On Wed, Oct 18, 2017 at 12:05 AM, Vivek Goyal <vgoyal@xxxxxxxxxx> wrote:
> 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.
>
> Like index feature, when overlay is mounted, on root upper directory we
> set ORIGIN which points to lower. And at later mount time it is verified
> again. This hopes to get the configuration right. But this does only so
> much as we don't verify all the lowers. So it is possible that a lower is
> missing and later data copy up fails.
Like index feature, please error mount if ovl_inuse_trylock fails.
As you know, this error is only conditional because of backward
compatibility, so any new opt-in feature should enforce it.
>
> Signed-off-by: Vivek Goyal <vgoyal@xxxxxxxxxx>
> ---
> fs/overlayfs/Kconfig | 8 ++++++++
> fs/overlayfs/ovl_entry.h | 1 +
> fs/overlayfs/super.c | 38 +++++++++++++++++++++++++++++++++++---
> 3 files changed, 44 insertions(+), 3 deletions(-)
>
> diff --git a/fs/overlayfs/Kconfig b/fs/overlayfs/Kconfig
> index cbfc196e5dc5..17a0b17ad14c 100644
> --- a/fs/overlayfs/Kconfig
> +++ b/fs/overlayfs/Kconfig
> @@ -43,3 +43,11 @@ 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
> + 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..32e3d4be1a71 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;
> @@ -644,9 +664,16 @@ static int ovl_lower_dir(const char *name, struct path *path,
> * The inodes index feature needs to encode and decode file
> * handles, so it requires that all layers support them.
> */
> - if (ofs->config.index && !ovl_can_decode_fh(path->dentry->d_sb)) {
> + if ((ofs->config.index || ofs->config.metacopy) &&
> + !ovl_can_decode_fh(path->dentry->d_sb)) {
> + if (ofs->config.index)
> + pr_warn("overlayfs: fs on '%s' does not support file handles, falling back to index=off.\n", name);
> +
> + if (ofs->config.metacopy)
> + pr_warn("overlayfs: fs on '%s' does not support file handles, falling back to metacopy=off.\n", name);
> +
In my verify_dir patches I used the following more compact warning
style instead of granular warnings:
pr_warn("overlayfs: fs on '%s' does not support file handles,
falling back to index=off,metacopy=off.\n", name);
It is a bit less informative, but IMO the result in nicer to look at,
both in the code and in dmesg.
Others may have a different opinion. Please consider.
For example, see how the following warning from my verify_dir patches
has expanded and imagine how
much more messier it would be if we broke it into separate warnings:
pr_warn("overlayfs: upper fs does not support xattr, falling back
to redirect_dir=off, index=off, no verify_dir and no opaque dir.\n");
> ofs->config.index = false;
> - pr_warn("overlayfs: fs on '%s' does not support file handles, falling back to index=off.\n", name);
> + ofs->config.metacopy = false;
> }
>
> return 0;
> @@ -847,6 +874,8 @@ 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;
> + ufs->config.metacopy = ovl_metacopy_def;
> +
> err = ovl_parse_opt((char *) data, &ufs->config);
> if (err)
> goto out_free_config;
> @@ -1057,7 +1086,8 @@ static int ovl_fill_super(struct super_block *sb, void *data, int silent)
> else if (ufs->upper_mnt->mnt_sb != ufs->same_sb)
> ufs->same_sb = NULL;
>
> - if (!(ovl_force_readonly(ufs)) && ufs->config.index) {
> + if (!(ovl_force_readonly(ufs)) &&
> + (ufs->config.index || ufs->config.metacopy)) {
> /* Verify lower root is upper root origin */
> err = ovl_verify_origin(upperpath.dentry, ufs->lower_mnt[0],
> stack[0].dentry, false, true);
> @@ -1065,7 +1095,9 @@ static int ovl_fill_super(struct super_block *sb, void *data, int silent)
> pr_err("overlayfs: failed to verify upper root origin\n");
> goto out_put_lower_mnt;
> }
> + }
>
> + if (!(ovl_force_readonly(ufs)) && ufs->config.index) {
> ufs->indexdir = ovl_workdir_create(sb, ufs, workpath.dentry,
> OVL_INDEXDIR_NAME, true);
> if (ufs->indexdir) {
> --
> 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
