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IB/ipath: Convert ipath_user_sdma_pin_pages() to use get_user_pages_fast()

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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_fast() and leave
mmap_sem locking for mm.

This deadlock has actually been observed in the wild when the node
is under memory pressure.

Cc: <stable@vger.kernel.org>
Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Mike Marciniszyn <mike.marciniszyn@intel.com>

[ Merged in fix for call to get_user_pages_fast from Tetsuo Handa
  <penguin-kernel@I-love.SAKURA.ne.jp>.  - Roland ]

Signed-off-by: Roland Dreier <roland@purestorage.com>
This commit is contained in:
Jan Kara 2013-10-04 09:29:06 -04:00 committed by Roland Dreier
parent 959f58544b
commit 4adcf7fb67
1 changed files with 1 additions and 6 deletions
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7
drivers/infiniband/hw/ipath/ipath_user_sdma.c
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@ -280,9 +280,7 @@ 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_fast(addr, npages, 0, pages);
if (ret != npages) {
int i;
@ -811,10 +809,7 @@ 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 {