Add a sanity check to del_gendisk to do nothing when the disk wasn't
successfully added.  This papers over the complete lack of add_disk
error handling, which is about to get fixed gradually.
Signed-off-by: NChristoph Hellwig <hch@lst.de>
Reviewed-by: NHannes Reinecke <hare@suse.de>
Link: https://lore.kernel.org/r/20210818144542.19305-2-hch@lst.deSigned-off-by: NJens Axboe <axboe@kernel.dk>

Replace the magic lookup through the kobject tree with an explicit
backpointer, given that the device model links are set up and torn
down at times when I/O is still possible, leading to potential
NULL or invalid pointer dereferences.

Fixes: edb0872f ("block: move the bdi from the request_queue to the gendisk")
Reported-by: Nsyzbot <syzbot+aa0801b6b32dca9dda82@syzkaller.appspotmail.com>
Signed-off-by: NChristoph Hellwig <hch@lst.de>
Tested-by: NSven Schnelle <svens@linux.ibm.com>
Link: https://lore.kernel.org/r/20210816134624.GA24234@lst.deSigned-off-by: NJens Axboe <axboe@kernel.dk>

Acquire the queue ref dropped in disk_release in __blk_alloc_disk so any
allocate gendisk always has a queue reference.
Signed-off-by: NChristoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20210816131910.615153-9-hch@lst.deSigned-off-by: NJens Axboe <axboe@kernel.dk>

Pass in a request_queue and assign disk->queue in __blk_alloc_disk to
ensure struct gendisk always has a valid ->queue pointer.
Signed-off-by: NChristoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20210816131910.615153-8-hch@lst.deSigned-off-by: NJens Axboe <axboe@kernel.dk>

This was a leftover from the legacy alloc_disk interface.  Switch
the scsi ULPs and dasd to set ->minors directly like all other
drivers and remove the argument.
Signed-off-by: NChristoph Hellwig <hch@lst.de>
Reviewed-by: Stefan Haberland <sth@linux.ibm.com>	[dasd]
Link: https://lore.kernel.org/r/20210816131910.615153-7-hch@lst.deSigned-off-by: NJens Axboe <axboe@kernel.dk>

Pass the lockdep name to the low-level __blk_alloc_disk helper and
hardcode the name for it given that the number of minors or node_id
are not very useful information.  While this passes a pointless
argument for non-lockdep builds that is not really an issue as
disk allocation is a probe time only slow path.
Signed-off-by: NChristoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20210816131910.615153-5-hch@lst.deSigned-off-by: NJens Axboe <axboe@kernel.dk>

inode_detach_wb references the "main" bdi of the inode.  With the
recent change to move the bdi from the request_queue to the gendisk
this causes a guaranteed use after free when using certain cgroup
configurations.  The big itself is older through as any non-default
inode reference (e.g. an open file descriptor) could have injected
this use after free even before that.

Fixes: 52ebea74 ("writeback: make backing_dev_info host cgroup-specific bdi_writebacks")
Reported-by: NQian Cai <quic_qiancai@quicinc.com>
Reported-by: Nsyzbot <syzbot+1fb38bb7d3ce0fa3e1c4@syzkaller.appspotmail.com>
Signed-off-by: NChristoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20210816122614.601358-3-hch@lst.deSigned-off-by: NJens Axboe <axboe@kernel.dk>

The dev_t is used as the inode hash, so we should only released it
once then block device inode is gone from the inode cache.  Move it
to bdev_free_inode to ensure that.
Signed-off-by: NChristoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20210816122614.601358-2-hch@lst.deSigned-off-by: NJens Axboe <axboe@kernel.dk>

Just check inode_unhashed on the whole device bdev inode instead,
and provide a helper to check for that information.
Signed-off-by: NChristoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20210809064028.1198327-9-hch@lst.deSigned-off-by: NJens Axboe <axboe@kernel.dk>

