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powerpc/mm: Handle VM_FAULT_RETRY earlier 

In do_page_fault() if handle_mm_fault() returns VM_FAULT_RETRY, retry
the page fault handling before anything else.

This would simplify the handling of the mmap_sem lock in this part of
the code.

Reviewed-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Signed-off-by: Laurent Dufour <ldufour@linux.vnet.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
This commit is contained in:
Laurent Dufour 2017-02-14 17:45:11 +01:00 committed by Michael Ellerman
parent c2294e0ffe
commit 14c02e419a
1 changed files with 37 additions and 28 deletions
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65
arch/powerpc/mm/fault.c
View File

@ -458,6 +458,26 @@ int do_page_fault(struct pt_regs *regs, unsigned long address,
* the fault.
*/
fault = handle_mm_fault(vma, address, flags);
/*
* Handle the retry right now, the mmap_sem has been released in that
* case.
*/
if (unlikely(fault & VM_FAULT_RETRY)) {
/* We retry only once */
if (flags & FAULT_FLAG_ALLOW_RETRY) {
/*
* Clear FAULT_FLAG_ALLOW_RETRY to avoid any risk
* of starvation.
*/
flags &= ~FAULT_FLAG_ALLOW_RETRY;
flags |= FAULT_FLAG_TRIED;
if (!fatal_signal_pending(current))
goto retry;
}
/* We will enter mm_fault_error() below */
}
if (unlikely(fault & (VM_FAULT_RETRY|VM_FAULT_ERROR))) {
if (fault & VM_FAULT_SIGSEGV)
goto bad_area;
@ -469,38 +489,27 @@ int do_page_fault(struct pt_regs *regs, unsigned long address,
}
/*
* Major/minor page fault accounting is only done on the
* initial attempt. If we go through a retry, it is extremely
* likely that the page will be found in page cache at that point.
* Major/minor page fault accounting.
*/
if (flags & FAULT_FLAG_ALLOW_RETRY) {
if (fault & VM_FAULT_MAJOR) {
current->maj_flt++;
perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MAJ, 1,
regs, address);
if (fault & VM_FAULT_MAJOR) {
current->maj_flt++;
perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MAJ, 1,
regs, address);
#ifdef CONFIG_PPC_SMLPAR
if (firmware_has_feature(FW_FEATURE_CMO)) {
u32 page_ins;
if (firmware_has_feature(FW_FEATURE_CMO)) {
u32 page_ins;
preempt_disable();
page_ins = be32_to_cpu(get_lppaca()->page_ins);
page_ins += 1 << PAGE_FACTOR;
get_lppaca()->page_ins = cpu_to_be32(page_ins);
preempt_enable();
}
preempt_disable();
page_ins = be32_to_cpu(get_lppaca()->page_ins);
page_ins += 1 << PAGE_FACTOR;
get_lppaca()->page_ins = cpu_to_be32(page_ins);
preempt_enable();
}
#endif /* CONFIG_PPC_SMLPAR */
} else {
current->min_flt++;
perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MIN, 1,
regs, address);
}
if (fault & VM_FAULT_RETRY) {
/* Clear FAULT_FLAG_ALLOW_RETRY to avoid any risk
* of starvation. */
flags &= ~FAULT_FLAG_ALLOW_RETRY;
flags |= FAULT_FLAG_TRIED;
goto retry;
}
} else {
current->min_flt++;
perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MIN, 1,
regs, address);
}
up_read(&mm->mmap_sem);