Commit 02bcd157 authored by Amir Goldstein's avatar Amir Goldstein Committed by Miklos Szeredi
Browse files

ovl: introduce the inodes index dir feature 



Create the index dir on mount. The index dir will contain hardlinks to
upper inodes, named after the hex representation of their origin lower
inodes.

The index dir is going to be used to prevent breaking lower hardlinks
on copy up and to implement overlayfs NFS export.

Because the feature is not fully backward compat, enabling the feature
is opt-in by config/module/mount option.

Signed-off-by: default avatarAmir Goldstein <amir73il@gmail.com>
Signed-off-by: default avatarMiklos Szeredi <mszeredi@redhat.com>
parent 6b8aa129

fs/overlayfs/Kconfig

+20 −0
Original line number Diff line number Diff line
@@ -23,3 +23,23 @@ config OVERLAY_FS_REDIRECT_DIR 
	  Note, that redirects are not backward compatible.  That is, mounting

	  an overlay which has redirects on a kernel that doesn't support this

	  feature will have unexpected results.



config OVERLAY_FS_INDEX

	bool "Overlayfs: turn on inodes index feature by default"

	depends on OVERLAY_FS

	help

	  If this config option is enabled then overlay filesystems will use

	  the inodes index dir to map lower inodes to upper inodes by default.

	  In this case it is still possible to turn off index globally with the

	  "index=off" module option or on a filesystem instance basis with the

	  "index=off" mount option.



	  The inodes index feature prevents breaking of lower hardlinks on copy

	  up.



	  Note, that the inodes index feature is read-only backward compatible.

	  That is, mounting an overlay which has an index dir on a kernel that

	  doesn't support this feature read-only, will not have any negative

	  outcomes.  However, mounting the same overlay with an old kernel

	  read-write and then mounting it again with a new kernel, will have

	  unexpected results.

fs/overlayfs/copy_up.c

+4 −5
Original line number Diff line number Diff line
@@ -233,12 +233,13 @@ int ovl_set_attr(struct dentry *upperdentry, struct kstat *stat) 
	return err;

}



static struct ovl_fh *ovl_encode_fh(struct dentry *lower, uuid_t *uuid)

static struct ovl_fh *ovl_encode_fh(struct dentry *lower)

{

	struct ovl_fh *fh;

	int fh_type, fh_len, dwords;

	void *buf;

	int buflen = MAX_HANDLE_SZ;

	uuid_t *uuid = &lower->d_sb->s_uuid;



	buf = kmalloc(buflen, GFP_TEMPORARY);

	if (!buf)
@@ -283,7 +284,6 @@ out: 
static int ovl_set_origin(struct dentry *dentry, struct dentry *lower,

			  struct dentry *upper)

{

	struct super_block *sb = lower->d_sb;

	const struct ovl_fh *fh = NULL;

	int err;
@@ -292,9 +292,8 @@ static int ovl_set_origin(struct dentry *dentry, struct dentry *lower, 
	 * so we can use the overlay.origin xattr to distignuish between a copy

	 * up and a pure upper inode.

	 */

	if (sb->s_export_op && sb->s_export_op->fh_to_dentry &&

	    !uuid_is_null(&sb->s_uuid)) {

		fh = ovl_encode_fh(lower, &sb->s_uuid);

	if (ovl_can_decode_fh(lower->d_sb)) {

		fh = ovl_encode_fh(lower);

		if (IS_ERR(fh))

			return PTR_ERR(fh);

