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authorTrond Myklebust <Trond.Myklebust@netapp.com>2006-06-09 17:34:17 +0400
committerTrond Myklebust <Trond.Myklebust@netapp.com>2006-06-09 17:34:17 +0400
commit5528f911b4c43a5de5da34bcbd7e3f2a62503617 (patch)
tree2c888b1dc0b3743855d795a1a02730637d6ba0aa /fs/namespace.c
parent1f5ce9e93aa96a867f195ed45f6f77935175f12e (diff)
downloadlinux-5528f911b4c43a5de5da34bcbd7e3f2a62503617.tar.xz
VFS: Add shrink_submounts()
Allow a submount to be marked as being 'shrinkable' by means of the vfsmount->mnt_flags, and then add a function 'shrink_submounts()' which attempts to recursively unmount these submounts. Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
Diffstat (limited to 'fs/namespace.c')
-rw-r--r--fs/namespace.c124
1 files changed, 99 insertions, 25 deletions
diff --git a/fs/namespace.c b/fs/namespace.c
index bf478addb852..b22e469ab560 100644
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -1163,13 +1163,46 @@ static void expire_mount(struct vfsmount *mnt, struct list_head *mounts,
}
/*
+ * go through the vfsmounts we've just consigned to the graveyard to
+ * - check that they're still dead
+ * - delete the vfsmount from the appropriate namespace under lock
+ * - dispose of the corpse
+ */
+static void expire_mount_list(struct list_head *graveyard, struct list_head *mounts)
+{
+ struct namespace *namespace;
+ struct vfsmount *mnt;
+
+ while (!list_empty(graveyard)) {
+ LIST_HEAD(umounts);
+ mnt = list_entry(graveyard->next, struct vfsmount, mnt_expire);
+ list_del_init(&mnt->mnt_expire);
+
+ /* don't do anything if the namespace is dead - all the
+ * vfsmounts from it are going away anyway */
+ namespace = mnt->mnt_namespace;
+ if (!namespace || !namespace->root)
+ continue;
+ get_namespace(namespace);
+
+ spin_unlock(&vfsmount_lock);
+ down_write(&namespace_sem);
+ expire_mount(mnt, mounts, &umounts);
+ up_write(&namespace_sem);
+ release_mounts(&umounts);
+ mntput(mnt);
+ put_namespace(namespace);
+ spin_lock(&vfsmount_lock);
+ }
+}
+
+/*
* process a list of expirable mountpoints with the intent of discarding any
* mountpoints that aren't in use and haven't been touched since last we came
* here
*/
void mark_mounts_for_expiry(struct list_head *mounts)
{
- struct namespace *namespace;
struct vfsmount *mnt, *next;
LIST_HEAD(graveyard);
@@ -1193,38 +1226,79 @@ void mark_mounts_for_expiry(struct list_head *mounts)
list_move(&mnt->mnt_expire, &graveyard);
}
- /*
- * go through the vfsmounts we've just consigned to the graveyard to
- * - check that they're still dead
- * - delete the vfsmount from the appropriate namespace under lock
- * - dispose of the corpse
- */
- while (!list_empty(&graveyard)) {
- LIST_HEAD(umounts);
- mnt = list_entry(graveyard.next, struct vfsmount, mnt_expire);
- list_del_init(&mnt->mnt_expire);
+ expire_mount_list(&graveyard, mounts);
- /* don't do anything if the namespace is dead - all the
- * vfsmounts from it are going away anyway */
- namespace = mnt->mnt_namespace;
- if (!namespace || !namespace->root)
+ spin_unlock(&vfsmount_lock);
+}
+
+EXPORT_SYMBOL_GPL(mark_mounts_for_expiry);
+
+/*
+ * Ripoff of 'select_parent()'
+ *
+ * search the list of submounts for a given mountpoint, and move any
+ * shrinkable submounts to the 'graveyard' list.
+ */
+static int select_submounts(struct vfsmount *parent, struct list_head *graveyard)
+{
+ struct vfsmount *this_parent = parent;
+ struct list_head *next;
+ int found = 0;
+
+repeat:
+ next = this_parent->mnt_mounts.next;
+resume:
+ while (next != &this_parent->mnt_mounts) {
+ struct list_head *tmp = next;
+ struct vfsmount *mnt = list_entry(tmp, struct vfsmount, mnt_child);
+
+ next = tmp->next;
+ if (!(mnt->mnt_flags & MNT_SHRINKABLE))
continue;
- get_namespace(namespace);
+ /*
+ * Descend a level if the d_mounts list is non-empty.
+ */
+ if (!list_empty(&mnt->mnt_mounts)) {
+ this_parent = mnt;
+ goto repeat;
+ }
- spin_unlock(&vfsmount_lock);
- down_write(&namespace_sem);
- expire_mount(mnt, mounts, &umounts);
- up_write(&namespace_sem);
- release_mounts(&umounts);
- mntput(mnt);
- put_namespace(namespace);
- spin_lock(&vfsmount_lock);
+ if (!propagate_mount_busy(mnt, 1)) {
+ mntget(mnt);
+ list_move_tail(&mnt->mnt_expire, graveyard);
+ found++;
+ }
}
+ /*
+ * All done at this level ... ascend and resume the search
+ */
+ if (this_parent != parent) {
+ next = this_parent->mnt_child.next;
+ this_parent = this_parent->mnt_parent;
+ goto resume;
+ }
+ return found;
+}
+
+/*
+ * process a list of expirable mountpoints with the intent of discarding any
+ * submounts of a specific parent mountpoint
+ */
+void shrink_submounts(struct vfsmount *mountpoint, struct list_head *mounts)
+{
+ LIST_HEAD(graveyard);
+ int found;
+
+ spin_lock(&vfsmount_lock);
+
+ /* extract submounts of 'mountpoint' from the expiration list */
+ while ((found = select_submounts(mountpoint, &graveyard)) != 0)
+ expire_mount_list(&graveyard, mounts);
spin_unlock(&vfsmount_lock);
}
-EXPORT_SYMBOL_GPL(mark_mounts_for_expiry);
+EXPORT_SYMBOL_GPL(shrink_submounts);
/*
* Some copy_from_user() implementations do not return the exact number of