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Commit db14fc3a authored by Miklos Szeredi's avatar Miklos Szeredi Committed by Al Viro
Browse files

vfs: add d_walk() 



This one replaces three instances open coded tree walking (have_submounts,
select_parent, d_genocide) with a common helper.

In addition to slightly reducing the kernel size, this simplifies the
callers and makes them less bug prone.

Signed-off-by: default avatarMiklos Szeredi <mszeredi@suse.cz>
Signed-off-by: default avatarAl Viro <viro@zeniv.linux.org.uk>
parent 01ddc4ed

fs/dcache.c

+148 −161
Original line number Diff line number Diff line
@@ -1031,34 +1031,56 @@ static struct dentry *try_to_ascend(struct dentry *old, int locked, unsigned seq 
	return new;

}





/*

 * Search for at least 1 mount point in the dentry's subdirs.

 * We descend to the next level whenever the d_subdirs

 * list is non-empty and continue searching.

 */

/**

 * enum d_walk_ret - action to talke during tree walk

 * @D_WALK_CONTINUE:	contrinue walk

 * @D_WALK_QUIT:	quit walk

 * @D_WALK_NORETRY:	quit when retry is needed

 * @D_WALK_SKIP:	skip this dentry and its children

 */

enum d_walk_ret {

	D_WALK_CONTINUE,

	D_WALK_QUIT,

	D_WALK_NORETRY,

	D_WALK_SKIP,

};



/**

 * have_submounts - check for mounts over a dentry

 * @parent: dentry to check.

 * d_walk - walk the dentry tree

 * @parent:	start of walk

 * @data:	data passed to @enter() and @finish()

 * @enter:	callback when first entering the dentry

 * @finish:	callback when successfully finished the walk

 *

 * Return true if the parent or its subdirectories contain

 * a mount point

 * The @enter() and @finish() callbacks are called with d_lock held.

 */

int have_submounts(struct dentry *parent)

static void d_walk(struct dentry *parent, void *data,

		   enum d_walk_ret (*enter)(void *, struct dentry *),

		   void (*finish)(void *))

{

	struct dentry *this_parent;

	struct list_head *next;

	unsigned seq;

	int locked = 0;

	enum d_walk_ret ret;

	bool retry = true;



	seq = read_seqbegin(&rename_lock);

again:

	this_parent = parent;



	if (d_mountpoint(parent))

		goto positive;

	spin_lock(&this_parent->d_lock);



	ret = enter(data, this_parent);

	switch (ret) {

	case D_WALK_CONTINUE:

		break;

	case D_WALK_QUIT:

	case D_WALK_SKIP:

		goto out_unlock;

	case D_WALK_NORETRY:

		retry = false;

		break;

	}

repeat:

	next = this_parent->d_subdirs.next;

resume:
@@ -1068,12 +1090,22 @@ resume: 
		next = tmp->next;



		spin_lock_nested(&dentry->d_lock, DENTRY_D_LOCK_NESTED);

		/* Have we found a mount point ? */

		if (d_mountpoint(dentry)) {



		ret = enter(data, dentry);

		switch (ret) {

		case D_WALK_CONTINUE:

			break;

		case D_WALK_QUIT:

			spin_unlock(&dentry->d_lock);

			spin_unlock(&this_parent->d_lock);

			goto positive;

			goto out_unlock;

		case D_WALK_NORETRY:

			retry = false;

			break;

		case D_WALK_SKIP:

			spin_unlock(&dentry->d_lock);

			continue;

		}



		if (!list_empty(&dentry->d_subdirs)) {

			spin_unlock(&this_parent->d_lock);

			spin_release(&dentry->d_lock.dep_map, 1, _RET_IP_);
@@ -1094,26 +1126,61 @@ resume: 
		next = child->d_u.d_child.next;

		goto resume;

