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IB/qib: Convert qib_user_sdma_pin_pages() to use get_user_pages_fast()

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commit 603e772992 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 <mike.marciniszyn@intel.com>
Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Roland Dreier <roland@purestorage.com>
[Backported to 3.10: (Thanks to Ben Huthings)
 - Adjust context
 - Adjust indentation and nr_pages argument in qib_user_sdma_pin_pages()]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
Signed-off-by: Mike Marciniszyn <mike.marciniszyn@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Jan Kara
2013-10-04 09:29:12 -04:00
committed by Greg Kroah-Hartman
parent b0d4c0f812
commit 2d9258e499
1 changed files with 1 additions and 5 deletions
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6
drivers/infiniband/hw/qib/qib_user_sdma.c
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@@ -284,8 +284,7 @@ static int qib_user_sdma_pin_pages(const struct qib_devdata *dd,
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_ctxtdata *rcd,
while (dim) {
const int mxp = 8;
down_write(&current->mm->mmap_sem);
ret = qib_user_sdma_queue_pkts(dd, pq, &list, iov, dim, mxp);
up_write(&current->mm->mmap_sem);
if (ret <= 0)
goto done_unlock;
else {