| Message ID | 20180628235914.20706-1-abrodkin@synopsys.com |
|---|---|
| State | New |
| Headers | show |
| Series | ARC: Fix __swp_offset() implementation | expand |
On 06/28/2018 04:59 PM, Alexey Brodkin wrote: > We encode offset from swapcache page in __swp_entry() this way, see [1]: > | /* Encode swap {type,off} tuple into PTE > | * We reserve 13 bits for 5-bit @type, keeping bits 12-5 zero, ensuring that > | * PAGE_PRESENT is zero in a PTE holding swap "identifier" > | */ > | #define __swp_entry(type, off) ((swp_entry_t) { \ > | ((type) & 0x1f) | ((off) << 13) }) > > But decode in __swp_offset() as: > | #define __swp_offset(pte_lookalike) ((pte_lookalike).val << 13) > which is obviously wrong, we should ">> 13" instead. > > This basically fixes swap usage on ARC finally. Nice. Wish all fixes were so simple ;-) I've added this to for-curr and will also make its way to stable, but lets clean up this mess of hardcoded 13 properly as a cleanup patch. There are good references to look at : arm, riscv etc Thx, -Vineet
diff --git a/arch/arc/include/asm/pgtable.h b/arch/arc/include/asm/pgtable.h index 08fe33830d4b..77676e18da69 100644 --- a/arch/arc/include/asm/pgtable.h +++ b/arch/arc/include/asm/pgtable.h @@ -379,7 +379,7 @@ void update_mmu_cache(struct vm_area_struct *vma, unsigned long address, /* Decode a PTE containing swap "identifier "into constituents */ #define __swp_type(pte_lookalike) (((pte_lookalike).val) & 0x1f) -#define __swp_offset(pte_lookalike) ((pte_lookalike).val << 13) +#define __swp_offset(pte_lookalike) ((pte_lookalike).val >> 13) /* NOPs, to keep generic kernel happy */ #define __pte_to_swp_entry(pte) ((swp_entry_t) { pte_val(pte) })
We encode offset from swapcache page in __swp_entry() this way, see [1]: | /* Encode swap {type,off} tuple into PTE | * We reserve 13 bits for 5-bit @type, keeping bits 12-5 zero, ensuring that | * PAGE_PRESENT is zero in a PTE holding swap "identifier" | */ | #define __swp_entry(type, off) ((swp_entry_t) { \ | ((type) & 0x1f) | ((off) << 13) }) But decode in __swp_offset() as: | #define __swp_offset(pte_lookalike) ((pte_lookalike).val << 13) which is obviously wrong, we should ">> 13" instead. This basically fixes swap usage on ARC finally. | # mkswap /dev/sda2 | | # swapon -a -e /dev/sda2 | Adding 500728k swap on /dev/sda2. Priority:-2 extents:1 across:500728k | | # free | total used free shared buffers cached | Mem: 765104 13456 751648 4736 8 4736 | -/+ buffers/cache: 8712 756392 | Swap: 500728 0 500728 [1] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/arch/arc/include/asm/pgtable.h#n375 Signed-off-by: Alexey Brodkin <abrodkin@synopsys.com> Cc: stable@vger.kernel.org --- arch/arc/include/asm/pgtable.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)