This is a note to let you know that I've just added the patch titled
IB/qib: Convert qib_user_sdma_pin_pages() to use get_user_pages_fast()
to the 3.4-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
ib-qib-convert-qib_user_sdma_pin_pages-to-use-get_user_pages_fast.patch
and it can be found in the queue-3.4 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <[email protected]> know about it.
>From 603e7729920e42b3c2f4dbfab9eef4878cb6e8fa Mon Sep 17 00:00:00 2001
From: Jan Kara <[email protected]>
Date: Fri, 4 Oct 2013 09:29:12 -0400
Subject: IB/qib: Convert qib_user_sdma_pin_pages() to use get_user_pages_fast()
From: Jan Kara <[email protected]>
commit 603e7729920e42b3c2f4dbfab9eef4878cb6e8fa upstream.
qib_user_sdma_queue_pkts() gets called with mmap_sem held for
writing. Except for get_user_pages() deep down in
qib_user_sdma_pin_pages() we don't seem to need mmap_sem at all. Even
more interestingly the function qib_user_sdma_queue_pkts() (and also
qib_user_sdma_coalesce() called somewhat later) call copy_from_user()
which can hit a page fault and we deadlock on trying to get mmap_sem
when handling that fault.
So just make qib_user_sdma_pin_pages() use get_user_pages_fast() and
leave mmap_sem locking for mm.
This deadlock has actually been observed in the wild when the node
is under memory pressure.
Reviewed-by: Mike Marciniszyn <[email protected]>
Signed-off-by: Jan Kara <[email protected]>
Signed-off-by: Roland Dreier <[email protected]>
[Backported to 3.4: (Thank to Ben Hutchings)
- Adjust context
- Adjust indentation and nr_pages argument in qib_user_sdma_pin_pages()]
Signed-off-by: Ben Hutchings <[email protected]>
Signed-off-by: Mike Marciniszyn <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>
---
drivers/infiniband/hw/qib/qib_user_sdma.c | 6 +-----
1 file changed, 1 insertion(+), 5 deletions(-)
--- a/drivers/infiniband/hw/qib/qib_user_sdma.c
+++ b/drivers/infiniband/hw/qib/qib_user_sdma.c
@@ -284,8 +284,7 @@ static int qib_user_sdma_pin_pages(const
int j;
int ret;
- ret = get_user_pages(current, current->mm, addr,
- npages, 0, 1, pages, NULL);
+ ret = get_user_pages_fast(addr, npages, 0, pages);
if (ret != npages) {
int i;
@@ -830,10 +829,7 @@ int qib_user_sdma_writev(struct qib_ctxt
while (dim) {
const int mxp = 8;
- down_write(¤t->mm->mmap_sem);
ret = qib_user_sdma_queue_pkts(dd, pq, &list, iov, dim, mxp);
- up_write(¤t->mm->mmap_sem);
-
if (ret <= 0)
goto done_unlock;
else {
Patches currently in stable-queue which might be from [email protected] are
queue-3.4/ib-qib-convert-qib_user_sdma_pin_pages-to-use-get_user_pages_fast.patch
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