[v2,39/42] example for future extension: mm:gup/writeback: add callbacks for inaccessible pages: error cases
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Message ID 20200214222658.12946-40-borntraeger@de.ibm.com
State New
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Series
  • KVM: s390: Add support for protected VMs
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Commit Message

Christian Borntraeger Feb. 14, 2020, 10:26 p.m. UTC
From: Claudio Imbrenda <imbrenda@linux.ibm.com>

This is a potential extension to do error handling if we fail to
make the page accessible if we know what others need.

Signed-off-by: Claudio Imbrenda <imbrenda@linux.ibm.com>
---
 mm/gup.c            | 17 ++++++++++++-----
 mm/page-writeback.c |  6 +++++-
 2 files changed, 17 insertions(+), 6 deletions(-)

Comments

Will Deacon Feb. 18, 2020, 4:25 p.m. UTC | #1
On Fri, Feb 14, 2020 at 05:26:55PM -0500, Christian Borntraeger wrote:
> From: Claudio Imbrenda <imbrenda@linux.ibm.com>
> 
> This is a potential extension to do error handling if we fail to
> make the page accessible if we know what others need.
> 
> Signed-off-by: Claudio Imbrenda <imbrenda@linux.ibm.com>
> ---
>  mm/gup.c            | 17 ++++++++++++-----
>  mm/page-writeback.c |  6 +++++-
>  2 files changed, 17 insertions(+), 6 deletions(-)

Sorry, I missed this when replying elsewhere in the thread!
Anyway, looks good to me:

Acked-by: Will Deacon <will@kernel.org>

Thanks,

Will
Christian Borntraeger Feb. 18, 2020, 4:30 p.m. UTC | #2
On 18.02.20 17:25, Will Deacon wrote:
> On Fri, Feb 14, 2020 at 05:26:55PM -0500, Christian Borntraeger wrote:
>> From: Claudio Imbrenda <imbrenda@linux.ibm.com>
>>
>> This is a potential extension to do error handling if we fail to
>> make the page accessible if we know what others need.
>>
>> Signed-off-by: Claudio Imbrenda <imbrenda@linux.ibm.com>
>> ---
>>  mm/gup.c            | 17 ++++++++++++-----
>>  mm/page-writeback.c |  6 +++++-
>>  2 files changed, 17 insertions(+), 6 deletions(-)
> 
> Sorry, I missed this when replying elsewhere in the thread!
> Anyway, looks good to me:
> 
> Acked-by: Will Deacon <will@kernel.org>

I can use that for a combined patch (this one merged into the first) ? Correct?
Will Deacon Feb. 18, 2020, 4:33 p.m. UTC | #3
On Tue, Feb 18, 2020 at 05:30:40PM +0100, Christian Borntraeger wrote:
> On 18.02.20 17:25, Will Deacon wrote:
> > On Fri, Feb 14, 2020 at 05:26:55PM -0500, Christian Borntraeger wrote:
> >> From: Claudio Imbrenda <imbrenda@linux.ibm.com>
> >>
> >> This is a potential extension to do error handling if we fail to
> >> make the page accessible if we know what others need.
> >>
> >> Signed-off-by: Claudio Imbrenda <imbrenda@linux.ibm.com>
> >> ---
> >>  mm/gup.c            | 17 ++++++++++++-----
> >>  mm/page-writeback.c |  6 +++++-
> >>  2 files changed, 17 insertions(+), 6 deletions(-)
> > 
> > Sorry, I missed this when replying elsewhere in the thread!
> > Anyway, looks good to me:
> > 
> > Acked-by: Will Deacon <will@kernel.org>
> 
> I can use that for a combined patch (this one merged into the first) ? Correct?

Fine by me!

Will

Patch
diff mbox series

diff --git a/mm/gup.c b/mm/gup.c
index a1c15d029f7c..354bcfbd844b 100644
--- a/mm/gup.c
+++ b/mm/gup.c
@@ -193,6 +193,7 @@  static struct page *follow_page_pte(struct vm_area_struct *vma,
 	struct page *page;
 	spinlock_t *ptl;
 	pte_t *ptep, pte;
+	int ret;
 
 	/* FOLL_GET and FOLL_PIN are mutually exclusive. */
 	if (WARN_ON_ONCE((flags & (FOLL_PIN | FOLL_GET)) ==
@@ -250,8 +251,6 @@  static struct page *follow_page_pte(struct vm_area_struct *vma,
 		if (is_zero_pfn(pte_pfn(pte))) {
 			page = pte_page(pte);
 		} else {
-			int ret;
-
 			ret = follow_pfn_pte(vma, address, ptep, flags);
 			page = ERR_PTR(ret);
 			goto out;
@@ -259,7 +258,6 @@  static struct page *follow_page_pte(struct vm_area_struct *vma,
 	}
 
 	if (flags & FOLL_SPLIT && PageTransCompound(page)) {
-		int ret;
 		get_page(page);
 		pte_unmap_unlock(ptep, ptl);
 		lock_page(page);
@@ -276,7 +274,12 @@  static struct page *follow_page_pte(struct vm_area_struct *vma,
 			page = ERR_PTR(-ENOMEM);
 			goto out;
 		}
-		arch_make_page_accessible(page);
+		ret = arch_make_page_accessible(page);
+		if (ret) {
+			put_page(page);
+			page = ERR_PTR(ret);
+			goto out;
+		}
 	}
 	if (flags & FOLL_TOUCH) {
 		if ((flags & FOLL_WRITE) &&
@@ -1920,7 +1923,11 @@  static int gup_pte_range(pmd_t pmd, unsigned long addr, unsigned long end,
 
 		VM_BUG_ON_PAGE(compound_head(page) != head, page);
 
-		arch_make_page_accessible(page);
+		ret = arch_make_page_accessible(page);
+		if (ret) {
+			put_page(head);
+			goto pte_unmap;
+		}
 		SetPageReferenced(page);
 		pages[*nr] = page;
 		(*nr)++;
diff --git a/mm/page-writeback.c b/mm/page-writeback.c
index 4c020e4ae71c..558d7063c117 100644
--- a/mm/page-writeback.c
+++ b/mm/page-writeback.c
@@ -2807,7 +2807,11 @@  int __test_set_page_writeback(struct page *page, bool keep_write)
 		inc_zone_page_state(page, NR_ZONE_WRITE_PENDING);
 	}
 	unlock_page_memcg(page);
-	arch_make_page_accessible(page);
+	/*
+	 * If writeback has been triggered on a page that cannot be made
+	 * accessible, it is too late.
+	 */
+	WARN_ON(arch_make_page_accessible(page));
 	return ret;
 
 }