Commit 16aac5ad authored by Amir Goldstein's avatar Amir Goldstein
Browse files

ovl: support encoding non-decodable file handles 



When all layers support file handles, we support encoding non-decodable
file handles (a.k.a. fid) even with nfs_export=off.

When file handles do not need to be decoded, we do not need to copy up
redirected lower directories on encode, and we encode also non-indexed
upper with lower file handle, so fid will not change on copy up.

This enables reporting fanotify events with file handles on overlayfs
with default config/mount options.

Signed-off-by: default avatarAmir Goldstein <amir73il@gmail.com>
parent 0c71faf5

fs/overlayfs/export.c

+20 −6
Original line number Diff line number Diff line
@@ -174,28 +174,37 @@ static int ovl_connect_layer(struct dentry *dentry) 
 * U = upper file handle

 * L = lower file handle

 *

 * (*) Connecting an overlay dir from real lower dentry is not always

 * (*) Decoding a connected overlay dir from real lower dentry is not always

 * possible when there are redirects in lower layers and non-indexed merge dirs.

 * To mitigate those case, we may copy up the lower dir ancestor before encode

 * a lower dir file handle.

 * of a decodable file handle for non-upper dir.

 *

 * Return 0 for upper file handle, > 0 for lower file handle or < 0 on error.

 */

static int ovl_check_encode_origin(struct dentry *dentry)

{

	struct ovl_fs *ofs = dentry->d_sb->s_fs_info;

	bool decodable = ofs->config.nfs_export;



	/* Lower file handle for non-upper non-decodable */

	if (!ovl_dentry_upper(dentry) && !decodable)

		return 0;



	/* Upper file handle for pure upper */

	if (!ovl_dentry_lower(dentry))

		return 0;



	/*

	 * Upper file handle for non-indexed upper.

	 *

	 * Root is never indexed, so if there's an upper layer, encode upper for

	 * root.

	 */

	if (ovl_dentry_upper(dentry) &&

	if (dentry == dentry->d_sb->s_root)

		return 0;



	/*

	 * Upper decodable file handle for non-indexed upper.

	 */

	if (ovl_dentry_upper(dentry) && decodable &&

	    !ovl_test_flag(OVL_INDEX, d_inode(dentry)))

		return 0;
@@ -205,7 +214,7 @@ static int ovl_check_encode_origin(struct dentry *dentry) 
	 * ovl_connect_layer() will try to make origin's layer "connected" by

	 * copying up a "connectable" ancestor.

	 */

	if (d_is_dir(dentry) && ovl_upper_mnt(ofs))

	if (d_is_dir(dentry) && ovl_upper_mnt(ofs) && decodable)

		return ovl_connect_layer(dentry);



	/* Lower file handle for indexed and non-upper dir/non-dir */
@@ -876,3 +885,8 @@ const struct export_operations ovl_export_operations = { 
	.get_name	= ovl_get_name,

	.get_parent	= ovl_get_parent,

};



/* encode_fh() encodes non-decodable file handles with nfs_export=off */

const struct export_operations ovl_export_fid_operations = {

	.encode_fh	= ovl_encode_fh,

};

fs/overlayfs/inode.c

+1 −1
Original line number Diff line number Diff line
@@ -1311,7 +1311,7 @@ static bool ovl_hash_bylower(struct super_block *sb, struct dentry *upper, 
		return false;



	/* No, if non-indexed upper with NFS export */

	if (sb->s_export_op && upper)

	if (ofs->config.nfs_export && upper)

		return false;



	/* Otherwise, hash by lower inode for fsnotify */

fs/overlayfs/overlayfs.h

+1 −0
Original line number Diff line number Diff line
@@ -799,6 +799,7 @@ int ovl_set_origin(struct ovl_fs *ofs, struct dentry *lower, 


/* export.c */

extern const struct export_operations ovl_export_operations;

extern const struct export_operations ovl_export_fid_operations;



/* super.c */

int ovl_fill_super(struct super_block *sb, struct fs_context *fc);

fs/overlayfs/ovl_entry.h

+1 −0
Original line number Diff line number Diff line
@@ -82,6 +82,7 @@ struct ovl_fs { 
	const struct cred *creator_cred;

	bool tmpfile;

	bool noxattr;

	bool nofh;

	/* Did we take the inuse lock? */

	bool upperdir_locked;

	bool workdir_locked;

fs/overlayfs/super.c

+9 −0
Original line number Diff line number Diff line
@@ -400,6 +400,7 @@ static int ovl_lower_dir(const char *name, struct path *path, 
		pr_warn("fs on '%s' does not support file handles, falling back to index=off,nfs_export=off.\n",

			name);

	}

	ofs->nofh |= !fh_type;

	/*

	 * Decoding origin file handle is required for persistent st_ino.

	 * Without persistent st_ino, xino=auto falls back to xino=off.
@@ -818,6 +819,7 @@ static int ovl_make_workdir(struct super_block *sb, struct ovl_fs *ofs, 
		ofs->config.index = false;

		pr_warn("upper fs does not support file handles, falling back to index=off.\n");

	}

	ofs->nofh |= !fh_type;



	/* Check if upper fs has 32bit inode numbers */

	if (fh_type != FILEID_INO32_GEN)
@@ -1452,8 +1454,15 @@ int ovl_fill_super(struct super_block *sb, struct fs_context *fc) 
		ofs->config.nfs_export = false;

	}



	/*

	 * Support encoding decodable file handles with nfs_export=on

	 * and encoding non-decodable file handles with nfs_export=off

	 * if all layers support file handles.

	 */

	if (ofs->config.nfs_export)

		sb->s_export_op = &ovl_export_operations;

	else if (!ofs->nofh)

		sb->s_export_op = &ovl_export_fid_operations;



	/* Never override disk quota limits or use reserved space */

	cap_lower(cred->cap_effective, CAP_SYS_RESOURCE);