diff options
| -rw-r--r-- | Documentation/filesystems/overlayfs.txt | 12 | ||||
| -rw-r--r-- | fs/overlayfs/super.c | 110 |
2 files changed, 95 insertions, 27 deletions
diff --git a/Documentation/filesystems/overlayfs.txt b/Documentation/filesystems/overlayfs.txt index a27c950ece61..b37092886dcc 100644 --- a/Documentation/filesystems/overlayfs.txt +++ b/Documentation/filesystems/overlayfs.txt @@ -159,6 +159,18 @@ overlay filesystem (though an operation on the name of the file such as rename or unlink will of course be noticed and handled). +Multiple lower layers +--------------------- + +Multiple lower layers can now be given using the the colon (":") as a +separator character between the directory names. For example: + + mount -t overlay overlay -olowerdir=/lower1:/lower2:/lower3 /merged + +As the example shows, "upperdir=" and "workdir=" may be omitted. In that case +the overlay will be read-only. + + Non-standard behavior --------------------- diff --git a/fs/overlayfs/super.c b/fs/overlayfs/super.c index 35bb0adf10cf..5c495a17a5a3 100644 --- a/fs/overlayfs/super.c +++ b/fs/overlayfs/super.c @@ -60,6 +60,8 @@ struct ovl_entry { struct path lowerstack[]; }; +#define OVL_MAX_STACK 500 + const char *ovl_opaque_xattr = "trusted.overlay.opaque"; static struct dentry *__ovl_dentry_lower(struct ovl_entry *oe) @@ -692,8 +694,12 @@ static bool ovl_is_allowed_fs_type(struct dentry *root) static int ovl_mount_dir_noesc(const char *name, struct path *path) { - int err; + 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); @@ -735,7 +741,7 @@ static int ovl_lower_dir(const char *name, struct path *path, long *namelen, int err; struct kstatfs statfs; - err = ovl_mount_dir(name, path); + err = ovl_mount_dir_noesc(name, path); if (err) goto out; @@ -767,15 +773,38 @@ static bool ovl_workdir_ok(struct dentry *workdir, struct dentry *upperdir) return ok; } +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; +} + static int ovl_fill_super(struct super_block *sb, void *data, int silent) { - struct path lowerpath; struct path upperpath = { NULL, NULL }; struct path workpath = { NULL, NULL }; struct dentry *root_dentry; struct ovl_entry *oe; struct ovl_fs *ufs; - struct vfsmount *mnt; + struct path *stack = NULL; + char *lowertmp; + char *lower; + unsigned int numlower; + unsigned int stacklen = 0; unsigned int i; int err; @@ -820,13 +849,31 @@ static int ovl_fill_super(struct super_block *sb, void *data, int silent) } sb->s_stack_depth = upperpath.mnt->mnt_sb->s_stack_depth; } - - err = ovl_lower_dir(ufs->config.lowerdir, &lowerpath, - &ufs->lower_namelen, &sb->s_stack_depth); - if (err) + err = -ENOMEM; + lowertmp = kstrdup(ufs->config.lowerdir, GFP_KERNEL); + if (!lowertmp) goto out_put_workpath; err = -EINVAL; + stacklen = ovl_split_lowerdirs(lowertmp); + if (stacklen > OVL_MAX_STACK) + goto out_free_lowertmp; + + stack = kcalloc(stacklen, sizeof(struct path), GFP_KERNEL); + if (!stack) + goto out_free_lowertmp; + + lower = lowertmp; + for (numlower = 0; numlower < stacklen; numlower++) { + err = ovl_lower_dir(lower, &stack[numlower], + &ufs->lower_namelen, &sb->s_stack_depth); + if (err) + goto out_put_lowerpath; + + lower = strchr(lower, '\0') + 1; + } + + err = -EINVAL; sb->s_stack_depth++; if (sb->s_stack_depth > FILESYSTEM_MAX_STACK_DEPTH) { pr_err("overlayfs: maximum fs stacking depth exceeded\n"); @@ -850,24 +897,25 @@ static int ovl_fill_super(struct super_block *sb, void *data, int silent) } } - ufs->lower_mnt = kcalloc(1, sizeof(struct vfsmount *), GFP_KERNEL); + ufs->lower_mnt = kcalloc(numlower, sizeof(struct vfsmount *), GFP_KERNEL); if (ufs->lower_mnt == NULL) goto out_put_workdir; + for (i = 0; i < numlower; i++) { + struct vfsmount *mnt = clone_private_mount(&stack[i]); - mnt = clone_private_mount(&lowerpath); - err = PTR_ERR(mnt); - if (IS_ERR(mnt)) { - pr_err("overlayfs: failed to clone lowerpath\n"); - goto out_put_lower_mnt; - } - /* - * Make lower_mnt R/O. That way fchmod/fchown on lower file - * will fail instead of modifying lower fs. - */ - mnt->mnt_flags |= MNT_READONLY; + if (IS_ERR(mnt)) { + pr_err("overlayfs: failed to clone lowerpath\n"); + goto out_put_lower_mnt; + } + /* + * Make lower_mnt R/O. That way fchmod/fchown on lower file + * will fail instead of modifying lower fs. + */ + mnt->mnt_flags |= MNT_READONLY; - ufs->lower_mnt[0] = mnt; - ufs->numlower = 1; + ufs->lower_mnt[ufs->numlower] = mnt; + ufs->numlower++; + } /* If the upper fs is r/o or nonexistent, we mark overlayfs r/o too */ if (!ufs->upper_mnt || (ufs->upper_mnt->mnt_sb->s_flags & MS_RDONLY)) @@ -876,7 +924,7 @@ static int ovl_fill_super(struct super_block *sb, void *data, int silent) sb->s_d_op = &ovl_dentry_operations; err = -ENOMEM; - oe = ovl_alloc_entry(1); + oe = ovl_alloc_entry(numlower); if (!oe) goto out_put_lower_mnt; @@ -885,12 +933,16 @@ static int ovl_fill_super(struct super_block *sb, void *data, int silent) goto out_free_oe; mntput(upperpath.mnt); - mntput(lowerpath.mnt); + for (i = 0; i < numlower; i++) + mntput(stack[i].mnt); path_put(&workpath); + kfree(lowertmp); oe->__upperdentry = upperpath.dentry; - oe->lowerstack[0].dentry = lowerpath.dentry; - oe->lowerstack[0].mnt = ufs->lower_mnt[0]; + for (i = 0; i < numlower; i++) { + oe->lowerstack[i].dentry = stack[i].dentry; + oe->lowerstack[i].mnt = ufs->lower_mnt[i]; + } root_dentry->d_fsdata = oe; @@ -912,7 +964,11 @@ out_put_workdir: out_put_upper_mnt: mntput(ufs->upper_mnt); out_put_lowerpath: - path_put(&lowerpath); + for (i = 0; i < numlower; i++) + path_put(&stack[i]); + kfree(stack); +out_free_lowertmp: + kfree(lowertmp); out_put_workpath: path_put(&workpath); out_put_upperpath: |