![Miklos Szeredi](/assets/img/avatar_default.png)
Impure directories are ones which contain objects with origins (i.e. those that have been copied up). These are relevant to readdir operation only because of the d_ino field, no other transformation is necessary. Also a directory can become impure between two getdents(2) calls. This patch creates a cache for impure directories. Unlike the cache for merged directories, this one only contains entries with origin and is not refcounted but has a its lifetime tied to that of the dentry. Similarly to the merged cache, the impure cache is invalidated based on a version number. This version number is incremented when an entry with origin is added or removed from the directory. If the cache is empty, then the impure xattr is removed from the directory. This patch also fixes up handling of d_ino for the ".." entry if the parent directory is merged. Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
560 lines
13 KiB
C
560 lines
13 KiB
C
/*
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* Copyright (C) 2011 Novell Inc.
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* Copyright (C) 2016 Red Hat, Inc.
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*
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* This program is free software; you can redistribute it and/or modify it
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* under the terms of the GNU General Public License version 2 as published by
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* the Free Software Foundation.
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*/
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#include <linux/fs.h>
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#include <linux/mount.h>
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#include <linux/slab.h>
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#include <linux/cred.h>
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#include <linux/xattr.h>
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#include <linux/exportfs.h>
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#include <linux/uuid.h>
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#include <linux/namei.h>
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#include <linux/ratelimit.h>
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#include "overlayfs.h"
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#include "ovl_entry.h"
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int ovl_want_write(struct dentry *dentry)
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{
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struct ovl_fs *ofs = dentry->d_sb->s_fs_info;
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return mnt_want_write(ofs->upper_mnt);
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}
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void ovl_drop_write(struct dentry *dentry)
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{
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struct ovl_fs *ofs = dentry->d_sb->s_fs_info;
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mnt_drop_write(ofs->upper_mnt);
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}
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struct dentry *ovl_workdir(struct dentry *dentry)
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{
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struct ovl_fs *ofs = dentry->d_sb->s_fs_info;
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return ofs->workdir;
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}
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const struct cred *ovl_override_creds(struct super_block *sb)
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{
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struct ovl_fs *ofs = sb->s_fs_info;
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return override_creds(ofs->creator_cred);
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}
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struct super_block *ovl_same_sb(struct super_block *sb)
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{
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struct ovl_fs *ofs = sb->s_fs_info;
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return ofs->same_sb;
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}
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bool ovl_can_decode_fh(struct super_block *sb)
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{
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return (sb->s_export_op && sb->s_export_op->fh_to_dentry &&
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!uuid_is_null(&sb->s_uuid));
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}
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struct dentry *ovl_indexdir(struct super_block *sb)
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{
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struct ovl_fs *ofs = sb->s_fs_info;
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return ofs->indexdir;
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}
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struct ovl_entry *ovl_alloc_entry(unsigned int numlower)
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{
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size_t size = offsetof(struct ovl_entry, lowerstack[numlower]);
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struct ovl_entry *oe = kzalloc(size, GFP_KERNEL);
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if (oe)
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oe->numlower = numlower;
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return oe;
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}
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bool ovl_dentry_remote(struct dentry *dentry)
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{
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return dentry->d_flags &
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(DCACHE_OP_REVALIDATE | DCACHE_OP_WEAK_REVALIDATE |
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DCACHE_OP_REAL);
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}
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bool ovl_dentry_weird(struct dentry *dentry)
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{
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return dentry->d_flags & (DCACHE_NEED_AUTOMOUNT |
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DCACHE_MANAGE_TRANSIT |
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DCACHE_OP_HASH |
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DCACHE_OP_COMPARE);
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}
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enum ovl_path_type ovl_path_type(struct dentry *dentry)
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{
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struct ovl_entry *oe = dentry->d_fsdata;
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enum ovl_path_type type = 0;
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if (ovl_dentry_upper(dentry)) {
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type = __OVL_PATH_UPPER;
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/*
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* Non-dir dentry can hold lower dentry of its copy up origin.