The backing device information only makes sense for file system I/O,
and thus belongs into the gendisk and not the lower level request_queue
structure.  Move it there.
Signed-off-by: NChristoph Hellwig <hch@lst.de>
Reviewed-by: NJohannes Thumshirn <johannes.thumshirn@wdc.com>
Link: https://lore.kernel.org/r/20210809141744.1203023-5-hch@lst.deSigned-off-by: NJens Axboe <axboe@kernel.dk>

Now that device mapper has been changed to register the disk once
it is fully ready all this code is unused.
Signed-off-by: NChristoph Hellwig <hch@lst.de>
Reviewed-by: NMike Snitzer <snitzer@redhat.com>
Link: https://lore.kernel.org/r/20210804094147.459763-9-hch@lst.deSigned-off-by: NJens Axboe <axboe@kernel.dk>

device mapper needs to register holders before it is ready to do I/O.
Currently it does so by registering the disk early, which can leave
the disk and queue in a weird half state where the queue is registered
with the disk, except for sysfs and the elevator.  And this state has
been a bit promlematic before, and will get more so when sorting out
the responsibilities between the queue and the disk.

Support registering holders on an initialized but not registered disk
instead by delaying the sysfs registration until the disk is registered.
Signed-off-by: NChristoph Hellwig <hch@lst.de>
Reviewed-by: NMike Snitzer <snitzer@redhat.com>
Link: https://lore.kernel.org/r/20210804094147.459763-5-hch@lst.deSigned-off-by: NJens Axboe <axboe@kernel.dk>

Invert they way the holder relations are tracked.  This very
slightly reduces the memory overhead for partitioned devices.
Signed-off-by: NChristoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20210804094147.459763-4-hch@lst.deSigned-off-by: NJens Axboe <axboe@kernel.dk>

Add a new sysfs handle to export the new diskseq value.
Place it in <sysfs>/block/<disk>/diskseq and document it.

    $ grep . /sys/class/block/*/diskseq
    /sys/class/block/loop0/diskseq:13
    /sys/class/block/loop1/diskseq:14
    /sys/class/block/loop2/diskseq:5
    /sys/class/block/loop3/diskseq:6
    /sys/class/block/ram0/diskseq:1
    /sys/class/block/ram1/diskseq:2
    /sys/class/block/vda/diskseq:7
Reviewed-by: NChristoph Hellwig <hch@lst.de>
Signed-off-by: NMatteo Croce <mcroce@microsoft.com>
Tested-by: NLuca Boccassi <bluca@debian.org>
Link: https://lore.kernel.org/r/20210712230530.29323-5-mcroce@linux.microsoft.comSigned-off-by: NJens Axboe <axboe@kernel.dk>

Export the newly introduced diskseq in uevents:

    $ udevadm info /sys/class/block/* |grep -e DEVNAME -e DISKSEQ
    E: DEVNAME=/dev/loop0
    E: DISKSEQ=1
    E: DEVNAME=/dev/loop1
    E: DISKSEQ=2
    E: DEVNAME=/dev/loop2
    E: DISKSEQ=3
    E: DEVNAME=/dev/loop3
    E: DISKSEQ=4
    E: DEVNAME=/dev/loop4
    E: DISKSEQ=5
    E: DEVNAME=/dev/loop5
    E: DISKSEQ=6
    E: DEVNAME=/dev/loop6
    E: DISKSEQ=7
    E: DEVNAME=/dev/loop7
    E: DISKSEQ=8
    E: DEVNAME=/dev/nvme0n1
    E: DISKSEQ=9
    E: DEVNAME=/dev/nvme0n1p1
    E: DISKSEQ=9
    E: DEVNAME=/dev/nvme0n1p2
    E: DISKSEQ=9
    E: DEVNAME=/dev/nvme0n1p3
    E: DISKSEQ=9
    E: DEVNAME=/dev/nvme0n1p4
    E: DISKSEQ=9
    E: DEVNAME=/dev/nvme0n1p5
    E: DISKSEQ=9
    E: DEVNAME=/dev/sda
    E: DISKSEQ=10
    E: DEVNAME=/dev/sda1
    E: DISKSEQ=10
    E: DEVNAME=/dev/sda2
    E: DISKSEQ=10
Reviewed-by: NChristoph Hellwig <hch@lst.de>
Signed-off-by: NMatteo Croce <mcroce@microsoft.com>
Tested-by: NLuca Boccassi <bluca@debian.org>
Link: https://lore.kernel.org/r/20210712230530.29323-3-mcroce@linux.microsoft.comSigned-off-by: NJens Axboe <axboe@kernel.dk>

