[RFC][PATCH 3/4] change mnt_writers[] spinlock to mutex

Dave Hansen
2008-01-10T19:07:54Z

---

linux-2.6.git-dave/fs/namespace.c | 21 ++++++++++-----------
1 file changed, 10 insertions(+), 11 deletions(-)

diff -puN fs/namespace.c~change-spinlock-to-mutex fs/namespace.c
--- linux-2.6.git/fs/namespace.c~change-spinlock-to-mutex 2008-01-10 10:45:47.000000000 -0800
+++ linux-2.6.git-dave/fs/namespace.c 2008-01-10 10:46:01.000000000 -0800
@@ -118,7 +118,7 @@ struct mnt_writer {
* If holding multiple instances of this lock, they
* must be ordered by cpu number.
*/
- spinlock_t lock;
+ struct mutex lock;
struct lock_class_key lock_class; /* compiles out with !lockdep */
unsigned long count;
struct vfsmount *mnt;
@@ -130,7 +130,7 @@ static int __init init_mnt_writers(void)
int cpu;
for_each_possible_cpu(cpu) {
struct mnt_writer *writer = &per_cpu(mnt_writers, cpu);
- spin_lock_init(&writer->lock);
+ mutex_init(&writer->lock);
lockdep_set_class(&writer->lock, &writer->lock_class);
writer->count = 0;
}
@@ -145,7 +145,7 @@ static void mnt_unlock_cpus(void)

for_each_possible_cpu(cpu) {
cpu_writer = &per_cpu(mnt_writers, cpu);
- spin_unlock(&cpu_writer->lock);
+ mutex_unlock(&cpu_writer->lock);
}
}

@@ -191,8 +191,8 @@ int mnt_want_write(struct vfsmount *mnt)
int ret = 0;
struct mnt_writer *cpu_writer;

- cpu_writer = &get_cpu_var(mnt_writers);
- spin_lock(&cpu_writer->lock);
+ cpu_writer = &__get_cpu_var(mnt_writers);
+ mutex_lock(&cpu_writer->lock);
if (__mnt_is_readonly(mnt)) {
ret = -EROFS;
goto out;
@@ -200,8 +200,7 @@ int mnt_want_write(struct vfsmount *mnt)
use_cpu_writer_for_mount(cpu_writer, mnt);
cpu_writer->count++;
out:
- spin_unlock(&cpu_writer->lock);
- put_cpu_var(mnt_writers);
+ mutex_unlock(&cpu_writer->lock);
return ret;
}
EXPORT_SYMBOL_GPL(mnt_want_write);
@@ -213,7 +212,7 @@ static void lock_and_coalesce_cpu_mnt_wr

for_each_possible_cpu(cpu) {
cpu_writer = &per_cpu(mnt_writers, cpu);
- spin_lock(&cpu_writer->lock);
+ mutex_lock(&cpu_writer->lock);
__clear_mnt_count(cpu_writer);
cpu_writer->mnt = NULL;
}
@@ -269,7 +268,7 @@ void mnt_drop_write(struct vfsmount *mnt

retry:
cpu_writer = &__get_cpu_var(mnt_writers);
- spin_lock(&cpu_writer->lock);
+ mutex_lock(&cpu_writer->lock);

use_cpu_writer_for_mount(cpu_writer, mnt);
if (cpu_writer->count > 0) {
@@ -286,14 +285,14 @@ retry:
*/
if (atomic_read(&mnt->__mnt_writers) <
MNT_WRITER_UNDERFLOW_LIMIT) {
- spin_unlock(&cpu_writer->lock);
+ mutex_unlock(&cpu_writer->lock);
goto retry;
}
atomic_dec(&mnt->__mnt_writers);
must_check_underflow = 1;
}

- spin_unlock(&cpu_writer->lock);
+ mutex_unlock(&cpu_writer->lock);
/*
* Logically, we could call this each time,
* but the __mnt_writers cacheline tends to
_