Release 4.10 fs/overlayfs/super.c

/*
 *
 * Copyright (C) 2011 Novell Inc.
 *
 * This program is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 as published by
 * the Free Software Foundation.
 */

#include <linux/fs.h>
#include <linux/namei.h>
#include <linux/xattr.h>
#include <linux/mount.h>
#include <linux/parser.h>
#include <linux/module.h>
#include <linux/statfs.h>
#include <linux/seq_file.h>
#include <linux/posix_acl_xattr.h>
#include "overlayfs.h"
#include "ovl_entry.h"

MODULE_AUTHOR("Miklos Szeredi <miklos@szeredi.hu>");
MODULE_DESCRIPTION("Overlay filesystem");
MODULE_LICENSE("GPL");


struct ovl_dir_cache;


#define OVL_MAX_STACK 500


static bool ovl_redirect_dir_def = IS_ENABLED(CONFIG_OVERLAY_FS_REDIRECT_DIR);
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 void ovl_dentry_release(struct dentry *dentry)
{
	struct ovl_entry *oe = dentry->d_fsdata;

	if (oe) {
		unsigned int i;

		dput(oe->__upperdentry);
		kfree(oe->redirect);
		for (i = 0; i < oe->numlower; i++)
			dput(oe->lowerstack[i].dentry);
		kfree_rcu(oe, rcu);
	}
}

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static struct dentry *ovl_d_real(struct dentry *dentry,
				 const struct inode *inode,
				 unsigned int open_flags)
{
	struct dentry *real;

	if (!d_is_reg(dentry)) {
		if (!inode || inode == d_inode(dentry))
			return dentry;
		goto bug;
	}

	if (d_is_negative(dentry))
		return dentry;

	if (open_flags) {
		int err = ovl_open_maybe_copy_up(dentry, open_flags);

		if (err)
			return ERR_PTR(err);
	}

	real = ovl_dentry_upper(dentry);
	if (real && (!inode || inode == d_inode(real)))
		return real;

	real = ovl_dentry_lower(dentry);
	if (!real)
		goto bug;

	/* Handle recursion */
	real = d_real(real, inode, open_flags);

	if (!inode || inode == d_inode(real))
		return real;
bug:
	WARN(1, "ovl_d_real(%pd4, %s:%lu): real dentry not found\n", dentry,
	     inode ? inode->i_sb->s_id : "NULL", inode ? inode->i_ino : 0);
	return dentry;
}

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9
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hujianyang
hujianyang
4
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1
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192
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10
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static int ovl_dentry_revalidate(struct dentry *dentry, unsigned int flags)
{
	struct ovl_entry *oe = dentry->d_fsdata;
	unsigned int i;
	int ret = 1;

	for (i = 0; i < oe->numlower; i++) {
		struct dentry *d = oe->lowerstack[i].dentry;

		if (d->d_flags & DCACHE_OP_REVALIDATE) {
			ret = d->d_op->d_revalidate(d, flags);
			if (ret < 0)
				return ret;
			if (!ret) {
				if (!(flags & LOOKUP_RCU))
					d_invalidate(d);
				return -ESTALE;
			}
		}
	}
	return 1;
}

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static int ovl_dentry_weak_revalidate(struct dentry *dentry, unsigned int flags)
{
	struct ovl_entry *oe = dentry->d_fsdata;
	unsigned int i;
	int ret = 1;

	for (i = 0; i < oe->numlower; i++) {
		struct dentry *d = oe->lowerstack[i].dentry;

		if (d->d_flags & DCACHE_OP_WEAK_REVALIDATE) {
			ret = d->d_op->d_weak_revalidate(d, flags);
			if (ret <= 0)
				break;
		}
	}
	return ret;
}

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static const struct dentry_operations ovl_dentry_operations = {
	.d_release = ovl_dentry_release,
	.d_real = ovl_d_real,
};


static const struct dentry_operations ovl_reval_dentry_operations = {
	.d_release = ovl_dentry_release,
	.d_real = ovl_d_real,
	.d_revalidate = ovl_dentry_revalidate,
	.d_weak_revalidate = ovl_dentry_weak_revalidate,
};



static void ovl_put_super(struct super_block *sb)
{
	struct ovl_fs *ufs = sb->s_fs_info;
	unsigned i;

	dput(ufs->workdir);
	mntput(ufs->upper_mnt);
	for (i = 0; i < ufs->numlower; i++)
		mntput(ufs->lower_mnt[i]);
	kfree(ufs->lower_mnt);

	kfree(ufs->config.lowerdir);
	kfree(ufs->config.upperdir);
	kfree(ufs->config.workdir);
	put_cred(ufs->creator_cred);
	kfree(ufs);
}

