ioremap: rework pXd_free_pYd_page() API

The recently merged API for ensuring break-before-make on page-table
entries when installing huge mappings in the vmalloc/ioremap region is
fairly counter-intuitive, resulting in the arch freeing functions (e.g.
pmd_free_pte_page()) being called even on entries that aren't present.
This resulted in a minor bug in the arm64 implementation, giving rise to
spurious VM_WARN messages.

This patch moves the pXd_present() checks out into the core code,
refactoring the callsites at the same time so that we avoid the complex
conjunctions when determining whether or not we can put down a huge
mapping.

Link: http://lkml.kernel.org/r/1544120495-17438-2-git-send-email-will.deacon@arm.com
Signed-off-by: Will Deacon <will.deacon@arm.com>
Reviewed-by: Toshi Kani <toshi.kani@hpe.com>
Suggested-by: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Chintan Pandya <cpandya@codeaurora.org>
Cc: Toshi Kani <toshi.kani@hpe.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Michal Hocko <mhocko@suse.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Sean Christopherson <sean.j.christopherson@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/lib/ioremap.c b/lib/ioremap.c
index 517f585..6c72764 100644 (file)
--- a/lib/ioremap.c
+++ b/lib/ioremap.c
@@ -76,6 +76,25 @@ static int ioremap_pte_range(pmd_t *pmd, unsigned long addr,
        return 0;
 }
 
+static int ioremap_try_huge_pmd(pmd_t *pmd, unsigned long addr,
+                               unsigned long end, phys_addr_t phys_addr,
+                               pgprot_t prot)
+{
+       if (!ioremap_pmd_enabled())
+               return 0;
+
+       if ((end - addr) != PMD_SIZE)
+               return 0;
+
+       if (!IS_ALIGNED(phys_addr, PMD_SIZE))
+               return 0;
+
+       if (pmd_present(*pmd) && !pmd_free_pte_page(pmd, addr))
+               return 0;
+
+       return pmd_set_huge(pmd, phys_addr, prot);
+}
+
 static inline int ioremap_pmd_range(pud_t *pud, unsigned long addr,
                unsigned long end, phys_addr_t phys_addr, pgprot_t prot)
 {
@@ -89,13 +108,8 @@ static inline int ioremap_pmd_range(pud_t *pud, unsigned long addr,
        do {
                next = pmd_addr_end(addr, end);
 
-               if (ioremap_pmd_enabled() &&
-                   ((next - addr) == PMD_SIZE) &&
-                   IS_ALIGNED(phys_addr + addr, PMD_SIZE) &&
-                   pmd_free_pte_page(pmd, addr)) {
-                       if (pmd_set_huge(pmd, phys_addr + addr, prot))
-                               continue;
-               }
+               if (ioremap_try_huge_pmd(pmd, addr, next, phys_addr + addr, prot))
+                       continue;
 
                if (ioremap_pte_range(pmd, addr, next, phys_addr + addr, prot))
                        return -ENOMEM;
@@ -103,6 +117,25 @@ static inline int ioremap_pmd_range(pud_t *pud, unsigned long addr,
        return 0;
 }
 
+static int ioremap_try_huge_pud(pud_t *pud, unsigned long addr,
+                               unsigned long end, phys_addr_t phys_addr,
+                               pgprot_t prot)
+{
+       if (!ioremap_pud_enabled())
+               return 0;
+
+       if ((end - addr) != PUD_SIZE)
+               return 0;
+
+       if (!IS_ALIGNED(phys_addr, PUD_SIZE))
+               return 0;
+
+       if (pud_present(*pud) && !pud_free_pmd_page(pud, addr))
+               return 0;
+
+       return pud_set_huge(pud, phys_addr, prot);
+}
+
 static inline int ioremap_pud_range(p4d_t *p4d, unsigned long addr,
                unsigned long end, phys_addr_t phys_addr, pgprot_t prot)
 {
@@ -116,13 +149,8 @@ static inline int ioremap_pud_range(p4d_t *p4d, unsigned long addr,
        do {
                next = pud_addr_end(addr, end);
 
-               if (ioremap_pud_enabled() &&
-                   ((next - addr) == PUD_SIZE) &&
-                   IS_ALIGNED(phys_addr + addr, PUD_SIZE) &&
-                   pud_free_pmd_page(pud, addr)) {
-                       if (pud_set_huge(pud, phys_addr + addr, prot))
-                               continue;
-               }
+               if (ioremap_try_huge_pud(pud, addr, next, phys_addr + addr, prot))
+                       continue;
 
                if (ioremap_pmd_range(pud, addr, next, phys_addr + addr, prot))
                        return -ENOMEM;