[RFC v5 11/11] powerpc/mm: Add speculative page fault

[Laurent Dufour]

This patch enable the speculative page fault on the PowerPC
architecture.

This will try a speculative page fault without holding the mmap_sem,
if it returns with WM_FAULT_RETRY, the mmap_sem is acquired and the
traditional page fault processing is done.

Signed-off-by: Laurent Dufour 
---
 arch/powerpc/mm/fault.c | 25 -
 1 file changed, 24 insertions(+), 1 deletion(-)

diff --git a/arch/powerpc/mm/fault.c b/arch/powerpc/mm/fault.c
index 3a7d580fdc59..4b6d0ed517ca 100644
--- a/arch/powerpc/mm/fault.c
+++ b/arch/powerpc/mm/fault.c
@@ -290,9 +290,31 @@ int do_page_fault(struct pt_regs *regs, unsigned long 
address,
if (!is_exec && user_mode(regs))
store_update_sp = store_updates_sp(regs);
 
-   if (user_mode(regs))
+   if (user_mode(regs)) {
flags |= FAULT_FLAG_USER;
 
+   /* let's try a speculative page fault without grabbing the
+* mmap_sem.
+*/
+
+   /*
+* flags is set later based on the VMA's flags, for the common
+* speculative service, we need some flags to be set.
+*/
+   if (is_write)
+   flags |= FAULT_FLAG_WRITE;
+
+   fault = handle_speculative_fault(mm, address, flags);
+   if (!(fault & VM_FAULT_RETRY || fault & VM_FAULT_ERROR))
+   goto done;
+
+   /*
+* Resetting flags since the following code assumes
+* FAULT_FLAG_WRITE is not set.
+*/
+   flags &= ~FAULT_FLAG_WRITE;
+   }
+
/* When running in the kernel we expect faults to occur only to
 * addresses in user space.  All other faults represent errors in the
 * kernel and should generate an OOPS.  Unfortunately, in the case of an
@@ -478,6 +500,7 @@ int do_page_fault(struct pt_regs *regs, unsigned long 
address,
rc = 0;
}
 
+done:
/*
 * Major/minor page fault accounting.
 */
-- 
2.7.4

[RFC v5 11/11] powerpc/mm: Add speculative page fault

[Laurent Dufour]

This patch enable the speculative page fault on the PowerPC
architecture.

This will try a speculative page fault without holding the mmap_sem,
if it returns with WM_FAULT_RETRY, the mmap_sem is acquired and the
traditional page fault processing is done.

Signed-off-by: Laurent Dufour 
---
 arch/powerpc/mm/fault.c | 25 -
 1 file changed, 24 insertions(+), 1 deletion(-)

diff --git a/arch/powerpc/mm/fault.c b/arch/powerpc/mm/fault.c
index 3a7d580fdc59..4b6d0ed517ca 100644
--- a/arch/powerpc/mm/fault.c
+++ b/arch/powerpc/mm/fault.c
@@ -290,9 +290,31 @@ int do_page_fault(struct pt_regs *regs, unsigned long 
address,
if (!is_exec && user_mode(regs))
store_update_sp = store_updates_sp(regs);
 
-   if (user_mode(regs))
+   if (user_mode(regs)) {
flags |= FAULT_FLAG_USER;
 
+   /* let's try a speculative page fault without grabbing the
+* mmap_sem.
+*/
+
+   /*
+* flags is set later based on the VMA's flags, for the common
+* speculative service, we need some flags to be set.
+*/
+   if (is_write)
+   flags |= FAULT_FLAG_WRITE;
+
+   fault = handle_speculative_fault(mm, address, flags);
+   if (!(fault & VM_FAULT_RETRY || fault & VM_FAULT_ERROR))
+   goto done;
+
+   /*
+* Resetting flags since the following code assumes
+* FAULT_FLAG_WRITE is not set.
+*/
+   flags &= ~FAULT_FLAG_WRITE;
+   }
+
/* When running in the kernel we expect faults to occur only to
 * addresses in user space.  All other faults represent errors in the
 * kernel and should generate an OOPS.  Unfortunately, in the case of an
@@ -478,6 +500,7 @@ int do_page_fault(struct pt_regs *regs, unsigned long 
address,
rc = 0;
}
 
+done:
/*
 * Major/minor page fault accounting.
 */
-- 
2.7.4