block: move bdev_mark_dead out of disk_check_media_change

disk_check_media_change is mostly called from ->open where it makes
little sense to mark the file system on the device as dead, as we
are just opening it. So instead of calling bdev_mark_dead from
disk_check_media_change move it into the few callers that are not
in an open instance. This avoid calling into bdev_mark_dead and
thus taking s_umount with open_mutex held.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20231017184823.1383356-4-hch@lst.de
Reviewed-by: Ming Lei <ming.lei@redhat.com>
Reviewed-by: Christian Brauner <brauner@kernel.org>
Reviewed-by: Jan Kara <jack@suse.cz>
Reviewed-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Christian Brauner <brauner@kernel.org>

block: fix kernel-doc for disk_force_media_change()

Drop one function parameter's kernel-doc comment since the parameter
was removed. This prevents a kernel-doc warning:

block/disk-events.c:300: warning: Excess function parameter 'events' description in 'disk_force_media_change'

Fixes: ab6860f62bfe ("block: simplify the disk_force_media_change interface")
Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Reported-by: kernel test robot <lkp@intel.com>
Closes: lore.kernel.org/r/202309060957.vfl0mUur-lkp@intel.com
Cc: Christoph Hellwig <hch@lst.de>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: linux-block@vger.kernel.org
Reviewed-by: Christoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20230926005232.23666-1-rdunlap@infradead.org
Signed-off-by: Jens Axboe <axboe@kernel.dk>

block: consolidate __invalidate_device and fsync_bdev

We currently have two interfaces that take a block_devices and the find
a mounted file systems to flush or invaldidate data on it. Both are a
bit problematic because they only work for the "main" block devices
that is used as s_dev for the super_block, and because they don't call
into the file system at all.

Merge the two into a new bdev_mark_dead helper that does both the
syncing and invalidation and which is properly documented. This is
in preparation of merging the functionality into the ->mark_dead
holder operation so that it will work on additional block devices
used by a file systems and give us a single entry point for invalidation
of dead devices or media.

Note that a single standalone fsync_bdev call for an obscure ioctl
remains for now, but that one will also be deal with in a bit.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Message-Id: <20230811100828.1897174-14-hch@lst.de>
Signed-off-by: Christian Brauner <brauner@kernel.org>

block: drop the "busy inodes on changed media" log message

This message isn't exactly helpful, and file systems already print way more
useful messages when shut down while active.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Message-Id: <20230811100828.1897174-13-hch@lst.de>
Signed-off-by: Christian Brauner <brauner@kernel.org>

block: simplify the disk_force_media_change interface

Hard code the events to DISK_EVENT_MEDIA_CHANGE as that is the only
useful use case, and drop the superfluous return value.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Message-Id: <20230811100828.1897174-9-hch@lst.de>
Signed-off-by: Christian Brauner <brauner@kernel.org>

block: increment diskseq on all media change events

Currently, associating a loop device with a different file descriptor
does not increment its diskseq. This allows the following race
condition:

1. Program X opens a loop device
2. Program X gets the diskseq of the loop device.
3. Program X associates a file with the loop device.
4. Program X passes the loop device major, minor, and diskseq to
something.
5. Program X exits.
6. Program Y detaches the file from the loop device.
7. Program Y attaches a different file to the loop device.
8. The opener finally gets around to opening the loop device and checks
that the diskseq is what it expects it to be. Even though the
diskseq is the expected value, the result is that the opener is
accessing the wrong file.

From discussions with Christoph Hellwig, it appears that
disk_force_media_change() was supposed to call inc_diskseq(), but in
fact it does not. Adding a Fixes: tag to indicate this. Christoph's
Reported-by is because he stated that disk_force_media_change()
calls inc_diskseq(), which is what led me to discover that it should but
does not.