	}

fs/overlayfs/overlayfs.h

+2 −0
Original line number Diff line number Diff line
@@ -183,6 +183,8 @@ void ovl_drop_write(struct dentry *dentry); 
struct dentry *ovl_workdir(struct dentry *dentry);

const struct cred *ovl_override_creds(struct super_block *sb);

struct super_block *ovl_same_sb(struct super_block *sb);

bool ovl_can_decode_fh(struct super_block *sb);

struct dentry *ovl_indexdir(struct super_block *sb);

struct ovl_entry *ovl_alloc_entry(unsigned int numlower);

bool ovl_dentry_remote(struct dentry *dentry);

bool ovl_dentry_weird(struct dentry *dentry);

fs/overlayfs/ovl_entry.h

+3 −0
Original line number Diff line number Diff line
@@ -14,6 +14,7 @@ struct ovl_config { 
	char *workdir;

	bool default_permissions;

	bool redirect_dir;

	bool index;

};



/* private information held for overlayfs's superblock */
@@ -25,6 +26,8 @@ struct ovl_fs { 
	struct dentry *workbasedir;

	/* workdir is the 'work' directory under workbasedir */

	struct dentry *workdir;

	/* index directory listing overlay inodes by origin file handle */

	struct dentry *indexdir;

	long namelen;

	/* pathnames of lower and upper dirs, for show_options */

	struct ovl_config config;

fs/overlayfs/super.c

+64 −2
Original line number Diff line number Diff line
@@ -34,6 +34,11 @@ module_param_named(redirect_dir, ovl_redirect_dir_def, bool, 0644); 
MODULE_PARM_DESC(ovl_redirect_dir_def,

		 "Default to on or off for the redirect_dir feature");



static bool ovl_index_def = IS_ENABLED(CONFIG_OVERLAY_FS_INDEX);

module_param_named(index, ovl_index_def, bool, 0644);

MODULE_PARM_DESC(ovl_index_def,

		 "Default to on or off for the inodes index feature");



static void ovl_dentry_release(struct dentry *dentry)

{

	struct ovl_entry *oe = dentry->d_fsdata;
@@ -203,6 +208,7 @@ static void ovl_put_super(struct super_block *sb) 
	struct ovl_fs *ufs = sb->s_fs_info;

	unsigned i;



	dput(ufs->indexdir);

	dput(ufs->workdir);

	ovl_inuse_unlock(ufs->workbasedir);

	dput(ufs->workbasedir);
@@ -265,6 +271,12 @@ static int ovl_statfs(struct dentry *dentry, struct kstatfs *buf) 
	return err;

}



/* Will this overlay be forced to mount/remount ro? */

static bool ovl_force_readonly(struct ovl_fs *ufs)

{

	return (!ufs->upper_mnt || !ufs->workdir);

}



/**

 * ovl_show_options

 *
@@ -286,6 +298,9 @@ static int ovl_show_options(struct seq_file *m, struct dentry *dentry) 
	if (ufs->config.redirect_dir != ovl_redirect_dir_def)

		seq_printf(m, ",redirect_dir=%s",

			   ufs->config.redirect_dir ? "on" : "off");

	if (ufs->config.index != ovl_index_def)

		seq_printf(m, ",index=%s",

			   ufs->config.index ? "on" : "off");

	return 0;

}
@@ -293,7 +308,7 @@ static int ovl_remount(struct super_block *sb, int *flags, char *data) 
{

	struct ovl_fs *ufs = sb->s_fs_info;



	if (!(*flags & MS_RDONLY) && (!ufs->upper_mnt || !ufs->workdir))

	if (!(*flags & MS_RDONLY) && ovl_force_readonly(ufs))

		return -EROFS;



	return 0;
@@ -317,6 +332,8 @@ enum { 
	OPT_DEFAULT_PERMISSIONS,

	OPT_REDIRECT_DIR_ON,

	OPT_REDIRECT_DIR_OFF,

	OPT_INDEX_ON,

	OPT_INDEX_OFF,

	OPT_ERR,

};
@@ -327,6 +344,8 @@ static const match_table_t ovl_tokens = { 
	{OPT_DEFAULT_PERMISSIONS,	"default_permissions"},

