Unlike common disk filesystems, overlay filesystem enable features
through mount options(e.g. -o index=on will enable index feature),
so it's a good time to save enabled features on the upper root dir
according to mount options. The given feature will be enabled when
user give option "-o xxx=on" during mount time.
This patch add three already support features: redirect_dir, index
and nfs_export, the first one belongs to the incompatable feature set,
and the other two belong to the ro_compatable feature set.
eg:
mount -t overlay -olowerdir=lower,upperdir=upper,workdir=work \
-oredirect_dir=on,index=on,nfs_export=on overlay merge
trusted.overlay.feature_ro_compat="index,nfs_export"
trusted.overlay.feature_incompat="redirect_dir"
This patch also introduce three sets of feature check/set helper
functions ovl_has_xxx_feature() and ovl_set_xxx_feature() which
learn from ext4 filesystem driver.
Suggested-by: Amir Goldstein <amir73il@xxxxxxxxx>
Signed-off-by: zhangyi (F) <yi.zhang@xxxxxxxxxx>
---
fs/overlayfs/overlayfs.h | 73 ++++++++++++++++++++++++++++++++++++++++++++++++
fs/overlayfs/ovl_entry.h | 2 ++
fs/overlayfs/super.c | 71 ++++++++++++++++++++++++++++++++++++++++++++++
3 files changed, 146 insertions(+)
diff --git a/fs/overlayfs/overlayfs.h b/fs/overlayfs/overlayfs.h
index 121e81cc1550..53ed4e73f889 100644
--- a/fs/overlayfs/overlayfs.h
+++ b/fs/overlayfs/overlayfs.h
@@ -47,6 +47,79 @@ enum ovl_entry_flag {
};
/* Features */
+enum ovl_feature_flag {
+ OVL_FEATURE_COMPAT,
+ OVL_FEATURE_RO_COMPAT,
+ OVL_FEATURE_INCOMPAT,
+ OVL_FEATURE_MAX,
+};
+
+#define OVL_FEATURE_RO_COMPAT_INDEX "index"
+#define OVL_FEATURE_RO_COMPAT_NFS_EXPORT "nfs_export"
+
+#define OVL_FEATURE_INCOMPAT_REDIRECT_DIR "redirect_dir"
+
+int ovl_set_feature_set(struct super_block *sb,
+ enum ovl_feature_flag flag, const char *new);
+
+#define OVL_FEATURE_COMPAT_FUNCS(name, flagname) \
+static inline bool ovl_has_feature_##name(struct super_block *sb) \
+{ \
+ bool exist;\
+ down_read(&OVL_FS(sb)->feature.lock); \
+ exist = ((OVL_FS(sb)->feature.compat) && \
+ (strstr(OVL_FS(sb)->feature.compat, \
+ OVL_FEATURE_COMPAT_##flagname))); \
+ up_read(&OVL_FS(sb)->feature.lock); \
+ return exist; \
+} \
+static inline int ovl_set_feature_##name(struct super_block *sb) \
+{ \
+ return ovl_set_feature_set(sb, OVL_FEATURE_COMPAT, \
+ OVL_FEATURE_COMPAT_##flagname); \
+} \
+
+#define OVL_FEATURE_RO_COMPAT_FUNCS(name, flagname) \
+static inline bool ovl_has_feature_##name(struct super_block *sb) \
+{ \
+ bool exist;\
+ down_read(&OVL_FS(sb)->feature.lock); \
+ exist = ((OVL_FS(sb)->feature.ro_compat) && \
+ (strstr(OVL_FS(sb)->feature.ro_compat, \
+ OVL_FEATURE_RO_COMPAT_##flagname))); \
+ up_read(&OVL_FS(sb)->feature.lock); \
+ return exist; \
+} \
+static inline int ovl_set_feature_##name(struct super_block *sb) \
+{ \
+ return ovl_set_feature_set(sb, OVL_FEATURE_RO_COMPAT, \
+ OVL_FEATURE_RO_COMPAT_##flagname); \
+} \
+
+#define OVL_FEATURE_INCOMPAT_FUNCS(name, flagname) \
+static inline bool ovl_has_feature_##name(struct super_block *sb) \
+{ \
+ bool exist;\
+ down_read(&OVL_FS(sb)->feature.lock); \
+ exist = ((OVL_FS(sb)->feature.incompat) && \
+ (strstr(OVL_FS(sb)->feature.incompat, \
+ OVL_FEATURE_INCOMPAT_##flagname))); \
+ up_read(&OVL_FS(sb)->feature.lock); \
+ return exist; \
+} \
+static inline int ovl_set_feature_##name(struct super_block *sb) \
+{ \
+ return ovl_set_feature_set(sb, OVL_FEATURE_INCOMPAT, \
+ OVL_FEATURE_INCOMPAT_##flagname); \
+} \
+
+
+OVL_FEATURE_RO_COMPAT_FUNCS(index, INDEX)
