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Message-ID: <20070517045041.GA4462@in.ibm.com>
Date: Thu, 17 May 2007 10:20:41 +0530
From: Bharata B Rao <bharata@...ux.vnet.ibm.com>
To: linux-kernel@...r.kernel.org
Subject: Convert namespace_sem to a mutex
From: Bharata B Rao <bharata@...ux.vnet.ibm.com>
namespace_sem is a rwsem. It is acquired as read sem at only one place(used
by /proc/mounts, /proc/<pid>/mounts and /proc/<pid>/mountstats). In all other
cases it is acquired as a write sem. So, as there is not more than one reader
for this sem, this can be a generic sem (and not rwsem) and if so it can be
a mutex.
Patch is for 2.6.22-rc1-mm1.
Signed-off-by: Bharata B Rao <bharata@...ux.vnet.ibm.com>
---
fs/namespace.c | 48 ++++++++++++++++++++++++------------------------
1 files changed, 24 insertions(+), 24 deletions(-)
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -37,7 +37,7 @@ static int event;
static struct list_head *mount_hashtable __read_mostly;
static int hash_mask __read_mostly, hash_bits __read_mostly;
static struct kmem_cache *mnt_cache __read_mostly;
-static struct rw_semaphore namespace_sem;
+static struct mutex namespace_mutex;
int nr_user_mounts;
int max_user_mounts = 1024;
@@ -396,7 +396,7 @@ static void *m_start(struct seq_file *m,
struct list_head *p;
loff_t l = *pos;
- down_read(&namespace_sem);
+ mutex_lock(&namespace_mutex);
list_for_each(p, &n->list)
if (!l--)
return list_entry(p, struct vfsmount, mnt_list);
@@ -413,7 +413,7 @@ static void *m_next(struct seq_file *m,
static void m_stop(struct seq_file *m, void *v)
{
- up_read(&namespace_sem);
+ mutex_unlock(&namespace_mutex);
}
static inline void mangle(struct seq_file *m, const char *s)
@@ -683,7 +683,7 @@ static int do_umount(struct vfsmount *mn
return retval;
}
- down_write(&namespace_sem);
+ mutex_lock(&namespace_mutex);
spin_lock(&vfsmount_lock);
event++;
@@ -696,7 +696,7 @@ static int do_umount(struct vfsmount *mn
spin_unlock(&vfsmount_lock);
if (retval)
security_sb_umount_busy(mnt);
- up_write(&namespace_sem);
+ mutex_unlock(&namespace_mutex);
release_mounts(&umount_list);
return retval;
}
@@ -1002,12 +1002,12 @@ static int do_change_type(struct nameida
if (nd->dentry != nd->mnt->mnt_root)
return -EINVAL;
- down_write(&namespace_sem);
+ mutex_lock(&namespace_mutex);
spin_lock(&vfsmount_lock);
for (m = mnt; m; m = (recurse ? next_mnt(m, mnt) : NULL))
change_mnt_propagation(m, type);
spin_unlock(&vfsmount_lock);
- up_write(&namespace_sem);
+ mutex_unlock(&namespace_mutex);
return 0;
}
@@ -1030,7 +1030,7 @@ static int do_loopback(struct nameidata
if (err)
return err;
- down_write(&namespace_sem);
+ mutex_lock(&namespace_mutex);
err = -EINVAL;
if (IS_MNT_UNBINDABLE(old_nd.mnt))
goto out;
@@ -1062,7 +1062,7 @@ static int do_loopback(struct nameidata
}
out:
- up_write(&namespace_sem);
+ mutex_unlock(&namespace_mutex);
path_release(&old_nd);
return err;
}
@@ -1124,7 +1124,7 @@ static int do_move_mount(struct nameidat
if (err)
return err;
- down_write(&namespace_sem);
+ mutex_lock(&namespace_mutex);
while (d_mountpoint(nd->dentry) && follow_down(&nd->mnt, &nd->dentry))
