ovl: support multiple lower layers
Allow "lowerdir=" option to contain multiple lower directories separated by a colon (e.g. "lowerdir=/bin:/usr/bin"). Colon characters in filenames can be escaped with a backslash. Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
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@ -159,6 +159,18 @@ overlay filesystem (though an operation on the name of the file such as
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rename or unlink will of course be noticed and handled).
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rename or unlink will of course be noticed and handled).
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Multiple lower layers
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---------------------
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Multiple lower layers can now be given using the the colon (":") as a
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separator character between the directory names. For example:
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mount -t overlay overlay -olowerdir=/lower1:/lower2:/lower3 /merged
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As the example shows, "upperdir=" and "workdir=" may be omitted. In that case
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the overlay will be read-only.
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Non-standard behavior
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Non-standard behavior
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---------------------
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---------------------
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@ -60,6 +60,8 @@ struct ovl_entry {
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struct path lowerstack[];
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struct path lowerstack[];
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};
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};
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#define OVL_MAX_STACK 500
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const char *ovl_opaque_xattr = "trusted.overlay.opaque";
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const char *ovl_opaque_xattr = "trusted.overlay.opaque";
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static struct dentry *__ovl_dentry_lower(struct ovl_entry *oe)
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static struct dentry *__ovl_dentry_lower(struct ovl_entry *oe)
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@ -692,8 +694,12 @@ static bool ovl_is_allowed_fs_type(struct dentry *root)
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static int ovl_mount_dir_noesc(const char *name, struct path *path)
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static int ovl_mount_dir_noesc(const char *name, struct path *path)
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{
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{
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int err;
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int err = -EINVAL;
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if (!*name) {
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pr_err("overlayfs: empty lowerdir\n");
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goto out;
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}
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err = kern_path(name, LOOKUP_FOLLOW, path);
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err = kern_path(name, LOOKUP_FOLLOW, path);
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if (err) {
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if (err) {
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pr_err("overlayfs: failed to resolve '%s': %i\n", name, err);
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pr_err("overlayfs: failed to resolve '%s': %i\n", name, err);
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@ -735,7 +741,7 @@ static int ovl_lower_dir(const char *name, struct path *path, long *namelen,
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int err;
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int err;
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struct kstatfs statfs;
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struct kstatfs statfs;
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err = ovl_mount_dir(name, path);
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err = ovl_mount_dir_noesc(name, path);
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if (err)
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if (err)
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goto out;
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goto out;
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@ -767,15 +773,38 @@ static bool ovl_workdir_ok(struct dentry *workdir, struct dentry *upperdir)
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return ok;
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return ok;
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}
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}
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static unsigned int ovl_split_lowerdirs(char *str)
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{
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unsigned int ctr = 1;
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char *s, *d;
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for (s = d = str;; s++, d++) {
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if (*s == '\\') {
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s++;
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} else if (*s == ':') {
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*d = '\0';
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ctr++;
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continue;
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}
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*d = *s;
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if (!*s)
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break;
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}
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return ctr;
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}
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static int ovl_fill_super(struct super_block *sb, void *data, int silent)
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static int ovl_fill_super(struct super_block *sb, void *data, int silent)
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{
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{
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struct path lowerpath;
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struct path upperpath = { NULL, NULL };
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struct path upperpath = { NULL, NULL };
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struct path workpath = { NULL, NULL };
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struct path workpath = { NULL, NULL };
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struct dentry *root_dentry;
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struct dentry *root_dentry;
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struct ovl_entry *oe;
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struct ovl_entry *oe;
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struct ovl_fs *ufs;
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struct ovl_fs *ufs;
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struct vfsmount *mnt;
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struct path *stack = NULL;
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char *lowertmp;
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char *lower;
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unsigned int numlower;
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unsigned int stacklen = 0;
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unsigned int i;
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unsigned int i;
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int err;
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int err;
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@ -820,12 +849,30 @@ static int ovl_fill_super(struct super_block *sb, void *data, int silent)
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}
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}
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sb->s_stack_depth = upperpath.mnt->mnt_sb->s_stack_depth;
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sb->s_stack_depth = upperpath.mnt->mnt_sb->s_stack_depth;
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}
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}
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err = -ENOMEM;
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err = ovl_lower_dir(ufs->config.lowerdir, &lowerpath,
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lowertmp = kstrdup(ufs->config.lowerdir, GFP_KERNEL);
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&ufs->lower_namelen, &sb->s_stack_depth);
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if (!lowertmp)
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if (err)
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goto out_put_workpath;
