From 4a9e1cda274893eca7d178d7dc265503ccb9d87a Mon Sep 17 00:00:00 2001 From: Dominik Dingel Date: Fri, 15 Jan 2016 16:57:04 -0800 Subject: mm: bring in additional flag for fixup_user_fault to signal unlock During Jason's work with postcopy migration support for s390 a problem regarding gmap faults was discovered. The gmap code will call fixup_user_fault which will end up always in handle_mm_fault. Till now we never cared about retries, but as the userfaultfd code kind of relies on it. this needs some fix. This patchset does not take care of the futex code. I will now look closer at this. This patch (of 2): With the introduction of userfaultfd, kvm on s390 needs fixup_user_fault to pass in FAULT_FLAG_ALLOW_RETRY and give feedback if during the faulting we ever unlocked mmap_sem. This patch brings in the logic to handle retries as well as it cleans up the current documentation. fixup_user_fault was not having the same semantics as filemap_fault. It never indicated if a retry happened and so a caller wasn't able to handle that case. So we now changed the behaviour to always retry a locked mmap_sem. Signed-off-by: Dominik Dingel Reviewed-by: Andrea Arcangeli Cc: "Kirill A. Shutemov" Cc: Martin Schwidefsky Cc: Christian Borntraeger Cc: "Jason J. Herne" Cc: David Rientjes Cc: Eric B Munson Cc: Naoya Horiguchi Cc: Mel Gorman Cc: Heiko Carstens Cc: Dominik Dingel Cc: Paolo Bonzini Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- include/linux/mm.h | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) (limited to 'include/linux/mm.h') diff --git a/include/linux/mm.h b/include/linux/mm.h index 792f2469c142..1d6ec55d8b25 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -1194,7 +1194,8 @@ int invalidate_inode_page(struct page *page); extern int handle_mm_fault(struct mm_struct *mm, struct vm_area_struct *vma, unsigned long address, unsigned int flags); extern int fixup_user_fault(struct task_struct *tsk, struct mm_struct *mm, - unsigned long address, unsigned int fault_flags); + unsigned long address, unsigned int fault_flags, + bool *unlocked); #else static inline int handle_mm_fault(struct mm_struct *mm, struct vm_area_struct *vma, unsigned long address, @@ -1206,7 +1207,7 @@ static inline int handle_mm_fault(struct mm_struct *mm, } static inline int fixup_user_fault(struct task_struct *tsk, struct mm_struct *mm, unsigned long address, - unsigned int fault_flags) + unsigned int fault_flags, bool *unlocked) { /* should never happen if there's no MMU */ BUG(); -- cgit v1.2.3-70-g09d2