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Commit 5528f911 authored by Trond Myklebust's avatar Trond Myklebust
Browse files

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: default avatarTrond Myklebust <Trond.Myklebust@netapp.com>
parent 1f5ce9e9

fs/namespace.c

+99 −25
Original line number Diff line number Diff line
@@ -1162,6 +1162,40 @@ 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
@@ -1169,7 +1203,6 @@ static void expire_mount(struct vfsmount *mnt, struct list_head *mounts, 
 */

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);

	}



	expire_mount_list(&graveyard, mounts);



	spin_unlock(&vfsmount_lock);

}



EXPORT_SYMBOL_GPL(mark_mounts_for_expiry);



/*

	 * 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

 * Ripoff of 'select_parent()'

 *

 * search the list of submounts for a given mountpoint, and move any

 * shrinkable submounts to the 'graveyard' list.

 */

	while (!list_empty(&graveyard)) {

		LIST_HEAD(umounts);

		mnt = list_entry(graveyard.next, struct vfsmount, mnt_expire);

		list_del_init(&mnt->mnt_expire);

static int select_submounts(struct vfsmount *parent, struct list_head *graveyard)

{

	struct vfsmount *this_parent = parent;

	struct list_head *next;

	int found = 0;



		/* 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)

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

include/linux/mount.h

+3 −0
Original line number Diff line number Diff line
@@ -23,6 +23,8 @@ 
#define MNT_NOATIME	0x08

#define MNT_NODIRATIME	0x10



#define MNT_SHRINKABLE	0x100



#define MNT_SHARED	0x1000	/* if the vfsmount is a shared mount */

#define MNT_UNBINDABLE	0x2000	/* if the vfsmount is a unbindable mount */

#define MNT_PNODE_MASK	0x3000	/* propogation flag mask */
@@ -84,6 +86,7 @@ extern int do_add_mount(struct vfsmount *newmnt, struct nameidata *nd, 
			int mnt_flags, struct list_head *fslist);



extern void mark_mounts_for_expiry(struct list_head *mounts);

extern void shrink_submounts(struct vfsmount *mountpoint, struct list_head *mounts);



extern spinlock_t vfsmount_lock;

extern dev_t name_to_dev_t(char *name);