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block: Make blk_get_backing_dev_info() safe without open bdev
Currenly blk_get_backing_dev_info() is not safe to be called when the block device is not open as bdev->bd_disk is NULL in that case. However inode_to_bdi() uses this function and may be call called from flusher worker or other writeback related functions without bdev being open which leads to crashes such as: [113031.075540] Unable to handle kernel paging request for data at address 0x00000000 [113031.075614] Faulting instruction address: 0xc0000000003692e0 0:mon> t [c0000000fb65f900] c00000000036cb6c writeback_sb_inodes+0x30c/0x590 [c0000000fb65fa10] c00000000036ced4 __writeback_inodes_wb+0xe4/0x150 [c0000000fb65fa70] c00000000036d33c wb_writeback+0x30c/0x450 [c0000000fb65fb40] c00000000036e198 wb_workfn+0x268/0x580 [c0000000fb65fc50] c0000000000f3470 process_one_work+0x1e0/0x590 [c0000000fb65fce0] c0000000000f38c8 worker_thread+0xa8/0x660 [c0000000fb65fd80] c0000000000fc4b0 kthread+0x110/0x130 [c0000000fb65fe30] c0000000000098f0 ret_from_kernel_thread+0x5c/0x6c Signed-off-by: Jens Axboe <axboe@fb.com>
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parent
d03f6cdc1f
commit
b1d2dc5659
3 changed files with 11 additions and 5 deletions
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@ -110,14 +110,12 @@ void blk_queue_congestion_threshold(struct request_queue *q)
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* @bdev: device
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*
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* Locates the passed device's request queue and returns the address of its
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* backing_dev_info. This function can only be called if @bdev is opened
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* and the return value is never NULL.
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* backing_dev_info. The return value is never NULL however we may return
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* &noop_backing_dev_info if the bdev is not currently open.
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*/
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struct backing_dev_info *blk_get_backing_dev_info(struct block_device *bdev)
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{
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struct request_queue *q = bdev_get_queue(bdev);
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return q->backing_dev_info;
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return bdev->bd_bdi;
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}
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EXPORT_SYMBOL(blk_get_backing_dev_info);
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@ -884,6 +884,8 @@ static void bdev_evict_inode(struct inode *inode)
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spin_lock(&bdev_lock);
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list_del_init(&bdev->bd_list);
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spin_unlock(&bdev_lock);
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if (bdev->bd_bdi != &noop_backing_dev_info)
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bdi_put(bdev->bd_bdi);
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}
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static const struct super_operations bdev_sops = {
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@ -986,6 +988,7 @@ struct block_device *bdget(dev_t dev)
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bdev->bd_contains = NULL;
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bdev->bd_super = NULL;
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bdev->bd_inode = inode;
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bdev->bd_bdi = &noop_backing_dev_info;
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bdev->bd_block_size = (1 << inode->i_blkbits);
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bdev->bd_part_count = 0;
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bdev->bd_invalidated = 0;
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@ -1542,6 +1545,8 @@ static int __blkdev_get(struct block_device *bdev, fmode_t mode, int for_part)
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bdev->bd_disk = disk;
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bdev->bd_queue = disk->queue;
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bdev->bd_contains = bdev;
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if (bdev->bd_bdi == &noop_backing_dev_info)
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bdev->bd_bdi = bdi_get(disk->queue->backing_dev_info);
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if (!partno) {
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ret = -ENXIO;
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@ -1637,6 +1642,8 @@ static int __blkdev_get(struct block_device *bdev, fmode_t mode, int for_part)
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bdev->bd_disk = NULL;
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bdev->bd_part = NULL;
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bdev->bd_queue = NULL;
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bdi_put(bdev->bd_bdi);
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bdev->bd_bdi = &noop_backing_dev_info;
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if (bdev != bdev->bd_contains)
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__blkdev_put(bdev->bd_contains, mode, 1);
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bdev->bd_contains = NULL;
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@ -423,6 +423,7 @@ struct block_device {
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int bd_invalidated;
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struct gendisk * bd_disk;
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struct request_queue * bd_queue;
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struct backing_dev_info *bd_bdi;
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struct list_head bd_list;
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/*
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* Private data. You must have bd_claim'ed the block_device
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