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miklos szeredi
miklos szeredi
70
64.81%
2
40.00%
erez zadok
erez zadok
28
25.93%
1
20.00%
antonio murdaca
antonio murdaca
7
6.48%
1
20.00%
konstantin khlebnikov
konstantin khlebnikov
3
2.78%
1
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108
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5
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/**
 * ovl_statfs
 * @sb: The overlayfs super block
 * @buf: The struct kstatfs to fill in with stats
 *
 * Get the filesystem statistics.  As writes always target the upper layer
 * filesystem pass the statfs to the upper filesystem (if it exists)
 */


static int ovl_statfs(struct dentry *dentry, struct kstatfs *buf)
{
	struct ovl_fs *ofs = dentry->d_sb->s_fs_info;
	struct dentry *root_dentry = dentry->d_sb->s_root;
	struct path path;
	int err;

	ovl_path_real(root_dentry, &path);

	err = vfs_statfs(&path, buf);
	if (!err) {
		buf->f_namelen = ofs->namelen;
		buf->f_type = OVERLAYFS_SUPER_MAGIC;
	}

	return err;
}

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andy whitcroft
andy whitcroft
85
97.70%
1
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/**
 * ovl_show_options
 *
 * Prints the mount options for a given superblock.
 * Returns zero; does not fail.
 */


static int ovl_show_options(struct seq_file *m, struct dentry *dentry)
{
	struct super_block *sb = dentry->d_sb;
	struct ovl_fs *ufs = sb->s_fs_info;

	seq_show_option(m, "lowerdir", ufs->config.lowerdir);
	if (ufs->config.upperdir) {
		seq_show_option(m, "upperdir", ufs->config.upperdir);
		seq_show_option(m, "workdir", ufs->config.workdir);
	}
	if (ufs->config.default_permissions)
		seq_puts(m, ",default_permissions");
	if (ufs->config.redirect_dir != ovl_redirect_dir_def)
		seq_printf(m, ",redirect_dir=%s",
			   ufs->config.redirect_dir ? "on" : "off");
	return 0;
}

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erez zadok
erez zadok
70
54.69%
1
20.00%
amir goldstein
amir goldstein
27
21.09%
1
20.00%
miklos szeredi
miklos szeredi
25
19.53%
2
40.00%
kees cook
kees cook
6
4.69%
1
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5
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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))
		return -EROFS;

	return 0;
}

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seunghun lee
seunghun lee
50
87.72%
1
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miklos szeredi
7
12.28%
1
50.00%
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57
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2
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static const struct super_operations ovl_super_operations = {
	.put_super	= ovl_put_super,
	.statfs		= ovl_statfs,
	.show_options	= ovl_show_options,
	.remount_fs	= ovl_remount,
	.drop_inode	= generic_delete_inode,
};

enum {
	
OPT_LOWERDIR,
	
OPT_UPPERDIR,
	
OPT_WORKDIR,
	
OPT_DEFAULT_PERMISSIONS,
	
OPT_REDIRECT_DIR_ON,
	
OPT_REDIRECT_DIR_OFF,
	
OPT_ERR,
};


static const match_table_t ovl_tokens = {
	{OPT_LOWERDIR,			"lowerdir=%s"},
	{OPT_UPPERDIR,			"upperdir=%s"},
	{OPT_WORKDIR,			"workdir=%s"},
	{OPT_DEFAULT_PERMISSIONS,	"default_permissions"},
	{OPT_REDIRECT_DIR_ON,		"redirect_dir=on"},
	{OPT_REDIRECT_DIR_OFF,		"redirect_dir=off"},
	{OPT_ERR,			NULL}
};



static char *ovl_next_opt(char **s)
{
	char *sbegin = *s;
	char *p;

	if (sbegin == NULL)
		return NULL;

	for (p = sbegin; *p; p++) {
		if (*p == '\\') {
			p++;
			if (!*p)
				break;
		} else if (*p == ',') {
			*p = '\0';
			*s = p + 1;
			return sbegin;
		}
	}
	*s = NULL;
	return sbegin;
}

