Messages in this thread Patch in this message | | | From | Laurent Dufour <> | Subject | [PATCH 2/3] powerpc/mm: handle VM_FAULT_RETRY earlier | Date | Tue, 14 Feb 2017 17:45:11 +0100 |
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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.
Signed-off-by: Laurent Dufour <ldufour@linux.vnet.ibm.com> --- arch/powerpc/mm/fault.c | 67 ++++++++++++++++++++++++++++--------------------- 1 file changed, 38 insertions(+), 29 deletions(-)
diff --git a/arch/powerpc/mm/fault.c b/arch/powerpc/mm/fault.c index ee09604bbe12..2a6bc7e6e69a 100644 --- a/arch/powerpc/mm/fault.c +++ b/arch/powerpc/mm/fault.c @@ -434,6 +434,26 @@ 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; @@ -445,38 +465,27 @@ 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; - - 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; + 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(); } +#endif /* CONFIG_PPC_SMLPAR */ + } else { + current->min_flt++; + perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MIN, 1, + regs, address); } up_read(&mm->mmap_sem); -- 2.7.4
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