By default metadata only copy up is disabled. Provide a mount option so
that users can choose one way or other.
Also metadata copyup is conditional on index=on. If index=off and user
specifies metacopy=on, it goes back to metacopy=off and a warning is
printed.
Also provide a kernel config and module option to enable/disable
metacopy feature.
Signed-off-by: Vivek Goyal <vgoyal@xxxxxxxxxx>
---
fs/overlayfs/Kconfig | 9 +++++++++
fs/overlayfs/ovl_entry.h | 1 +
fs/overlayfs/super.c | 32 ++++++++++++++++++++++++++++++++
3 files changed, 42 insertions(+)
diff --git a/fs/overlayfs/Kconfig b/fs/overlayfs/Kconfig
index cbfc196e5dc5..94d4c61719c8 100644
--- a/fs/overlayfs/Kconfig
+++ b/fs/overlayfs/Kconfig
@@ -43,3 +43,12 @@ config OVERLAY_FS_INDEX
outcomes. However, mounting the same overlay with an old kernel
read-write and then mounting it again with a new kernel, will have
unexpected results.
+
+config OVERLAY_FS_METACOPY
+ bool "Overlayfs: turn on metadata only copy up feature by default"
+ depends on OVERLAY_FS
+ depends on OVERLAY_FS_INDEX
+ help
+ If this config option is enabled then overlay filesystems will
+ copy up only metadata where appropriate and data copy up will
+ happen when a file is opended for WRITE operation.
diff --git a/fs/overlayfs/ovl_entry.h b/fs/overlayfs/ovl_entry.h
index 25d9b5adcd42..6806f0b0fbc2 100644
--- a/fs/overlayfs/ovl_entry.h
+++ b/fs/overlayfs/ovl_entry.h
@@ -15,6 +15,7 @@ struct ovl_config {
bool default_permissions;
bool redirect_dir;
bool index;
+ bool metacopy;
};
/* private information held for overlayfs's superblock */
diff --git a/fs/overlayfs/super.c b/fs/overlayfs/super.c
index 092d150643c1..6f4c32e49298 100644
--- a/fs/overlayfs/super.c
+++ b/fs/overlayfs/super.c
@@ -39,6 +39,11 @@ module_param_named(index, ovl_index_def, bool, 0644);
MODULE_PARM_DESC(ovl_index_def,
"Default to on or off for the inodes index feature");
+static bool ovl_metacopy_def = IS_ENABLED(CONFIG_OVERLAY_FS_METACOPY);
+module_param_named(metacopy, ovl_metacopy_def, bool, 0644);
+MODULE_PARM_DESC(ovl_metacopy_def,
+ "Default to on or off for the metadata only copy up feature");
+
static void ovl_dentry_release(struct dentry *dentry)
{
struct ovl_entry *oe = dentry->d_fsdata;
@@ -303,6 +308,9 @@ static int ovl_show_options(struct seq_file *m, struct dentry *dentry)
if (ufs->config.index != ovl_index_def)
seq_printf(m, ",index=%s",
ufs->config.index ? "on" : "off");
+ if (ufs->config.metacopy != ovl_metacopy_def)
+ seq_printf(m, ",metacopy=%s",
+ ufs->config.metacopy ? "on" : "off");
return 0;
}
@@ -336,6 +344,8 @@ enum {
OPT_REDIRECT_DIR_OFF,
OPT_INDEX_ON,
OPT_INDEX_OFF,
+ OPT_METACOPY_ON,
+ OPT_METACOPY_OFF,
OPT_ERR,
};
@@ -348,6 +358,8 @@ static const match_table_t ovl_tokens = {
{OPT_REDIRECT_DIR_OFF, "redirect_dir=off"},
{OPT_INDEX_ON, "index=on"},
{OPT_INDEX_OFF, "index=off"},
+ {OPT_METACOPY_ON, "metacopy=on"},
+ {OPT_METACOPY_OFF, "metacopy=off"},
{OPT_ERR, NULL}
};
@@ -428,6 +440,14 @@ static int ovl_parse_opt(char *opt, struct ovl_config *config)
config->index = false;
break;
+ case OPT_METACOPY_ON:
+ config->metacopy = true;
+ break;
+
+ case OPT_METACOPY_OFF:
+ config->metacopy = false;
+ break;
+
default:
pr_err("overlayfs: unrecognized mount option \"%s\" or missing value\n", p);
return -EINVAL;
@@ -847,6 +867,12 @@ static int ovl_fill_super(struct super_block *sb, void *data, int silent)
ufs->config.redirect_dir = ovl_redirect_dir_def;
ufs->config.index = ovl_index_def;
+ if (ovl_metacopy_def && !ovl_index_def) {
+ pr_warn("overlayfs: metadata copy up can not be enabled by default as index feature is not enabled by default.\n");
+ ovl_metacopy_def = false;
+ }
+ ufs->config.metacopy = ovl_metacopy_def;
+
err = ovl_parse_opt((char *) data, &ufs->config);
if (err)
goto out_free_config;
@@ -1091,6 +1117,12 @@ static int ovl_fill_super(struct super_block *sb, void *data, int silent)
if (!ufs->indexdir)
ufs->config.index = false;
+ /* As of now metacopy=on is dependent on index=on */
+ if (ufs->config.metacopy && !ufs->config.index) {
+ pr_warn("overlayfs: can not enable metadata only copyup with index=off. Falling back to metacopy=off\n");
+ ufs->config.metacopy = false;
+ }
+
if (remote)
sb->s_d_op = &ovl_reval_dentry_operations;
else
--
2.13.5
--
To unsubscribe from this list: send the line "unsubscribe linux-unionfs" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
