On Fri, Nov 27, 2020 at 01:20:58AM -0800, Sargun Dhillon wrote:
> Volatile remounts validate the following at the moment:
> * Has the module been reloaded / the system rebooted
> * Has the workdir been remounted
>
> This adds a new check for errors detected via the superblock's
> errseq_t. At mount time, the errseq_t is snapshotted to disk,
> and upon remount it's re-verified. This allows for kernel-level
> detection of errors without forcing userspace to perform a
> sync and allows for the hidden detection of writeback errors.
>
> Signed-off-by: Sargun Dhillon <sargun@xxxxxxxxx>
> Cc: linux-fsdevel@xxxxxxxxxxxxxxx
> Cc: linux-unionfs@xxxxxxxxxxxxxxx
> Cc: Miklos Szeredi <miklos@xxxxxxxxxx>
> Cc: Amir Goldstein <amir73il@xxxxxxxxx>
> Cc: Vivek Goyal <vgoyal@xxxxxxxxxx>
> ---
> fs/overlayfs/overlayfs.h | 1 +
> fs/overlayfs/readdir.c | 6 ++++++
> fs/overlayfs/super.c | 1 +
> 3 files changed, 8 insertions(+)
>
> diff --git a/fs/overlayfs/overlayfs.h b/fs/overlayfs/overlayfs.h
> index de694ee99d7c..e8a711953b64 100644
> --- a/fs/overlayfs/overlayfs.h
> +++ b/fs/overlayfs/overlayfs.h
> @@ -85,6 +85,7 @@ struct ovl_volatile_info {
> */
> uuid_t ovl_boot_id; /* Must stay first member */
> u64 s_instance_id;
> + errseq_t errseq; /* Implemented as a u32 */
> } __packed;
>
> /*
> diff --git a/fs/overlayfs/readdir.c b/fs/overlayfs/readdir.c
> index 7b66fbb20261..5795b28bb4cf 100644
> --- a/fs/overlayfs/readdir.c
> +++ b/fs/overlayfs/readdir.c
> @@ -1117,6 +1117,12 @@ static int ovl_verify_volatile_info(struct ovl_fs *ofs,
> return -EINVAL;
> }
>
> + err = errseq_check(&volatiledir->d_sb->s_wb_err, info.errseq);
> + if (err) {
> + pr_debug("Workdir filesystem reports errors: %d\n", err);
It probably will make sense to make it pr_err() instead? Will be good
to know if kernel logic detected errors.
Thanks
Vivek
