[PATCH v4 1/7] mm, x86: Document return values of mapping funcs

[Toshi Kani <toshi.kani@hp.com>]

Document the return values of KVA mapping functions,
pud_set_huge(), pmd_set_huge, pud_clear_huge() and
pmd_clear_huge().

Simplify the conditions to select HAVE_ARCH_HUGE_VMAP
in the Kconfig, since X86_PAE depends on X86_32.

There is no functional change in this patch.

Signed-off-by: Toshi Kani <toshi.kani@hp.com>
---
 arch/x86/Kconfig      |    2 +-
 arch/x86/mm/pgtable.c |   36 ++++++++++++++++++++++++++++--------
 2 files changed, 29 insertions(+), 9 deletions(-)

diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index cb23206..2ea27da 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -99,7 +99,7 @@ config X86
 	select IRQ_FORCED_THREADING
 	select HAVE_BPF_JIT if X86_64
 	select HAVE_ARCH_TRANSPARENT_HUGEPAGE
-	select HAVE_ARCH_HUGE_VMAP if X86_64 || (X86_32 && X86_PAE)
+	select HAVE_ARCH_HUGE_VMAP if X86_64 || X86_PAE
 	select ARCH_HAS_SG_CHAIN
 	select CLKEVT_I8253
 	select ARCH_HAVE_NMI_SAFE_CMPXCHG
diff --git a/arch/x86/mm/pgtable.c b/arch/x86/mm/pgtable.c
index 0b97d2c..4891fa1 100644
--- a/arch/x86/mm/pgtable.c
+++ b/arch/x86/mm/pgtable.c
@@ -563,14 +563,19 @@ void native_set_fixmap(enum fixed_addresses idx, phys_addr_t phys,
 }
 
 #ifdef CONFIG_HAVE_ARCH_HUGE_VMAP
+/**
+ * pud_set_huge - setup kernel PUD mapping
+ *
+ * MTRR can override PAT memory types with 4KB granularity.  Therefore,
+ * it does not set up a huge page when the range is covered by a non-WB
+ * type of MTRR.  0xFF indicates that MTRR are disabled.
+ *
+ * Return 1 on success, and 0 when no PUD was set.
+ */
 int pud_set_huge(pud_t *pud, phys_addr_t addr, pgprot_t prot)
 {
 	u8 mtrr;
 
-	/*
-	 * Do not use a huge page when the range is covered by non-WB type
-	 * of MTRRs.
-	 */
 	mtrr = mtrr_type_lookup(addr, addr + PUD_SIZE);
 	if ((mtrr != MTRR_TYPE_WRBACK) && (mtrr != 0xFF))
 		return 0;
@@ -584,14 +589,19 @@ int pud_set_huge(pud_t *pud, phys_addr_t addr, pgprot_t prot)
 	return 1;
 }
 
+/**
+ * pmd_set_huge - setup kernel PMD mapping
+ *
+ * MTRR can override PAT memory types with 4KB granularity.  Therefore,
+ * it does not set up a huge page when the range is covered by a non-WB
+ * type of MTRR.  0xFF indicates that MTRR are disabled.
+ *
+ * Return 1 on success, and 0 when no PMD was set.
+ */
 int pmd_set_huge(pmd_t *pmd, phys_addr_t addr, pgprot_t prot)
 {
 	u8 mtrr;
 
-	/*
-	 * Do not use a huge page when the range is covered by non-WB type
-	 * of MTRRs.
-	 */
 	mtrr = mtrr_type_lookup(addr, addr + PMD_SIZE);
 	if ((mtrr != MTRR_TYPE_WRBACK) && (mtrr != 0xFF))
 		return 0;
@@ -605,6 +615,11 @@ int pmd_set_huge(pmd_t *pmd, phys_addr_t addr, pgprot_t prot)
 	return 1;
 }
 
+/**
+ * pud_clear_huge - clear kernel PUD mapping when it is set
+ *
+ * Return 1 on success, and 0 when no PUD map was found.
+ */
 int pud_clear_huge(pud_t *pud)
 {
 	if (pud_large(*pud)) {
@@ -615,6 +630,11 @@ int pud_clear_huge(pud_t *pud)
 	return 0;
 }
 
+/**
+ * pmd_clear_huge - clear kernel PMD mapping when it is set
+ *
+ * Return 1 on success, and 0 when no PMD map was found.
+ */
 int pmd_clear_huge(pmd_t *pmd)
 {
 	if (pmd_large(*pmd)) {

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