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authorTim Chen <tim.c.chen@linux.intel.com>2011-07-19 09:32:38 -0700
committerAl Viro <viro@zeniv.linux.org.uk>2011-07-24 10:08:32 -0400
commit423e0ab086ad8b33626e45fa94ac7613146b7ffa (patch)
tree249c9337a02254fe5dbede7436f78dfcc1ec508f /fs/namespace.c
parentbbd9d6f7fbb0305c9a592bf05a32e87eb364a4ff (diff)
VFS : mount lock scalability for internal mounts
For a number of file systems that don't have a mount point (e.g. sockfs and pipefs), they are not marked as long term. Therefore in mntput_no_expire, all locks in vfs_mount lock are taken instead of just local cpu's lock to aggregate reference counts when we release reference to file objects. In fact, only local lock need to have been taken to update ref counts as these file systems are in no danger of going away until we are ready to unregister them. The attached patch marks file systems using kern_mount without mount point as long term. The contentions of vfs_mount lock is now eliminated. Before un-registering such file system, kern_unmount should be called to remove the long term flag and make the mount point ready to be freed. Signed-off-by: Tim Chen <tim.c.chen@linux.intel.com> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Diffstat (limited to 'fs/namespace.c')
-rw-r--r--fs/namespace.c21
1 files changed, 20 insertions, 1 deletions
diff --git a/fs/namespace.c b/fs/namespace.c
index cda50fe9250..22bfe8273c6 100644
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -2721,6 +2721,25 @@ EXPORT_SYMBOL(put_mnt_ns);
struct vfsmount *kern_mount_data(struct file_system_type *type, void *data)
{
- return vfs_kern_mount(type, MS_KERNMOUNT, type->name, data);
+ struct vfsmount *mnt;
+ mnt = vfs_kern_mount(type, MS_KERNMOUNT, type->name, data);
+ if (!IS_ERR(mnt)) {
+ /*
+ * it is a longterm mount, don't release mnt until
+ * we unmount before file sys is unregistered
+ */
+ mnt_make_longterm(mnt);
+ }
+ return mnt;
}
EXPORT_SYMBOL_GPL(kern_mount_data);
+
+void kern_unmount(struct vfsmount *mnt)
+{
+ /* release long term mount so mount point can be released */
+ if (!IS_ERR_OR_NULL(mnt)) {
+ mnt_make_shortterm(mnt);
+ mntput(mnt);
+ }
+}
+EXPORT_SYMBOL(kern_unmount);