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*/
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if (oe->numlower) {
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type |= __OVL_PATH_ORIGIN;
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if (d_is_dir(dentry))
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type |= __OVL_PATH_MERGE;
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}
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} else {
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if (oe->numlower > 1)
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type |= __OVL_PATH_MERGE;
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}
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return type;
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}
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void ovl_path_upper(struct dentry *dentry, struct path *path)
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{
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struct ovl_fs *ofs = dentry->d_sb->s_fs_info;
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path->mnt = ofs->upper_mnt;
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path->dentry = ovl_dentry_upper(dentry);
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}
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void ovl_path_lower(struct dentry *dentry, struct path *path)
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{
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struct ovl_entry *oe = dentry->d_fsdata;
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*path = oe->numlower ? oe->lowerstack[0] : (struct path) { };
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}
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enum ovl_path_type ovl_path_real(struct dentry *dentry, struct path *path)
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{
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enum ovl_path_type type = ovl_path_type(dentry);
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if (!OVL_TYPE_UPPER(type))
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ovl_path_lower(dentry, path);
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else
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ovl_path_upper(dentry, path);
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return type;
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}
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struct dentry *ovl_dentry_upper(struct dentry *dentry)
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{
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return ovl_upperdentry_dereference(OVL_I(d_inode(dentry)));
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}
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struct dentry *ovl_dentry_lower(struct dentry *dentry)
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{
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struct ovl_entry *oe = dentry->d_fsdata;
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return oe->numlower ? oe->lowerstack[0].dentry : NULL;
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}
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struct dentry *ovl_dentry_real(struct dentry *dentry)
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{
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return ovl_dentry_upper(dentry) ?: ovl_dentry_lower(dentry);
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}
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struct dentry *ovl_i_dentry_upper(struct inode *inode)
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{
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return ovl_upperdentry_dereference(OVL_I(inode));
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}
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struct inode *ovl_inode_upper(struct inode *inode)
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{
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struct dentry *upperdentry = ovl_i_dentry_upper(inode);
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return upperdentry ? d_inode(upperdentry) : NULL;
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}
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struct inode *ovl_inode_lower(struct inode *inode)
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{
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return OVL_I(inode)->lower;
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}
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struct inode *ovl_inode_real(struct inode *inode)
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{
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return ovl_inode_upper(inode) ?: ovl_inode_lower(inode);
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}
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struct ovl_dir_cache *ovl_dir_cache(struct inode *inode)
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{
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return OVL_I(inode)->cache;
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}
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void ovl_set_dir_cache(struct inode *inode, struct ovl_dir_cache *cache)
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{
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OVL_I(inode)->cache = cache;
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}
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bool ovl_dentry_is_opaque(struct dentry *dentry)
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{
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struct ovl_entry *oe = dentry->d_fsdata;
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return oe->opaque;
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}
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bool ovl_dentry_is_whiteout(struct dentry *dentry)
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{
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return !dentry->d_inode && ovl_dentry_is_opaque(dentry);
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}
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void ovl_dentry_set_opaque(struct dentry *dentry)
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{
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struct ovl_entry *oe = dentry->d_fsdata;
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oe->opaque = true;
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}
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/*
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* For hard links it's possible for ovl_dentry_upper() to return positive, while
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* there's no actual upper alias for the inode. Copy up code needs to know
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* about the existence of the upper alias, so it can't use ovl_dentry_upper().
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*/
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bool ovl_dentry_has_upper_alias(struct dentry *dentry)
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{
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struct ovl_entry *oe = dentry->d_fsdata;
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return oe->has_upper;
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}
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void ovl_dentry_set_upper_alias(struct dentry *dentry)
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{
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struct ovl_entry *oe = dentry->d_fsdata;
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oe->has_upper = true;
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}
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bool ovl_redirect_dir(struct super_block *sb)
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{
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struct ovl_fs *ofs = sb->s_fs_info;
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return ofs->config.redirect_dir && !ofs->noxattr;
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}
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const char *ovl_dentry_get_redirect(struct dentry *dentry)
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{
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return OVL_I(d_inode(dentry))->redirect;
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}
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void ovl_dentry_set_redirect(struct dentry *dentry, const char *redirect)
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{
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struct ovl_inode *oi = OVL_I(d_inode(dentry));
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kfree(oi->redirect);
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oi->redirect = redirect;
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}
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void ovl_inode_init(struct inode *inode, struct dentry *upperdentry,
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struct dentry *lowerdentry)
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{
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if (upperdentry)
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OVL_I(inode)->__upperdentry = upperdentry;
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if (lowerdentry)
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OVL_I(inode)->lower = d_inode(lowerdentry);
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ovl_copyattr(d_inode(upperdentry ?: lowerdentry), inode);
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}
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void ovl_inode_update(struct inode *inode, struct dentry *upperdentry)
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{
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struct inode *upperinode = d_inode(upperdentry);
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WARN_ON(OVL_I(inode)->__upperdentry);
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/*
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* Make sure upperdentry is consistent before making it visible
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*/
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smp_wmb();
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OVL_I(inode)->__upperdentry = upperdentry;
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if (!S_ISDIR(upperinode->i_mode) && inode_unhashed(inode)) {
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inode->i_private = upperinode;
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__insert_inode_hash(inode, (unsigned long) upperinode);
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}
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}
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void ovl_dentry_version_inc(struct dentry *dentry, bool impurity)
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{
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struct inode *inode = d_inode(dentry);
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WARN_ON(!inode_is_locked(inode));
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/*
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* Version is used by readdir code to keep cache consistent. For merge
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* dirs all changes need to be noted. For non-merge dirs, cache only
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* contains impure (ones which have been copied up and have origins)
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* entries, so only need to note changes to impure entries.
