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authorVivek Goyal <vgoyal@redhat.com>2018-05-11 11:49:27 -0400
committerMiklos Szeredi <mszeredi@redhat.com>2018-07-20 09:56:06 +0200
commitd5791044d2e5749ef4de84161cec5532e2111540 (patch)
tree3abb05f2e56381c9d591b8f74bc838836ef4f6fd /fs/overlayfs
parentd6eac039133b31f9db1c63d2e51b88df61d075cc (diff)
ovl: Provide a mount option metacopy=on/off for metadata copyup
By default metadata only copy up is disabled. Provide a mount option so that users can choose one way or other. Also provide a kernel config and module option to enable/disable metacopy feature. metacopy feature requires redirect_dir=on when upper is present. Otherwise, it requires redirect_dir=follow atleast. As of now, metacopy does not work with nfs_export=on. So if both metacopy=on and nfs_export=on then nfs_export is disabled. Signed-off-by: Vivek Goyal <vgoyal@redhat.com> Reviewed-by: Amir Goldstein <amir73il@gmail.com> Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
Diffstat (limited to 'fs/overlayfs')
-rw-r--r--fs/overlayfs/Kconfig19
-rw-r--r--fs/overlayfs/ovl_entry.h1
-rw-r--r--fs/overlayfs/super.c46
3 files changed, 63 insertions, 3 deletions
diff --git a/fs/overlayfs/Kconfig b/fs/overlayfs/Kconfig
index 9384164253ac..2ef91be2a04e 100644
--- a/fs/overlayfs/Kconfig
+++ b/fs/overlayfs/Kconfig
@@ -64,6 +64,7 @@ config OVERLAY_FS_NFS_EXPORT
bool "Overlayfs: turn on NFS export feature by default"
depends on OVERLAY_FS
depends on OVERLAY_FS_INDEX
+ depends on !OVERLAY_FS_METACOPY
help
If this config option is enabled then overlay filesystems will use
the index directory to decode overlay NFS file handles by default.
@@ -103,3 +104,21 @@ config OVERLAY_FS_XINO_AUTO
For more information, see Documentation/filesystems/overlayfs.txt
If unsure, say N.
+
+config OVERLAY_FS_METACOPY
+ bool "Overlayfs: turn on metadata only copy up feature by default"
+ depends on OVERLAY_FS
+ select OVERLAY_FS_REDIRECT_DIR
+ 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 opened for WRITE operation. It is still
+ possible to turn off this feature globally with the "metacopy=off"
+ module option or on a filesystem instance basis with the
+ "metacopy=off" mount option.
+
+ Note, that this feature is not backward compatible. That is,
+ mounting an overlay which has metacopy only inodes on a kernel
+ that doesn't support this feature will have unexpected results.
+
+ If unsure, say N.
diff --git a/fs/overlayfs/ovl_entry.h b/fs/overlayfs/ovl_entry.h
index 41655a7d6894..ea4134e97d0d 100644
--- a/fs/overlayfs/ovl_entry.h
+++ b/fs/overlayfs/ovl_entry.h
@@ -19,6 +19,7 @@ struct ovl_config {
bool index;
bool nfs_export;
int xino;
+ bool metacopy;
};
struct ovl_sb {
diff --git a/fs/overlayfs/super.c b/fs/overlayfs/super.c
index 0e84593af84e..d4caeee051ee 100644
--- a/fs/overlayfs/super.c
+++ b/fs/overlayfs/super.c
@@ -64,6 +64,11 @@ static void ovl_entry_stack_free(struct ovl_entry *oe)
dput(oe->lowerstack[i].dentry);
}
+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;
@@ -347,6 +352,9 @@ static int ovl_show_options(struct seq_file *m, struct dentry *dentry)
"on" : "off");
if (ofs->config.xino != ovl_xino_def())
