Re: [PATCH 07/20] mm: Add orig_pte field into vm_fault
From: Ross Zwisler <hidden>
Date: 2016-10-17 16:45:12
Also in:
linux-fsdevel, nvdimm
On Tue, Sep 27, 2016 at 06:08:11PM +0200, Jan Kara wrote:
Add orig_pte field to vm_fault structure to allow ->page_mkwrite handlers to fully handle the fault. This also allows us to save some passing of extra arguments around. Signed-off-by: Jan Kara <jack@suse.cz> ---
quoted hunk ↗ jump to hunk
diff --git a/mm/khugepaged.c b/mm/khugepaged.c index f88b2d3810a7..66bc77f2d1d2 100644 --- a/mm/khugepaged.c +++ b/mm/khugepaged.c@@ -890,11 +890,12 @@ static bool __collapse_huge_page_swapin(struct mm_struct *mm, vmf.pte = pte_offset_map(pmd, address); for (; vmf.address < address + HPAGE_PMD_NR*PAGE_SIZE; vmf.pte++, vmf.address += PAGE_SIZE) { - pteval = *vmf.pte; + vmf.orig_pte = *vmf.pte; + pteval = vmf.orig_pte; if (!is_swap_pte(pteval)) continue;
'pteval' is now only used once. It's probably cleaner to just remove it and use vmf.orig_pte for the is_swap_pte() check.
quoted hunk ↗ jump to hunk
@@ -3484,8 +3484,7 @@ static int handle_pte_fault(struct vm_fault *vmf) * So now it's safe to run pte_offset_map(). */ vmf->pte = pte_offset_map(vmf->pmd, vmf->address); - - entry = *vmf->pte; + vmf->orig_pte = *vmf->pte; /* * some architectures can have larger ptes than wordsize,@@ -3496,6 +3495,7 @@ static int handle_pte_fault(struct vm_fault *vmf) * ptl lock held. So here a barrier will do. */ barrier(); + entry = vmf->orig_pte;
This set of 'entry' is now on the other side of the barrier(). I'll admit that I don't fully grok the need for the barrier. Does it apply to only the setting of vmf->pte and vmf->orig_pte, or does 'entry' also matter because it too is of type pte_t, and thus could be bigger than the architecture's word size? My guess is that 'entry' matters, too, and should remain before the barrier() call. If not, can you help me understand why? -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>