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block: prevent block device lookups at the beginning of del_gendisk
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: Christoph Hellwig <hch@lst.de> Reviewed-by: Ming Lei <ming.lei@redhat.com> Link: https://lore.kernel.org/r/20210514131842.1600568-2-hch@lst.de Signed-off-by: Jens Axboe <axboe@kernel.dk>
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@ -29,8 +29,6 @@
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static struct kobject *block_depr;
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DECLARE_RWSEM(bdev_lookup_sem);
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/* for extended dynamic devt allocation, currently only one major is used */
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#define NR_EXT_DEVT (1 << MINORBITS)
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static DEFINE_IDA(ext_devt_ida);
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@ -609,13 +607,8 @@ void del_gendisk(struct gendisk *disk)
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blk_integrity_del(disk);
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disk_del_events(disk);
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/*
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* Block lookups of the disk until all bdevs are unhashed and the
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* disk is marked as dead (GENHD_FL_UP cleared).
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*/
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down_write(&bdev_lookup_sem);
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mutex_lock(&disk->part0->bd_mutex);
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disk->flags &= ~GENHD_FL_UP;
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blk_drop_partitions(disk);
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mutex_unlock(&disk->part0->bd_mutex);
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@ -629,8 +622,6 @@ void del_gendisk(struct gendisk *disk)
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remove_inode_hash(disk->part0->bd_inode);
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set_capacity(disk, 0);
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disk->flags &= ~GENHD_FL_UP;
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up_write(&bdev_lookup_sem);
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if (!(disk->flags & GENHD_FL_HIDDEN)) {
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sysfs_remove_link(&disk_to_dev(disk)->kobj, "bdi");
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@ -1298,6 +1298,9 @@ static int __blkdev_get(struct block_device *bdev, fmode_t mode)
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struct gendisk *disk = bdev->bd_disk;
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int ret = 0;
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if (!(disk->flags & GENHD_FL_UP))
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return -ENXIO;
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if (!bdev->bd_openers) {
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if (!bdev_is_partition(bdev)) {
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ret = 0;
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@ -1332,8 +1335,7 @@ static int __blkdev_get(struct block_device *bdev, fmode_t mode)
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whole->bd_part_count++;
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mutex_unlock(&whole->bd_mutex);
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if (!(disk->flags & GENHD_FL_UP) ||
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!bdev_nr_sectors(bdev)) {
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if (!bdev_nr_sectors(bdev)) {
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__blkdev_put(whole, mode, 1);
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bdput(whole);
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return -ENXIO;
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@ -1364,16 +1366,12 @@ struct block_device *blkdev_get_no_open(dev_t dev)
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struct block_device *bdev;
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struct gendisk *disk;
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down_read(&bdev_lookup_sem);
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bdev = bdget(dev);
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if (!bdev) {
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up_read(&bdev_lookup_sem);
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blk_request_module(dev);
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down_read(&bdev_lookup_sem);
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bdev = bdget(dev);
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if (!bdev)
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goto unlock;
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return NULL;
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}
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disk = bdev->bd_disk;
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@ -1383,14 +1381,11 @@ struct block_device *blkdev_get_no_open(dev_t dev)
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goto put_disk;
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if (!try_module_get(bdev->bd_disk->fops->owner))
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goto put_disk;
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up_read(&bdev_lookup_sem);
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return bdev;
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put_disk:
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put_disk(disk);
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bdput:
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bdput(bdev);
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unlock:
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up_read(&bdev_lookup_sem);
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return NULL;
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}
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@ -306,8 +306,6 @@ static inline void bd_unlink_disk_holder(struct block_device *bdev,
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}
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#endif /* CONFIG_SYSFS */
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extern struct rw_semaphore bdev_lookup_sem;
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dev_t blk_lookup_devt(const char *name, int partno);
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void blk_request_module(dev_t devt);
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#ifdef CONFIG_BLOCK
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