block: Revalidate i_bdev reference in bd_aquire()
When a device gets removed, block device inode unhashed so that it is not used anymore (bdget() will not find it anymore). Later when a new device gets created with the same device number, we create new block device inode. However there may be file system device inodes whose i_bdev still points to the original block device inode and thus we get two active block device inodes for the same device. They will share the same gendisk so the only visible differences will be that page caches will not be coherent and BDIs will be different (the old block device inode still points to unregistered BDI). Fix the problem by checking in bd_acquire() whether i_bdev still points to active block device inode and re-lookup the block device if not. That way any open of a block device happening after the old device has been removed will get correct block device inode. Tested-by: Lekshmi Pillai <lekshmicpillai@in.ibm.com> Acked-by: Tejun Heo <tj@kernel.org> Signed-off-by: Jan Kara <jack@suse.cz> Signed-off-by: Jens Axboe <axboe@fb.com>
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@ -1043,13 +1043,22 @@ static struct block_device *bd_acquire(struct inode *inode)
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spin_lock(&bdev_lock);
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bdev = inode->i_bdev;
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if (bdev) {
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if (bdev && !inode_unhashed(bdev->bd_inode)) {
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bdgrab(bdev);
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spin_unlock(&bdev_lock);
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return bdev;
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}
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spin_unlock(&bdev_lock);
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/*
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* i_bdev references block device inode that was already shut down
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* (corresponding device got removed). Remove the reference and look
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* up block device inode again just in case new device got
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* reestablished under the same device number.
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*/
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if (bdev)
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bd_forget(inode);
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bdev = bdget(inode->i_rdev);
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if (bdev) {
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spin_lock(&bdev_lock);
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