On Sun, Jun 28, 2015 at 05:38:35PM +0300, sa wrote:
> On 04.06.2015 16:29, Miklos Szeredi wrote:
>
> >Two small patches implementing this follow. Comments and testing welcome.
> > git://git.kernel.org/pub/scm/linux/kernel/git/mszeredi/vfs.git
> > overlayfs-next
> >---
> > fs/overlayfs/super.c | 81
> > +++++++++++++++++++++++++++++++++++++++++++++++-----
> > 1 file changed, 74 insertions(+), 7 deletions(-)
>
> Thank you, it works in our environment mostly as expected, except
> of the following:
> files already existing in readonly NFS lowerdir can't be opened
> for writing (but can be deleted). Newly created files are writable
> as expected. The same lowerdir works with aufs without problem.
> Is it a bug or am I missing something?
Is the lower fs exported read-only on the NFS server?
If so, can you please apply the following patch and specify
'default_permissions' mount option?
Thanks,
Miklos
---
fs/overlayfs/inode.c | 23 +++++++++++++++++++++++
fs/overlayfs/overlayfs.h | 3 +++
fs/overlayfs/super.c | 28 ++++++++++++++++++++++++++++
3 files changed, 54 insertions(+)
--- a/fs/overlayfs/overlayfs.h
+++ b/fs/overlayfs/overlayfs.h
@@ -142,7 +142,10 @@ struct dentry *ovl_dentry_upper(struct d
struct dentry *ovl_dentry_lower(struct dentry *dentry);
struct dentry *ovl_dentry_real(struct dentry *dentry);
struct dentry *ovl_entry_real(struct ovl_entry *oe, bool *is_upper);
+struct vfsmount *ovl_entry_mnt_real(struct ovl_entry *oe, struct inode *inode,
+ bool is_upper);
struct ovl_dir_cache *ovl_dir_cache(struct dentry *dentry);
+bool ovl_is_default_permissions(struct inode *inode);
void ovl_set_dir_cache(struct dentry *dentry, struct ovl_dir_cache *cache);
struct dentry *ovl_workdir(struct dentry *dentry);
int ovl_want_write(struct dentry *dentry);
--- a/fs/overlayfs/super.c
+++ b/fs/overlayfs/super.c
@@ -30,6 +30,7 @@ struct ovl_config {
char *lowerdir;
char *upperdir;
char *workdir;
+ bool default_permissions;
};
/* private information held for overlayfs's superblock */
@@ -154,6 +155,18 @@ struct dentry *ovl_entry_real(struct ovl
return realdentry;
}
+struct vfsmount *ovl_entry_mnt_real(struct ovl_entry *oe, struct inode *inode,
+ bool is_upper)
+{
+ if (is_upper) {
+ struct ovl_fs *ofs = inode->i_sb->s_fs_info;
+
+ return ofs->upper_mnt;
+ } else {
+ return oe->numlower ? oe->lowerstack[0].mnt : NULL;
+ }
+}
+
struct ovl_dir_cache *ovl_dir_cache(struct dentry *dentry)
{
struct ovl_entry *oe = dentry->d_fsdata;
@@ -161,6 +174,13 @@ struct ovl_dir_cache *ovl_dir_cache(stru
return oe->cache;
}
+bool ovl_is_default_permissions(struct inode *inode)
+{
+ struct ovl_fs *ofs = inode->i_sb->s_fs_info;
+
+ return ofs->config.default_permissions;
+}
+
void ovl_set_dir_cache(struct dentry *dentry, struct ovl_dir_cache *cache)
{
struct ovl_entry *oe = dentry->d_fsdata;
@@ -592,6 +612,8 @@ static int ovl_show_options(struct seq_f
seq_printf(m, ",upperdir=%s", ufs->config.upperdir);
seq_printf(m, ",workdir=%s", ufs->config.workdir);
}
+ if (ufs->config.default_permissions)
+ seq_puts(m, ",default_permissions");
return 0;
}
@@ -616,6 +638,7 @@ enum {
OPT_LOWERDIR,
OPT_UPPERDIR,
OPT_WORKDIR,
+ OPT_DEFAULT_PERMISSIONS,
OPT_ERR,
};
@@ -623,6 +646,7 @@ static const match_table_t ovl_tokens =
{OPT_LOWERDIR, "lowerdir=%s"},
{OPT_UPPERDIR, "upperdir=%s"},
{OPT_WORKDIR, "workdir=%s"},
+ {OPT_DEFAULT_PERMISSIONS, "default_permissions"},
{OPT_ERR, NULL}
};
@@ -683,6 +707,10 @@ static int ovl_parse_opt(char *opt, stru
return -ENOMEM;
break;
+ case OPT_DEFAULT_PERMISSIONS:
+ config->default_permissions = true;
+ break;
+
default:
pr_err("overlayfs: unrecognized mount option \"%s\" or
missing value\n", p);
return -EINVAL;
--- a/fs/overlayfs/inode.c
+++ b/fs/overlayfs/inode.c
@@ -98,6 +98,29 @@ int ovl_permission(struct inode *inode,
realdentry = ovl_entry_real(oe, &is_upper);
+ if (ovl_is_default_permissions(inode)) {
+ struct kstat stat;
+ struct path realpath = { .dentry = realdentry };
+
+ if (mask & MAY_NOT_BLOCK)
+ return -ECHILD;
+
+ realpath.mnt = ovl_entry_mnt_real(oe, inode, is_upper);
+
+ err = vfs_getattr(&realpath, &stat);
+ if (err)
+ return err;
+
+ if ((stat.mode ^ inode->i_mode) & S_IFMT)
+ return -ESTALE;
+
+ inode->i_mode = stat.mode;
+ inode->i_uid = stat.uid;
+ inode->i_gid = stat.gid;
+
+ return generic_permission(inode, mask);
+ }
+
/* Careful in RCU walk mode */
realinode = ACCESS_ONCE(realdentry->d_inode);
if (!realinode) {
--
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