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static int ovl_parse_opt(char *opt, struct ovl_config *config)
{
	char *p;

	while ((p = ovl_next_opt(&opt)) != NULL) {
		int token;
		substring_t args[MAX_OPT_ARGS];

		if (!*p)
			continue;

		token = match_token(p, ovl_tokens, args);
		switch (token) {
		case OPT_UPPERDIR:
			kfree(config->upperdir);
			config->upperdir = match_strdup(&args[0]);
			if (!config->upperdir)
				return -ENOMEM;
			break;

		case OPT_LOWERDIR:
			kfree(config->lowerdir);
			config->lowerdir = match_strdup(&args[0]);
			if (!config->lowerdir)
				return -ENOMEM;
			break;

		case OPT_WORKDIR:
			kfree(config->workdir);
			config->workdir = match_strdup(&args[0]);
			if (!config->workdir)
				return -ENOMEM;
			break;

		case OPT_DEFAULT_PERMISSIONS:
			config->default_permissions = true;
			break;

		case OPT_REDIRECT_DIR_ON:
			config->redirect_dir = true;
			break;

		case OPT_REDIRECT_DIR_OFF:
			config->redirect_dir = false;
			break;

		default:
			pr_err("overlayfs: unrecognized mount option \"%s\" or missing value\n", p);
			return -EINVAL;
		}
	}

	/* Workdir is useless in non-upper mount */
	if (!config->upperdir && config->workdir) {
		pr_info("overlayfs: option \"workdir=%s\" is useless in a non-upper mount, ignore\n",
			config->workdir);
		kfree(config->workdir);
		config->workdir = NULL;
	}

	return 0;
}

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miklos szeredi
211
83.07%
4
66.67%
hujianyang
hujianyang
43
16.93%
2
33.33%
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254
100.00%
6
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#define OVL_WORKDIR_NAME "work"



static struct dentry *ovl_workdir_create(struct vfsmount *mnt,
					 struct dentry *dentry)
{
	struct inode *dir = dentry->d_inode;
	struct dentry *work;
	int err;
	bool retried = false;

	err = mnt_want_write(mnt);
	if (err)
		return ERR_PTR(err);

	inode_lock_nested(dir, I_MUTEX_PARENT);
retry:
	work = lookup_one_len(OVL_WORKDIR_NAME, dentry,
			      strlen(OVL_WORKDIR_NAME));

	if (!IS_ERR(work)) {
		struct iattr attr = {
			.ia_valid = ATTR_MODE,
			.ia_mode = S_IFDIR | 0,
                };

		if (work->d_inode) {
			err = -EEXIST;
			if (retried)
				goto out_dput;

			retried = true;
			ovl_workdir_cleanup(dir, mnt, work, 0);
			dput(work);
			goto retry;
		}

		err = ovl_create_real(dir, work,
				      &(struct cattr){.mode = S_IFDIR | 0},
				      NULL, true);
		if (err)
			goto out_dput;

		/*
                 * Try to remove POSIX ACL xattrs from workdir.  We are good if:
                 *
                 * a) success (there was a POSIX ACL xattr and was removed)
                 * b) -ENODATA (there was no POSIX ACL xattr)
                 * c) -EOPNOTSUPP (POSIX ACL xattrs are not supported)
                 *
                 * There are various other error values that could effectively
                 * mean that the xattr doesn't exist (e.g. -ERANGE is returned
                 * if the xattr name is too long), but the set of filesystems
                 * allowed as upper are limited to "normal" ones, where checking
                 * for the above two errors is sufficient.
                 */
		err = vfs_removexattr(work, XATTR_NAME_POSIX_ACL_DEFAULT);
		if (err && err != -ENODATA && err != -EOPNOTSUPP)
			goto out_dput;

		err = vfs_removexattr(work, XATTR_NAME_POSIX_ACL_ACCESS);
		if (err && err != -ENODATA && err != -EOPNOTSUPP)
			goto out_dput;

		/* Clear any inherited mode bits */
		inode_lock(work->d_inode);
		err = notify_change(work, &attr, NULL);
		inode_unlock(work->d_inode);
		if (err)
			goto out_dput;
	}
out_unlock:
	inode_unlock(dir);
	mnt_drop_write(mnt);

	return work;

out_dput:
	dput(work);
	work = ERR_PTR(err);
	goto out_unlock;
}

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miklos szeredi
287
94.41%
5
71.43%
al viro
al viro
17
5.59%
2
28.57%
Total
304
100.00%
7
100.00%



static void ovl_unescape(char *s)
{
	char *d = s;

	for (;; s++, d++) {
		if (*s == '\\')
			s++;
		*d = *s;
		if (!*s)
			break;
	}
}

