Commit 20aae9ef authored by David Hildenbrand's avatar David Hildenbrand Committed by Andrew Morton
Browse files

arm/mm: support __HAVE_ARCH_PTE_SWP_EXCLUSIVE 

Let's support __HAVE_ARCH_PTE_SWP_EXCLUSIVE by stealing one bit from the
offset.  This reduces the maximum swap space per file to 64 GiB (was 128
GiB).

While at it drop the PTE_TYPE_FAULT from __swp_entry_to_pte() which is
defined to be 0 and is rather confusing because we should be dealing with
"Linux PTEs" not "hardware PTEs".  Also, properly mask the type in
__swp_entry().

Link: https://lkml.kernel.org/r/20230113171026.582290-5-david@redhat.com


Signed-off-by: default avatarDavid Hildenbrand <david@redhat.com>
Reviewed-by: default avatarRussell King (Oracle) <rmk+kernel@armlinux.org.uk>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
parent 4a446b3d

arch/arm/include/asm/pgtable-2level.h

+3 −0
Original line number Diff line number Diff line
@@ -126,6 +126,9 @@ 
#define L_PTE_SHARED		(_AT(pteval_t, 1) << 10)	/* shared(v6), coherent(xsc3) */

#define L_PTE_NONE		(_AT(pteval_t, 1) << 11)



/* We borrow bit 7 to store the exclusive marker in swap PTEs. */

#define L_PTE_SWP_EXCLUSIVE	L_PTE_RDONLY



/*

 * These are the memory types, defined to be compatible with

 * pre-ARMv6 CPUs cacheable and bufferable bits: n/a,n/a,C,B

arch/arm/include/asm/pgtable-3level.h

+3 −0
Original line number Diff line number Diff line
@@ -76,6 +76,9 @@ 
#define L_PTE_NONE		(_AT(pteval_t, 1) << 57)	/* PROT_NONE */

#define L_PTE_RDONLY		(_AT(pteval_t, 1) << 58)	/* READ ONLY */



/* We borrow bit 7 to store the exclusive marker in swap PTEs. */

#define L_PTE_SWP_EXCLUSIVE	(_AT(pteval_t, 1) << 7)



#define L_PMD_SECT_VALID	(_AT(pmdval_t, 1) << 0)

#define L_PMD_SECT_DIRTY	(_AT(pmdval_t, 1) << 55)

#define L_PMD_SECT_NONE		(_AT(pmdval_t, 1) << 57)

arch/arm/include/asm/pgtable.h

+28 −7
Original line number Diff line number Diff line
@@ -271,27 +271,48 @@ static inline pte_t pte_modify(pte_t pte, pgprot_t newprot) 
}



/*

 * Encode and decode a swap entry.  Swap entries are stored in the Linux

 * page tables as follows:

 * Encode/decode swap entries and swap PTEs. Swap PTEs are all PTEs that

 * are !pte_none() && !pte_present().

 *

 * Format of swap PTEs:

 *

 *   3 3 2 2 2 2 2 2 2 2 2 2 1 1 1 1 1 1 1 1 1 1

 *   1 0 9 8 7 6 5 4 3 2 1 0 9 8 7 6 5 4 3 2 1 0 9 8 7 6 5 4 3 2 1 0

 *   <--------------- offset ------------------------> < type -> 0 0

 *   <------------------- offset ------------------> E < type -> 0 0

 *

 *   E is the exclusive marker that is not stored in swap entries.

 *

 * This gives us up to 31 swap files and 128GB per swap file.  Note that

 * This gives us up to 31 swap files and 64GB per swap file.  Note that

 * the offset field is always non-zero.

 */

#define __SWP_TYPE_SHIFT	2

#define __SWP_TYPE_BITS		5

#define __SWP_TYPE_MASK		((1 << __SWP_TYPE_BITS) - 1)

#define __SWP_OFFSET_SHIFT	(__SWP_TYPE_BITS + __SWP_TYPE_SHIFT)

#define __SWP_OFFSET_SHIFT	(__SWP_TYPE_BITS + __SWP_TYPE_SHIFT + 1)



#define __swp_type(x)		(((x).val >> __SWP_TYPE_SHIFT) & __SWP_TYPE_MASK)

#define __swp_offset(x)		((x).val >> __SWP_OFFSET_SHIFT)

#define __swp_entry(type,offset) ((swp_entry_t) { ((type) << __SWP_TYPE_SHIFT) | ((offset) << __SWP_OFFSET_SHIFT) })

#define __swp_entry(type, offset) ((swp_entry_t) { (((type) & __SWP_TYPE_BITS) << __SWP_TYPE_SHIFT) | \

						   ((offset) << __SWP_OFFSET_SHIFT) })



#define __pte_to_swp_entry(pte)	((swp_entry_t) { pte_val(pte) })

#define __swp_entry_to_pte(swp)	__pte((swp).val | PTE_TYPE_FAULT)

#define __swp_entry_to_pte(swp)	__pte((swp).val)



#define __HAVE_ARCH_PTE_SWP_EXCLUSIVE

static inline int pte_swp_exclusive(pte_t pte)

{

	return pte_isset(pte, L_PTE_SWP_EXCLUSIVE);

}



static inline pte_t pte_swp_mkexclusive(pte_t pte)

{

	return set_pte_bit(pte, __pgprot(L_PTE_SWP_EXCLUSIVE));

}



static inline pte_t pte_swp_clear_exclusive(pte_t pte)

{

	return clear_pte_bit(pte, __pgprot(L_PTE_SWP_EXCLUSIVE));

}



/*

 * It is an error for the kernel to have more swap files than we can