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goto out_put_workpath;
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err = -EINVAL;
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stacklen = ovl_split_lowerdirs(lowertmp);
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if (stacklen > OVL_MAX_STACK)
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goto out_free_lowertmp;
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stack = kcalloc(stacklen, sizeof(struct path), GFP_KERNEL);
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if (!stack)
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goto out_free_lowertmp;
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lower = lowertmp;
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for (numlower = 0; numlower < stacklen; numlower++) {
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err = ovl_lower_dir(lower, &stack[numlower],
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&ufs->lower_namelen, &sb->s_stack_depth);
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if (err)
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goto out_put_lowerpath;
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lower = strchr(lower, '\0') + 1;
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}
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err = -EINVAL;
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err = -EINVAL;
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sb->s_stack_depth++;
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sb->s_stack_depth++;
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if (sb->s_stack_depth > FILESYSTEM_MAX_STACK_DEPTH) {
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if (sb->s_stack_depth > FILESYSTEM_MAX_STACK_DEPTH) {
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@ -850,24 +897,25 @@ static int ovl_fill_super(struct super_block *sb, void *data, int silent)
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}
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}
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}
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}
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ufs->lower_mnt = kcalloc(1, sizeof(struct vfsmount *), GFP_KERNEL);
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ufs->lower_mnt = kcalloc(numlower, sizeof(struct vfsmount *), GFP_KERNEL);
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if (ufs->lower_mnt == NULL)
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if (ufs->lower_mnt == NULL)
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goto out_put_workdir;
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goto out_put_workdir;
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for (i = 0; i < numlower; i++) {
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struct vfsmount *mnt = clone_private_mount(&stack[i]);
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mnt = clone_private_mount(&lowerpath);
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if (IS_ERR(mnt)) {
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err = PTR_ERR(mnt);
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pr_err("overlayfs: failed to clone lowerpath\n");
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if (IS_ERR(mnt)) {
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goto out_put_lower_mnt;
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pr_err("overlayfs: failed to clone lowerpath\n");
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}
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goto out_put_lower_mnt;
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/*
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* Make lower_mnt R/O. That way fchmod/fchown on lower file
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* will fail instead of modifying lower fs.
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*/
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mnt->mnt_flags |= MNT_READONLY;
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ufs->lower_mnt[ufs->numlower] = mnt;
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ufs->numlower++;
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}
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}
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/*
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* Make lower_mnt R/O. That way fchmod/fchown on lower file
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* will fail instead of modifying lower fs.
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*/
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mnt->mnt_flags |= MNT_READONLY;
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ufs->lower_mnt[0] = mnt;
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ufs->numlower = 1;
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/* If the upper fs is r/o or nonexistent, we mark overlayfs r/o too */
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/* If the upper fs is r/o or nonexistent, we mark overlayfs r/o too */
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if (!ufs->upper_mnt || (ufs->upper_mnt->mnt_sb->s_flags & MS_RDONLY))
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if (!ufs->upper_mnt || (ufs->upper_mnt->mnt_sb->s_flags & MS_RDONLY))
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@ -876,7 +924,7 @@ static int ovl_fill_super(struct super_block *sb, void *data, int silent)
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sb->s_d_op = &ovl_dentry_operations;
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sb->s_d_op = &ovl_dentry_operations;
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err = -ENOMEM;
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err = -ENOMEM;
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oe = ovl_alloc_entry(1);
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oe = ovl_alloc_entry(numlower);
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if (!oe)
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if (!oe)
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goto out_put_lower_mnt;
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goto out_put_lower_mnt;
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@ -885,12 +933,16 @@ static int ovl_fill_super(struct super_block *sb, void *data, int silent)
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goto out_free_oe;
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goto out_free_oe;
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mntput(upperpath.mnt);
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mntput(upperpath.mnt);
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mntput(lowerpath.mnt);
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for (i = 0; i < numlower; i++)
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mntput(stack[i].mnt);
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path_put(&workpath);
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path_put(&workpath);
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kfree(lowertmp);
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oe->__upperdentry = upperpath.dentry;
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oe->__upperdentry = upperpath.dentry;
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oe->lowerstack[0].dentry = lowerpath.dentry;
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for (i = 0; i < numlower; i++) {
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oe->lowerstack[0].mnt = ufs->lower_mnt[0];
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oe->lowerstack[i].dentry = stack[i].dentry;
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oe->lowerstack[i].mnt = ufs->lower_mnt[i];
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}
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root_dentry->d_fsdata = oe;
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root_dentry->d_fsdata = oe;
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@ -912,7 +964,11 @@ out_put_workdir:
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out_put_upper_mnt:
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out_put_upper_mnt:
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mntput(ufs->upper_mnt);
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mntput(ufs->upper_mnt);
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out_put_lowerpath:
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out_put_lowerpath:
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path_put(&lowerpath);
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for (i = 0; i < numlower; i++)
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path_put(&stack[i]);
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kfree(stack);
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out_free_lowertmp:
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kfree(lowertmp);
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out_put_workpath:
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out_put_workpath:
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path_put(&workpath);
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path_put(&workpath);
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out_put_upperpath:
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out_put_upperpath:
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