	{OPT_REDIRECT_DIR_ON,		"redirect_dir=on"},

	{OPT_REDIRECT_DIR_OFF,		"redirect_dir=off"},

	{OPT_INDEX_ON,			"index=on"},

	{OPT_INDEX_OFF,			"index=off"},

	{OPT_ERR,			NULL}

};
@@ -399,6 +418,14 @@ static int ovl_parse_opt(char *opt, struct ovl_config *config) 
			config->redirect_dir = false;

			break;



		case OPT_INDEX_ON:

			config->index = true;

			break;



		case OPT_INDEX_OFF:

			config->index = false;

			break;



		default:

			pr_err("overlayfs: unrecognized mount option \"%s\" or missing value\n", p);

			return -EINVAL;
@@ -417,6 +444,7 @@ static int ovl_parse_opt(char *opt, struct ovl_config *config) 
}



#define OVL_WORKDIR_NAME "work"

#define OVL_INDEXDIR_NAME "index"



static struct dentry *ovl_workdir_create(struct super_block *sb,

					 struct ovl_fs *ufs,
@@ -610,6 +638,15 @@ static int ovl_lower_dir(const char *name, struct path *path, 
	if (ovl_dentry_remote(path->dentry))

		*remote = true;



	/*

	 * The inodes index feature needs to encode and decode file

	 * handles, so it requires that all layers support them.

	 */

	if (ofs->config.index && !ovl_can_decode_fh(path->dentry->d_sb)) {

		ofs->config.index = false;

		pr_warn("overlayfs: fs on '%s' does not support file handles, falling back to index=off.\n", name);

	}



	return 0;



out_put:
@@ -807,6 +844,7 @@ static int ovl_fill_super(struct super_block *sb, void *data, int silent) 
		goto out;



	ufs->config.redirect_dir = ovl_redirect_dir_def;

	ufs->config.index = ovl_index_def;

	err = ovl_parse_opt((char *) data, &ufs->config);

	if (err)

		goto out_free_config;
@@ -965,6 +1003,13 @@ static int ovl_fill_super(struct super_block *sb, void *data, int silent) 
			} else {

				vfs_removexattr(ufs->workdir, OVL_XATTR_OPAQUE);

			}



			/* Check if upper/work fs supports file handles */

			if (ufs->config.index &&

			    !ovl_can_decode_fh(ufs->workdir->d_sb)) {

				ufs->config.index = false;

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

			}

		}

	}
@@ -1002,6 +1047,21 @@ static int ovl_fill_super(struct super_block *sb, void *data, int silent) 
	else if (ufs->upper_mnt->mnt_sb != ufs->same_sb)

		ufs->same_sb = NULL;



	if (!(ovl_force_readonly(ufs)) && ufs->config.index) {

		ufs->indexdir = ovl_workdir_create(sb, ufs, workpath.dentry,

						   OVL_INDEXDIR_NAME, true);

		err = PTR_ERR(ufs->indexdir);

		if (IS_ERR(ufs->indexdir))

			goto out_put_lower_mnt;



		if (!ufs->indexdir)

			pr_warn("overlayfs: try deleting index dir or mounting with '-o index=off' to disable inodes index.\n");

	}



	/* Show index=off/on in /proc/mounts for any of the reasons above */

	if (!ufs->indexdir)

		ufs->config.index = false;



	if (remote)

		sb->s_d_op = &ovl_reval_dentry_operations;

	else
@@ -1009,7 +1069,7 @@ static int ovl_fill_super(struct super_block *sb, void *data, int silent) 


	ufs->creator_cred = cred = prepare_creds();

	if (!cred)

		goto out_put_lower_mnt;

		goto out_put_indexdir;



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

	cap_lower(cred->cap_effective, CAP_SYS_RESOURCE);
@@ -1058,6 +1118,8 @@ out_free_oe: 
	kfree(oe);

out_put_cred:

	put_cred(ufs->creator_cred);

out_put_indexdir:

	dput(ufs->indexdir);

out_put_lower_mnt:

	for (i = 0; i < ufs->numlower; i++)

		mntput(ufs->lower_mnt[i]);

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