Hi,Michal, Whether need me to modify according your modification and
resubmit a new patch?
在 2017/11/25 9:52, 郭雪楠 写道:
Yes , your modification is much better! thanks.
在 2017/11/24 21:08, Michal Hocko 写道:
On Fri 24-11-17 20:51:29, 郭雪楠 wrote:
Sorry,I explained wrong before. But,I've tested using trinity in DAX
mode,and I'am sure it has possibility of triggering an soft lockup. I
have
encountered the problem of endless loop here .
I had a little problem here,I correct it .
under Initial state :
[ start = vam->vm_start < vam->vm_end < end ]
When [start = vam->vm_start] the program enters for{;;} loop
,find_vma_prev() will set the pointer vma and the pointer prev (prev =
vam->vm_prev ). Normally ,madvise_vma() will always move the pointer
prev
,but when use DAX mode , it will never update .
[...]
if (prev) // here prev not NULL,it will always enter this branch ..
vma = prev->vm_next;
else /* madvise_remove dropped mmap_sem */
vma = find_vma(current->mm, start);
You are right! My fault, I managed to confuse myself in the code flow.
It really looks like this has been broken for more than 10 years since
fe77ba6f4f97 ("[PATCH] xip: madvice/fadvice: execute in place").
Maybe the following would be more readable and less error prone?
---
diff --git a/mm/madvise.c b/mm/madvise.c
index 375cf32087e4..a631c414f915 100644
--- a/mm/madvise.c
+++ b/mm/madvise.c
@@ -276,30 +276,26 @@ static long madvise_willneed(struct
vm_area_struct *vma,
{
struct file *file = vma->vm_file;
+ *prev = vma;
#ifdef CONFIG_SWAP
if (!file) {
- *prev = vma;
force_swapin_readahead(vma, start, end);
return 0;
}
- if (shmem_mapping(file->f_mapping)) {
- *prev = vma;
+ if (shmem_mapping(file->f_mapping))
force_shm_swapin_readahead(vma, start, end,
file->f_mapping);
return 0;
- }
#else
if (!file)
return -EBADF;
#endif
- if (IS_DAX(file_inode(file))) {
+ if (IS_DAX(file_inode(file)))
/* no bad return value, but ignore advice */
return 0;
- }
- *prev = vma;
start = ((start - vma->vm_start) >> PAGE_SHIFT) + vma->vm_pgoff;
if (end > vma->vm_end)
end = vma->vm_end;
--
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