In the process IO direction, dio_refill_pages will call get_user_pages_fast
to map the page from user space. If ret is less than 0 and IO is write, the
function will create a zero page to fill data. This may work for some file
system, but in some device operate we prefer whole write or fail, not half
data half zero, e.g. fs metadata, like inode, identy.
This happens often when kill a process which is doing direct IO. Consider
the following cases, the process A is doing IO process, may enter __get_user_pages
function, if other processes send process A SIG_KILL, A will enter the
following branches
/*
* If we have a pending SIGKILL, don't keep faulting
* pages and potentially allocating memory.
*/
if (unlikely(fatal_signal_pending(current)))
return i ? i : -ERESTARTSYS;
Return current pages. direct IO will write the pages, the subsequent pages
which can’t get will use zero page instead.
This patch will modify this judgment, if receive SIG_KILL, release pages and
return an error. Direct IO will find no blocks_available and return error
direct, rather than half IO data and half zero page.
Signed-off-by: Xishi Qiu <qiuxishi@xxxxxxxxxx>
Signed-off-by: Bin Yang <robin.yb@xxxxxxxxxx>
---
mm/memory.c | 10 ++++++++--
1 files changed, 8 insertions(+), 2 deletions(-)
diff --git a/mm/memory.c b/mm/memory.c
index 6768ce9..0568faa 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -1799,8 +1799,14 @@ long __get_user_pages(struct task_struct *tsk, struct mm_struct *mm,
* If we have a pending SIGKILL, don't keep faulting
* pages and potentially allocating memory.
*/
- if (unlikely(fatal_signal_pending(current)))
- return i ? i : -ERESTARTSYS;
+ if (unlikely(fatal_signal_pending(current))) {
+ int j;
+ for (j = 0; j < i; j++) {
+ put_page(pages[j]);
+ pages[j] = NULL;
+ }
+ return -ERESTARTSYS;
+ }
cond_resched();
while (!(page = follow_page_mask(vma, start,
--
1.7.1
--
To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
