off-by: Zhen Lei <thunder.leizhen@huawei.com>
Cc: Baoquan He <bhe@redhat.com>
Cc: Cong Wang <amwang@redhat.com>
Cc: Eric W. Biederman <ebiederm@xmission.com>
Cc: Michael Holzheu <holzheu@linux.vnet.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 kernel/kexec_core.c |   15 +++++----------
 1 file changed, 5 insertions(+), 10 deletions(-)

--- a/kernel/kexec_core.c~kexec-improve-the-readability-of-crash_shrink_memory
+++ a/kernel/kexec_core.c
@@ -1108,7 +1108,6 @@ ssize_t crash_get_memory_size(void)
 int crash_shrink_memory(unsigned long new_size)
 {
 	int ret = 0;
-	unsigned long start, end;
 	unsigned long old_size;
 	struct resource *ram_res;
 
@@ -1119,9 +1118,7 @@ int crash_shrink_memory(unsigned long ne
 		ret = -ENOENT;
 		goto unlock;
 	}
-	start = crashk_res.start;
-	end = crashk_res.end;
-	old_size = (end == 0) ? 0 : end - start + 1;
+	old_size = !crashk_res.end ? 0 : resource_size(&crashk_res);
 	new_size = roundup(new_size, KEXEC_CRASH_MEM_ALIGN);
 	if (new_size >= old_size) {
 		ret = (new_size == old_size) ? 0 : -EINVAL;
@@ -1134,22 +1131,20 @@ int crash_shrink_memory(unsigned long ne
 		goto unlock;
 	}
 
-	end = start + new_size;
-	crash_free_reserved_phys_range(end, crashk_res.end);
-
-	ram_res->start = end;
+	ram_res->start = crashk_res.start + new_size;
 	ram_res->end = crashk_res.end;
 	ram_res->flags = IORESOURCE_BUSY | IORESOURCE_SYSTEM_RAM;
 	ram_res->name = "System RAM";
 
-	if (start == end) {
+	if (!new_size) {
 		release_resource(&crashk_res);
 		crashk_res.start = 0;
 		crashk_res.end = 0;
 	} else {
-		crashk_res.end = end - 1;
+		crashk_res.end = ram_res->start - 1;
 	}
 
+	crash_free_reserved_phys_range(ram_res->start, ram_res->end);
 	insert_resource(&iomem_resource, ram_res);
 
 unlock:
_

Patches currently in -mm which might be from thunder.leizhen@huawei.com are

kexec-fix-a-memory-leak-in-crash_shrink_memory.patch
kexec-delete-a-useless-check-in-crash_shrink_memory.patch
kexec-clear-crashk_res-if-all-its-memory-has-been-released.patch
kexec-improve-the-readability-of-crash_shrink_memory.patch
kexec-add-helper-__crash_shrink_memory.patch
kexec-enable-kexec_crash_size-to-support-two-crash-kernel-regions.patch