@@ -143,15 +143,16 @@ static int rds_ib_recv_refill_one(struct rds_connection *conn,
int ret = -ENOMEM;
if (recv->r_ibinc == NULL) {
- if (atomic_read(&rds_ib_allocation) >= rds_ib_sysctl_max_recv_allocation) {
+ if (!atomic_add_unless(&rds_ib_allocation, 1, rds_ib_sysctl_max_recv_allocation)) {
rds_ib_stats_inc(s_ib_rx_alloc_limit);
goto out;
}
recv->r_ibinc = kmem_cache_alloc(rds_ib_incoming_slab,
kptr_gfp);
- if (recv->r_ibinc == NULL)
+ if (recv->r_ibinc == NULL) {
+ atomic_dec(&rds_ib_allocation);
goto out;
- atomic_inc(&rds_ib_allocation);
+ }
INIT_LIST_HEAD(&recv->r_ibinc->ii_frags);
rds_inc_init(&recv->r_ibinc->ii_inc, conn, conn->c_faddr);
}
@@ -143,15 +143,16 @@ static int rds_iw_recv_refill_one(struct rds_connection *conn,
int ret = -ENOMEM;
if (recv->r_iwinc == NULL) {
- if (atomic_read(&rds_iw_allocation) >= rds_iw_sysctl_max_recv_allocation) {
+ if (!atomic_add_unless(&rds_iw_allocation, 1, rds_iw_sysctl_max_recv_allocation)) {
rds_iw_stats_inc(s_iw_rx_alloc_limit);
goto out;
}
recv->r_iwinc = kmem_cache_alloc(rds_iw_incoming_slab,
kptr_gfp);
- if (recv->r_iwinc == NULL)
+ if (recv->r_iwinc == NULL) {
+ atomic_dec(&rds_iw_allocation);
goto out;
- atomic_inc(&rds_iw_allocation);
+ }
INIT_LIST_HEAD(&recv->r_iwinc->ii_frags);
rds_inc_init(&recv->r_iwinc->ii_inc, conn, conn->c_faddr);
}
From Shin Hong: "At rds_ib_recv_refill_one(), it first executes atomic_read(&rds_ib_allocation) for if-condition checking, and then executes atomic_inc(&rds_ib_allocation) if the condition was not satisfied. However, if any other code which updates rds_ib_allocation executes between these two atomic operation executions, it seems that it may result race condition. (especially when rds_ib_allocation + 1 == rds_ib_sysctl_max_recv_allocation)" This patch fixes this by using atomic_inc_unless to eliminate the possibility of allocating more than rds_ib_sysctl_max_recv_allocation and then decrementing the count if the allocation fails. It also makes an identical change to the iwarp transport. Reported-by: Shin Hong <hongshin@gmail.com> Signed-off-by: Andy Grover <andy.grover@oracle.com> --- net/rds/ib_recv.c | 7 ++++--- net/rds/iw_recv.c | 7 ++++--- 2 files changed, 8 insertions(+), 6 deletions(-)