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IB: Add a QP creation flag to use GFP_NOIO allocations

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This addresses a problem where NFS client writes over IPoIB connected
mode may deadlock on memory allocation/writeback.

The problem is not directly memory reclamation.  There is an indirect
dependency between network filesystems writing back pages and
ipoib_cm_tx_init() due to how a kworker is used.  Page reclaim cannot
make forward progress until ipoib_cm_tx_init() succeeds and it is
stuck in page reclaim itself waiting for network transmission.
Ordinarily this situation may be avoided by having the caller use
GFP_NOFS but ipoib_cm_tx_init() does not have that information.

To address this, take a general approach and add a new QP creation
flag that tells the low-level hardware driver to use GFP_NOIO for the
memory allocations related to the new QP.

Use the new flag in the ipoib connected mode path, and if the driver
doesn't support it, re-issue the QP creation without the flag.

Signed-off-by: Mel Gorman <[email protected]>
Signed-off-by: Jiri Kosina <[email protected]>
Signed-off-by: Or Gerlitz <[email protected]>
Signed-off-by: Roland Dreier <[email protected]>
This commit is contained in:
Or Gerlitz 2014-05-11 15:15:11 +03:00 • committed by Roland Dreier
commit 09b93088d7
2 changed files with 16 additions and 3 deletions
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1
include/rdma/ib_verbs.h
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@ -783,6 +783,7 @@ enum ib_qp_create_flags {
IB_QP_CREATE_BLOCK_MULTICAST_LOOPBACK = 1 << 1,
IB_QP_CREATE_NETIF_QP = 1 << 5,
IB_QP_CREATE_SIGNATURE_EN = 1 << 6,
IB_QP_CREATE_USE_GFP_NOIO = 1 << 7,
/* reserve bits 26-31 for low level drivers' internal use */
IB_QP_CREATE_RESERVED_START = 1 << 26,
IB_QP_CREATE_RESERVED_END = 1 << 31,