mm: change return values of finish_mkwrite_fault()
Currently finish_mkwrite_fault() returns 0 when PTE got changed before
we acquired PTE lock and VM_FAULT_WRITE when we succeeded in modifying
the PTE. This is somewhat confusing since 0 generally means success, it
is also inconsistent with finish_fault() which returns 0 on success.
Change finish_mkwrite_fault() to return 0 on success and VM_FAULT_NOPAGE
when PTE changed. Practically, there should be no behavioral difference
since we bail out from the fault the same way regardless whether we
return 0, VM_FAULT_NOPAGE, or VM_FAULT_WRITE. Also note that
VM_FAULT_WRITE has no effect for shared mappings since the only two
places that check it - KSM and GUP - care about private mappings only.
Generally the meaning of VM_FAULT_WRITE for shared mappings is not well
defined and we should probably clean that up.
Link: http://lkml.kernel.org/r/1479460644-25076-17-git-send-email-jack@suse.cz
Signed-off-by: Jan Kara <jack@suse.cz>
Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Ross Zwisler <ross.zwisler@linux.intel.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/mm/memory.c b/mm/memory.c
index bbc25da..8b7f065 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -2295,10 +2295,10 @@
*/
if (!pte_same(*vmf->pte, vmf->orig_pte)) {
pte_unmap_unlock(vmf->pte, vmf->ptl);
- return 0;
+ return VM_FAULT_NOPAGE;
}
wp_page_reuse(vmf);
- return VM_FAULT_WRITE;
+ return 0;
}
/*
@@ -2341,8 +2341,7 @@
return tmp;
}
tmp = finish_mkwrite_fault(vmf);
- if (unlikely(!tmp || (tmp &
- (VM_FAULT_ERROR | VM_FAULT_NOPAGE)))) {
+ if (unlikely(tmp & (VM_FAULT_ERROR | VM_FAULT_NOPAGE))) {
unlock_page(vmf->page);
put_page(vmf->page);
return tmp;