	}

	if (!locked && read_seqretry(&rename_lock, seq)) {

		spin_unlock(&this_parent->d_lock);

	if (!locked && read_seqretry(&rename_lock, seq))

		goto rename_retry;

	if (locked)

		write_sequnlock(&rename_lock);

	return 0; /* No mount points found in tree */

positive:

	if (!locked && read_seqretry(&rename_lock, seq))

		goto rename_retry;

	}

	if (finish)

		finish(data);



out_unlock:

	spin_unlock(&this_parent->d_lock);

	if (locked)

		write_sequnlock(&rename_lock);

	return 1;

	return;



rename_retry:

	if (!retry)

		return;

	if (locked)

		goto again;

	locked = 1;

	write_seqlock(&rename_lock);

	goto again;

}



/*

 * Search for at least 1 mount point in the dentry's subdirs.

 * We descend to the next level whenever the d_subdirs

 * list is non-empty and continue searching.

 */



/**

 * have_submounts - check for mounts over a dentry

 * @parent: dentry to check.

 *

 * Return true if the parent or its subdirectories contain

 * a mount point

 */



static enum d_walk_ret check_mount(void *data, struct dentry *dentry)

{

	int *ret = data;

	if (d_mountpoint(dentry)) {

		*ret = 1;

		return D_WALK_QUIT;

	}

	return D_WALK_CONTINUE;

}



int have_submounts(struct dentry *parent)

{

	int ret = 0;



	d_walk(parent, &ret, check_mount, NULL);



	return ret;

}

EXPORT_SYMBOL(have_submounts);



/*
@@ -1130,27 +1197,20 @@ EXPORT_SYMBOL(have_submounts); 
 * drop the lock and return early due to latency

 * constraints.

 */

static int select_parent(struct dentry *parent, struct list_head *dispose)

{

	struct dentry *this_parent;

	struct list_head *next;

	unsigned seq;

	int found = 0;

	int locked = 0;



	seq = read_seqbegin(&rename_lock);

again:

	this_parent = parent;

	spin_lock(&this_parent->d_lock);

repeat:

	next = this_parent->d_subdirs.next;

resume:

	while (next != &this_parent->d_subdirs) {

		struct list_head *tmp = next;

		struct dentry *dentry = list_entry(tmp, struct dentry, d_u.d_child);

		next = tmp->next;

struct select_data {

	struct dentry *start;

	struct list_head dispose;

	int found;

};



		spin_lock_nested(&dentry->d_lock, DENTRY_D_LOCK_NESTED);

static enum d_walk_ret select_collect(void *_data, struct dentry *dentry)

{

	struct select_data *data = _data;

	enum d_walk_ret ret = D_WALK_CONTINUE;



	if (data->start == dentry)

		goto out;



	/*

	 * move only zero ref count dentries to the dispose list.
@@ -1163,60 +1223,20 @@ resume: 
	if (dentry->d_lockref.count) {

		dentry_lru_del(dentry);

	} else if (!(dentry->d_flags & DCACHE_SHRINK_LIST)) {

			dentry_lru_move_list(dentry, dispose);

		dentry_lru_move_list(dentry, &data->dispose);

		dentry->d_flags |= DCACHE_SHRINK_LIST;

			found++;

		data->found++;

		ret = D_WALK_NORETRY;

	}

	/*

	 * We can return to the caller if we have found some (this

	 * ensures forward progress). We'll be coming back to find

	 * the rest.

	 */

		if (found && need_resched()) {

			spin_unlock(&dentry->d_lock);

			goto out;

		}



		/*

		 * Descend a level if the d_subdirs list is non-empty.

		 */

		if (!list_empty(&dentry->d_subdirs)) {

			spin_unlock(&this_parent->d_lock);

			spin_release(&dentry->d_lock.dep_map, 1, _RET_IP_);

			this_parent = dentry;

			spin_acquire(&this_parent->d_lock.dep_map, 0, 1, _RET_IP_);

			goto repeat;

		}



		spin_unlock(&dentry->d_lock);

	}

	/*

	 * All done at this level ... ascend and resume the search.

