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-rw-r--r--include/linux/mm.h3
-rw-r--r--mm/filemap.c6
-rw-r--r--mm/memory.c5
3 files changed, 11 insertions, 3 deletions
diff --git a/include/linux/mm.h b/include/linux/mm.h
index 1f82adc85352..901435e3a9a9 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -151,6 +151,7 @@ extern pgprot_t protection_map[16];
#define FAULT_FLAG_NONLINEAR 0x02 /* Fault was via a nonlinear mapping */
#define FAULT_FLAG_MKWRITE 0x04 /* Fault was mkwrite of existing pte */
#define FAULT_FLAG_ALLOW_RETRY 0x08 /* Retry fault if blocking */
+#define FAULT_FLAG_RETRY_NOWAIT 0x10 /* Don't drop mmap_sem and wait when retrying */
/*
* This interface is used by x86 PAT code to identify a pfn mapping that is
@@ -1545,6 +1546,8 @@ struct page *follow_page(struct vm_area_struct *, unsigned long address,
#define FOLL_GET 0x04 /* do get_page on page */
#define FOLL_DUMP 0x08 /* give error on hole if it would be zero */
#define FOLL_FORCE 0x10 /* get_user_pages read/write w/o permission */
+#define FOLL_NOWAIT 0x20 /* if a disk transfer is needed, start the IO
+ * and return without waiting upon it */
#define FOLL_MLOCK 0x40 /* mark page as mlocked */
#define FOLL_SPLIT 0x80 /* don't return transhuge pages, split them */
#define FOLL_HWPOISON 0x100 /* check page is hwpoisoned */
diff --git a/mm/filemap.c b/mm/filemap.c
index 83a45d35468b..312b6eb78430 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -621,8 +621,10 @@ int __lock_page_or_retry(struct page *page, struct mm_struct *mm,
__lock_page(page);
return 1;
} else {
- up_read(&mm->mmap_sem);
- wait_on_page_locked(page);
+ if (!(flags & FAULT_FLAG_RETRY_NOWAIT)) {
+ up_read(&mm->mmap_sem);
+ wait_on_page_locked(page);
+ }
return 0;
}
}
diff --git a/mm/memory.c b/mm/memory.c
index e48945ab362b..615be5127ce1 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -1569,6 +1569,8 @@ int __get_user_pages(struct task_struct *tsk, struct mm_struct *mm,
fault_flags |= FAULT_FLAG_WRITE;
if (nonblocking)
fault_flags |= FAULT_FLAG_ALLOW_RETRY;
+ if (foll_flags & FOLL_NOWAIT)
+ fault_flags |= (FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_RETRY_NOWAIT);
ret = handle_mm_fault(mm, vma, start,
fault_flags);
@@ -1595,7 +1597,8 @@ int __get_user_pages(struct task_struct *tsk, struct mm_struct *mm,
tsk->min_flt++;
if (ret & VM_FAULT_RETRY) {
- *nonblocking = 0;
+ if (nonblocking)
+ *nonblocking = 0;
return i;
}