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51
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1
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51
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static int ovl_mount_dir_noesc(const char *name, struct path *path)
{
	int err = -EINVAL;

	if (!*name) {
		pr_err("overlayfs: empty lowerdir\n");
		goto out;
	}
	err = kern_path(name, LOOKUP_FOLLOW, path);
	if (err) {
		pr_err("overlayfs: failed to resolve '%s': %i\n", name, err);
		goto out;
	}
	err = -EINVAL;
	if (ovl_dentry_weird(path->dentry)) {
		pr_err("overlayfs: filesystem on '%s' not supported\n", name);
		goto out_put;
	}
	if (!d_is_dir(path->dentry)) {
		pr_err("overlayfs: '%s' not a directory\n", name);
		goto out_put;
	}
	return 0;

out_put:
	path_put(path);
out:
	return err;
}

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6
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130
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static int ovl_mount_dir(const char *name, struct path *path)
{
	int err = -ENOMEM;
	char *tmp = kstrdup(name, GFP_KERNEL);

	if (tmp) {
		ovl_unescape(tmp);
		err = ovl_mount_dir_noesc(tmp, path);

		if (!err)
			if (ovl_dentry_remote(path->dentry)) {
				pr_err("overlayfs: filesystem on '%s' not supported as upperdir\n",
				       tmp);
				path_put(path);
				err = -EINVAL;
			}
		kfree(tmp);
	}
	return err;
}

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miklos szeredi
94
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4
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94
100.00%
4
100.00%



static int ovl_check_namelen(struct path *path, struct ovl_fs *ofs,
			     const char *name)
{
	struct kstatfs statfs;
	int err = vfs_statfs(path, &statfs);

	if (err)
		pr_err("overlayfs: statfs failed on '%s'\n", name);
	else
		ofs->namelen = max(ofs->namelen, statfs.f_namelen);

	return err;
}

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66
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1
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66
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static int ovl_lower_dir(const char *name, struct path *path,
			 struct ovl_fs *ofs, int *stack_depth, bool *remote)
{
	int err;

	err = ovl_mount_dir_noesc(name, path);
	if (err)
		goto out;

	err = ovl_check_namelen(path, ofs, name);
	if (err)
		goto out_put;

	*stack_depth = max(*stack_depth, path->mnt->mnt_sb->s_stack_depth);

	if (ovl_dentry_remote(path->dentry))
		*remote = true;

	return 0;

out_put:
	path_put(path);
out:
	return err;
}

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miklos szeredi
112
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5
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112
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5
100.00%

/* Workdir should not be subdir of upperdir and vice versa */


static bool ovl_workdir_ok(struct dentry *workdir, struct dentry *upperdir)
{
	bool ok = false;

	if (workdir != upperdir) {
		ok = (lock_rename(workdir, upperdir) == NULL);
		unlock_rename(workdir, upperdir);
	}
	return ok;
}

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52
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52
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static unsigned int ovl_split_lowerdirs(char *str)
{
	unsigned int ctr = 1;
	char *s, *d;

	for (s = d = str;; s++, d++) {
		if (*s == '\\') {
			s++;
		} else if (*s == ':') {
			*d = '\0';
			ctr++;
			continue;
		}
		*d = *s;
		if (!*s)
			break;
	}
	return ctr;
}

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88
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1
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88
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static int __maybe_unused

ovl_posix_acl_xattr_get(const struct xattr_handler *handler,
			struct dentry *dentry, struct inode *inode,
			const char *name, void *buffer, size_t size)
{
	return ovl_xattr_get(dentry, handler->name, buffer, size);
}

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andreas gruenbacher
andreas gruenbacher
47
95.92%
2
66.67%
miklos szeredi
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2
4.08%
1
33.33%
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49
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3
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static int __maybe_unused

ovl_posix_acl_xattr_set(const struct xattr_handler *handler,
			struct dentry *dentry, struct inode *inode,
			const char *name, const void *value,
			size_t size, int flags)
{
	struct dentry *workdir = ovl_workdir(dentry);
	struct inode *realinode = ovl_inode_real(inode, NULL);
	struct posix_acl *acl = NULL;
	int err;

	/* Check that everything is OK before copy-up */
	if (value) {
		acl = posix_acl_from_xattr(&init_user_ns, value, size);
		if (IS_ERR(acl))
			return PTR_ERR(acl);
	}
	err = -EOPNOTSUPP;
	if (!IS_POSIXACL(d_inode(workdir)))
		goto out_acl_release;
	if (!realinode->i_op->set_acl)
		goto out_acl_release;
	if (handler->flags == ACL_TYPE_DEFAULT && !S_ISDIR(inode->i_mode)) {
		err = acl ? -EACCES : 0;
		goto out_acl_release;
	}
	err = -EPERM;
	if (!inode_owner_or_capable(inode))
		goto out_acl_release;

	posix_acl_release(acl);

