ovl: whiteout index when union nlink drops to zero

With NFS export feature enabled, when overlay inode nlink drops to
zero, instead of removing the index entry, replace it with a whiteout
index entry.

This is needed for NFS export in order to prevent future open by handle
from opening the lower file directly.

Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>

diff --git a/fs/overlayfs/dir.c b/fs/overlayfs/dir.c
index a1a7606..839709c 100644 (file)
--- a/fs/overlayfs/dir.c
+++ b/fs/overlayfs/dir.c
@@ -63,8 +63,7 @@ struct dentry *ovl_lookup_temp(struct dentry *workdir)
 }
 
 /* caller holds i_mutex on workdir */
-static struct dentry *ovl_whiteout(struct dentry *workdir,
-                                  struct dentry *dentry)
+static struct dentry *ovl_whiteout(struct dentry *workdir)
 {
        int err;
        struct dentry *whiteout;
@@ -83,6 +82,38 @@ static struct dentry *ovl_whiteout(struct dentry *workdir,
        return whiteout;
 }
 
+/* Caller must hold i_mutex on both workdir and dir */
+int ovl_cleanup_and_whiteout(struct dentry *workdir, struct inode *dir,
+                            struct dentry *dentry)
+{
+       struct inode *wdir = workdir->d_inode;
+       struct dentry *whiteout;
+       int err;
+       int flags = 0;
+
+       whiteout = ovl_whiteout(workdir);
+       err = PTR_ERR(whiteout);
+       if (IS_ERR(whiteout))
+               return err;
+
+       if (d_is_dir(dentry))
+               flags = RENAME_EXCHANGE;
+
+       err = ovl_do_rename(wdir, whiteout, dir, dentry, flags);
+       if (err)
+               goto kill_whiteout;
+       if (flags)
+               ovl_cleanup(wdir, dentry);
+
+out:
+       dput(whiteout);
+       return err;
+
+kill_whiteout:
+       ovl_cleanup(wdir, whiteout);
+       goto out;
+}
+
 int ovl_create_real(struct inode *dir, struct dentry *newdentry,
                    struct cattr *attr, struct dentry *hardlink, bool debug)
 {
@@ -591,14 +622,10 @@ static int ovl_remove_and_whiteout(struct dentry *dentry,
                                   struct list_head *list)
 {
        struct dentry *workdir = ovl_workdir(dentry);
-       struct inode *wdir = workdir->d_inode;
        struct dentry *upperdir = ovl_dentry_upper(dentry->d_parent);
-       struct inode *udir = upperdir->d_inode;
-       struct dentry *whiteout;
        struct dentry *upper;
        struct dentry *opaquedir = NULL;
        int err;
-       int flags = 0;
 
        if (WARN_ON(!workdir))
                return -EROFS;
@@ -627,24 +654,13 @@ static int ovl_remove_and_whiteout(struct dentry *dentry,
                goto out_dput_upper;
        }
 
-       whiteout = ovl_whiteout(workdir, dentry);
-       err = PTR_ERR(whiteout);
-       if (IS_ERR(whiteout))
-               goto out_dput_upper;
-
-       if (d_is_dir(upper))
-               flags = RENAME_EXCHANGE;
-
-       err = ovl_do_rename(wdir, whiteout, udir, upper, flags);
+       err = ovl_cleanup_and_whiteout(workdir, d_inode(upperdir), upper);
        if (err)
-               goto kill_whiteout;
-       if (flags)
-               ovl_cleanup(wdir, upper);
+               goto out_d_drop;
 
        ovl_dentry_version_inc(dentry->d_parent, true);
 out_d_drop:
        d_drop(dentry);
-       dput(whiteout);
 out_dput_upper:
        dput(upper);
 out_unlock:
@@ -653,10 +669,6 @@ out_dput:
        dput(opaquedir);
 out:
        return err;
-
-kill_whiteout:
-       ovl_cleanup(wdir, whiteout);
-       goto out_d_drop;
 }
 
 static int ovl_remove_upper(struct dentry *dentry, bool is_dir,

diff --git a/fs/overlayfs/overlayfs.h b/fs/overlayfs/overlayfs.h
index d7e6528..8f4313c 100644 (file)
--- a/fs/overlayfs/overlayfs.h
+++ b/fs/overlayfs/overlayfs.h
@@ -321,6 +321,8 @@ static inline void ovl_copyattr(struct inode *from, struct inode *to)
 /* dir.c */
 extern const struct inode_operations ovl_dir_inode_operations;
 struct dentry *ovl_lookup_temp(struct dentry *workdir);
+int ovl_cleanup_and_whiteout(struct dentry *workdir, struct inode *dir,
+                            struct dentry *dentry);
 struct cattr {
        dev_t rdev;
        umode_t mode;

diff --git a/fs/overlayfs/util.c b/fs/overlayfs/util.c
index 6b11e11..aa2234d 100644 (file)
--- a/fs/overlayfs/util.c
+++ b/fs/overlayfs/util.c
@@ -487,7 +487,8 @@ bool ovl_need_index(struct dentry *dentry)
 /* Caller must hold OVL_I(inode)->lock */
 static void ovl_cleanup_index(struct dentry *dentry)
 {
-       struct inode *dir = ovl_indexdir(dentry->d_sb)->d_inode;
+       struct dentry *indexdir = ovl_indexdir(dentry->d_sb);
+       struct inode *dir = indexdir->d_inode;
        struct dentry *lowerdentry = ovl_dentry_lower(dentry);
        struct dentry *upperdentry = ovl_dentry_upper(dentry);
        struct dentry *index = NULL;
@@ -518,13 +519,17 @@ static void ovl_cleanup_index(struct dentry *dentry)
        }
 
        inode_lock_nested(dir, I_MUTEX_PARENT);
-       /* TODO: whiteout instead of cleanup to block future open by handle */
-       index = lookup_one_len(name.name, ovl_indexdir(dentry->d_sb), name.len);
+       index = lookup_one_len(name.name, indexdir, name.len);
        err = PTR_ERR(index);
-       if (!IS_ERR(index))
-               err = ovl_cleanup(dir, index);
-       else
+       if (IS_ERR(index)) {
                index = NULL;
+       } else if (ovl_index_all(dentry->d_sb)) {
+               /* Whiteout orphan index to block future open by handle */
+               err = ovl_cleanup_and_whiteout(indexdir, dir, index);
+       } else {
+               /* Cleanup orphan index entries */
+               err = ovl_cleanup(dir, index);
+       }
 
        inode_unlock(dir);
        if (err)