Re: [PATCH 1/4] hugetlbfs: add arch_hugetlb_valid_size

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Le 18/03/2020 à 23:06, Mike Kravetz a écrit :
The architecture independent routine hugetlb_default_setup sets up
the default huge pages size.  It has no way to verify if the passed
value is valid, so it accepts it and attempts to validate at a later
time.  This requires undocumented cooperation between the arch specific
and arch independent code.

For architectures that support more than one huge page size, provide
a routine arch_hugetlb_valid_size to validate a huge page size.
hugetlb_default_setup can use this to validate passed values.

arch_hugetlb_valid_size will also be used in a subsequent patch to
move processing of the "hugepagesz=" in arch specific code to a common
routine in arch independent code.

Signed-off-by: Mike Kravetz <mike.kravetz@xxxxxxxxxx>
---
  arch/arm64/include/asm/hugetlb.h   |  2 ++
  arch/arm64/mm/hugetlbpage.c        | 19 ++++++++++++++-----
  arch/powerpc/include/asm/hugetlb.h |  3 +++
  arch/powerpc/mm/hugetlbpage.c      | 20 +++++++++++++-------
  arch/riscv/include/asm/hugetlb.h   |  3 +++
  arch/riscv/mm/hugetlbpage.c        | 28 ++++++++++++++++++----------
  arch/s390/include/asm/hugetlb.h    |  3 +++
  arch/s390/mm/hugetlbpage.c         | 18 +++++++++++++-----
  arch/sparc/include/asm/hugetlb.h   |  3 +++
  arch/sparc/mm/init_64.c            | 23 ++++++++++++++++-------
  arch/x86/include/asm/hugetlb.h     |  3 +++
  arch/x86/mm/hugetlbpage.c          | 21 +++++++++++++++------
  include/linux/hugetlb.h            |  7 +++++++
  mm/hugetlb.c                       | 16 +++++++++++++---
  14 files changed, 126 insertions(+), 43 deletions(-)


[snip]

diff --git a/arch/powerpc/include/asm/hugetlb.h b/arch/powerpc/include/asm/hugetlb.h
index bd6504c28c2f..3b5939016955 100644
--- a/arch/powerpc/include/asm/hugetlb.h
+++ b/arch/powerpc/include/asm/hugetlb.h
@@ -64,6 +64,9 @@ static inline void arch_clear_hugepage_flags(struct page *page)
  {
  }
+#define arch_hugetlb_valid_size arch_hugetlb_valid_size
+extern bool __init arch_hugetlb_valid_size(unsigned long long size);

Don't add 'extern' keyword, it is irrelevant for a function declaration.

checkpatch --strict doesn't like it either (https://openpower.xyz/job/snowpatch/job/snowpatch-linux-checkpatch/12318//artifact/linux/checkpatch.log)

+
  #include <asm-generic/hugetlb.h>
#else /* ! CONFIG_HUGETLB_PAGE */
diff --git a/arch/powerpc/mm/hugetlbpage.c b/arch/powerpc/mm/hugetlbpage.c
index 33b3461d91e8..b78f660252f3 100644
--- a/arch/powerpc/mm/hugetlbpage.c
+++ b/arch/powerpc/mm/hugetlbpage.c
@@ -558,7 +558,7 @@ unsigned long vma_mmu_pagesize(struct vm_area_struct *vma)
  	return vma_kernel_pagesize(vma);
  }
-static int __init add_huge_page_size(unsigned long long size)
+bool __init arch_hugetlb_valid_size(unsigned long long size)
  {
  	int shift = __ffs(size);
  	int mmu_psize;
@@ -566,20 +566,26 @@ static int __init add_huge_page_size(unsigned long long size)
  	/* Check that it is a page size supported by the hardware and
  	 * that it fits within pagetable and slice limits. */
  	if (size <= PAGE_SIZE || !is_power_of_2(size))
-		return -EINVAL;
+		return false;
mmu_psize = check_and_get_huge_psize(shift);
  	if (mmu_psize < 0)
-		return -EINVAL;
+		return false;
BUG_ON(mmu_psize_defs[mmu_psize].shift != shift); - /* Return if huge page size has already been setup */
-	if (size_to_hstate(size))
-		return 0;
+	return true;
+}
- hugetlb_add_hstate(shift - PAGE_SHIFT);
+static int __init add_huge_page_size(unsigned long long size)
+{
+	int shift = __ffs(size);
+
+	if (!arch_hugetlb_valid_size(size))
+		return -EINVAL;
+ if (!size_to_hstate(size))
+		hugetlb_add_hstate(shift - PAGE_SHIFT);
  	return 0;
  }