	/*
         * Check if sgid bit needs to be cleared (actual setacl operation will
         * be done with mounter's capabilities and so that won't do it for us).
         */
	if (unlikely(inode->i_mode & S_ISGID) &&
	    handler->flags == ACL_TYPE_ACCESS &&
	    !in_group_p(inode->i_gid) &&
	    !capable_wrt_inode_uidgid(inode, CAP_FSETID)) {
		struct iattr iattr = { .ia_valid = ATTR_KILL_SGID };

		err = ovl_setattr(dentry, &iattr);
		if (err)
			return err;
	}

	err = ovl_xattr_set(dentry, handler->name, value, size, flags);
	if (!err)
		ovl_copyattr(ovl_inode_real(inode, NULL), inode);

	return err;

out_acl_release:
	posix_acl_release(acl);
	return err;
}

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292
98.65%
3
60.00%
andreas gruenbacher
andreas gruenbacher
4
1.35%
2
40.00%
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296
100.00%
5
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static int ovl_own_xattr_get(const struct xattr_handler *handler,
			     struct dentry *dentry, struct inode *inode,
			     const char *name, void *buffer, size_t size)
{
	return -EOPNOTSUPP;
}

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andreas gruenbacher
andreas gruenbacher
37
97.37%
1
50.00%
amir goldstein
amir goldstein
1
2.63%
1
50.00%
Total
38
100.00%
2
100.00%



static int ovl_own_xattr_set(const struct xattr_handler *handler,
			     struct dentry *dentry, struct inode *inode,
			     const char *name, const void *value,
			     size_t size, int flags)
{
	return -EOPNOTSUPP;
}

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miklos szeredi
miklos szeredi
39
92.86%
1
33.33%
andreas gruenbacher
andreas gruenbacher
2
4.76%
1
33.33%
amir goldstein
amir goldstein
1
2.38%
1
33.33%
Total
42
100.00%
3
100.00%



static int ovl_other_xattr_get(const struct xattr_handler *handler,
			       struct dentry *dentry, struct inode *inode,
			       const char *name, void *buffer, size_t size)
{
	return ovl_xattr_get(dentry, name, buffer, size);
}

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andreas gruenbacher
andreas gruenbacher
46
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1
100.00%
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46
100.00%
1
100.00%



static int ovl_other_xattr_set(const struct xattr_handler *handler,
			       struct dentry *dentry, struct inode *inode,
			       const char *name, const void *value,
			       size_t size, int flags)
{
	return ovl_xattr_set(dentry, name, value, size, flags);
}

Contributors
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miklos szeredi
miklos szeredi
39
75.00%
1
50.00%
andreas gruenbacher
andreas gruenbacher
13
25.00%
1
50.00%
Total
52
100.00%
2
100.00%

static const struct xattr_handler __maybe_unused

ovl_posix_acl_access_xattr_handler = {
	.name = XATTR_NAME_POSIX_ACL_ACCESS,
	.flags = ACL_TYPE_ACCESS,
	.get = ovl_posix_acl_xattr_get,
	.set = ovl_posix_acl_xattr_set,
};

static const struct xattr_handler __maybe_unused

ovl_posix_acl_default_xattr_handler = {
	.name = XATTR_NAME_POSIX_ACL_DEFAULT,
	.flags = ACL_TYPE_DEFAULT,
	.get = ovl_posix_acl_xattr_get,
	.set = ovl_posix_acl_xattr_set,
};


static const struct xattr_handler ovl_own_xattr_handler = {
	.prefix	= OVL_XATTR_PREFIX,
	.get = ovl_own_xattr_get,
	.set = ovl_own_xattr_set,
};


static const struct xattr_handler ovl_other_xattr_handler = {
	.prefix	= "", /* catch all */
	.get = ovl_other_xattr_get,
	.set = ovl_other_xattr_set,
};


static const struct xattr_handler *ovl_xattr_handlers[] = {
#ifdef CONFIG_FS_POSIX_ACL
	&ovl_posix_acl_access_xattr_handler,
	&ovl_posix_acl_default_xattr_handler,
#endif
	&ovl_own_xattr_handler,
	&ovl_other_xattr_handler,
	NULL
};



static int ovl_fill_super(struct super_block *sb, void *data, int silent)
{
	struct path upperpath = { NULL, NULL };
	struct path workpath = { NULL, NULL };
	struct dentry *root_dentry;
	struct inode *realinode;
	struct ovl_entry *oe;
	struct ovl_fs *ufs;
	struct path *stack = NULL;