Commit b10cdcdc authored by Amir Goldstein's avatar Amir Goldstein Committed by Miklos Szeredi
Browse files

ovl: untangle copy up call chain 



In an attempt to dedup ~100 LOC, we ended up creating a tangled call chain,
whose branches merge and diverge in several points according to the
immutable c->tmpfile copy up mode.

This call chain was hard to analyse for locking correctness because the
locking requirements for the c->tmpfile flow were very different from the
locking requirements for the !c->tmpfile flow (i.e. directory vs.  regulare
file copy up).

Split the copy up helpers of the c->tmpfile flow from those of the
!c->tmpfile (i.e. workdir) flow and remove the c->tmpfile mode from copy up
context.

Suggested-by: default avatarAl Viro <viro@zeniv.linux.org.uk>
Signed-off-by: default avatarAmir Goldstein <amir73il@gmail.com>
Signed-off-by: default avatarMiklos Szeredi <mszeredi@redhat.com>
parent 007ea448

fs/overlayfs/copy_up.c

+159 −86
Original line number Diff line number Diff line
@@ -395,7 +395,6 @@ struct ovl_copy_up_ctx { 
	struct dentry *destdir;

	struct qstr destname;

	struct dentry *workdir;

	bool tmpfile;

	bool origin;

	bool indexed;

	bool metacopy;
@@ -440,30 +439,58 @@ static int ovl_link_up(struct ovl_copy_up_ctx *c) 
	return err;

}



static int ovl_install_temp(struct ovl_copy_up_ctx *c, struct dentry *temp,

			    struct dentry **newdentry)

static int ovl_copy_up_inode(struct ovl_copy_up_ctx *c, struct dentry *temp)

{

	int err;

	struct dentry *upper;

	struct inode *udir = d_inode(c->destdir);



	upper = lookup_one_len(c->destname.name, c->destdir, c->destname.len);

	if (IS_ERR(upper))

		return PTR_ERR(upper);

	err = ovl_copy_xattr(c->lowerpath.dentry, temp);

	if (err)

		return err;



	if (c->tmpfile)

		err = ovl_do_link(temp, udir, upper);

	else

		err = ovl_do_rename(d_inode(c->workdir), temp, udir, upper, 0);

	/*

	 * Store identifier of lower inode in upper inode xattr to

	 * allow lookup of the copy up origin inode.

	 *

	 * Don't set origin when we are breaking the association with a lower

	 * hard link.

	 */

	if (c->origin) {

		err = ovl_set_origin(c->dentry, c->lowerpath.dentry, temp);

		if (err)

			return err;

	}



	if (S_ISREG(c->stat.mode) && !c->metacopy) {

		struct path upperpath, datapath;



		ovl_path_upper(c->dentry, &upperpath);

		BUG_ON(upperpath.dentry != NULL);

		upperpath.dentry = temp;



		ovl_path_lowerdata(c->dentry, &datapath);

		err = ovl_copy_up_data(&datapath, &upperpath, c->stat.size);

		if (err)

			return err;

	}



	if (c->metacopy) {

		err = ovl_check_setxattr(c->dentry, temp, OVL_XATTR_METACOPY,

					 NULL, 0, -EOPNOTSUPP);

		if (err)

			return err;

	}



	inode_lock(temp->d_inode);

	if (c->metacopy)

		err = ovl_set_size(temp, &c->stat);

	if (!err)

		*newdentry = dget(c->tmpfile ? upper : temp);

	dput(upper);

		err = ovl_set_attr(temp, &c->stat);

	inode_unlock(temp->d_inode);



	return err;

}



static struct dentry *ovl_get_tmpfile(struct ovl_copy_up_ctx *c)

static struct dentry *ovl_get_workdir_temp(struct ovl_copy_up_ctx *c)

{

	int err;

	struct dentry *temp;
@@ -483,9 +510,6 @@ static struct dentry *ovl_get_tmpfile(struct ovl_copy_up_ctx *c) 
	if (new_creds)

		old_creds = override_creds(new_creds);



	if (c->tmpfile)

		temp = ovl_do_tmpfile(c->workdir, c->stat.mode);

	else

	temp = ovl_create_temp(c->workdir, &cattr);



	if (new_creds) {
@@ -496,61 +520,136 @@ static struct dentry *ovl_get_tmpfile(struct ovl_copy_up_ctx *c) 
	return temp;

}



static int ovl_copy_up_inode(struct ovl_copy_up_ctx *c, struct dentry *temp)

/*

 * Move temp file from workdir into place on upper dir.

 * Used when copying up directories and when upper fs doesn't support O_TMPFILE.

 *

 * Caller must hold ovl_lock_rename_workdir().

 */

static int ovl_rename_temp(struct ovl_copy_up_ctx *c, struct dentry *temp,

			   struct dentry **newdentry)

{

	int err;

	struct dentry *upper;

	struct inode *udir = d_inode(c->destdir);



	upper = lookup_one_len(c->destname.name, c->destdir, c->destname.len);

	if (IS_ERR(upper))

		return PTR_ERR(upper);



	err = ovl_do_rename(d_inode(c->workdir), temp, udir, upper, 0);

	if (!err)

		*newdentry = dget(temp);

	dput(upper);



	err = ovl_copy_xattr(c->lowerpath.dentry, temp);

	if (err)

	return err;

}



/*

	 * Store identifier of lower inode in upper inode xattr to

	 * allow lookup of the copy up origin inode.

	 *

	 * Don't set origin when we are breaking the association with a lower

	 * hard link.

 * Copyup using workdir to prepare temp file.  Used when copying up directories,

 * special files or when upper fs doesn't support O_TMPFILE.

