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-rw-r--r--src/responder/nss/nsssrv_mmap_cache.c279
1 files changed, 279 insertions, 0 deletions
diff --git a/src/responder/nss/nsssrv_mmap_cache.c b/src/responder/nss/nsssrv_mmap_cache.c
index 65939f4c..2f90d826 100644
--- a/src/responder/nss/nsssrv_mmap_cache.c
+++ b/src/responder/nss/nsssrv_mmap_cache.c
@@ -44,6 +44,11 @@
m->b1 = m->b2; \
} while (0)
+#define MC_RAISE_INVALID_BARRIER(m) do { \
+ m->b2 = MC_INVALID_VAL; \
+ __sync_synchronize(); \
+} while (0)
+
struct sss_mc_ctx {
char *name; /* mmap cache name */
enum sss_mc_type type; /* mmap cache type */
@@ -67,6 +72,280 @@ struct sss_mc_ctx {
uint32_t dt_size; /* size of data table */
};
+#define MC_FIND_BIT(base, num) \
+ uint32_t n = (num); \
+ uint8_t *b = (base) + n / 8; \
+ uint8_t c = 0x80 >> (n % 8);
+
+#define MC_SET_BIT(base, num) do { \
+ MC_FIND_BIT(base, num) \
+ *b |= c; \
+} while (0)
+
+#define MC_CLEAR_BIT(base, num) do { \
+ MC_FIND_BIT(base, num) \
+ *b &= ~c; \
+} while (0)
+
+#define MC_PROBE_BIT(base, num, used) do { \
+ MC_FIND_BIT(base, num) \
+ if (*b & c) used = true; \
+ else used = false; \
+} while (0)
+
+static uint32_t sss_mc_hash(struct sss_mc_ctx *mcc,
+ const char *key, size_t len)
+{
+ return murmurhash3(key, len, mcc->seed) % MC_HT_ELEMS(mcc->ht_size);
+}
+
+static void sss_mc_add_rec_to_chain(struct sss_mc_ctx *mcc,
+ struct sss_mc_rec *rec,
+ uint32_t hash)
+{
+ struct sss_mc_rec *cur;
+ uint32_t slot;
+
+ slot = mcc->hash_table[hash];
+ if (slot == MC_INVALID_VAL) {
+ /* no previous record/collision, just add to hash table */
+ mcc->hash_table[hash] = MC_PTR_TO_SLOT(mcc->data_table, rec);
+ return;
+ }
+
+ do {
+ cur = MC_SLOT_TO_PTR(mcc->data_table, slot, struct sss_mc_rec);
+ if (cur == rec) {
+ /* rec already stored in hash chain */
+ return;
+ }
+ slot = cur->next;
+ } while (slot != MC_INVALID_VAL);
+ /* end of chain, append our record here */
+
+ /* changing a single uint32_t is atomic, so there is no
+ * need to use barriers in this case */
+ cur->next = MC_PTR_TO_SLOT(mcc->data_table, rec);
+}
+
+static void sss_mc_rm_rec_from_chain(struct sss_mc_ctx *mcc,
+ struct sss_mc_rec *rec,
+ uint32_t hash)
+{
+ struct sss_mc_rec *prev = NULL;
+ struct sss_mc_rec *cur = NULL;
+ uint32_t slot;
+
+ slot = mcc->hash_table[hash];
+ cur = MC_SLOT_TO_PTR(mcc->data_table, slot, struct sss_mc_rec);
+ if (cur == rec) {
+ mcc->hash_table[hash] = rec->next;
+ } else {
+ slot = cur->next;
+ while (slot != MC_INVALID_VAL) {
+ prev = cur;
+ cur = MC_SLOT_TO_PTR(mcc->data_table, slot, struct sss_mc_rec);
+ if (cur == rec) {
+ /* changing a single uint32_t is atomic, so there is no
+ * need to use barriers in this case */
+ prev->next = cur->next;
+ slot = MC_INVALID_VAL;
+ } else {
+ slot = cur->next;
+ }
+ }
+ }
+}
+
+static void sss_mc_invalidate_rec(struct sss_mc_ctx *mcc,
+ struct sss_mc_rec *rec)
+{
+ if (rec->b1 == MC_INVALID_VAL) {
+ /* record already invalid */
+ return;
+ }
+
+ /* hash chain 1 */
+ sss_mc_rm_rec_from_chain(mcc, rec, rec->hash1);
+ /* hash chain 2 */
+ sss_mc_rm_rec_from_chain(mcc, rec, rec->hash2);
+
+ MC_RAISE_INVALID_BARRIER(rec);
+ memset(rec->data, 'X', rec->len - sizeof(struct sss_mc_rec));
+ rec->len = MC_INVALID_VAL;
+ rec->expire = (uint64_t)-1;
+ rec->next = MC_INVALID_VAL;
+ rec->hash1 = MC_INVALID_VAL;
+ rec->hash2 = MC_INVALID_VAL;
+ MC_LOWER_BARRIER(rec);
+}
+
+/* FIXME: This is a very simplistic, inefficient, memory allocator,
+ * it will just free the oldest entries regardless of expiration if it
+ * cycled the whole freebits map and found no empty slot */
+static int sss_mc_find_free_slots(struct sss_mc_ctx *mcc, int num_slots)
+{
+ struct sss_mc_rec *rec;
+ uint32_t tot_slots;
+ uint32_t cur;
+ uint32_t i;
+ uint32_t t;
+ bool used;
+
+ tot_slots = mcc->ft_size * 8;
+