	 */

	if (this_parent != parent) {

		struct dentry *child = this_parent;

		this_parent = try_to_ascend(this_parent, locked, seq);

		if (!this_parent)

			goto rename_retry;

		next = child->d_u.d_child.next;

		goto resume;

	}

	if (data->found && need_resched())

		ret = D_WALK_QUIT;

out:

	spin_unlock(&this_parent->d_lock);

	if (!locked && read_seqretry(&rename_lock, seq))

		goto rename_retry;

	if (locked)

		write_sequnlock(&rename_lock);

	return found;



rename_retry:

	if (found)

		return found;

	if (locked)

		goto again;

	locked = 1;

	write_seqlock(&rename_lock);

	goto again;

	return ret;

}



/**
@@ -1227,11 +1247,18 @@ rename_retry: 
 */

void shrink_dcache_parent(struct dentry *parent)

{

	LIST_HEAD(dispose);

	int found;

	for (;;) {

		struct select_data data;



	while ((found = select_parent(parent, &dispose)) != 0) {

		shrink_dentry_list(&dispose);

		INIT_LIST_HEAD(&data.dispose);

		data.start = parent;

		data.found = 0;



		d_walk(parent, &data, select_collect, NULL);

		if (!data.found)

			break;



		shrink_dentry_list(&data.dispose);

		cond_resched();

	}

}
@@ -2928,64 +2955,24 @@ int is_subdir(struct dentry *new_dentry, struct dentry *old_dentry) 
	return result;

}



void d_genocide(struct dentry *root)

static enum d_walk_ret d_genocide_kill(void *data, struct dentry *dentry)

{

	struct dentry *this_parent;

	struct list_head *next;

	unsigned seq;

	int locked = 0;



	seq = read_seqbegin(&rename_lock);

again:

	this_parent = root;

	spin_lock(&this_parent->d_lock);

repeat:

	next = this_parent->d_subdirs.next;

resume:

	while (next != &this_parent->d_subdirs) {

		struct list_head *tmp = next;

		struct dentry *dentry = list_entry(tmp, struct dentry, d_u.d_child);

		next = tmp->next;

	struct dentry *root = data;

	if (dentry != root) {

		if (d_unhashed(dentry) || !dentry->d_inode)

			return D_WALK_SKIP;



		spin_lock_nested(&dentry->d_lock, DENTRY_D_LOCK_NESTED);

		if (d_unhashed(dentry) || !dentry->d_inode) {

			spin_unlock(&dentry->d_lock);

			continue;

		}

		if (!(dentry->d_flags & DCACHE_GENOCIDE)) {

			dentry->d_flags |= DCACHE_GENOCIDE;

			dentry->d_lockref.count--;

		}

		if (!list_empty(&dentry->d_subdirs)) {

			spin_unlock(&this_parent->d_lock);

			spin_release(&dentry->d_lock.dep_map, 1, _RET_IP_);

			this_parent = dentry;

			spin_acquire(&this_parent->d_lock.dep_map, 0, 1, _RET_IP_);

			goto repeat;

	}

		spin_unlock(&dentry->d_lock);

	return D_WALK_CONTINUE;

}

	if (this_parent != root) {

		struct dentry *child = this_parent;

		this_parent = try_to_ascend(this_parent, locked, seq);

		if (!this_parent)

			goto rename_retry;

		next = child->d_u.d_child.next;

		goto resume;

	}

	spin_unlock(&this_parent->d_lock);

	if (!locked && read_seqretry(&rename_lock, seq))

		goto rename_retry;

	if (locked)

		write_sequnlock(&rename_lock);

	return;



rename_retry:

	if (locked)

		goto again;

	locked = 1;

	write_seqlock(&rename_lock);

	goto again;

void d_genocide(struct dentry *parent)

{

	d_walk(parent, parent, d_genocide_kill, NULL);

}



void d_tmpfile(struct dentry *dentry, struct inode *inode)