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*/
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if (OVL_TYPE_MERGE(ovl_path_type(dentry)) || impurity)
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OVL_I(inode)->version++;
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}
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u64 ovl_dentry_version_get(struct dentry *dentry)
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{
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struct inode *inode = d_inode(dentry);
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WARN_ON(!inode_is_locked(inode));
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return OVL_I(inode)->version;
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}
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bool ovl_is_whiteout(struct dentry *dentry)
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{
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struct inode *inode = dentry->d_inode;
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return inode && IS_WHITEOUT(inode);
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}
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struct file *ovl_path_open(struct path *path, int flags)
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{
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return dentry_open(path, flags | O_NOATIME, current_cred());
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}
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int ovl_copy_up_start(struct dentry *dentry)
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{
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struct ovl_inode *oi = OVL_I(d_inode(dentry));
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int err;
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err = mutex_lock_interruptible(&oi->lock);
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if (!err && ovl_dentry_has_upper_alias(dentry)) {
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err = 1; /* Already copied up */
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mutex_unlock(&oi->lock);
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}
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return err;
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}
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void ovl_copy_up_end(struct dentry *dentry)
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{
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mutex_unlock(&OVL_I(d_inode(dentry))->lock);
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}
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bool ovl_check_dir_xattr(struct dentry *dentry, const char *name)
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{
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int res;
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char val;
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if (!d_is_dir(dentry))
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return false;
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res = vfs_getxattr(dentry, name, &val, 1);
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if (res == 1 && val == 'y')
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return true;
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return false;
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}
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int ovl_check_setxattr(struct dentry *dentry, struct dentry *upperdentry,
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const char *name, const void *value, size_t size,
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int xerr)
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{
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int err;
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struct ovl_fs *ofs = dentry->d_sb->s_fs_info;
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if (ofs->noxattr)
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return xerr;
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err = ovl_do_setxattr(upperdentry, name, value, size, 0);
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if (err == -EOPNOTSUPP) {
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pr_warn("overlayfs: cannot set %s xattr on upper\n", name);
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ofs->noxattr = true;
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return xerr;
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}
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return err;
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}
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int ovl_set_impure(struct dentry *dentry, struct dentry *upperdentry)
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{
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int err;
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if (ovl_test_flag(OVL_IMPURE, d_inode(dentry)))
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return 0;
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/*
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* Do not fail when upper doesn't support xattrs.
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* Upper inodes won't have origin nor redirect xattr anyway.
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*/
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err = ovl_check_setxattr(dentry, upperdentry, OVL_XATTR_IMPURE,
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"y", 1, 0);
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if (!err)
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ovl_set_flag(OVL_IMPURE, d_inode(dentry));
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return err;
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}
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void ovl_set_flag(unsigned long flag, struct inode *inode)
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{
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set_bit(flag, &OVL_I(inode)->flags);
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}
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void ovl_clear_flag(unsigned long flag, struct inode *inode)
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{
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clear_bit(flag, &OVL_I(inode)->flags);
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}
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bool ovl_test_flag(unsigned long flag, struct inode *inode)
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{
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return test_bit(flag, &OVL_I(inode)->flags);
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}
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/**
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* Caller must hold a reference to inode to prevent it from being freed while
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* it is marked inuse.
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*/
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bool ovl_inuse_trylock(struct dentry *dentry)
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{
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struct inode *inode = d_inode(dentry);
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bool locked = false;
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spin_lock(&inode->i_lock);
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if (!(inode->i_state & I_OVL_INUSE)) {
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inode->i_state |= I_OVL_INUSE;
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locked = true;
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}
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spin_unlock(&inode->i_lock);
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return locked;
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}
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void ovl_inuse_unlock(struct dentry *dentry)
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{
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if (dentry) {
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struct inode *inode = d_inode(dentry);
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spin_lock(&inode->i_lock);
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WARN_ON(!(inode->i_state & I_OVL_INUSE));
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inode->i_state &= ~I_OVL_INUSE;
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spin_unlock(&inode->i_lock);
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}
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}
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/* Called must hold OVL_I(inode)->oi_lock */
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static void ovl_cleanup_index(struct dentry *dentry)
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{
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struct inode *dir = ovl_indexdir(dentry->d_sb)->d_inode;
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struct dentry *lowerdentry = ovl_dentry_lower(dentry);
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struct dentry *upperdentry = ovl_dentry_upper(dentry);
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struct dentry *index = NULL;
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struct inode *inode;
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struct qstr name;
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int err;
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err = ovl_get_index_name(lowerdentry, &name);
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if (err)
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goto fail;
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inode = d_inode(upperdentry);
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if (inode->i_nlink != 1) {
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pr_warn_ratelimited("overlayfs: cleanup linked index (%pd2, ino=%lu, nlink=%u)\n",
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upperdentry, inode->i_ino, inode->i_nlink);
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/*
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* We either have a bug with persistent union nlink or a lower
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* hardlink was added while overlay is mounted. Adding a lower
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* hardlink and then unlinking all overlay hardlinks would drop
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* overlay nlink to zero before all upper inodes are unlinked.
