[PATCH 3.16 101/306] IB/srp: Fix infinite loop when FMR sg[0].offset != 0

Ben Hutchings
2017-02-15T23:43:32Z

From: Bart Van Assche <bart.vanassche@sandisk.com>

commit 681cc3608355737c1effebc8145f95c8c3344bc3 upstream.

Avoid that mapping an sg-list in which the first element has a
non-zero offset triggers an infinite loop when using FMR. This
patch makes the FMR mapping code similar to that of ib_sg_to_pages().

Note: older Mellanox HCAs do not support non-zero offsets for FMR.
See also commit 8c4037b501ac ("IB/srp: always avoid non-zero offsets
into an FMR").

Reported-by: Alex Estrin <alex.estrin@intel.com>
Signed-off-by: Bart Van Assche <bart.vanassche@sandisk.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>
[bwh: Backported to 3.16: adjust context]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
---
drivers/infiniband/ulp/srp/ib_srp.c | 8 +++++---
1 file changed, 5 insertions(+), 3 deletions(-)

--- a/drivers/infiniband/ulp/srp/ib_srp.c
+++ b/drivers/infiniband/ulp/srp/ib_srp.c
@@ -1310,7 +1310,9 @@ static int srp_map_sg_entry(struct srp_m

while (dma_len) {
unsigned offset = dma_addr & ~dev->mr_page_mask;
- if (state->npages == dev->max_pages_per_mr || offset != 0) {
+
+ if (state->npages == dev->max_pages_per_mr ||
+ (state->npages > 0 && offset != 0)) {
ret = srp_finish_mapping(state, target);
if (ret)
return ret;
@@ -1329,12 +1331,12 @@ static int srp_map_sg_entry(struct srp_m
}

/*
- * If the last entry of the MR wasn't a full page, then we need to
+ * If the end of the MR is not on a page boundary then we need to
* close it out and start a new one -- we can only merge at page
* boundries.
*/
ret = 0;
- if (len != dev->mr_page_size) {
+ if ((dma_addr & ~dev->mr_page_mask) != 0) {
ret = srp_finish_mapping(state, target);
if (!ret)
srp_map_update_start(state, NULL, 0, 0);