block: remove redundant GD_NEED_PART_SCAN in add_disk_final()

add_disk_final() sets GD_NEED_PART_SCAN before calling bdev_add(),
then calls disk_scan_partitions() which sets the flag itself. The
early set is redundant and introduces a race.

Between bdev_add() and disk_scan_partitions(), concurrent openers
(multipathd, blkid, LVM) see the flag in blkdev_get_whole() and
trigger bdev_disk_changed(). When disk_scan_partitions() then runs,
it calls bdev_disk_changed() again, dropping the partitions the
concurrent opener already created before re-adding them, which can
result in transient partition disappearances.

The race is observable by inserting an msleep() between bdev_add()
and disk_scan_partitions() while running concurrent open() calls
during device bind. Without artificial delay, it manifests under
scheduling pressure during boot on systems with aggressive device
scanners (multipathd, systemd-udevd).

Therefore, do not set GD_NEED_PART_SCAN in add_disk_final(). Other
GD_NEED_PART_SCAN consumers (blkdev_get_whole(),
sd_need_revalidate()) should not be affected as the flag
is set internally by disk_scan_partitions().

The retry-on-next-open intention from commit e5cfefa97bcc
("block: fix scan partition for exclusively open device again")
should also not be affected as the early return paths in
disk_scan_partitions() should be unreachable at device registration
time (bd_holder is NULL and open_partitions is zero).

Fixes: e5cfefa97bcc ("block: fix scan partition for exclusively open device again")
Cc: stable@vger.kernel.org
Signed-off-by: Connor Williamson <connordw@amazon.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Link: https://patch.msgid.link/20260615130715.53693-1-connordw@amazon.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>

0 files changed, 0 insertions, 0 deletions