diff mbox

[08/20] mm: Allow full handling of COW faults in ->fault handlers

Message ID 1474992504-20133-9-git-send-email-jack@suse.cz (mailing list archive)
State New, archived
Headers show

Commit Message

Jan Kara Sept. 27, 2016, 4:08 p.m. UTC 
To allow full handling of COW faults add memcg field to struct vm_fault
and a return value of ->fault() handler meaning that COW fault is fully
handled and memcg charge must not be canceled. This will allow us to
remove knowledge about special DAX locking from the generic fault code.

Signed-off-by: Jan Kara <jack@suse.cz>
---
 include/linux/mm.h | 4 +++-
 mm/memory.c        | 8 +++++---
 2 files changed, 8 insertions(+), 4 deletions(-)

Comments

Ross Zwisler Oct. 17, 2016, 4:50 p.m. UTC | #1 
On Tue, Sep 27, 2016 at 06:08:12PM +0200, Jan Kara wrote:
> To allow full handling of COW faults add memcg field to struct vm_fault
> and a return value of ->fault() handler meaning that COW fault is fully
> handled and memcg charge must not be canceled. This will allow us to
> remove knowledge about special DAX locking from the generic fault code.
> 
> Signed-off-by: Jan Kara <jack@suse.cz>

Reviewed-by: Ross Zwisler <ross.zwisler@linux.intel.com>
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diff mbox

Patch

diff --git a/include/linux/mm.h b/include/linux/mm.h
index c908fd7243ea..faa77b15e9a6 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -303,7 +303,8 @@  struct vm_fault {
 					 * the 'address' */
 	pte_t orig_pte;			/* Value of PTE at the time of fault */
 
-	struct page *cow_page;		/* Handler may choose to COW */
+	struct page *cow_page;		/* Page handler may use for COW fault */
+	struct mem_cgroup *memcg;	/* Cgroup cow_page belongs to */
 	struct page *page;		/* ->fault handlers should return a
 					 * page here, unless VM_FAULT_NOPAGE
 					 * is set (which is also implied by
@@ -1117,6 +1118,7 @@  static inline void clear_page_pfmemalloc(struct page *page)
 #define VM_FAULT_RETRY	0x0400	/* ->fault blocked, must retry */
 #define VM_FAULT_FALLBACK 0x0800	/* huge page fault failed, fall back to small */
 #define VM_FAULT_DAX_LOCKED 0x1000	/* ->fault has locked DAX entry */
+#define VM_FAULT_DONE_COW   0x2000	/* ->fault has fully handled COW */
 
 #define VM_FAULT_HWPOISON_LARGE_MASK 0xf000 /* encodes hpage index for large hwpoison */
 
diff --git a/mm/memory.c b/mm/memory.c
index 0c8779c23925..17db88a38e8a 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -2844,9 +2844,8 @@  static int __do_fault(struct vm_fault *vmf)
 	int ret;
 
 	ret = vma->vm_ops->fault(vma, vmf);
-	if (unlikely(ret & (VM_FAULT_ERROR | VM_FAULT_NOPAGE | VM_FAULT_RETRY)))
-		return ret;
-	if (ret & VM_FAULT_DAX_LOCKED)
+	if (unlikely(ret & (VM_FAULT_ERROR | VM_FAULT_NOPAGE | VM_FAULT_RETRY |
+			    VM_FAULT_DAX_LOCKED | VM_FAULT_DONE_COW)))
 		return ret;
 
 	if (unlikely(PageHWPoison(vmf->page))) {
@@ -3205,9 +3204,12 @@  static int do_cow_fault(struct vm_fault *vmf)
 	}
 
 	vmf->cow_page = new_page;
+	vmf->memcg = memcg;
 	ret = __do_fault(vmf);
 	if (unlikely(ret & (VM_FAULT_ERROR | VM_FAULT_NOPAGE | VM_FAULT_RETRY)))
 		goto uncharge_out;
+	if (ret & VM_FAULT_DONE_COW)
+		return ret;
 
 	if (!(ret & VM_FAULT_DAX_LOCKED))
 		copy_user_highpage(new_page, vmf->page, vmf->address, vma);