[PATCH 3/3] powerpc/mm: move mmap_sem unlocking in do_page_fault()

Laurent Dufour
2017-02-14T16:45:45Z

Since the fault retry is now handled earlier, we can release the
mmap_sem lock earlier too and remove later unlocking previously done in
mm_fault_error().

Signed-off-by: Laurent Dufour <ldufour@linux.vnet.ibm.com>
---
arch/powerpc/mm/fault.c | 19 ++++---------------
1 file changed, 4 insertions(+), 15 deletions(-)

diff --git a/arch/powerpc/mm/fault.c b/arch/powerpc/mm/fault.c
index 2a6bc7e6e69a..21e06cce8984 100644
--- a/arch/powerpc/mm/fault.c
+++ b/arch/powerpc/mm/fault.c
@@ -151,13 +151,6 @@ static int mm_fault_error(struct pt_regs *regs, unsigned long addr, int fault)
* continue the pagefault.
*/
if (fatal_signal_pending(current)) {
- /*
- * If we have retry set, the mmap semaphore will have
- * alrady been released in __lock_page_or_retry(). Else
- * we release it now.
- */
- if (!(fault & VM_FAULT_RETRY))
- up_read(&current->mm->mmap_sem);
/* Coming from kernel, we need to deal with uaccess fixups */
if (user_mode(regs))
return MM_FAULT_RETURN;
@@ -170,8 +163,6 @@ static int mm_fault_error(struct pt_regs *regs, unsigned long addr, int fault)

/* Out of memory */
if (fault & VM_FAULT_OOM) {
- up_read(&current->mm->mmap_sem);
-
/*
* We ran out of memory, or some other thing happened to us that
* made us unable to handle the page fault gracefully.
@@ -182,10 +173,8 @@ static int mm_fault_error(struct pt_regs *regs, unsigned long addr, int fault)
return MM_FAULT_RETURN;
}

- if (fault & (VM_FAULT_SIGBUS|VM_FAULT_HWPOISON|VM_FAULT_HWPOISON_LARGE)) {
- up_read(&current->mm->mmap_sem);
+ if (fault & (VM_FAULT_SIGBUS|VM_FAULT_HWPOISON|VM_FAULT_HWPOISON_LARGE))
return do_sigbus(regs, addr, fault);
- }

/* We don't understand the fault code, this is fatal */
BUG();
@@ -452,11 +441,12 @@ int do_page_fault(struct pt_regs *regs, unsigned long address,
goto retry;
}
/* We will enter mm_fault_error() below */
- }
+ } else
+ up_read(&current->mm->mmap_sem);

if (unlikely(fault & (VM_FAULT_RETRY|VM_FAULT_ERROR))) {
if (fault & VM_FAULT_SIGSEGV)
- goto bad_area;
+ goto bad_area_nosemaphore;
rc = mm_fault_error(regs, address, fault);
if (rc >= MM_FAULT_RETURN)
goto bail;
@@ -488,7 +478,6 @@ int do_page_fault(struct pt_regs *regs, unsigned long address,
regs, address);
}

- up_read(&mm->mmap_sem);
goto bail;

bad_area:
--
2.7.4