On January 15, 2015 2:20:57 PM GMT+09:00, hujianyang <hujianyang@xxxxxxxxxx> wrote:
>After importing multi-lower layer support, users could mount a r/o
>partition as the left most lowerdir instead of using it as upperdir.
>And a r/o upperdir may cause an error like
>
> overlayfs: failed to create directory ./workdir/work
>
>during mount.
>
>This patch check the *s_flags* of upper fs and return an error if
>it is a r/o partition. The checking of *upper_mnt->mnt_sb->s_flags*
>can be removed now.
>
>This patch also remove
>
> /* FIXME: workdir is not needed for a R/O mount */
>
>from ovl_fill_super() because:
>
>1) for upper fs r/o case
>Setting a r/o partition as upper is prevented, no need to care about
>workdir in this case.
>
>2) for "mount overlay -o ro" with a r/w upper fs case
>Users could remount overlayfs to r/w in this case, so workdir should
>not be omitted.
>
>Signed-off-by: hujianyang <hujianyang@xxxxxxxxxx>
>---
> fs/overlayfs/super.c | 24 +++++++++++++++++++-----
> 1 files changed, 19 insertions(+), 5 deletions(-)
>
>diff --git a/fs/overlayfs/super.c b/fs/overlayfs/super.c
>index edbb3eb..0e7a477 100644
>--- a/fs/overlayfs/super.c
>+++ b/fs/overlayfs/super.c
>@@ -529,8 +529,7 @@ static int ovl_remount(struct super_block *sb, int
>*flags, char *data)
> {
> struct ovl_fs *ufs = sb->s_fs_info;
>
>- if (!(*flags & MS_RDONLY) &&
>- (!ufs->upper_mnt || (ufs->upper_mnt->mnt_sb->s_flags &
>MS_RDONLY)))
>+ if (!(*flags & MS_RDONLY) && (!ufs->upper_mnt))
> return -EROFS;
>
> return 0;
>@@ -619,6 +618,15 @@ static int ovl_parse_opt(char *opt, struct
>ovl_config *config)
> return -EINVAL;
> }
> }
>+
>+ /* Workdir is useless in non-upper mount */
>+ if (!config->upperdir && config->workdir) {
>+ pr_info("overlayfs: option \"workdir=%s\" is useless in a non-upper
>mount, ignore\n",
>+ config->workdir);
>+ kfree(config->workdir);
>+ config->workdir = NULL;
>+ }
>+
> return 0;
> }
>
>@@ -838,7 +846,6 @@ static int ovl_fill_super(struct super_block *sb,
>void *data, int silent)
>
> sb->s_stack_depth = 0;
> if (ufs->config.upperdir) {
>- /* FIXME: workdir is not needed for a R/O mount */
> if (!ufs->config.workdir) {
> pr_err("overlayfs: missing 'workdir'\n");
> goto out_free_config;
>@@ -848,6 +855,13 @@ static int ovl_fill_super(struct super_block *sb,
>void *data, int silent)
> if (err)
> goto out_free_config;
>
>+ /* Upper fs should not be r/o */
>+ if (upperpath.mnt->mnt_sb->s_flags & MS_RDONLY) {
>+ pr_err("overlayfs: upper fs is r/o, try multi-lower layers
>mount\n");
>+ err = -EINVAL;
>+ goto out_put_upperpath;
>+ }
>+
> err = ovl_mount_dir(ufs->config.workdir, &workpath);
> if (err)
> goto out_put_upperpath;
>@@ -939,8 +953,8 @@ static int ovl_fill_super(struct super_block *sb,
>void *data, int silent)
> ufs->numlower++;
> }
>
>- /* If the upper fs is r/o or nonexistent, we mark overlayfs r/o too
>*/
>- if (!ufs->upper_mnt || (ufs->upper_mnt->mnt_sb->s_flags & MS_RDONLY))
>+ /* If the upper fs is nonexistent, we mark overlayfs r/o too */
>+ if (!ufs->upper_mnt)
> sb->s_flags |= MS_RDONLY;
>
> sb->s_d_op = &ovl_dentry_operations;
It works fine to me.
And I think it is better than my implementation : )
Thanks.
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