leandrof/linux
1
0
Fork 0
Code Issues Pull Requests Packages Projects Releases Wiki Activity

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

Browse Source 
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.

Cc: <stable@vger.kernel.org>
Reviewed-by: Mike Marciniszyn <mike.marciniszyn@intel.com>
Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Roland Dreier <roland@purestorage.com>
This commit is contained in:
Jan Kara 2013-10-04 09:29:12 -04:00 committed by Roland Dreier
parent 4adcf7fb67
commit 603e772992
1 changed files with 1 additions and 5 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

6
drivers/infiniband/hw/qib/qib_user_sdma.c
View File

@ -594,8 +594,7 @@ static int qib_user_sdma_pin_pages(const struct qib_devdata *dd,
else
j = npages;
ret = get_user_pages(current, current->mm, addr,
j, 0, 1, pages, NULL);
ret = get_user_pages_fast(addr, j, 0, pages);
if (ret != j) {
i = 0;
j = ret;
@ -1294,11 +1293,8 @@ int qib_user_sdma_writev(struct qib_ctxtdata *rcd,
int mxp = 8;
int ndesc = 0;
down_write(&current->mm->mmap_sem);
ret = qib_user_sdma_queue_pkts(dd, ppd, pq,
iov, dim, &list, &mxp, &ndesc);
up_write(&current->mm->mmap_sem);
if (ret < 0)
goto done_unlock;
else {