On Mon, Jun 24, 2019 at 03:10:06PM +0100, David Howells wrote: > Add a notification count on mount objects so that the user can easily check > to see if a mount has changed its attributes or its children. > > Future patches will: > > (1) Provide this value through fsinfo() attributes. > > (2) Hook into the notify_mount() function to provide a notification > interface for userspace to monitor.
Sorry, I might have missed this. Is this based on your notification patchset and thus presupposing that your notification patchset has been merged? (One further question below.) > > Signed-off-by: David Howells <[email protected]> > --- > > fs/mount.h | 22 ++++++++++++++++++++++ > fs/namespace.c | 13 +++++++++++++ > 2 files changed, 35 insertions(+) > > diff --git a/fs/mount.h b/fs/mount.h > index 6250de544760..47795802f78e 100644 > --- a/fs/mount.h > +++ b/fs/mount.h > @@ -70,6 +70,7 @@ struct mount { > struct hlist_head mnt_pins; > struct fs_pin mnt_umount; > struct dentry *mnt_ex_mountpoint; > + atomic_t mnt_notify_counter; /* Number of notifications generated */ > } __randomize_layout; > > #define MNT_NS_INTERNAL ERR_PTR(-EINVAL) /* distinct from any mnt_namespace > */ > @@ -151,3 +152,24 @@ static inline bool is_anon_ns(struct mnt_namespace *ns) > { > return ns->seq == 0; > } > + > +/* > + * Type of mount topology change notification. > + */ > +enum mount_notification_subtype { > + NOTIFY_MOUNT_NEW_MOUNT = 0, /* New mount added */ > + NOTIFY_MOUNT_UNMOUNT = 1, /* Mount removed manually */ > + NOTIFY_MOUNT_EXPIRY = 2, /* Automount expired */ > + NOTIFY_MOUNT_READONLY = 3, /* Mount R/O state changed */ > + NOTIFY_MOUNT_SETATTR = 4, /* Mount attributes changed */ > + NOTIFY_MOUNT_MOVE_FROM = 5, /* Mount moved from here */ > + NOTIFY_MOUNT_MOVE_TO = 6, /* Mount moved to here (compare op_id) */ > +}; > + > +static inline void notify_mount(struct mount *changed, > + struct mount *aux, > + enum mount_notification_subtype subtype, > + u32 info_flags) > +{ > + atomic_inc(&changed->mnt_notify_counter); > +} > diff --git a/fs/namespace.c b/fs/namespace.c > index a49a7d9ed482..1450faab96b9 100644 > --- a/fs/namespace.c > +++ b/fs/namespace.c > @@ -513,6 +513,8 @@ static int mnt_make_readonly(struct mount *mnt) > smp_wmb(); > mnt->mnt.mnt_flags &= ~MNT_WRITE_HOLD; > unlock_mount_hash(); > + if (ret == 0) > + notify_mount(mnt, NULL, NOTIFY_MOUNT_READONLY, 0x10000); > return ret; > } > > @@ -521,6 +523,7 @@ static int __mnt_unmake_readonly(struct mount *mnt) > lock_mount_hash(); > mnt->mnt.mnt_flags &= ~MNT_READONLY; > unlock_mount_hash(); > + notify_mount(mnt, NULL, NOTIFY_MOUNT_READONLY, 0); > return 0; > } > > @@ -833,6 +836,7 @@ static void umount_mnt(struct mount *mnt) > { > /* old mountpoint will be dropped when we can do that */ > mnt->mnt_ex_mountpoint = mnt->mnt_mountpoint; > + notify_mount(mnt->mnt_parent, mnt, NOTIFY_MOUNT_UNMOUNT, 0); > unhash_mnt(mnt); > } > > @@ -1472,6 +1476,7 @@ static void umount_tree(struct mount *mnt, enum > umount_tree_flags how) > p = list_first_entry(&tmp_list, struct mount, mnt_list); > list_del_init(&p->mnt_expire); > list_del_init(&p->mnt_list); > + > ns = p->mnt_ns; > if (ns) { > ns->mounts--; > @@ -2095,7 +2100,10 @@ static int attach_recursive_mnt(struct mount > *source_mnt, > lock_mount_hash(); > } > if (parent_path) { > + notify_mount(source_mnt->mnt_parent, source_mnt, > + NOTIFY_MOUNT_MOVE_FROM, 0); > detach_mnt(source_mnt, parent_path); > + notify_mount(dest_mnt, source_mnt, NOTIFY_MOUNT_MOVE_TO, 0); > attach_mnt(source_mnt, dest_mnt, dest_mp); > touch_mnt_namespace(source_mnt->mnt_ns); > } else { > @@ -2104,6 +2112,9 @@ static int attach_recursive_mnt(struct mount > *source_mnt, > list_del_init(&source_mnt->mnt_ns->list); > } > mnt_set_mountpoint(dest_mnt, dest_mp, source_mnt); > + notify_mount(dest_mnt, source_mnt, NOTIFY_MOUNT_NEW_MOUNT, > + source_mnt->mnt.mnt_sb->s_flags & SB_SUBMOUNT ? > + 0x10000 : 0); What's that magic 0x10000 mean? > commit_tree(source_mnt); > } > > @@ -2480,6 +2491,7 @@ static void set_mount_attributes(struct mount *mnt, > unsigned int mnt_flags) > mnt->mnt.mnt_flags = mnt_flags; > touch_mnt_namespace(mnt->mnt_ns); > unlock_mount_hash(); > + notify_mount(mnt, NULL, NOTIFY_MOUNT_SETATTR, 0); > } > > /* > @@ -2880,6 +2892,7 @@ void mark_mounts_for_expiry(struct list_head *mounts) > if (!xchg(&mnt->mnt_expiry_mark, 1) || > propagate_mount_busy(mnt, 1)) > continue; > + notify_mount(mnt, NULL, NOTIFY_MOUNT_EXPIRY, 0); > list_move(&mnt->mnt_expire, &graveyard); > } > while (!list_empty(&graveyard)) { >
