Re: [PATCH] mm/vmemmap/devdax: Fix kernel crash when probing devdax devices

["Aneesh Kumar K.V" <aneesh.kumar@linux.ibm.com>]

Jane Chu <jane.chu@oracle.com> writes:

> On 4/7/2023 5:23 AM, Aneesh Kumar K.V wrote:
>> diff --git a/mm/Kconfig b/mm/Kconfig
>> index ff7b209dec05..99f87c1be1e8 100644
>> --- a/mm/Kconfig
>> +++ b/mm/Kconfig
>> @@ -461,6 +461,9 @@ config SPARSEMEM_VMEMMAP
>>   	  pfn_to_page and page_to_pfn operations.  This is the most
>>   	  efficient option when sufficient kernel resources are available.
>>   
>> +config ARCH_WANT_OPTIMIZE_VMEMMAP
>> +	bool
>> +
>
> Could this devdax specific config switch be added to drivers/dax/Kconfig 
> ? also, how about adding 'DAX' to the config switch name?

I would say we want to make it more generic. ie, both hugetlb and devdax
can now derive the feature support via ARCH_WANT_OPTIMIZE_VMEMAP

commit aafb4790ea0250c8d2450e9d23a4be80c663d2ec
Author: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
Date:   Sat Apr 8 15:41:48 2023 +0530

    mm/hugetlb: Remove ARCH_WANT_HUGETLB_PAGE_OPTIMIZE_VMEMMAP
    
    We can depend on the more generic ARCH_WACH_OPTIMIZE_VMEMAP
    which is now used to enable both hugetlb and devddax vmemmap optimization.
    
    Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>

diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
index d3f5945f0aff..77d9713dcd9c 100644
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig
@@ -100,7 +100,6 @@ config ARM64
 	select ARCH_WANT_DEFAULT_TOPDOWN_MMAP_LAYOUT
 	select ARCH_WANT_FRAME_POINTERS
 	select ARCH_WANT_HUGE_PMD_SHARE if ARM64_4K_PAGES || (ARM64_16K_PAGES && !ARM64_VA_BITS_36)
-	select ARCH_WANT_HUGETLB_PAGE_OPTIMIZE_VMEMMAP
 	select ARCH_WANT_LD_ORPHAN_WARN
 	select ARCH_WANTS_NO_INSTR
 	select ARCH_WANT_OPTIMIZE_VMEMMAP
diff --git a/arch/loongarch/Kconfig b/arch/loongarch/Kconfig
index ce5802066d0e..9cb00f962de1 100644
--- a/arch/loongarch/Kconfig
+++ b/arch/loongarch/Kconfig
@@ -53,7 +53,6 @@ config LOONGARCH
 	select ARCH_USE_QUEUED_RWLOCKS
 	select ARCH_USE_QUEUED_SPINLOCKS
 	select ARCH_WANT_DEFAULT_TOPDOWN_MMAP_LAYOUT
-	select ARCH_WANT_HUGETLB_PAGE_OPTIMIZE_VMEMMAP
 	select ARCH_WANT_LD_ORPHAN_WARN
 	select ARCH_WANTS_NO_INSTR
 	select ARCH_WANT_OPTIMIZE_VMEMMAP
diff --git a/arch/s390/Kconfig b/arch/s390/Kconfig
index abffccd937b2..df2cd510480a 100644
--- a/arch/s390/Kconfig
+++ b/arch/s390/Kconfig
@@ -126,7 +126,6 @@ config S390
 	select ARCH_WANTS_NO_INSTR
 	select ARCH_WANT_DEFAULT_BPF_JIT
 	select ARCH_WANT_IPC_PARSE_VERSION
-	select ARCH_WANT_HUGETLB_PAGE_OPTIMIZE_VMEMMAP
 	select ARCH_WANT_OPTIMIZE_VMEMMAP
 	select BUILDTIME_TABLE_SORT
 	select CLONE_BACKWARDS2
diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index e8d66d834b4f..5269131cc248 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -125,7 +125,6 @@ config X86
 	select ARCH_WANTS_NO_INSTR
 	select ARCH_WANT_GENERAL_HUGETLB
 	select ARCH_WANT_HUGE_PMD_SHARE
-	select ARCH_WANT_HUGETLB_PAGE_OPTIMIZE_VMEMMAP	if X86_64
 	select ARCH_WANT_LD_ORPHAN_WARN
 	select ARCH_WANT_OPTIMIZE_VMEMMAP	if X86_64
 	select ARCH_WANTS_THP_SWAP		if X86_64
diff --git a/fs/Kconfig b/fs/Kconfig
index e99830c65033..cc07a0cd3172 100644
--- a/fs/Kconfig
+++ b/fs/Kconfig
@@ -250,16 +250,9 @@ config HUGETLBFS
 config HUGETLB_PAGE
 	def_bool HUGETLBFS
 
-#
-# Select this config option from the architecture Kconfig, if it is preferred
-# to enable the feature of HugeTLB Vmemmap Optimization (HVO).
-#
-config ARCH_WANT_HUGETLB_PAGE_OPTIMIZE_VMEMMAP
-	bool
-
 config HUGETLB_PAGE_OPTIMIZE_VMEMMAP
 	def_bool HUGETLB_PAGE
-	depends on ARCH_WANT_HUGETLB_PAGE_OPTIMIZE_VMEMMAP
+	depends on ARCH_WANT_OPTIMIZE_VMEMMAP
 	depends on SPARSEMEM_VMEMMAP
 
 config HUGETLB_PAGE_OPTIMIZE_VMEMMAP_DEFAULT_ON
diff --git a/mm/Kconfig b/mm/Kconfig
index 99f87c1be1e8..09ac60894763 100644
--- a/mm/Kconfig
+++ b/mm/Kconfig
@@ -460,7 +460,10 @@ config SPARSEMEM_VMEMMAP
 	  SPARSEMEM_VMEMMAP uses a virtually mapped memmap to optimise
 	  pfn_to_page and page_to_pfn operations.  This is the most
 	  efficient option when sufficient kernel resources are available.
-
+#
+# Select this config option from the architecture Kconfig, if it is preferred
+# to enable the feature of HugeTLB/dev_dax vmemmap optimization.
+#
 config ARCH_WANT_OPTIMIZE_VMEMMAP
 	bool