| Message ID | 156173703546.15650.14319137940607993268.stgit@warthog.procyon.org.uk (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | Mount and superblock notifications [ver #5] | expand |
Hi David, On 6/28/19 8:50 AM, David Howells wrote: > Signed-off-by: David Howells <dhowells@redhat.com> > --- > > Documentation/watch_queue.rst | 20 +++++++++++++++++++- > drivers/misc/Kconfig | 5 +++-- > 2 files changed, 22 insertions(+), 3 deletions(-) > > diff --git a/Documentation/watch_queue.rst b/Documentation/watch_queue.rst > index 4087a8e670a8..1bec2018d549 100644 > --- a/Documentation/watch_queue.rst > +++ b/Documentation/watch_queue.rst > @@ -13,6 +13,10 @@ receive notifications from the kernel. This can be used in conjunction with:: > > * USB subsystem event notifications > > + * Mount topology change notifications > + > + * Superblock event notifications > + > > The notifications buffers can be enabled by: > > @@ -324,6 +328,19 @@ Any particular buffer can be fed from multiple sources. Sources include: > for buses and devices. Watchpoints of this type are set on the global > device watch list. > > + * WATCH_TYPE_MOUNT_NOTIFY > + > + Notifications of this type indicate mount tree topology changes and mount > + attribute changes. A watch can be set on a particular file or directory > + and notifications from the path subtree rooted at that point will be > + intercepted. > + > + * WATCH_TYPE_SB_NOTIFY > + > + Notifications of this type indicate superblock events, such as quota limits > + being hit, I/O errors being produced or network server loss/reconnection. > + Watches of this type are set directly on superblocks. > + > > Event Filtering > =============== > @@ -365,7 +382,8 @@ Where: > (watch.info & info_mask) == info_filter > > This could be used, for example, to ignore events that are not exactly on > - the watched point in a mount tree. > + the watched point in a mount tree by specifying NOTIFY_MOUNT_IN_SUBTREE > + must be 0. I'm having a little trouble parsing that sentence. Could you clarify it or maybe rewrite/modify it? Thanks. > > * ``subtype_filter`` is a bitmask indicating the subtypes that are of > interest. Bit 0 of subtype_filter[0] corresponds to subtype 0, bit 1 to
Randy Dunlap <rdunlap@infradead.org> wrote: > I'm having a little trouble parsing that sentence. > Could you clarify it or maybe rewrite/modify it? > Thanks. How about: * ``info_filter`` and ``info_mask`` act as a filter on the info field of the notification record. The notification is only written into the buffer if:: (watch.info & info_mask) == info_filter This could be used, for example, to ignore events that are not exactly on the watched point in a mount tree by specifying NOTIFY_MOUNT_IN_SUBTREE must not be set, e.g.:: { .type = WATCH_TYPE_MOUNT_NOTIFY, .info_filter = 0, .info_mask = NOTIFY_MOUNT_IN_SUBTREE, .subtype_filter = ..., } as an event would be only permissible with this filter if:: (watch.info & NOTIFY_MOUNT_IN_SUBTREE) == 0 David
On 7/1/19 1:52 AM, David Howells wrote: > Randy Dunlap <rdunlap@infradead.org> wrote: > >> I'm having a little trouble parsing that sentence. >> Could you clarify it or maybe rewrite/modify it? >> Thanks. > > How about: > > * ``info_filter`` and ``info_mask`` act as a filter on the info field of the > notification record. The notification is only written into the buffer if:: > > (watch.info & info_mask) == info_filter > > This could be used, for example, to ignore events that are not exactly on > the watched point in a mount tree by specifying NOTIFY_MOUNT_IN_SUBTREE > must not be set, e.g.:: > > { > .type = WATCH_TYPE_MOUNT_NOTIFY, > .info_filter = 0, > .info_mask = NOTIFY_MOUNT_IN_SUBTREE, > .subtype_filter = ..., > } > > as an event would be only permissible with this filter if:: > > (watch.info & NOTIFY_MOUNT_IN_SUBTREE) == 0 > > David > Yes, better. Thanks.
diff --git a/Documentation/watch_queue.rst b/Documentation/watch_queue.rst index 4087a8e670a8..1bec2018d549 100644 --- a/Documentation/watch_queue.rst +++ b/Documentation/watch_queue.rst @@ -13,6 +13,10 @@ receive notifications from the kernel. This can be used in conjunction with:: * USB subsystem event notifications + * Mount topology change notifications + + * Superblock event notifications + The notifications buffers can be enabled by: @@ -324,6 +328,19 @@ Any particular buffer can be fed from multiple sources. Sources include: for buses and devices. Watchpoints of this type are set on the global device watch list. + * WATCH_TYPE_MOUNT_NOTIFY + + Notifications of this type indicate mount tree topology changes and mount + attribute changes. A watch can be set on a particular file or directory + and notifications from the path subtree rooted at that point will be + intercepted. + + * WATCH_TYPE_SB_NOTIFY + + Notifications of this type indicate superblock events, such as quota limits + being hit, I/O errors being produced or network server loss/reconnection. + Watches of this type are set directly on superblocks. + Event Filtering =============== @@ -365,7 +382,8 @@ Where: (watch.info & info_mask) == info_filter This could be used, for example, to ignore events that are not exactly on - the watched point in a mount tree. + the watched point in a mount tree by specifying NOTIFY_MOUNT_IN_SUBTREE + must be 0. * ``subtype_filter`` is a bitmask indicating the subtypes that are of interest. Bit 0 of subtype_filter[0] corresponds to subtype 0, bit 1 to diff --git a/drivers/misc/Kconfig b/drivers/misc/Kconfig index e53f88783fe7..8b13103b17c0 100644 --- a/drivers/misc/Kconfig +++ b/drivers/misc/Kconfig @@ -11,8 +11,9 @@ config WATCH_QUEUE help This is a general notification queue for the kernel to pass events to userspace through a mmap()'able ring buffer. It can be used in - conjunction with watches for key/keyring change notifications and device - notifications. + conjunction with watches for key/keyring change notifications, device + notifications, mount topology change notifications, and superblock + change notifications. Note that in theory this should work fine with NOMMU, but I'm not sure how to make that work.
Signed-off-by: David Howells <dhowells@redhat.com> --- Documentation/watch_queue.rst | 20 +++++++++++++++++++- drivers/misc/Kconfig | 5 +++-- 2 files changed, 22 insertions(+), 3 deletions(-)