diff options
| author | Jan Kara | 2017-02-02 15:56:52 +0100 |
|---|---|---|
| committer | Jens Axboe | 2017-02-02 08:20:53 -0700 |
| commit | b1d2dc5659b41741f5a29b2ade76ffb4e5bb13d8 (patch) | |
| tree | 6f01d065b95e5d7a94a26d3892142db6ea60dae5 | |
| parent | d03f6cdc1fc422accb734c7c07a661a0018d8631 (diff) | |
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>
| -rw-r--r-- | block/blk-core.c | 8 | ||||
| -rw-r--r-- | fs/block_dev.c | 7 | ||||
| -rw-r--r-- | include/linux/fs.h | 1 |
3 files changed, 11 insertions, 5 deletions
diff --git a/block/blk-core.c b/block/blk-core.c index d2bba4700e65..6375674e719b 100644 --- a/block/blk-core.c +++ b/block/blk-core.c @@ -110,14 +110,12 @@ void blk_queue_congestion_threshold(struct request_queue *q) * @bdev: device * * Locates the passed device's request queue and returns the address of its - * backing_dev_info. This function can only be called if @bdev is opened - * and the return value is never NULL. + * backing_dev_info. The return value is never NULL however we may return + * &noop_backing_dev_info if the bdev is not currently open. */ struct backing_dev_info *blk_get_backing_dev_info(struct block_device *bdev) { - struct request_queue *q = bdev_get_queue(bdev); - - return q->backing_dev_info; + return bdev->bd_bdi; } EXPORT_SYMBOL(blk_get_backing_dev_info); diff --git a/fs/block_dev.c b/fs/block_dev.c index ed6a34be7a1e..601b71b76d7f 100644 --- a/fs/block_dev.c +++ b/fs/block_dev.c @@ -884,6 +884,8 @@ static void bdev_evict_inode(struct inode *inode) spin_lock(&bdev_lock); list_del_init(&bdev->bd_list); spin_unlock(&bdev_lock); + if (bdev->bd_bdi != &noop_backing_dev_info) + bdi_put(bdev->bd_bdi); } static const struct super_operations bdev_sops = { @@ -986,6 +988,7 @@ struct block_device *bdget(dev_t dev) bdev->bd_contains = NULL; bdev->bd_super = NULL; bdev->bd_inode = inode; + bdev->bd_bdi = &noop_backing_dev_info; bdev->bd_block_size = (1 << inode->i_blkbits); bdev->bd_part_count = 0; bdev->bd_invalidated = 0; @@ -1542,6 +1545,8 @@ static int __blkdev_get(struct block_device *bdev, fmode_t mode, int for_part) bdev->bd_disk = disk; bdev->bd_queue = disk->queue; bdev->bd_contains = bdev; + if (bdev->bd_bdi == &noop_backing_dev_info) + bdev->bd_bdi = bdi_get(disk->queue->backing_dev_info); if (!partno) { ret = -ENXIO; @@ -1637,6 +1642,8 @@ static int __blkdev_get(struct block_device *bdev, fmode_t mode, int for_part) bdev->bd_disk = NULL; bdev->bd_part = NULL; bdev->bd_queue = NULL; + bdi_put(bdev->bd_bdi); + bdev->bd_bdi = &noop_backing_dev_info; if (bdev != bdev->bd_contains) __blkdev_put(bdev->bd_contains, mode, 1); bdev->bd_contains = NULL; diff --git a/include/linux/fs.h b/include/linux/fs.h index 702cb6c50194..c930cbc19342 100644 --- a/include/linux/fs.h +++ b/include/linux/fs.h @@ -423,6 +423,7 @@ struct block_device { int bd_invalidated; struct gendisk * bd_disk; struct request_queue * bd_queue; + struct backing_dev_info *bd_bdi; struct list_head bd_list; /* * Private data. You must have bd_claim'ed the block_device |