diff options
Diffstat (limited to '')
| -rw-r--r-- | mm/gup.c | 30 |
1 files changed, 25 insertions, 5 deletions
@@ -618,6 +618,8 @@ EXPORT_SYMBOL(__get_user_pages); * @mm: mm_struct of target mm * @address: user address * @fault_flags:flags to pass down to handle_mm_fault() + * @unlocked: did we unlock the mmap_sem while retrying, maybe NULL if caller + * does not allow retry * * This is meant to be called in the specific scenario where for locking reasons * we try to access user memory in atomic context (within a pagefault_disable() @@ -629,22 +631,28 @@ EXPORT_SYMBOL(__get_user_pages); * The main difference with get_user_pages() is that this function will * unconditionally call handle_mm_fault() which will in turn perform all the * necessary SW fixup of the dirty and young bits in the PTE, while - * handle_mm_fault() only guarantees to update these in the struct page. + * get_user_pages() only guarantees to update these in the struct page. * * This is important for some architectures where those bits also gate the * access permission to the page because they are maintained in software. On * such architectures, gup() will not be enough to make a subsequent access * succeed. * - * This has the same semantics wrt the @mm->mmap_sem as does filemap_fault(). + * This function will not return with an unlocked mmap_sem. So it has not the + * same semantics wrt the @mm->mmap_sem as does filemap_fault(). */ 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) { struct vm_area_struct *vma; vm_flags_t vm_flags; - int ret; + int ret, major = 0; + + if (unlocked) + fault_flags |= FAULT_FLAG_ALLOW_RETRY; +retry: vma = find_extend_vma(mm, address); if (!vma || address < vma->vm_start) return -EFAULT; @@ -654,6 +662,7 @@ int fixup_user_fault(struct task_struct *tsk, struct mm_struct *mm, return -EFAULT; ret = handle_mm_fault(mm, vma, address, fault_flags); + major |= ret & VM_FAULT_MAJOR; if (ret & VM_FAULT_ERROR) { if (ret & VM_FAULT_OOM) return -ENOMEM; @@ -663,8 +672,19 @@ int fixup_user_fault(struct task_struct *tsk, struct mm_struct *mm, return -EFAULT; BUG(); } + + if (ret & VM_FAULT_RETRY) { + down_read(&mm->mmap_sem); + if (!(fault_flags & FAULT_FLAG_TRIED)) { + *unlocked = true; + fault_flags &= ~FAULT_FLAG_ALLOW_RETRY; + fault_flags |= FAULT_FLAG_TRIED; + goto retry; + } + } + if (tsk) { - if (ret & VM_FAULT_MAJOR) + if (major) tsk->maj_flt++; else tsk->min_flt++; |