;
err = -EINVAL;
@@ -1176,7 +1176,7 @@ static int do_move_mount(struct nameidat
out1:
mutex_unlock(&nd->dentry->d_inode->i_mutex);
out:
- up_write(&namespace_sem);
+ mutex_unlock(&namespace_mutex);
if (!err)
path_release(&parent_nd);
path_release(&old_nd);
@@ -1238,7 +1238,7 @@ int do_add_mount(struct vfsmount *newmnt
{
int err;
- down_write(&namespace_sem);
+ mutex_lock(&namespace_mutex);
/* Something was mounted here while we slept */
while (d_mountpoint(nd->dentry) && follow_down(&nd->mnt, &nd->dentry))
;
@@ -1267,11 +1267,11 @@ int do_add_mount(struct vfsmount *newmnt
list_add_tail(&newmnt->mnt_expire, fslist);
spin_unlock(&vfsmount_lock);
}
- up_write(&namespace_sem);
+ mutex_unlock(&namespace_mutex);
return 0;
unlock:
- up_write(&namespace_sem);
+ mutex_unlock(&namespace_mutex);
mntput(newmnt);
return err;
}
@@ -1337,9 +1337,9 @@ static void expire_mount_list(struct lis
get_mnt_ns(ns);
spin_unlock(&vfsmount_lock);
- down_write(&namespace_sem);
+ mutex_lock(&namespace_mutex);
expire_mount(mnt, mounts, &umounts);
- up_write(&namespace_sem);
+ mutex_unlock(&namespace_mutex);
release_mounts(&umounts);
mntput(mnt);
put_mnt_ns(ns);
@@ -1612,12 +1612,12 @@ static struct mnt_namespace *dup_mnt_ns(
init_waitqueue_head(&new_ns->poll);
new_ns->event = 0;
- down_write(&namespace_sem);
+ mutex_lock(&namespace_mutex);
/* First pass: copy the tree topology */
new_ns->root = copy_tree(mnt_ns->root, mnt_ns->root->mnt_root,
CL_COPY_ALL | CL_EXPIRE, 0);
if (IS_ERR(new_ns->root)) {
- up_write(&namespace_sem);
+ mutex_unlock(&namespace_mutex);
kfree(new_ns);
return NULL;
}
@@ -1651,7 +1651,7 @@ static struct mnt_namespace *dup_mnt_ns(
p = next_mnt(p, mnt_ns->root);
q = next_mnt(q, new_ns->root);
}
- up_write(&namespace_sem);
+ mutex_unlock(&namespace_mutex);
if (rootmnt)
mntput(rootmnt);
@@ -1850,7 +1850,7 @@ asmlinkage long sys_pivot_root(const cha
user_nd.mnt = mntget(current->fs->rootmnt);
user_nd.dentry = dget(current->fs->root);
read_unlock(¤t->fs->lock);
- down_write(&namespace_sem);
+ mutex_lock(&namespace_mutex);
mutex_lock(&old_nd.dentry->d_inode->i_mutex);
error = -EINVAL;
if (IS_MNT_SHARED(old_nd.mnt) ||
@@ -1905,7 +1905,7 @@ asmlinkage long sys_pivot_root(const cha
path_release(&parent_nd);
out2:
mutex_unlock(&old_nd.dentry->d_inode->i_mutex);
- up_write(&namespace_sem);
+ mutex_unlock(&namespace_mutex);
path_release(&user_nd);
path_release(&old_nd);
out1:
@@ -1951,7 +1951,7 @@ void __init mnt_init(unsigned long mempa
int i;
int err;
- init_rwsem(&namespace_sem);
+ mutex_init(&namespace_mutex);
mnt_cache = kmem_cache_create("mnt_cache", sizeof(struct vfsmount),
0, SLAB_HWCACHE_ALIGN | SLAB_PANIC, NULL, NULL);
@@ -2008,11 +2008,11 @@ void __put_mnt_ns(struct mnt_namespace *
LIST_HEAD(umount_list);
ns->root = NULL;
spin_unlock(&vfsmount_lock);
- down_write(&namespace_sem);
+ mutex_lock(&namespace_mutex);
spin_lock(&vfsmount_lock);
umount_tree(root, 0, &umount_list);
spin_unlock(&vfsmount_lock);
- up_write(&namespace_sem);
+ mutex_unlock(&namespace_mutex);
release_mounts(&umount_list);
kfree(ns);
}
-
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