[snip]

diff --git a/arch/x86/mm/hugetlbpage.c b/arch/x86/mm/hugetlbpage.c
index 5bfd5aef5378..51e6208fdeec 100644
--- a/arch/x86/mm/hugetlbpage.c
+++ b/arch/x86/mm/hugetlbpage.c
@@ -181,16 +181,25 @@ hugetlb_get_unmapped_area(struct file *file, unsigned long addr,
  #endif /* CONFIG_HUGETLB_PAGE */
#ifdef CONFIG_X86_64
+bool __init arch_hugetlb_valid_size(unsigned long long size)
+{
+	if (size == PMD_SIZE)
+		return true;
+	else if (size == PUD_SIZE && boot_cpu_has(X86_FEATURE_GBPAGES))
+		return true;
+	else
+		return false;
+}
+
  static __init int setup_hugepagesz(char *opt)
  {
-	unsigned long ps = memparse(opt, &opt);
-	if (ps == PMD_SIZE) {
-		hugetlb_add_hstate(PMD_SHIFT - PAGE_SHIFT);
-	} else if (ps == PUD_SIZE && boot_cpu_has(X86_FEATURE_GBPAGES)) {
-		hugetlb_add_hstate(PUD_SHIFT - PAGE_SHIFT);
+	unsigned long long ps = memparse(opt, &opt);
+
+	if (arch_hugetlb_valid_size(ps)) {
+		hugetlb_add_hstate(ilog2(ps) - PAGE_SHIFT);
  	} else {
  		hugetlb_bad_size();
-		printk(KERN_ERR "hugepagesz: Unsupported page size %lu M\n",
+		printk(KERN_ERR "hugepagesz: Unsupported page size %llu M\n",
  			ps >> 20);

Nowadays we use pr_err() instead of printk.

It would also likely allow you to have everything fit on a single line.

  		return 0;
  	}
diff --git a/include/linux/hugetlb.h b/include/linux/hugetlb.h
index b831e9fa1a26..33343eb980d0 100644
--- a/include/linux/hugetlb.h
+++ b/include/linux/hugetlb.h
@@ -678,6 +678,13 @@ static inline spinlock_t *huge_pte_lockptr(struct hstate *h,
  	return &mm->page_table_lock;
  }
+#ifndef arch_hugetlb_valid_size
+static inline bool arch_hugetlb_valid_size(unsigned long long size)
+{
+	return (size == HPAGE_SIZE);

Not sure the ( ) are necessary.

+}
+#endif
+
  #ifndef hugepages_supported
  /*
   * Some platform decide whether they support huge pages at boot
diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index d8ebd876871d..2f99359b93af 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -3224,12 +3224,22 @@ static int __init hugetlb_nrpages_setup(char *s)
  }
  __setup("hugepages=", hugetlb_nrpages_setup);
-static int __init hugetlb_default_setup(char *s)
+static int __init default_hugepagesz_setup(char *s)
  {
-	default_hstate_size = memparse(s, &s);
+	unsigned long long size;

Why unsigned long long ?

default_hstate_size is long.

I can't imagine 32 bits platforms having a hugepage with a 64 bits size.

+	char *saved_s = s;
+
+	size = memparse(s, &s);

The updated s is not reused after that so you can pass NULL instead of &s and then you don't need the saved_s.

+
+	if (!arch_hugetlb_valid_size(size)) {
+		pr_err("HugeTLB: unsupported default_hugepagesz %s\n", saved_s);
+		return 0;
+	}
+
+	default_hstate_size = size;
  	return 1;
  }
-__setup("default_hugepagesz=", hugetlb_default_setup);
+__setup("default_hugepagesz=", default_hugepagesz_setup);
static unsigned int cpuset_mems_nr(unsigned int *array)
  {



Christophe



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