+OVL_FEATURE_RO_COMPAT_FUNCS(nfs_export, NFS_EXPORT)
+
+OVL_FEATURE_INCOMPAT_FUNCS(redirect_dir, REDIRECT_DIR)
+
+
static inline bool ovl_has_unknown_compat_features(struct super_block *sb)
{
return (OVL_FS(sb)->feature.compat_unknown != NULL);
diff --git a/fs/overlayfs/ovl_entry.h b/fs/overlayfs/ovl_entry.h
index f8c5e0191a12..ff8bf783a097 100644
--- a/fs/overlayfs/ovl_entry.h
+++ b/fs/overlayfs/ovl_entry.h
@@ -36,6 +36,8 @@ struct ovl_feature {
char *compat;
char *ro_compat;
char *incompat;
+ struct rw_semaphore lock; /* protect feature string */
+
const char *compat_unknown;
const char *ro_compat_unknown;
const char *incompat_unknown;
diff --git a/fs/overlayfs/super.c b/fs/overlayfs/super.c
index 19b7d0869fbd..4787f9356dfd 100644
--- a/fs/overlayfs/super.c
+++ b/fs/overlayfs/super.c
@@ -189,13 +189,22 @@ static const char *ovl_feature_compat_supp[] = {
};
static const char *ovl_feature_ro_compat_supp[] = {
+ OVL_FEATURE_RO_COMPAT_INDEX,
+ OVL_FEATURE_RO_COMPAT_NFS_EXPORT,
NULL
};
static const char *ovl_feature_incompat_supp[] = {
+ OVL_FEATURE_INCOMPAT_REDIRECT_DIR,
NULL
};
+static const char *ovl_feature_set[] = {
+ OVL_XATTR_FEATURE_COMPAT,
+ OVL_XATTR_FEATURE_RO_COMPAT,
+ OVL_XATTR_FEATURE_INCOMPAT
+};
+
/*
* Get overlay feature from the real root dentry.
*
@@ -431,6 +440,8 @@ static int ovl_init_features(struct dentry *root, struct ovl_feature *of)
{
int err;
+ init_rwsem(&of->lock);
+
err = ovl_get_feature_set(root, OVL_XATTR_FEATURE_COMPAT,
ovl_feature_compat_supp, &of->compat,
&of->compat_unknown);
@@ -487,6 +498,49 @@ static bool ovl_check_feature_ok(struct super_block *sb, bool readonly)
return true;
}
+/*
+ * Set one specified feature to the upper root dir
+ *
+ * @sb: overlay super block
+ * @flag: feature set flag, compat/ro compat/incompat
+ * @new: new feature want to set
+ * Return 0 if success, errno otherwise.
+ */
+int ovl_set_feature_set(struct super_block *sb,
+ enum ovl_feature_flag flag, const char *new)
+{
+ struct ovl_feature *of = &OVL_FS(sb)->feature;
+ bool update = false;
+ char **feature;
+ int err;
+
+ /* Don't set feature if no upper layer */
+ if (!OVL_FS(sb)->upper_mnt)
+ return 0;
+
+ down_write(&of->lock);
+ if (flag == OVL_FEATURE_COMPAT)
+ feature = &of->compat;
+ else if (flag == OVL_FEATURE_RO_COMPAT)
+ feature = &of->ro_compat;
+ else
+ feature = &of->incompat;
+
+ err = ovl_update_feature(feature, new, &update);
+ if (err)
+ goto out;
+ if (!update)
+ goto out;
+
+ /* Set updated compat features to upper root dir */
+ err = ovl_set_feature(sb->s_root, ovl_dentry_upper(sb->s_root),
+ ovl_feature_set[flag], *feature);
+out:
+ up_write(&of->lock);
+ return err;
+}
+
+
static struct kmem_cache *ovl_inode_cachep;
static struct inode *ovl_alloc_inode(struct super_block *sb)
@@ -1689,6 +1743,23 @@ static int ovl_fill_super(struct super_block *sb, void *data, int silent)
if (!ovl_check_feature_ok(sb, (sb_rdonly(sb))))
goto out_free_root;
+ /* Turn on features according to mount options */
+ if (ofs->config.index && !ovl_has_feature_index(sb)) {
+ err = ovl_set_feature_index(sb);
+ if (err)
+ goto out_free_root;
+ }
+ if (ofs->config.nfs_export && !ovl_has_feature_nfs_export(sb)) {
+ err = ovl_set_feature_nfs_export(sb);
+ if (err)
+ goto out_free_root;
+ }
+ if (ofs->config.redirect_dir && !ovl_has_feature_redirect_dir(sb)) {
+ err = ovl_set_feature_redirect_dir(sb);
+ if (err)
+ goto out_free_root;
+ }
+
return 0;
out_free_root:
--
2.13.6
--
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