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fs: simplify rwlock to spinlock

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We're not taking the read_lock() anymore now that all lookup is
lockless. Just use a simple spinlock.

Link: https://lore.kernel.org/r/20241213-work-mount-rbtree-lockless-v3-6-6e3cdaf9b280@kernel.org
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Christian Brauner <brauner@kernel.org>
This commit is contained in:
Christian Brauner
2024-12-13 00:03:45 +01:00
parent 4368898b27
commit e7c8dde368
1 changed files with 6 additions and 9 deletions
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15
fs/namespace.c
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@@ -78,8 +78,7 @@ static struct kmem_cache *mnt_cache __ro_after_init;
static DECLARE_RWSEM(namespace_sem);
static HLIST_HEAD(unmounted); /* protected by namespace_sem */
static LIST_HEAD(ex_mountpoints); /* protected by namespace_sem */
static DEFINE_RWLOCK(mnt_ns_tree_lock);
static seqcount_rwlock_t mnt_ns_tree_seqcount = SEQCNT_RWLOCK_ZERO(mnt_ns_tree_seqcount, &mnt_ns_tree_lock);
static DEFINE_SEQLOCK(mnt_ns_tree_lock);
static struct rb_root mnt_ns_tree = RB_ROOT; /* protected by mnt_ns_tree_lock */
static LIST_HEAD(mnt_ns_list); /* protected by mnt_ns_tree_lock */
@@ -131,14 +130,12 @@ static int mnt_ns_cmp(struct rb_node *a, const struct rb_node *b)
static inline void mnt_ns_tree_write_lock(void)
{
write_lock(&mnt_ns_tree_lock);
write_seqcount_begin(&mnt_ns_tree_seqcount);
write_seqlock(&mnt_ns_tree_lock);
}
static inline void mnt_ns_tree_write_unlock(void)
{
write_seqcount_end(&mnt_ns_tree_seqcount);
write_unlock(&mnt_ns_tree_lock);
write_sequnlock(&mnt_ns_tree_lock);
}
static void mnt_ns_tree_add(struct mnt_namespace *ns)
@@ -163,7 +160,7 @@ static void mnt_ns_tree_add(struct mnt_namespace *ns)
static void mnt_ns_release(struct mnt_namespace *ns)
{
lockdep_assert_not_held(&mnt_ns_tree_lock);
lockdep_assert_not_held(&mnt_ns_tree_lock.lock);
/* keep alive for {list,stat}mount() */
if (refcount_dec_and_test(&ns->passive)) {
@@ -225,11 +222,11 @@ static struct mnt_namespace *lookup_mnt_ns(u64 mnt_ns_id)
guard(rcu)();
do {
seq = read_seqcount_begin(&mnt_ns_tree_seqcount);
seq = read_seqbegin(&mnt_ns_tree_lock);
node = rb_find_rcu(&mnt_ns_id, &mnt_ns_tree, mnt_ns_find);
if (node)
break;
} while (read_seqcount_retry(&mnt_ns_tree_seqcount, seq));
} while (read_seqretry(&mnt_ns_tree_lock, seq));
if (!node)
return NULL;