+ /* Try to find a free slot w/o removing a nything first */
+ /* FIXME: is it really worth it ? May be it is easier to
+ * just recycle the next set of slots ? */
+ if ((mcc->next_slot + num_slots) > tot_slots) {
+ cur = 0;
+ } else {
+ cur = mcc->next_slot;
+ }
+
+ /* search for enough (num_slots) consecutive zero bits, indicating
+ * consecutive empty slots */
+ for (i = 0; i < mcc->ft_size; i++) {
+ t = cur / 8;
+ /* if all full in this byte skip directly to the next */
+ if (mcc->free_table[t] == 0xff) {
+ cur = ((cur + 8) & ~7);
+ if (cur >= tot_slots) {
+ cur = 0;
+ }
+ continue;
+ }
+
+ /* at least one bit in this byte is marked as empty */
+ for (t = ((cur + 8) & ~7) ; cur < t; cur++) {
+ MC_PROBE_BIT(mcc->free_table, cur, used);
+ if (!used) break;
+ }
+ /* check if we have enough slots before hitting the table end */
+ if ((cur + num_slots) > tot_slots) {
+ cur = 0;
+ continue;
+ }
+
+ /* check if we have at least num_slots empty starting from the first
+ * we found in the previous steps */
+ for (t = cur + num_slots; cur < t; cur++) {
+ MC_PROBE_BIT(mcc->free_table, cur, used);
+ if (used) break;
+ }
+ if (cur == t) {
+ /* ok found num_slots consecutive free bits */
+ return cur - num_slots;
+ }
+ }
+
+ /* no free slots found, free occupied slots after next_slot */
+ if ((mcc->next_slot + num_slots) > tot_slots) {
+ cur = 0;
+ } else {
+ cur = mcc->next_slot;
+ }
+ for (i = 0; i < num_slots; i++) {
+ MC_PROBE_BIT(mcc->free_table, cur + i, used);
+ if (!used) continue;
+
+ rec = MC_SLOT_TO_PTR(mcc->data_table, cur + i, struct sss_mc_rec);
+ for (t = i + MC_SIZE_TO_SLOTS(rec->len); i < t; i++) {
+ MC_CLEAR_BIT(mcc->free_table, cur + i);
+ }
+ sss_mc_invalidate_rec(mcc, rec);
+ }
+
+ mcc->next_slot = cur + num_slots;
+ return cur;
+}
+
+static struct sss_mc_rec *sss_mc_find_record(struct sss_mc_ctx *mcc,
+ struct sized_string *key)
+{
+ struct sss_mc_rec *rec;
+ uint32_t hash;
+ uint32_t slot;
+ rel_ptr_t name_ptr;
+ char *t_key;
+
+ hash = sss_mc_hash(mcc, key->str, key->len);
+
+ slot = mcc->hash_table[hash];
+ if (slot > MC_SIZE_TO_SLOTS(mcc->dt_size)) {
+ return NULL;
+ }
+
+ while (slot != MC_INVALID_VAL) {
+ rec = MC_SLOT_TO_PTR(mcc->data_table, slot, struct sss_mc_rec);
+ name_ptr = *((rel_ptr_t *)rec->data);
+
+ t_key = (char *)rec->data + name_ptr;
+ if (strcmp(key->str, t_key) == 0) {
+ break;
+ }
+
+ slot = rec->next;
+ }
+
+ if (slot == MC_INVALID_VAL) {
+ return NULL;
+ }
+
+ return rec;
+}
+
+static struct sss_mc_rec *sss_mc_get_record(struct sss_mc_ctx *mcc,
+ size_t rec_len,
+ struct sized_string *key)
+{
+ struct sss_mc_rec *old_rec = NULL;
+ struct sss_mc_rec *rec;
+ int old_slots;
+ int num_slots;
+ uint32_t base_slot;
+ int i;
+
+ num_slots = MC_SIZE_TO_SLOTS(rec_len);
+
+ old_rec = sss_mc_find_record(mcc, key);
+ if (old_rec) {
+ old_slots = MC_SIZE_TO_SLOTS(old_rec->len);
+
+ if (old_slots == num_slots) {
+ return old_rec;
+ }
+
+ /* slot size changed, invalidate record and fall through to get a
+ * fully new record */
+ base_slot = MC_PTR_TO_SLOT(mcc->data_table, old_rec);
+ sss_mc_invalidate_rec(mcc, old_rec);
+
+ /* and now free slots */
+ for (i = 0; i < old_slots; i++) {
+ MC_CLEAR_BIT(mcc->free_table, base_slot + i);
+ }
+ }
+
+ /* we are going to use more space, find enough free slots */
+ base_slot = sss_mc_find_free_slots(mcc, num_slots);
+
+ rec = MC_SLOT_TO_PTR(mcc->data_table, base_slot, struct sss_mc_rec);
+
+ /* mark as not valid yet */
+ MC_RAISE_INVALID_BARRIER(rec);
+ rec->len = rec_len;
+ rec->next = MC_INVALID_VAL;
+ MC_LOWER_BARRIER(rec);
+
+ /* and now mark slots as used */
+ for (i = 0; i < num_slots; i++) {
+ MC_SET_BIT(mcc->free_table, base_slot + i);
+ }
+
+ return rec;
+}
+
/***************************************************************************
* initialization
generated by cgit (git 2.34.1) at 2024-12-21 13:27:15 +0000