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: NChristoph Hellwig <hch@lst.de>
Signed-off-by: NMatteo Croce <mcroce@microsoft.com>
Tested-by: NLuca Boccassi <bluca@debian.org>
Link: https://lore.kernel.org/r/20210712230530.29323-2-mcroce@linux.microsoft.comSigned-off-by: NJens Axboe <axboe@kernel.dk>

Remove the disk_name function now that all users are gone.
Signed-off-by: NChristoph Hellwig <hch@lst.de>
Reviewed-by: NMartin K. Petersen <martin.petersen@oracle.com>
Link: https://lore.kernel.org/r/20210727062518.122108-7-hch@lst.deSigned-off-by: NJens Axboe <axboe@kernel.dk>

Simplify printing the partition name by using the %pg format specifier
that is equivalent to a bdevname call.
Signed-off-by: NChristoph Hellwig <hch@lst.de>
Reviewed-by: NMartin K. Petersen <martin.petersen@oracle.com>
Link: https://lore.kernel.org/r/20210727062518.122108-4-hch@lst.deSigned-off-by: NJens Axboe <axboe@kernel.dk>

Simplify printing the partition name by using the %pg format specifier
that is equivalent to a bdevname call.
Signed-off-by: NChristoph Hellwig <hch@lst.de>
Reviewed-by: NMartin K. Petersen <martin.petersen@oracle.com>
Link: https://lore.kernel.org/r/20210727062518.122108-3-hch@lst.deSigned-off-by: NJens Axboe <axboe@kernel.dk>

I have compiled the kernel with a cross compiler "hppa-linux-gnu-" v9.3.0
on x86-64 host machine. I got the following warning:

block/genhd.c: In function ‘diskstats_show’:
block/genhd.c:1227:1: warning: the frame size of 1688 bytes is larger
than 1280 bytes [-Wframe-larger-than=]
 1227  |  }

By Reduced the stack footprint by using the %pg printk specifier instead
of disk_name to remove the need for the on-stack buffer.
Signed-off-by: NAbd-Alrhman Masalkhi <abd.masalkhi@gmail.com>
Signed-off-by: NChristoph Hellwig <hch@lst.de>
Reviewed-by: NHannes Reinecke <hare@suse.de>
Reviewed-by: NMartin K. Petersen <martin.petersen@oracle.com>
Link: https://lore.kernel.org/r/20210727062518.122108-2-hch@lst.deSigned-off-by: NJens Axboe <axboe@kernel.dk>

Now that we've stopped using inode references for anything meaninful
in the block layer get rid of the helper to put it and just open code
the call to iput on the block_device inode.
Signed-off-by: NChristoph Hellwig <hch@lst.de>
Reviewed-by: NJosef Bacik <josef@toxicpanda.com>
Reviewed-by: NChaitanya Kulkarni <ckulkarnilinux@gmail.com>
Link: https://lore.kernel.org/r/20210722075402.983367-10-hch@lst.deSigned-off-by: NJens Axboe <axboe@kernel.dk>

Unhash the whole device inode early in del_gendisk.  This allows to
remove the first GENHD_FL_UP check in the open path as we simply
won't find a just removed inode.  The second non-racy check after
taking open_mutex is still kept.
Signed-off-by: NChristoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20210722075402.983367-4-hch@lst.deSigned-off-by: NJens Axboe <axboe@kernel.dk>

blkdev_get_no_open acquires a reference to the block_device through
the block device inode and then tries to acquire a device model
reference to the gendisk.  But at this point the disk migh already
be freed (although the race is free).  Fix this by only freeing the
gendisk from the whole device bdevs ->free_inode callback as well.

