instance-id: Track existing allocations for each db instance
OFD locking allows merging and splitting of locks, which means that it
won't fail an attempt to "recursively" lock the range. We were relying
on that to prevent double allocation when the available instance IDs for
a TID were exhausted.
Given that we can't rely on it, explicitly track the allocations in the
local state.
Signed-off-by: Andrew Jeffery <andrew@aj.id.au>
Change-Id: Ic0f6903935ac712a86a7967d1cceb5a0c463878b
diff --git a/src/requester/instance-id.c b/src/requester/instance-id.c
index 3d39fd8..b746a96 100644
--- a/src/requester/instance-id.c
+++ b/src/requester/instance-id.c
@@ -7,11 +7,20 @@
#include <stdlib.h>
#include <unistd.h>
+#define BIT(i) (1UL << (i))
+
#define PLDM_TID_MAX 256
#define PLDM_INST_ID_MAX 32
+/* We need to track our allocations explicitly due to OFD lock merging/splitting
+ */
+struct pldm_tid_state {
+ pldm_instance_id_t prev;
+ uint32_t allocations;
+};
+
struct pldm_instance_db {
- pldm_instance_id_t prev[PLDM_TID_MAX];
+ struct pldm_tid_state state[PLDM_TID_MAX];
int lock_db_fd;
};
@@ -39,7 +48,7 @@
/* Initialise previous ID values so the next one is zero */
for (int i = 0; i < PLDM_TID_MAX; i++) {
- l_ctx->prev[i] = 31;
+ l_ctx->state[i].prev = 31;
}
/* Lock database may be read-only, either by permissions or mountpoint
@@ -89,16 +98,21 @@
return -EINVAL;
}
- l_iid = ctx->prev[tid];
+ l_iid = ctx->state[tid].prev;
if (l_iid >= PLDM_INST_ID_MAX) {
return -EPROTO;
}
- while ((l_iid = iid_next(l_iid)) != ctx->prev[tid]) {
+ while ((l_iid = iid_next(l_iid)) != ctx->state[tid].prev) {
struct flock flop;
off_t loff;
int rc;
+ /* Have we already allocated this instance ID? */
+ if (ctx->state[tid].allocations & BIT(l_iid)) {
+ continue;
+ }
+
/* Derive the instance ID offset in the lock database */
loff = tid * PLDM_INST_ID_MAX + l_iid;
@@ -138,7 +152,8 @@
/* F_UNLCK is the type of the lock if we could successfully
* promote it to F_WRLCK */
if (flop.l_type == F_UNLCK) {
- ctx->prev[tid] = l_iid;
+ ctx->state[tid].prev = l_iid;
+ ctx->state[tid].allocations |= BIT(l_iid);
*iid = l_iid;
return 0;
}
@@ -163,6 +178,11 @@
struct flock flop;
int rc;
+ /* Trying to free an instance ID that is not currently allocated */
+ if (!(ctx->state[tid].allocations & BIT(iid))) {
+ return -EINVAL;
+ }
+
flop = cflu;
flop.l_start = tid * PLDM_INST_ID_MAX + iid;
rc = fcntl(ctx->lock_db_fd, F_OFD_SETLK, &flop);
@@ -173,5 +193,8 @@
return -EPROTO;
}
+ /* Mark the instance ID as no-longer allocated */
+ ctx->state[tid].allocations &= ~BIT(iid);
+
return 0;
}