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Message-Id: <b765e16e66c9422c896294a11fe624ecb7e44384.1406058387.git.matthew.r.wilcox@intel.com> Date: Tue, 22 Jul 2014 15:47:50 -0400 From: Matthew Wilcox <matthew.r.wilcox@...el.com> To: linux-fsdevel@...r.kernel.org, linux-mm@...ck.org, linux-kernel@...r.kernel.org Cc: Matthew Wilcox <matthew.r.wilcox@...el.com>, willy@...ux.intel.com Subject: [PATCH v8 02/22] Allow page fault handlers to perform the COW Currently COW of an XIP file is done by first bringing in a read-only mapping, then retrying the fault and copying the page. It is much more efficient to tell the fault handler that a COW is being attempted (by passing in the pre-allocated page in the vm_fault structure), and allow the handler to perform the COW operation itself. Signed-off-by: Matthew Wilcox <matthew.r.wilcox@...el.com> Reviewed-by: Jan Kara <jack@...e.cz> --- include/linux/mm.h | 1 + mm/memory.c | 11 +++++++---- 2 files changed, 8 insertions(+), 4 deletions(-) diff --git a/include/linux/mm.h b/include/linux/mm.h index e03dd29..e04f531 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -208,6 +208,7 @@ struct vm_fault { pgoff_t pgoff; /* Logical page offset based on vma */ void __user *virtual_address; /* Faulting virtual address */ + struct page *cow_page; /* Handler may choose to COW */ struct page *page; /* ->fault handlers should return a * page here, unless VM_FAULT_NOPAGE * is set (which is also implied by diff --git a/mm/memory.c b/mm/memory.c index d67fd9f..42bf429 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -2003,6 +2003,7 @@ static int do_page_mkwrite(struct vm_area_struct *vma, struct page *page, vmf.pgoff = page->index; vmf.flags = FAULT_FLAG_WRITE|FAULT_FLAG_MKWRITE; vmf.page = page; + vmf.cow_page = NULL; ret = vma->vm_ops->page_mkwrite(vma, &vmf); if (unlikely(ret & (VM_FAULT_ERROR | VM_FAULT_NOPAGE))) @@ -2689,7 +2690,8 @@ oom: } static int __do_fault(struct vm_area_struct *vma, unsigned long address, - pgoff_t pgoff, unsigned int flags, struct page **page) + pgoff_t pgoff, unsigned int flags, + struct page *cow_page, struct page **page) { struct vm_fault vmf; int ret; @@ -2698,6 +2700,7 @@ static int __do_fault(struct vm_area_struct *vma, unsigned long address, vmf.pgoff = pgoff; vmf.flags = flags; vmf.page = NULL; + vmf.cow_page = cow_page; ret = vma->vm_ops->fault(vma, &vmf); if (unlikely(ret & (VM_FAULT_ERROR | VM_FAULT_NOPAGE | VM_FAULT_RETRY))) @@ -2890,7 +2893,7 @@ static int do_read_fault(struct mm_struct *mm, struct vm_area_struct *vma, pte_unmap_unlock(pte, ptl); } - ret = __do_fault(vma, address, pgoff, flags, &fault_page); + ret = __do_fault(vma, address, pgoff, flags, NULL, &fault_page); if (unlikely(ret & (VM_FAULT_ERROR | VM_FAULT_NOPAGE | VM_FAULT_RETRY))) return ret; @@ -2929,7 +2932,7 @@ static int do_cow_fault(struct mm_struct *mm, struct vm_area_struct *vma, return VM_FAULT_OOM; } - ret = __do_fault(vma, address, pgoff, flags, &fault_page); + ret = __do_fault(vma, address, pgoff, flags, new_page, &fault_page); if (unlikely(ret & (VM_FAULT_ERROR | VM_FAULT_NOPAGE | VM_FAULT_RETRY))) goto uncharge_out; @@ -2965,7 +2968,7 @@ static int do_shared_fault(struct mm_struct *mm, struct vm_area_struct *vma, int dirtied = 0; int ret, tmp; - ret = __do_fault(vma, address, pgoff, flags, &fault_page); + ret = __do_fault(vma, address, pgoff, flags, NULL, &fault_page); if (unlikely(ret & (VM_FAULT_ERROR | VM_FAULT_NOPAGE | VM_FAULT_RETRY))) return ret; -- 2.0.0 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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