Fixes: 22ae8ce8 ("block: simplify bdev/disk lookup in blkdev_get")
Signed-off-by: NChristoph Hellwig <hch@lst.de>
Reviewed-by: NJosef Bacik <josef@toxicpanda.com>
Reviewed-by: NMing Lei <ming.lei@redhat.com>
Link: https://lore.kernel.org/r/20210722075402.983367-2-hch@lst.deSigned-off-by: NJens Axboe <axboe@kernel.dk>

Sending uevents requires the struct device to be alive.  To
ensure that grab the device refcount instead of just an inode
reference.

Fixes: bc359d03 ("block: add a disk_uevent helper")
Signed-off-by: NChristoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20210701081638.246552-2-hch@lst.deSigned-off-by: NJens Axboe <axboe@kernel.dk>

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: NChristoph Hellwig <hch@lst.de>
Reviewed-by: NHannes Reinecke <hare@suse.de>
Link: https://lore.kernel.org/r/20210624073843.251178-3-hch@lst.deSigned-off-by: NJens Axboe <axboe@kernel.dk>

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: NChristoph Hellwig <hch@lst.de>
Reviewed-by: NHannes Reinecke <hare@suse.de>
Link: https://lore.kernel.org/r/20210624073843.251178-2-hch@lst.deSigned-off-by: NJens Axboe <axboe@kernel.dk>

Just opencode the xa_load in the callers, as none of them actually
needs a reference to the bdev.
Signed-off-by: NChristoph Hellwig <hch@lst.de>
Reviewed-by: NHannes Reinecke <hare@suse.de>
Reviewed-by: NMing Lei <ming.lei@redhat.com>
Link: https://lore.kernel.org/r/20210525061301.2242282-9-hch@lst.deSigned-off-by: NJens Axboe <axboe@kernel.dk>

Add a helper to find the dev_t for a disk + partno tuple.
Signed-off-by: NChristoph Hellwig <hch@lst.de>
Reviewed-by: NMing Lei <ming.lei@redhat.com>
Link: https://lore.kernel.org/r/20210525061301.2242282-8-hch@lst.deSigned-off-by: NJens Axboe <axboe@kernel.dk>

Replace the per-block device bd_mutex with a per-gendisk open_mutex,
thus simplifying locking wherever we deal with partitions.
Signed-off-by: NChristoph Hellwig <hch@lst.de>
Reviewed-by: NMing Lei <ming.lei@redhat.com>
Acked-by: NRoger Pau Monné <roger.pau@citrix.com>
Link: https://lore.kernel.org/r/20210525061301.2242282-4-hch@lst.deSigned-off-by: NJens Axboe <axboe@kernel.dk>

Add two new APIs to allocate and free a gendisk including the
request_queue for use with BIO based drivers.  This is to avoid
boilerplate code in drivers.
Signed-off-by: NChristoph Hellwig <hch@lst.de>
Reviewed-by: NHannes Reinecke <hare@suse.de>
Reviewed-by: NUlf Hansson <ulf.hansson@linaro.org>
Link: https://lore.kernel.org/r/20210521055116.1053587-6-hch@lst.deSigned-off-by: NJens Axboe <axboe@kernel.dk>

Add a flag to indicate that __device_add_disk did grab a queue reference
so that disk_release only drops it if we actually had it.  This sort
out one of the major pitfals with partially initialized gendisk that
a lot of drivers did get wrong or still do.
Signed-off-by: NChristoph Hellwig <hch@lst.de>
Reviewed-by: NHannes Reinecke <hare@suse.de>
Reviewed-by: NLuis Chamberlain <mcgrof@kernel.org>
Reviewed-by: NUlf Hansson <ulf.hansson@linaro.org>
Link: https://lore.kernel.org/r/20210521055116.1053587-5-hch@lst.deSigned-off-by: NJens Axboe <axboe@kernel.dk>

