Unverified Commit c4f8f862 authored by NeilBrown's avatar NeilBrown Committed by Christian Brauner
Browse files

ovl: change ovl_create_index() to take dir locks 



ovl_copy_up_workdir() currently take a rename lock on two directories,
then use the lock to both create a file in one directory, perform a
rename, and possibly unlink the file for cleanup.  This is incompatible
with proposed changes which will lock just the dentry of objects being
acted on.

This patch moves the call to ovl_create_index() earlier in
ovl_copy_up_workdir() to before the lock is taken.

ovl_create_index() then takes the required lock only when needed.

Reviewed-by: default avatarAmir Goldstein <amir73il@gmail.com>
Signed-off-by: default avatarNeilBrown <neil@brown.name>
Link: https://lore.kernel.org/20250716004725.1206467-3-neil@brown.name


Signed-off-by: default avatarChristian Brauner <brauner@kernel.org>
parent 9d23967b

fs/overlayfs/copy_up.c

+13 −9
Original line number Diff line number Diff line
@@ -517,8 +517,6 @@ static int ovl_set_upper_fh(struct ovl_fs *ofs, struct dentry *upper, 


/*

 * Create and install index entry.

 *

 * Caller must hold i_mutex on indexdir.

 */

static int ovl_create_index(struct dentry *dentry, const struct ovl_fh *fh,

			    struct dentry *upper)
@@ -550,7 +548,9 @@ static int ovl_create_index(struct dentry *dentry, const struct ovl_fh *fh, 
	if (err)

		return err;



	inode_lock(dir);

	temp = ovl_create_temp(ofs, indexdir, OVL_CATTR(S_IFDIR | 0));

	inode_unlock(dir);

	err = PTR_ERR(temp);

	if (IS_ERR(temp))

		goto free_name;
@@ -559,6 +559,9 @@ static int ovl_create_index(struct dentry *dentry, const struct ovl_fh *fh, 
	if (err)

		goto out;



	err = ovl_parent_lock(indexdir, temp);

	if (err)

		goto out;

	index = ovl_lookup_upper(ofs, name.name, indexdir, name.len);

	if (IS_ERR(index)) {

		err = PTR_ERR(index);
@@ -566,9 +569,10 @@ static int ovl_create_index(struct dentry *dentry, const struct ovl_fh *fh, 
		err = ovl_do_rename(ofs, indexdir, temp, indexdir, index, 0);

		dput(index);

	}

	ovl_parent_unlock(indexdir);

out:

	if (err)

		ovl_cleanup(ofs, dir, temp);

		ovl_cleanup_unlocked(ofs, indexdir, temp);

	dput(temp);

free_name:

	kfree(name.name);
@@ -798,6 +802,12 @@ static int ovl_copy_up_workdir(struct ovl_copy_up_ctx *c) 
	if (err)

		goto cleanup_unlocked;



	if (S_ISDIR(c->stat.mode) && c->indexed) {

		err = ovl_create_index(c->dentry, c->origin_fh, temp);

		if (err)

			goto cleanup_unlocked;

	}



	/*

	 * We cannot hold lock_rename() throughout this helper, because of

	 * lock ordering with sb_writers, which shouldn't be held when calling
@@ -818,12 +828,6 @@ static int ovl_copy_up_workdir(struct ovl_copy_up_ctx *c) 
	if (err)

		goto cleanup;



	if (S_ISDIR(c->stat.mode) && c->indexed) {

		err = ovl_create_index(c->dentry, c->origin_fh, temp);

		if (err)

			goto cleanup;

	}



	upper = ovl_lookup_upper(ofs, c->destname.name, c->destdir,

				 c->destname.len);

	err = PTR_ERR(upper);