From cc2596392af3b1404421aaef828a255303c46f93 Mon Sep 17 00:00:00 2001 From: Andy Whitcroft Date: Fri, 24 Oct 2014 00:14:38 +0200 Subject: [PATCH] overlayfs: add statfs support Add support for statfs to the overlayfs filesystem. As the upper layer is the target of all write operations assume that the space in that filesystem is the space in the overlayfs. There will be some inaccuracy as overwriting a file will copy it up and consume space we were not expecting, but it is better than nothing. Use the upper layer dentry and mount from the overlayfs root inode, passing the statfs call to that filesystem. Signed-off-by: Andy Whitcroft Signed-off-by: Miklos Szeredi --- fs/overlayfs/super.c | 40 ++++++++++++++++++++++++++++++++++++++++ 1 file changed, 40 insertions(+) diff --git a/fs/overlayfs/super.c b/fs/overlayfs/super.c index 227710a..aaf562b 100644 --- a/fs/overlayfs/super.c +++ b/fs/overlayfs/super.c @@ -16,17 +16,21 @@ #include #include #include +#include #include "overlayfs.h" MODULE_AUTHOR("Miklos Szeredi "); MODULE_DESCRIPTION("Overlay filesystem"); MODULE_LICENSE("GPL"); +#define OVERLAYFS_SUPER_MAGIC 0x794c764f + /* private information held for overlayfs's superblock */ struct ovl_fs { struct vfsmount *upper_mnt; struct vfsmount *lower_mnt; struct dentry *workdir; + long lower_namelen; }; struct ovl_dir_cache; @@ -383,8 +387,35 @@ static void ovl_put_super(struct super_block *sb) kfree(ufs); } +/** + * 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 same filesystem. + */ +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_upper(root_dentry, &path); + + err = vfs_statfs(&path, buf); + if (!err) { + buf->f_namelen = max(buf->f_namelen, ofs->lower_namelen); + buf->f_type = OVERLAYFS_SUPER_MAGIC; + } + + return err; +} + static const struct super_operations ovl_super_operations = { .put_super = ovl_put_super, + .statfs = ovl_statfs, }; struct ovl_config { @@ -556,6 +587,7 @@ static int ovl_fill_super(struct super_block *sb, void *data, int silent) struct ovl_entry *oe; struct ovl_fs *ufs; struct ovl_config config; + struct kstatfs statfs; int err; err = ovl_parse_opt((char *) data, &config); @@ -617,6 +649,13 @@ static int ovl_fill_super(struct super_block *sb, void *data, int silent) goto out_put_workpath; } + err = vfs_statfs(&lowerpath, &statfs); + if (err) { + pr_err("overlayfs: statfs failed on lowerpath\n"); + goto out_put_workpath; + } + ufs->lower_namelen = statfs.f_namelen; + ufs->upper_mnt = clone_private_mount(&upperpath); err = PTR_ERR(ufs->upper_mnt); if (IS_ERR(ufs->upper_mnt)) { @@ -669,6 +708,7 @@ static int ovl_fill_super(struct super_block *sb, void *data, int silent) root_dentry->d_fsdata = oe; + sb->s_magic = OVERLAYFS_SUPER_MAGIC; sb->s_op = &ovl_super_operations; sb->s_root = root_dentry; sb->s_fs_info = ufs; -- 2.7.4