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powerpc/mm: Move around testing of _PAGE_PRESENT in hash code 

Instead of adding _PAGE_PRESENT to the access permission mask
in each low level routine independently, we add it once from
hash_page().

We also move the preliminary access check (the racy one before
the PTE is locked) up so it applies to the huge page case. This
duplicates code in __hash_page_huge() which we'll remove in a
subsequent patch to fix a race in there.

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
This commit is contained in:
Benjamin Herrenschmidt 2010-07-23 08:53:23 +10:00
parent b1623e7eb2
commit ca91e6c09d
2 changed files with 11 additions and 17 deletions
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9
arch/powerpc/mm/hash_low_64.S
View File

@ -68,9 +68,6 @@ _GLOBAL(__hash_page_4K)
std r8,STK_PARM(r8)(r1)
std r9,STK_PARM(r9)(r1)
/* Add _PAGE_PRESENT to access */
ori r4,r4,_PAGE_PRESENT
/* Save non-volatile registers.
* r31 will hold "old PTE"
* r30 is "new PTE"
@ -347,9 +344,6 @@ _GLOBAL(__hash_page_4K)
std r8,STK_PARM(r8)(r1)
std r9,STK_PARM(r9)(r1)
/* Add _PAGE_PRESENT to access */
ori r4,r4,_PAGE_PRESENT
/* Save non-volatile registers.
* r31 will hold "old PTE"
* r30 is "new PTE"
@ -687,9 +681,6 @@ _GLOBAL(__hash_page_64K)
std r8,STK_PARM(r8)(r1)
std r9,STK_PARM(r9)(r1)
/* Add _PAGE_PRESENT to access */
ori r4,r4,_PAGE_PRESENT
/* Save non-volatile registers.
* r31 will hold "old PTE"
* r30 is "new PTE"

19
arch/powerpc/mm/hash_utils_64.c
View File

@ -955,6 +955,17 @@ int hash_page(unsigned long ea, unsigned long access, unsigned long trap)
return 1;
}
/* Add _PAGE_PRESENT to the required access perm */
access |= _PAGE_PRESENT;
/* Pre-check access permissions (will be re-checked atomically
* in __hash_page_XX but this pre-check is a fast path
*/
if (access & ~pte_val(*ptep)) {
DBG_LOW(" no access !\n");
return 1;
}
#ifdef CONFIG_HUGETLB_PAGE
if (hugeshift)
return __hash_page_huge(ea, access, vsid, ptep, trap, local,
@ -967,14 +978,6 @@ int hash_page(unsigned long ea, unsigned long access, unsigned long trap)
DBG_LOW(" i-pte: %016lx %016lx\n", pte_val(*ptep),
pte_val(*(ptep + PTRS_PER_PTE)));
#endif
/* Pre-check access permissions (will be re-checked atomically
* in __hash_page_XX but this pre-check is a fast path
*/
if (access & ~pte_val(*ptep)) {
DBG_LOW(" no access !\n");
return 1;
}
/* Do actual hashing */
#ifdef CONFIG_PPC_64K_PAGES
/* If _PAGE_4K_PFN is set, make sure this is a 4k segment */