If the expiring_list is empty, we can avoid a costly spinlock in the rcu-walk path through autofs4_d_manage (once the rest of the path becomes rcu-walk friendly).
Signed-off-by: NeilBrown <[email protected]> Reviewed-by: Ian Kent <[email protected]> --- fs/autofs4/root.c | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-) diff --git a/fs/autofs4/root.c b/fs/autofs4/root.c index cc87c1abac97..fb202cadd4b3 100644 --- a/fs/autofs4/root.c +++ b/fs/autofs4/root.c @@ -166,8 +166,10 @@ static struct dentry *autofs4_lookup_active(struct dentry *dentry) const unsigned char *str = name->name; struct list_head *p, *head; - spin_lock(&sbi->lookup_lock); head = &sbi->active_list; + if (list_empty(head)) + return NULL; + spin_lock(&sbi->lookup_lock); list_for_each(p, head) { struct autofs_info *ino; struct dentry *active; @@ -218,8 +220,10 @@ static struct dentry *autofs4_lookup_expiring(struct dentry *dentry) const unsigned char *str = name->name; struct list_head *p, *head; - spin_lock(&sbi->lookup_lock); head = &sbi->expiring_list; + if (list_empty(head)) + return NULL; + spin_lock(&sbi->lookup_lock); list_for_each(p, head) { struct autofs_info *ino; struct dentry *expiring; -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
