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authorJ. Bruce Fields <bfields@citi.umich.edu>2008-02-20 23:40:15 +0300
committerJ. Bruce Fields <bfields@citi.umich.edu>2008-04-24 00:13:39 +0400
commitd8421202121ce74daf4625ca9d1d825bbd7ce66a (patch)
tree0465a155e03b97660d2f887e702b8f2917889c75
parenta95e56e72c196970a8067cd515c658d064813170 (diff)
downloadlinux-d8421202121ce74daf4625ca9d1d825bbd7ce66a.tar.xz
lockd: convert nsm_mutex to a spinlock
There's no reason for a mutex here, except to allow an allocation under the lock, which we can avoid with the usual trick of preallocating memory for the new object and freeing it if it turns out to be unnecessary. Signed-off-by: J. Bruce Fields <bfields@citi.umich.edu>
-rw-r--r--fs/lockd/host.c34
1 files changed, 19 insertions, 15 deletions
diff --git a/fs/lockd/host.c b/fs/lockd/host.c
index de0ffb6106c4..c7854791898f 100644
--- a/fs/lockd/host.c
+++ b/fs/lockd/host.c
@@ -457,7 +457,7 @@ nlm_gc_hosts(void)
* Manage NSM handles
*/
static LIST_HEAD(nsm_handles);
-static DEFINE_MUTEX(nsm_mutex);
+static DEFINE_SPINLOCK(nsm_lock);
static struct nsm_handle *
__nsm_find(const struct sockaddr_in *sin,
@@ -479,7 +479,8 @@ __nsm_find(const struct sockaddr_in *sin,
return NULL;
}
- mutex_lock(&nsm_mutex);
+retry:
+ spin_lock(&nsm_lock);
list_for_each_entry(pos, &nsm_handles, sm_link) {
if (hostname && nsm_use_hostnames) {
@@ -489,28 +490,32 @@ __nsm_find(const struct sockaddr_in *sin,
} else if (!nlm_cmp_addr(&pos->sm_addr, sin))
continue;
atomic_inc(&pos->sm_count);
+ kfree(nsm);
nsm = pos;
- goto out;
+ goto found;
}
-
- if (!create) {
- nsm = NULL;
- goto out;
+ if (nsm) {
+ list_add(&nsm->sm_link, &nsm_handles);
+ goto found;
}
+ spin_unlock(&nsm_lock);
+
+ if (!create)
+ return NULL;
nsm = kzalloc(sizeof(*nsm) + hostname_len + 1, GFP_KERNEL);
if (nsm == NULL)
- goto out;
+ return NULL;
+
nsm->sm_addr = *sin;
nsm->sm_name = (char *) (nsm + 1);
memcpy(nsm->sm_name, hostname, hostname_len);
nsm->sm_name[hostname_len] = '\0';
atomic_set(&nsm->sm_count, 1);
+ goto retry;
- list_add(&nsm->sm_link, &nsm_handles);
-
-out:
- mutex_unlock(&nsm_mutex);
+found:
+ spin_unlock(&nsm_lock);
return nsm;
}
@@ -529,10 +534,9 @@ nsm_release(struct nsm_handle *nsm)
{
if (!nsm)
return;
- mutex_lock(&nsm_mutex);
- if (atomic_dec_and_test(&nsm->sm_count)) {
+ if (atomic_dec_and_lock(&nsm->sm_count, &nsm_lock)) {
list_del(&nsm->sm_link);
+ spin_unlock(&nsm_lock);
kfree(nsm);
}
- mutex_unlock(&nsm_mutex);
}