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* As a safety measure, when that situation is detected, set
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* the overlay nlink to the index inode nlink minus one for the
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* index entry itself.
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*/
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set_nlink(d_inode(dentry), inode->i_nlink - 1);
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ovl_set_nlink_upper(dentry);
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goto out;
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}
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inode_lock_nested(dir, I_MUTEX_PARENT);
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/* TODO: whiteout instead of cleanup to block future open by handle */
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index = lookup_one_len(name.name, ovl_indexdir(dentry->d_sb), name.len);
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err = PTR_ERR(index);
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if (!IS_ERR(index))
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err = ovl_cleanup(dir, index);
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inode_unlock(dir);
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if (err)
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goto fail;
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out:
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dput(index);
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return;
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fail:
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pr_err("overlayfs: cleanup index of '%pd2' failed (%i)\n", dentry, err);
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goto out;
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}
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/*
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* Operations that change overlay inode and upper inode nlink need to be
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* synchronized with copy up for persistent nlink accounting.
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*/
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int ovl_nlink_start(struct dentry *dentry, bool *locked)
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{
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struct ovl_inode *oi = OVL_I(d_inode(dentry));
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const struct cred *old_cred;
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int err;
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if (!d_inode(dentry) || d_is_dir(dentry))
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return 0;
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/*
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* With inodes index is enabled, we store the union overlay nlink
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* in an xattr on the index inode. When whiting out lower hardlinks
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* we need to decrement the overlay persistent nlink, but before the
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* first copy up, we have no upper index inode to store the xattr.
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*
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* As a workaround, before whiteout/rename over of a lower hardlink,
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* copy up to create the upper index. Creating the upper index will
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* initialize the overlay nlink, so it could be dropped if unlink
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* or rename succeeds.
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*
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* TODO: implement metadata only index copy up when called with
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* ovl_copy_up_flags(dentry, O_PATH).
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*/
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if (ovl_indexdir(dentry->d_sb) && !ovl_dentry_has_upper_alias(dentry) &&
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d_inode(ovl_dentry_lower(dentry))->i_nlink > 1) {
|
|
err = ovl_copy_up(dentry);
|
|
if (err)
|
|
return err;
|
|
}
|
|
|
|
err = mutex_lock_interruptible(&oi->lock);
|
|
if (err)
|
|
return err;
|
|
|
|
if (!ovl_test_flag(OVL_INDEX, d_inode(dentry)))
|
|
goto out;
|
|
|
|
old_cred = ovl_override_creds(dentry->d_sb);
|
|
/*
|
|
* The overlay inode nlink should be incremented/decremented IFF the
|
|
* upper operation succeeds, along with nlink change of upper inode.
|
|
* Therefore, before link/unlink/rename, we store the union nlink
|
|
* value relative to the upper inode nlink in an upper inode xattr.
|
|
*/
|
|
err = ovl_set_nlink_upper(dentry);
|
|
revert_creds(old_cred);
|
|
|
|
out:
|
|
if (err)
|
|
mutex_unlock(&oi->lock);
|
|
else
|
|
*locked = true;
|
|
|
|
return err;
|
|
}
|
|
|
|
void ovl_nlink_end(struct dentry *dentry, bool locked)
|
|
{
|
|
if (locked) {
|
|
if (ovl_test_flag(OVL_INDEX, d_inode(dentry)) &&
|
|
d_inode(dentry)->i_nlink == 0) {
|
|
const struct cred *old_cred;
|
|
|
|
old_cred = ovl_override_creds(dentry->d_sb);
|
|
ovl_cleanup_index(dentry);
|
|
revert_creds(old_cred);
|
|
}
|
|
|
|
mutex_unlock(&OVL_I(d_inode(dentry))->lock);
|
|
}
|
|
}
|