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net/rds: Wait for the FRMR_IS_FREE (or FRMR_IS_STALE) transition after posting IB_WR_LOCAL_INV 

In order to:
1) avoid a silly bouncing between "clean_list" and "drop_list"
   triggered by function "rds_ib_reg_frmr" as it is releases frmr
   regions whose state is not "FRMR_IS_FREE" right away.

2) prevent an invalid access error in a race from a pending
   "IB_WR_LOCAL_INV" operation with a teardown ("dma_unmap_sg", "put_page")
   and de-registration ("ib_dereg_mr") of the corresponding
   memory region.

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 15:29:02 -07:00 committed by David S. Miller
parent c9467447fc
commit 5f33141d2f
2 changed files with 40 additions and 27 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

65
net/rds/ib_frmr.c
View File

@ -76,6 +76,7 @@ static struct rds_ib_mr *rds_ib_alloc_frmr(struct rds_ib_device *rds_ibdev,
frmr->fr_state = FRMR_IS_FREE;
init_waitqueue_head(&frmr->fr_inv_done);
init_waitqueue_head(&frmr->fr_reg_done);
return ibmr;
out_no_cigar:
@ -124,6 +125,7 @@ static int rds_ib_post_reg_frmr(struct rds_ib_mr *ibmr)
*/
ib_update_fast_reg_key(frmr->mr, ibmr->remap_count++);
frmr->fr_state = FRMR_IS_INUSE;
frmr->fr_reg = true;
memset(&reg_wr, 0, sizeof(reg_wr));
reg_wr.wr.wr_id = (unsigned long)(void *)ibmr;
@ -144,7 +146,17 @@ static int rds_ib_post_reg_frmr(struct rds_ib_mr *ibmr)
if (printk_ratelimit())
pr_warn("RDS/IB: %s returned error(%d)\n",
__func__, ret);
goto out;
}
/* Wait for the registration to complete in order to prevent an invalid
* access error resulting from a race between the memory region already
* being accessed while registration is still pending.
*/
wait_event(frmr->fr_reg_done, !frmr->fr_reg);
out:
return ret;
}
@ -262,6 +274,19 @@ static int rds_ib_post_inv(struct rds_ib_mr *ibmr)
pr_err("RDS/IB: %s returned error(%d)\n", __func__, ret);
goto out;
}
/* Wait for the FRMR_IS_FREE (or FRMR_IS_STALE) transition in order to
* 1) avoid a silly bouncing between "clean_list" and "drop_list"
* triggered by function "rds_ib_reg_frmr" as it is releases frmr
* regions whose state is not "FRMR_IS_FREE" right away.
* 2) prevents an invalid access error in a race
* from a pending "IB_WR_LOCAL_INV" operation
* with a teardown ("dma_unmap_sg", "put_page")
* and de-registration ("ib_dereg_mr") of the corresponding
* memory region.
*/
wait_event(frmr->fr_inv_done, frmr->fr_state != FRMR_IS_INUSE);
out:
return ret;
}
@ -289,6 +314,11 @@ void rds_ib_mr_cqe_handler(struct rds_ib_connection *ic, struct ib_wc *wc)
wake_up(&frmr->fr_inv_done);
}
if (frmr->fr_reg) {
frmr->fr_reg = false;
wake_up(&frmr->fr_reg_done);
}
atomic_inc(&ic->i_fastreg_wrs);
}
@ -297,14 +327,18 @@ void rds_ib_unreg_frmr(struct list_head *list, unsigned int *nfreed,
{
struct rds_ib_mr *ibmr, *next;
struct rds_ib_frmr *frmr;
int ret = 0;
int ret = 0, ret2;
unsigned int freed = *nfreed;
/* String all ib_mr's onto one list and hand them to ib_unmap_fmr */
list_for_each_entry(ibmr, list, unmap_list) {
if (ibmr->sg_dma_len)
ret |= rds_ib_post_inv(ibmr);
if (ibmr->sg_dma_len) {
ret2 = rds_ib_post_inv(ibmr);
if (ret2 && !ret)
ret = ret2;
}
}
if (ret)
pr_warn("RDS/IB: %s failed (err=%d)\n", __func__, ret);
@ -347,31 +381,8 @@ struct rds_ib_mr *rds_ib_reg_frmr(struct rds_ib_device *rds_ibdev,
}
do {
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;
if (ibmr)
rds_ib_free_frmr(ibmr, true);
}
ibmr = rds_ib_alloc_frmr(rds_ibdev, nents);
if (IS_ERR(ibmr))
return ibmr;

2
net/rds/ib_mr.h
View File

@ -58,6 +58,8 @@ struct rds_ib_frmr {
enum rds_ib_fr_state fr_state;
bool fr_inv;
wait_queue_head_t fr_inv_done;
bool fr_reg;
wait_queue_head_t fr_reg_done;
struct ib_send_wr fr_wr;
unsigned int dma_npages;
unsigned int sg_byte_len;