On Fri, 2017-11-17 at 11:45 -0600, Joshua Watt wrote:
> The umount_end operation allows cleaning of state set by umount_begin in
> the event the filesystem doesn't actually get unmounted.
>
> Signed-off-by: Joshua Watt <JPEWhacker@xxxxxxxxx>
> ---
> fs/namespace.c | 22 ++++++++++++++++++++--
> include/linux/fs.h | 1 +
> 2 files changed, 21 insertions(+), 2 deletions(-)
>
> diff --git a/fs/namespace.c b/fs/namespace.c
> index d18deb4c410b..d2587be4d08b 100644
> --- a/fs/namespace.c
> +++ b/fs/namespace.c
> @@ -1524,6 +1524,12 @@ static void umount_tree(struct mount *mnt, enum umount_tree_flags how)
> }
> }
>
> +static void umount_end(struct super_block *sb, int flags)
> +{
> + if (flags & MNT_FORCE && sb->s_op->umount_end)
nit: might get some complaints from compiler about order of operations
there. I'd put parenthesis around the flags & MNT_FORCE.
> + sb->s_op->umount_end(sb);
> +}
> +
> static void shrink_submounts(struct mount *mnt);
>
> static int do_umount(struct mount *mnt, int flags)
> @@ -1589,12 +1595,16 @@ static int do_umount(struct mount *mnt, int flags)
> * Special case for "unmounting" root ...
> * we just try to remount it readonly.
> */
> - if (!capable(CAP_SYS_ADMIN))
> - return -EPERM;
> + if (!capable(CAP_SYS_ADMIN)) {
> + retval = -EPERM;
> + goto out_umount_end;
> + }
> down_write(&sb->s_umount);
> if (!sb_rdonly(sb))
> retval = do_remount_sb(sb, SB_RDONLY, NULL, 0);
> up_write(&sb->s_umount);
> + /* Still mounted. Always invoke the cleanup */
> + umount_end(sb, flags);
> return retval;
> }
>
> @@ -1617,6 +1627,14 @@ static int do_umount(struct mount *mnt, int flags)
> }
> unlock_mount_hash();
> namespace_unlock();
> +
> +out_umount_end:
> + /* If the umount failed and the file system is still mounted, allow the
> + * driver to cleanup any state it may have setup in umount_begin(). Note
> + * that this is purposely *not* called when MNT_DETACH is specified.
> + */
> + if (retval)
> + umount_end(sb, flags);
> return retval;
> }
>
> diff --git a/include/linux/fs.h b/include/linux/fs.h
> index 885266aae2d7..5443c22da18f 100644
> --- a/include/linux/fs.h
> +++ b/include/linux/fs.h
> @@ -1816,6 +1816,7 @@ struct super_operations {
> int (*statfs) (struct dentry *, struct kstatfs *);
> int (*remount_fs) (struct super_block *, int *, char *);
> void (*umount_begin) (struct super_block *);
> + void (*umount_end)(struct super_block *);
>
> int (*show_options)(struct seq_file *, struct dentry *);
> int (*show_devname)(struct seq_file *, struct dentry *);
Since this involves vfs-level changes, please cc linux-fsdevel@xxxxxxxxx
el.org on further postings. Other filesystem devs may be interested in
what you're doing here.
--
Jeff Layton <jlayton@xxxxxxxxxx>
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