As with other required upper fs features, we only warn if support
is missing to avoid breaking existing sub-optimal setups.
Signed-off-by: Amir Goldstein <amir73il@xxxxxxxxx>
---
fs/overlayfs/dir.c | 2 +-
fs/overlayfs/overlayfs.h | 1 +
fs/overlayfs/super.c | 69 ++++++++++++++++++++++++++++++++++++++++
3 files changed, 71 insertions(+), 1 deletion(-)
diff --git a/fs/overlayfs/dir.c b/fs/overlayfs/dir.c
index b3471ef51440..c91b5aae8e32 100644
--- a/fs/overlayfs/dir.c
+++ b/fs/overlayfs/dir.c
@@ -42,7 +42,7 @@ int ovl_cleanup(struct inode *wdir, struct dentry *wdentry)
return err;
}
-static struct dentry *ovl_lookup_temp(struct dentry *workdir)
+struct dentry *ovl_lookup_temp(struct dentry *workdir)
{
struct dentry *temp;
char name[20];
diff --git a/fs/overlayfs/overlayfs.h b/fs/overlayfs/overlayfs.h
index 8d67dc7c1c04..68df20512dca 100644
--- a/fs/overlayfs/overlayfs.h
+++ b/fs/overlayfs/overlayfs.h
@@ -448,6 +448,7 @@ struct ovl_cattr {
struct dentry *ovl_create_real(struct inode *dir, struct dentry *newdentry,
struct ovl_cattr *attr);
int ovl_cleanup(struct inode *dir, struct dentry *dentry);
+struct dentry *ovl_lookup_temp(struct dentry *workdir);
struct dentry *ovl_create_temp(struct dentry *workdir, struct ovl_cattr *attr);
/* file.c */
diff --git a/fs/overlayfs/super.c b/fs/overlayfs/super.c
index 19c79619529b..7322cf8faea4 100644
--- a/fs/overlayfs/super.c
+++ b/fs/overlayfs/super.c
@@ -1071,6 +1071,66 @@ static int ovl_get_upper(struct super_block *sb, struct ovl_fs *ofs,
return err;
}
+/*
+ * Returns 1 if RENAME_WHITEOUT is supported, 0 if not supported and
+ * negative values if error is encountered.
+ */
+static int ovl_check_rename_whiteout(struct dentry *workdir)
+{
+ struct inode *dir = d_inode(workdir);
+ struct dentry *temp;
+ struct dentry *dest;
+ struct dentry *whiteout;
+ struct name_snapshot name;
+ int err;
+
+ inode_lock_nested(dir, I_MUTEX_PARENT);
+
+ temp = ovl_create_temp(workdir, OVL_CATTR(S_IFREG | 0));
+ err = PTR_ERR(temp);
+ if (IS_ERR(temp))
+ goto out_unlock;
+
+ dest = ovl_lookup_temp(workdir);
+ err = PTR_ERR(dest);
+ if (IS_ERR(dest)) {
+ dput(temp);
+ goto out_unlock;
+ }
+
+ /* Name is inline and stable - using snapshot as a copy helper */
+ take_dentry_name_snapshot(&name, temp);
+ err = ovl_do_rename(dir, temp, dir, dest, RENAME_WHITEOUT);
+ if (err) {
+ if (err == -EINVAL)
+ err = 0;
+ goto cleanup_temp;
+ }
+
+ whiteout = lookup_one_len(name.name.name, workdir, name.name.len);
+ err = PTR_ERR(whiteout);
+ if (IS_ERR(whiteout))
+ goto cleanup_temp;
+
+ err = ovl_is_whiteout(whiteout);
+
+ /* Best effort cleanup of whiteout and temp file */
+ if (err)
+ ovl_cleanup(dir, whiteout);
+ dput(whiteout);
+
+cleanup_temp:
+ ovl_cleanup(dir, temp);
+ release_dentry_name_snapshot(&name);
+ dput(temp);
+ dput(dest);
+
+out_unlock:
+ inode_unlock(dir);
+
+ return err;
+}
+
static int ovl_make_workdir(struct super_block *sb, struct ovl_fs *ofs,
struct path *workpath)
{
@@ -1116,6 +1176,15 @@ static int ovl_make_workdir(struct super_block *sb, struct ovl_fs *ofs,
else
pr_warn("upper fs does not support tmpfile.\n");
+
+ /* Check if upper/work fs supports RENAME_WHITEOUT */
+ err = ovl_check_rename_whiteout(ofs->workdir);
+ if (err < 0)
+ goto out;
+
+ if (!err)
+ pr_warn("upper fs does not support RENAME_WHITEOUT.\n");
+
/*
* Check if upper/work fs supports trusted.overlay.* xattr
*/
--
2.17.1