 */

	if (c->origin) {

		err = ovl_set_origin(c->dentry, c->lowerpath.dentry, temp);

static int ovl_copy_up_workdir(struct ovl_copy_up_ctx *c)

{

	struct inode *inode;

	struct dentry *newdentry = NULL;

	struct dentry *temp;

	int err;



	err = ovl_lock_rename_workdir(c->workdir, c->destdir);

	if (err)

		return err;

	}



	if (S_ISREG(c->stat.mode) && !c->metacopy) {

		struct path upperpath, datapath;

	temp = ovl_get_workdir_temp(c);

	err = PTR_ERR(temp);

	if (IS_ERR(temp))

		goto unlock;



		ovl_path_upper(c->dentry, &upperpath);

		BUG_ON(upperpath.dentry != NULL);

		upperpath.dentry = temp;

	err = ovl_copy_up_inode(c, temp);

	if (err)

		goto cleanup;



		ovl_path_lowerdata(c->dentry, &datapath);

		err = ovl_copy_up_data(&datapath, &upperpath, c->stat.size);

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

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

		if (err)

			return err;

			goto cleanup;

	}



	if (c->metacopy) {

		err = ovl_check_setxattr(c->dentry, temp, OVL_XATTR_METACOPY,

					 NULL, 0, -EOPNOTSUPP);

	err = ovl_rename_temp(c, temp, &newdentry);

	if (err)

		goto cleanup;



	if (!c->metacopy)

		ovl_set_upperdata(d_inode(c->dentry));

	inode = d_inode(c->dentry);

	ovl_inode_update(inode, newdentry);

	if (S_ISDIR(inode->i_mode))

		ovl_set_flag(OVL_WHITEOUTS, inode);

out_dput:

	dput(temp);

unlock:

	unlock_rename(c->workdir, c->destdir);



	return err;



cleanup:

	ovl_cleanup(d_inode(c->workdir), temp);

	goto out_dput;

}



	inode_lock(temp->d_inode);

	if (c->metacopy)

		err = ovl_set_size(temp, &c->stat);

static struct dentry *ovl_get_tmpfile(struct ovl_copy_up_ctx *c)

{

	int err;

	struct dentry *temp;

	const struct cred *old_creds = NULL;

	struct cred *new_creds = NULL;



	err = security_inode_copy_up(c->dentry, &new_creds);

	if (err < 0)

		return ERR_PTR(err);



	if (new_creds)

		old_creds = override_creds(new_creds);



	temp = ovl_do_tmpfile(c->workdir, c->stat.mode);



	if (new_creds) {

		revert_creds(old_creds);

		put_cred(new_creds);

	}



	return temp;

}



/* Link O_TMPFILE into place on upper dir */

static int ovl_link_tmpfile(struct ovl_copy_up_ctx *c, struct dentry *temp,

			    struct dentry **newdentry)

{

	int err;

	struct dentry *upper;

	struct inode *udir = d_inode(c->destdir);



	inode_lock_nested(udir, I_MUTEX_PARENT);



	upper = lookup_one_len(c->destname.name, c->destdir, c->destname.len);

	err = PTR_ERR(upper);

	if (IS_ERR(upper))

		goto unlock;



	err = ovl_do_link(temp, udir, upper);

	if (!err)

		err = ovl_set_attr(temp, &c->stat);

	inode_unlock(temp->d_inode);

		*newdentry = dget(upper);

	dput(upper);



unlock:

	inode_unlock(udir);



	return err;

}



static int ovl_copy_up_locked(struct ovl_copy_up_ctx *c)

/* Copyup using O_TMPFILE which does not require cross dir locking */

static int ovl_copy_up_tmpfile(struct ovl_copy_up_ctx *c)

{

	struct inode *udir = c->destdir->d_inode;

	struct inode *inode;

	struct dentry *newdentry = NULL;

	struct dentry *temp;

	int err;
@@ -563,35 +662,17 @@ static int ovl_copy_up_locked(struct ovl_copy_up_ctx *c) 
	if (err)

		goto out;



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

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

		if (err)

			goto out;

	}



	if (c->tmpfile) {

		inode_lock_nested(udir, I_MUTEX_PARENT);

		err = ovl_install_temp(c, temp, &newdentry);

		inode_unlock(udir);

	} else {

		err = ovl_install_temp(c, temp, &newdentry);

	}

	err = ovl_link_tmpfile(c, temp, &newdentry);

	if (err)

		goto out;



	if (!c->metacopy)

		ovl_set_upperdata(d_inode(c->dentry));

	inode = d_inode(c->dentry);

	ovl_inode_update(inode, newdentry);

	if (S_ISDIR(inode->i_mode))

		ovl_set_flag(OVL_WHITEOUTS, inode);

	ovl_inode_update(d_inode(c->dentry), newdentry);



out:

	if (err && !c->tmpfile)

		ovl_cleanup(d_inode(c->workdir), temp);

	dput(temp);

	return err;



}



/*
@@ -645,18 +726,10 @@ static int ovl_do_copy_up(struct ovl_copy_up_ctx *c) 
	}



	/* Should we copyup with O_TMPFILE or with workdir? */

	if (S_ISREG(c->stat.mode) && ofs->tmpfile) {

		c->tmpfile = true;

		err = ovl_copy_up_locked(c);

	} else {

		err = ovl_lock_rename_workdir(c->workdir, c->destdir);

		if (!err) {

			err = ovl_copy_up_locked(c);

			unlock_rename(c->workdir, c->destdir);

		}

	}





	if (S_ISREG(c->stat.mode) && ofs->tmpfile)

		err = ovl_copy_up_tmpfile(c);

	else

		err = ovl_copy_up_workdir(c);

	if (err)

		goto out;

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