Automatically set the GENHD_FL_EXT_DEVT flag for all disks allocated
without an explicit number of minors.  This is what all new block
drivers should do, so make sure it is the default without boilerplate
code.
Signed-off-by: NChristoph Hellwig <hch@lst.de>
Reviewed-by: NHannes Reinecke <hare@suse.de>
Reviewed-by: NLuis Chamberlain <mcgrof@kernel.org>
Reviewed-by: NUlf Hansson <ulf.hansson@linaro.org>
Link: https://lore.kernel.org/r/20210521055116.1053587-4-hch@lst.deSigned-off-by: NJens Axboe <axboe@kernel.dk>

Keep this together with the first place that actually looks at
->minors and prepare for not passing a minors argument to
alloc_disk.
Signed-off-by: NChristoph Hellwig <hch@lst.de>
Reviewed-by: NHannes Reinecke <hare@suse.de>
Reviewed-by: NLuis Chamberlain <mcgrof@kernel.org>
Reviewed-by: NUlf Hansson <ulf.hansson@linaro.org>
Link: https://lore.kernel.org/r/20210521055116.1053587-3-hch@lst.deSigned-off-by: NJens Axboe <axboe@kernel.dk>

Untangle the mess around blk_alloc_devt by moving the check for
the used allocation scheme into the callers.
Signed-off-by: NChristoph Hellwig <hch@lst.de>
Reviewed-by: NHannes Reinecke <hare@suse.de>
Reviewed-by: NLuis Chamberlain <mcgrof@kernel.org>
Reviewed-by: NUlf Hansson <ulf.hansson@linaro.org>
Link: https://lore.kernel.org/r/20210521055116.1053587-2-hch@lst.deSigned-off-by: NJens Axboe <axboe@kernel.dk>

As an artifact of how gendisk lookup used to work in earlier kernels,
GENHD_FL_UP is only cleared very late in del_gendisk, and a global lock
is used to prevent opens from succeeding while del_gendisk is tearing
down the gendisk.  Switch to clearing the flag early and under bd_mutex
so that callers can use bd_mutex to stabilize the flag, which removes
the need for the global mutex.
Signed-off-by: NChristoph Hellwig <hch@lst.de>
Reviewed-by: NMing Lei <ming.lei@redhat.com>
Link: https://lore.kernel.org/r/20210514131842.1600568-2-hch@lst.deSigned-off-by: NJens Axboe <axboe@kernel.dk>

Just open code the xa_for_each in the remaining user.
Signed-off-by: NChristoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20210406062303.811835-12-hch@lst.deSigned-off-by: NJens Axboe <axboe@kernel.dk>

Just use xa_for_each to iterate over the partitions as there is no need
to grab a reference to each partition.
Signed-off-by: NChristoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20210406062303.811835-11-hch@lst.deSigned-off-by: NJens Axboe <axboe@kernel.dk>

Just use xa_for_each to iterate over the partitions as there is no need
to grab a reference to each partition.
Signed-off-by: NChristoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20210406062303.811835-10-hch@lst.deSigned-off-by: NJens Axboe <axboe@kernel.dk>

Just use xa_for_each to iterate over the partitions as there is no need
to grab a reference to each partition.
Signed-off-by: NChristoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20210406062303.811835-9-hch@lst.deSigned-off-by: NJens Axboe <axboe@kernel.dk>

There is nothing preventing an ioctl from trying do delete partition
concurrenly with del_gendisk, so take open_mutex to serialize against
that.
Signed-off-by: NChristoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20210406062303.811835-6-hch@lst.deSigned-off-by: NJens Axboe <axboe@kernel.dk>