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Date: Fri, 27 Apr 2018 04:34:26 -0700
From: Matthew Wilcox <willy@...radead.org>
To: Souptick Joarder <jrdr.linux@...il.com>
Cc: Ross Zwisler <ross.zwisler@...ux.intel.com>,
Jan Kara <jack@...e.cz>, Al Viro <viro@...iv.linux.org.uk>,
Andrew Morton <akpm@...ux-foundation.org>,
Dan Williams <dan.j.williams@...el.com>,
Michal Hocko <mhocko@...e.com>,
kirill.shutemov@...ux.intel.com,
linux-fsdevel <linux-fsdevel@...r.kernel.org>,
Linux-MM <linux-mm@...ck.org>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v6] fs: dax: Adding new return type vm_fault_t
On Fri, Apr 27, 2018 at 10:54:53AM +0530, Souptick Joarder wrote:
> > I noticed that we have the following status translation now in 4 places in 2
> > files:
> >
> > if (err == -ENOMEM)
> > return VM_FAULT_OOM;
> > if (err < 0 && err != -EBUSY)
> > return VM_FAULT_SIGBUS;
> > return VM_FAULT_NOPAGE;
> >
> >
> > This happens in vmf_insert_mixed_mkwrite(), vmf_insert_page(),
> > vmf_insert_mixed() and vmf_insert_pfn().
> >
> > I think it'd be a good idea to consolidate this translation into an inline
> > helper, in the spirit of dax_fault_return(). This will ensure that if/when we
> > start changing this status translation, we won't accidentally miss some of the
> > places which would make them get out of sync. No need to fold this into this
> > patch - it should be a separate change.
>
> Sure, I will send this as a separate patch.
No, this will entirely go away when vm_insert_foo() is removed. Here's what
it'll look like instead:
@@ -1703,23 +1703,23 @@ pte_t *__get_locked_pte(struct mm_struct *mm, unsigned long addr,
* old drivers should use this, and they needed to mark their
* pages reserved for the old functions anyway.
*/
-static int insert_page(struct vm_area_struct *vma, unsigned long addr,
+static vm_fault_t insert_page(struct vm_area_struct *vma, unsigned long addr,
struct page *page, pgprot_t prot)
{
struct mm_struct *mm = vma->vm_mm;
- int retval;
+ vm_fault_t ret;
pte_t *pte;
spinlock_t *ptl;
- retval = -EINVAL;
+ ret = VM_FAULT_SIGBUS;
if (PageAnon(page))
goto out;
- retval = -ENOMEM;
+ ret = VM_FAULT_OOM;
flush_dcache_page(page);
pte = get_locked_pte(mm, addr, &ptl);
if (!pte)
goto out;
- retval = -EBUSY;
+ ret = 0;
if (!pte_none(*pte))
goto out_unlock;
@@ -1729,17 +1729,14 @@ static int insert_page(struct vm_area_struct *vma, unsigned long addr,
page_add_file_rmap(page, false);
set_pte_at(mm, addr, pte, mk_pte(page, prot));
- retval = 0;
- pte_unmap_unlock(pte, ptl);
- return retval;
out_unlock:
pte_unmap_unlock(pte, ptl);
out:
- return retval;
+ return ret;
}
/**
- * vm_insert_page - insert single page into user vma
+ * vmf_insert_page - insert single page into user vma
* @vma: user vma to map to
* @addr: target user address of this page
* @page: source kernel page
@@ -1765,13 +1762,13 @@ static int insert_page(struct vm_area_struct *vma, unsigned long addr,
* Caller must set VM_MIXEDMAP on vma if it wants to call this
* function from other places, for example from page-fault handler.
*/
-int vm_insert_page(struct vm_area_struct *vma, unsigned long addr,
+vm_fault_t vmf_insert_page(struct vm_area_struct *vma, unsigned long addr,
struct page *page)
{
if (addr < vma->vm_start || addr >= vma->vm_end)
- return -EFAULT;
+ return VM_FAULT_SIGBUS;
if (!page_count(page))
- return -EINVAL;
+ return VM_FAULT_SIGBUS;
if (!(vma->vm_flags & VM_MIXEDMAP)) {
BUG_ON(down_read_trylock(&vma->vm_mm->mmap_sem));
BUG_ON(vma->vm_flags & VM_PFNMAP);
@@ -1779,21 +1776,21 @@ int vm_insert_page(struct vm_area_struct *vma, unsigned long addr,
}
return insert_page(vma, addr, page, vma->vm_page_prot);
}
-EXPORT_SYMBOL(vm_insert_page);
+EXPORT_SYMBOL(vmf_insert_page);
-static int insert_pfn(struct vm_area_struct *vma, unsigned long addr,
+static vm_fault_t insert_pfn(struct vm_area_struct *vma, unsigned long addr,
pfn_t pfn, pgprot_t prot, bool mkwrite)
{
struct mm_struct *mm = vma->vm_mm;
- int retval;
+ vm_fault_t ret;
pte_t *pte, entry;
spinlock_t *ptl;
- retval = -ENOMEM;
+ ret = VM_FAULT_OOM;
pte = get_locked_pte(mm, addr, &ptl);
if (!pte)
goto out;
- retval = -EBUSY;
+ ret = VM_FAULT_SIGBUS;
if (!pte_none(*pte)) {
if (mkwrite) {
/*
@@ -1826,20 +1823,20 @@ static int insert_pfn(struct vm_area_struct *vma, unsigned long addr,
set_pte_at(mm, addr, pte, entry);
update_mmu_cache(vma, addr, pte); /* XXX: why not for insert_page? */
- retval = 0;
+ ret = 0;
out_unlock:
pte_unmap_unlock(pte, ptl);
out:
- return retval;
+ return ret;
}
/**
- * vm_insert_pfn - insert single pfn into user vma
+ * vmf_insert_pfn - insert single pfn into user vma
* @vma: user vma to map to
* @addr: target user address of this page
* @pfn: source kernel pfn
*
- * Similar to vm_insert_page, this allows drivers to insert individual pages
+ * Similar to vmf_insert_page(), this allows drivers to insert individual pages
* they've allocated into a user vma. Same comments apply.
*
* This function should only be called from a vm_ops->fault handler, and
@@ -1850,21 +1847,21 @@ static int insert_pfn(struct vm_area_struct *vma, unsigned long addr,
* As this is called only for pages that do not currently exist, we
* do not need to flush old virtual caches or the TLB.
*/
-int vm_insert_pfn(struct vm_area_struct *vma, unsigned long addr,
+vm_fault_t vmf_insert_pfn(struct vm_area_struct *vma, unsigned long addr,
unsigned long pfn)
{
- return vm_insert_pfn_prot(vma, addr, pfn, vma->vm_page_prot);
+ return vmf_insert_pfn_prot(vma, addr, pfn, vma->vm_page_prot);
}
-EXPORT_SYMBOL(vm_insert_pfn);
+EXPORT_SYMBOL(vmf_insert_pfn);
... etc ...
But first, we have to finish removing all the calls to vm_insert_foo().
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