kernel/linux.git/block/disk-events.c, branch v6.6.141

loop: fix partition scan race between udev and loop_reread_partitions()

2026-05-23T11:03:05+00:00

[ Upstream commit 267ec4d7223a783f029a980f41b93c39b17996da ] When LOOP_CONFIGURE is called with LO_FLAGS_PARTSCAN, the following sequence occurs: 1. disk_force_media_change() sets GD_NEED_PART_SCAN 2. Uevent suppression is lifted and a KOBJ_CHANGE uevent is sent 3. loop_global_unlock() releases the lock 4. loop_reread_partitions() calls bdev_disk_changed() to scan There is a race between steps 2 and 4: when udev receives the uevent and opens the device before loop_reread_partitions() runs, blkdev_get_whole() in bdev.c sees GD_NEED_PART_SCAN set and calls bdev_disk_changed() for a first scan. Then loop_reread_partitions() does a second scan. The open_mutex serializes these two scans, but does not prevent both from running. The second scan in bdev_disk_changed() drops all partition devices from the first scan (via blk_drop_partitions()) before re-adding them, causing partition block devices to briefly disappear. This breaks any systemd unit with BindsTo= on the partition device: systemd observes the device going dead, fails the dependent units, and does not retry them when the device reappears. Fix this by removing the GD_NEED_PART_SCAN set from disk_force_media_change() entirely. None of the current callers need the lazy on-open partition scan triggered by this flag: - floppy: sets GENHD_FL_NO_PART, so disk_has_partscan() is always false and GD_NEED_PART_SCAN has no effect. - loop (loop_configure, loop_change_fd): when LO_FLAGS_PARTSCAN is set, loop_reread_partitions() performs an explicit scan. When not set, GD_SUPPRESS_PART_SCAN prevents the lazy scan path. - loop (__loop_clr_fd): calls bdev_disk_changed() explicitly if LO_FLAGS_PARTSCAN is set. - nbd (nbd_clear_sock_ioctl): capacity is set to zero immediately after; nbd manages GD_NEED_PART_SCAN explicitly elsewhere. With GD_NEED_PART_SCAN no longer set by disk_force_media_change(), udev opening the loop device after the uevent no longer triggers a redundant scan in blkdev_get_whole(), and only the single explicit scan from loop_reread_partitions() runs. A regression test for this bug has been submitted to blktests: https://github.com/linux-blktests/blktests/pull/240. Fixes: 9f65c489b68d ("loop: raise media_change event") Signed-off-by: Daan De Meyer Acked-by: Christian Brauner Link: https://patch.msgid.link/20260331105130.1077599-1-daan@amutable.com Signed-off-by: Jens Axboe Signed-off-by: Sasha Levin

block: fix kernel-doc for disk_force_media_change()

2023-09-26T06:43:34+00:00

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 Reported-by: kernel test robot Closes: lore.kernel.org/r/202309060957.vfl0mUur-lkp@intel.com Cc: Christoph Hellwig Cc: Jens Axboe Cc: linux-block@vger.kernel.org Reviewed-by: Christoph Hellwig Link: https://lore.kernel.org/r/20230926005232.23666-1-rdunlap@infradead.org Signed-off-by: Jens Axboe

block: consolidate __invalidate_device and fsync_bdev

2023-08-21T12:35:31+00:00

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 Reviewed-by: Josef Bacik Message-Id: <20230811100828.1897174-14-hch@lst.de> Signed-off-by: Christian Brauner

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

2023-08-21T12:35:31+00:00

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 Reviewed-by: Josef Bacik Message-Id: <20230811100828.1897174-13-hch@lst.de> Signed-off-by: Christian Brauner

block: simplify the disk_force_media_change interface

2023-08-21T12:35:30+00:00

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 Reviewed-by: Josef Bacik Message-Id: <20230811100828.1897174-9-hch@lst.de> Signed-off-by: Christian Brauner

block: increment diskseq on all media change events

2023-06-20T13:16:24+00:00

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

block: pass a gendisk on bdev_check_media_change

2023-06-12T14:04:03+00:00

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 Reviewed-by: Hannes Reinecke Acked-by: Christian Brauner Link: https://lore.kernel.org/r/20230608110258.189493-8-hch@lst.de Signed-off-by: Jens Axboe

block: remove genhd.h

2022-02-02T14:49:59+00:00

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 Reviewed-by: Chaitanya Kulkarni Reviewed-by: Martin K. Petersen Link: https://lore.kernel.org/r/20220124093913.742411-4-hch@lst.de Signed-off-by: Jens Axboe

block: return errors from disk_alloc_events

2021-08-23T18:55:45+00:00

Prepare for proper error handling in add_disk. Signed-off-by: Luis Chamberlain [hch: split from a larger patch] Signed-off-by: Christoph Hellwig Reviewed-by: Hannes Reinecke Link: https://lore.kernel.org/r/20210818144542.19305-9-hch@lst.de Signed-off-by: Jens Axboe

block: add a helper to raise a media changed event

2021-08-02T19:37:28+00:00

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 Signed-off-by: Christoph Hellwig Signed-off-by: Matteo Croce Tested-by: Luca Boccassi Link: https://lore.kernel.org/r/20210712230530.29323-6-mcroce@linux.microsoft.com Signed-off-by: Jens Axboe