rhashtable: Allow rhashtable to be used from irq-safe contexts

rhashtable currently only does bh-safe synchronization making it impossible
to use from irq-safe contexts. Switch it to use irq-safe synchronization to
remove the restriction.

v2: Update the lock functions to return the ulong flags value and unlock
    functions to take the value directly instead of passing around the
    pointer. Suggested by Linus.

Signed-off-by: Tejun Heo <tj@kernel.org>
Reviewed-by: David Vernet <dvernet@meta.com>
Acked-by: Josh Don <joshdon@google.com>
Acked-by: Hao Luo <haoluo@google.com>
Acked-by: Barret Rhoden <brho@google.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 10 insertions, 6 deletions

diff --git a/lib/rhashtable.c b/lib/rhashtable.c
index e12bbfb240b8..6ae2ba8e06a2 100644
--- a/lib/rhashtable.c
+++ b/lib/rhashtable.c
@@ -231,6 +231,7 @@ static int rhashtable_rehash_one(struct rhashtable *ht,
 	struct rhash_head *head, *next, *entry;
 	struct rhash_head __rcu **pprev = NULL;
 	unsigned int new_hash;
+	unsigned long flags;
 
 	if (new_tbl->nest)
 		goto out;
@@ -253,13 +254,14 @@ static int rhashtable_rehash_one(struct rhashtable *ht,
 
 	new_hash = head_hashfn(ht, new_tbl, entry);
 
-	rht_lock_nested(new_tbl, &new_tbl->buckets[new_hash], SINGLE_DEPTH_NESTING);
+	flags = rht_lock_nested(new_tbl, &new_tbl->buckets[new_hash],
+				SINGLE_DEPTH_NESTING);
 
 	head = rht_ptr(new_tbl->buckets + new_hash, new_tbl, new_hash);
 
 	RCU_INIT_POINTER(entry->next, head);
 
-	rht_assign_unlock(new_tbl, &new_tbl->buckets[new_hash], entry);
+	rht_assign_unlock(new_tbl, &new_tbl->buckets[new_hash], entry, flags);
 
 	if (pprev)
 		rcu_assign_pointer(*pprev, next);
@@ -276,18 +278,19 @@ static int rhashtable_rehash_chain(struct rhashtable *ht,
 {
 	struct bucket_table *old_tbl = rht_dereference(ht->tbl, ht);
 	struct rhash_lock_head __rcu **bkt = rht_bucket_var(old_tbl, old_hash);
+	unsigned long flags;
 	int err;
 
 	if (!bkt)
 		return 0;
-	rht_lock(old_tbl, bkt);
+	flags = rht_lock(old_tbl, bkt);
 
 	while (!(err = rhashtable_rehash_one(ht, bkt, old_hash)))
 		;
 
 	if (err == -ENOENT)
 		err = 0;
-	rht_unlock(old_tbl, bkt);
+	rht_unlock(old_tbl, bkt, flags);
 
 	return err;
 }
@@ -590,6 +593,7 @@ static void *rhashtable_try_insert(struct rhashtable *ht, const void *key,
 	struct bucket_table *new_tbl;
 	struct bucket_table *tbl;
 	struct rhash_lock_head __rcu **bkt;
+	unsigned long flags;
 	unsigned int hash;
 	void *data;
 
@@ -607,7 +611,7 @@ static void *rhashtable_try_insert(struct rhashtable *ht, const void *key,
 			new_tbl = rht_dereference_rcu(tbl->future_tbl, ht);
 			data = ERR_PTR(-EAGAIN);
 		} else {
-			rht_lock(tbl, bkt);
+			flags = rht_lock(tbl, bkt);
 			data = rhashtable_lookup_one(ht, bkt, tbl,
 						     hash, key, obj);
 			new_tbl = rhashtable_insert_one(ht, bkt, tbl,
@@ -615,7 +619,7 @@ static void *rhashtable_try_insert(struct rhashtable *ht, const void *key,
 			if (PTR_ERR(new_tbl) != -EEXIST)
 				data = ERR_CAST(new_tbl);
 
-			rht_unlock(tbl, bkt);
+			rht_unlock(tbl, bkt, flags);
 		}
 	} while (!IS_ERR_OR_NULL(new_tbl));