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net/rds: Give fr_state a chance to transition to FRMR_IS_FREE

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In the context of FRMR (ib_frmr.c):

Memory regions make it onto the "clean_list" via "rds_ib_flush_mr_pool",
after the memory region has been posted for invalidation via
"rds_ib_post_inv".

At that point in time, "fr_state" may still be in state "FRMR_IS_INUSE",
since the only place where "fr_state" transitions to "FRMR_IS_FREE"
is in "rds_ib_mr_cqe_handler", which is triggered by a tasklet.

So in case we notice that "fr_state != FRMR_IS_FREE" (see below),
we wait for "fr_inv_done" to trigger with a maximum of 10msec.
Then we check again, and only put the memory region onto the drop_list
(via "rds_ib_free_frmr") in case the situation remains unchanged.

This avoids the problem of memory-regions bouncing between "clean_list"
and "drop_list" before they even have a chance to be properly invalidated.

Signed-off-by: Gerd Rausch <gerd.rausch@oracle.com>
Acked-by: Santosh Shilimkar <santosh.shilimkar@oracle.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Gerd Rausch 2019-07-16 15:28:51 -07:00 committed by David S. Miller
parent f11fe1dae1
commit 2c7da8e6b0
2 changed files with 27 additions and 1 deletions
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27
net/rds/ib_frmr.c
View File

@ -75,6 +75,7 @@ static struct rds_ib_mr *rds_ib_alloc_frmr(struct rds_ib_device *rds_ibdev,
pool->max_items_soft = pool->max_items;
frmr->fr_state = FRMR_IS_FREE;
init_waitqueue_head(&frmr->fr_inv_done);
return ibmr;
out_no_cigar:
@ -285,6 +286,7 @@ void rds_ib_mr_cqe_handler(struct rds_ib_connection *ic, struct ib_wc *wc)
if (frmr->fr_inv) {
frmr->fr_state = FRMR_IS_FREE;
frmr->fr_inv = false;
wake_up(&frmr->fr_inv_done);
}
atomic_inc(&ic->i_fastreg_wrs);
@ -345,8 +347,31 @@ struct rds_ib_mr *rds_ib_reg_frmr(struct rds_ib_device *rds_ibdev,
}
do {
if (ibmr)
if (ibmr) {
/* Memory regions make it onto the "clean_list" via
* "rds_ib_flush_mr_pool", after the memory region has
* been posted for invalidation via "rds_ib_post_inv".
*
* At that point in time, "fr_state" may still be
* in state "FRMR_IS_INUSE", since the only place where
* "fr_state" transitions to "FRMR_IS_FREE" is in
* is in "rds_ib_mr_cqe_handler", which is
* triggered by a tasklet.
*
* So we wait for "fr_inv_done" to trigger
* and only put memory regions onto the drop_list
* that failed (i.e. not marked "FRMR_IS_FREE").
*
* This avoids the problem of memory-regions bouncing
* between "clean_list" and "drop_list" before they
* even have a chance to be properly invalidated.
*/
frmr = &ibmr->u.frmr;
wait_event(frmr->fr_inv_done, frmr->fr_state != FRMR_IS_INUSE);
if (frmr->fr_state == FRMR_IS_FREE)
break;
rds_ib_free_frmr(ibmr, true);
}
ibmr = rds_ib_alloc_frmr(rds_ibdev, nents);
if (IS_ERR(ibmr))
return ibmr;

1
net/rds/ib_mr.h
View File

@ -57,6 +57,7 @@ struct rds_ib_frmr {
struct ib_mr *mr;
enum rds_ib_fr_state fr_state;
bool fr_inv;
wait_queue_head_t fr_inv_done;
struct ib_send_wr fr_wr;
unsigned int dma_npages;
unsigned int sg_byte_len;