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Subject[PATCH 22/26] ib: Convert ipath_user_sdma_pin_pages() to use get_user_pages_unlocked()
Date
Function ipath_user_sdma_queue_pkts() gets called with mmap_sem held for
writing. Except for get_user_pages() deep down in
ipath_user_sdma_pin_pages() we don't seem to need mmap_sem at all. Even
more interestingly the function ipath_user_sdma_queue_pkts() (and also
ipath_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 ipath_user_sdma_pin_pages() use
get_user_pages_unlocked() and leave mmap_sem locking for mm.

CC: Mike Marciniszyn <infinipath@intel.com>
CC: Roland Dreier <roland@kernel.org>
CC: linux-rdma@vger.kernel.org
Signed-off-by: Jan Kara <jack@suse.cz>
---
drivers/infiniband/hw/ipath/ipath_user_sdma.c | 7 ++-----
1 file changed, 2 insertions(+), 5 deletions(-)

diff --git a/drivers/infiniband/hw/ipath/ipath_user_sdma.c b/drivers/infiniband/hw/ipath/ipath_user_sdma.c
index f5cb13b21445..462c9b136e85 100644
--- a/drivers/infiniband/hw/ipath/ipath_user_sdma.c
+++ b/drivers/infiniband/hw/ipath/ipath_user_sdma.c
@@ -280,8 +280,8 @@ static int ipath_user_sdma_pin_pages(const struct ipath_devdata *dd,
int j;
int ret;

- ret = get_user_pages(current, current->mm, addr,
- npages, 0, 1, pages, NULL);
+ ret = get_user_pages_unlocked(current, current->mm, addr,
+ npages, 0, 1, pages);

if (ret != npages) {
int i;
@@ -811,10 +811,7 @@ int ipath_user_sdma_writev(struct ipath_devdata *dd,
while (dim) {
const int mxp = 8;

- down_write(&current->mm->mmap_sem);
ret = ipath_user_sdma_queue_pkts(dd, pq, &list, iov, dim, mxp);
- up_write(&current->mm->mmap_sem);
-
if (ret <= 0)
goto done_unlock;
else {
--
1.8.1.4


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