Reported-by: Christoph Hellwig <hch@infradead.org>
Signed-off-by: Demi Marie Obenour <demi@invisiblethingslab.com>
Fixes: e6138dc12de9 ("block: add a helper to raise a media changed event")
Cc: stable@vger.kernel.org # 5.15+
Reviewed-by: Christoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20230607170837.1559-1-demi@invisiblethingslab.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>

block: pass a gendisk on bdev_check_media_change

bdev_check_media_change should only ever be called for the whole device.
Pass a gendisk to make that explicit and rename the function to
disk_check_media_change.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Hannes Reinecke <hare@suse.de>
Acked-by: Christian Brauner <brauner@kernel.org>
Link: https://lore.kernel.org/r/20230608110258.189493-8-hch@lst.de
Signed-off-by: Jens Axboe <axboe@kernel.dk>

block: remove genhd.h

There is no good reason to keep genhd.h separate from the main blkdev.h
header that includes it. So fold the contents of genhd.h into blkdev.h
and remove genhd.h entirely.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Chaitanya Kulkarni <kch@nvidia.com>
Reviewed-by: Martin K. Petersen <martin.petersen@oracle.com>
Link: https://lore.kernel.org/r/20220124093913.742411-4-hch@lst.de
Signed-off-by: Jens Axboe <axboe@kernel.dk>

block: return errors from disk_alloc_events

Prepare for proper error handling in add_disk.

Signed-off-by: Luis Chamberlain <mcgrof@kernel.org>
[hch: split from a larger patch]
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Hannes Reinecke <hare@suse.de>
Link: https://lore.kernel.org/r/20210818144542.19305-9-hch@lst.de
Signed-off-by: Jens Axboe <axboe@kernel.dk>

block: add a helper to raise a media changed event

Refactor disk_check_events() and move some code into disk_event_uevent().
Then add disk_force_media_change(), a helper which will be used by
devices to force issuing a DISK_EVENT_MEDIA_CHANGE event.

Co-developed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Matteo Croce <mcroce@microsoft.com>
Tested-by: Luca Boccassi <bluca@debian.org>
Link: https://lore.kernel.org/r/20210712230530.29323-6-mcroce@linux.microsoft.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>

block: add disk sequence number

Associating uevents with block devices in userspace is difficult and racy:
the uevent netlink socket is lossy, and on slow and overloaded systems
has a very high latency.
Block devices do not have exclusive owners in userspace, any process can
set one up (e.g. loop devices). Moreover, device names can be reused
(e.g. loop0 can be reused again and again). A userspace process setting
up a block device and watching for its events cannot thus reliably tell
whether an event relates to the device it just set up or another earlier
instance with the same name.

Being able to set a UUID on a loop device would solve the race conditions.
But it does not allow to derive orderings from uevents: if you see a
uevent with a UUID that does not match the device you are waiting for,
you cannot tell whether it's because the right uevent has not arrived yet,
or it was already sent and you missed it. So you cannot tell whether you
should wait for it or not.

Associating a unique, monotonically increasing sequential number to the
lifetime of each block device, which can be retrieved with an ioctl
immediately upon setting it up, allows to solve the race conditions with
uevents, and also allows userspace processes to know whether they should
wait for the uevent they need or if it was dropped and thus they should
move on.

Additionally, increment the disk sequence number when the media change,
i.e. on DISK_EVENT_MEDIA_CHANGE event.

Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Matteo Croce <mcroce@microsoft.com>
Tested-by: Luca Boccassi <bluca@debian.org>
Link: https://lore.kernel.org/r/20210712230530.29323-2-mcroce@linux.microsoft.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>

block: add the events* attributes to disk_attrs

Add the events attributes to the disk_attrs array, which ensures they are
added by the driver core when the device is created rather than adding
them after the device has been added, which is racy versus uevents and
requires more boilerplate code.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Hannes Reinecke <hare@suse.de>
Link: https://lore.kernel.org/r/20210624073843.251178-3-hch@lst.de
Signed-off-by: Jens Axboe <axboe@kernel.dk>

block: move the disk events code to a separate file

Move the code for handling disk events from genhd.c into a new file
as it isn't very related to the rest of the file while at the same
time requiring lots of forward declarations.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Hannes Reinecke <hare@suse.de>
Link: https://lore.kernel.org/r/20210624073843.251178-2-hch@lst.de
Signed-off-by: Jens Axboe <axboe@kernel.dk>