seq_printf(m, ",xino=%s", ovl_xino_str[ofs->config.xino]);
+ if (ofs->config.metacopy != ovl_metacopy_def)
+ seq_printf(m, ",metacopy=%s",
+ ofs->config.metacopy ? "on" : "off");
return 0;
}
@@ -384,6 +392,8 @@ enum {
OPT_XINO_ON,
OPT_XINO_OFF,
OPT_XINO_AUTO,
+ OPT_METACOPY_ON,
+ OPT_METACOPY_OFF,
OPT_ERR,
};
@@ -400,6 +410,8 @@ static const match_table_t ovl_tokens = {
{OPT_XINO_ON, "xino=on"},
{OPT_XINO_OFF, "xino=off"},
{OPT_XINO_AUTO, "xino=auto"},
+ {OPT_METACOPY_ON, "metacopy=on"},
+ {OPT_METACOPY_OFF, "metacopy=off"},
{OPT_ERR, NULL}
};
@@ -452,6 +464,7 @@ static int ovl_parse_redirect_mode(struct ovl_config *config, const char *mode)
static int ovl_parse_opt(char *opt, struct ovl_config *config)
{
char *p;
+ int err;
config->redirect_mode = kstrdup(ovl_redirect_mode_def(), GFP_KERNEL);
if (!config->redirect_mode)
@@ -526,6 +539,14 @@ static int ovl_parse_opt(char *opt, struct ovl_config *config)
config->xino = OVL_XINO_AUTO;
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;
@@ -540,7 +561,20 @@ static int ovl_parse_opt(char *opt, struct ovl_config *config)
config->workdir = NULL;
}
- return ovl_parse_redirect_mode(config, config->redirect_mode);
+ err = ovl_parse_redirect_mode(config, config->redirect_mode);
+ if (err)
+ return err;
+
+ /* metacopy feature with upper requires redirect_dir=on */
+ if (config->upperdir && config->metacopy && !config->redirect_dir) {
+ pr_warn("overlayfs: metadata only copy up requires \"redirect_dir=on\", falling back to metacopy=off.\n");
+ config->metacopy = false;
+ } else if (config->metacopy && !config->redirect_follow) {
+ pr_warn("overlayfs: metadata only copy up requires \"redirect_dir=follow\" on non-upper mount, falling back to metacopy=off.\n");
+ config->metacopy = false;
+ }
+
+ return 0;
}
#define OVL_WORKDIR_NAME "work"
@@ -1013,7 +1047,8 @@ static int ovl_make_workdir(struct ovl_fs *ofs, struct path *workpath)
if (err) {
ofs->noxattr = true;
ofs->config.index = false;
- pr_warn("overlayfs: upper fs does not support xattr, falling back to index=off.\n");
+ ofs->config.metacopy = false;
+ pr_warn("overlayfs: upper fs does not support xattr, falling back to index=off and metacopy=off.\n");
err = 0;
} else {
vfs_removexattr(ofs->workdir, OVL_XATTR_OPAQUE);
@@ -1035,7 +1070,6 @@ static int ovl_make_workdir(struct ovl_fs *ofs, struct path *workpath)
pr_warn("overlayfs: NFS export requires \"index=on\", falling back to nfs_export=off.\n");
ofs->config.nfs_export = false;
}
-
out:
mnt_drop_write(mnt);
return err;
@@ -1346,6 +1380,7 @@ static int ovl_fill_super(struct super_block *sb, void *data, int silent)
ofs->config.index = ovl_index_def;
ofs->config.nfs_export = ovl_nfs_export_def;
ofs->config.xino = ovl_xino_def();
+ ofs->config.metacopy = ovl_metacopy_def;
err = ovl_parse_opt((char *) data, &ofs->config);
if (err)
goto out_err;
@@ -1416,6 +1451,11 @@ static int ovl_fill_super(struct super_block *sb, void *data, int silent)
}
}
+ if (ofs->config.metacopy && ofs->config.nfs_export) {
+ pr_warn("overlayfs: NFS export is not supported with metadata only copy up, falling back to nfs_export=off.\n");
+ ofs->config.nfs_export = false;
+ }
+
if (ofs->config.nfs_export)
sb->s_export_op = &ovl_export_operations;