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btrfs: Fix a lockdep warning when running xfstest.
The following lockdep warning is triggered during xfstests: [ 1702.980872] ========================================================= [ 1702.981181] [ INFO: possible irq lock inversion dependency detected ] [ 1702.981482] 3.18.0-rc1 #27 Not tainted [ 1702.981781] --------------------------------------------------------- [ 1702.982095] kswapd0/77 just changed the state of lock: [ 1702.982415] (&delayed_node->mutex){+.+.-.}, at: [<ffffffffa03b0b51>] __btrfs_release_delayed_node+0x41/0x1f0 [btrfs] [ 1702.982794] but this lock took another, RECLAIM_FS-unsafe lock in the past: [ 1702.983160] (&fs_info->dev_replace.lock){+.+.+.} and interrupts could create inverse lock ordering between them. [ 1702.984675] other info that might help us debug this: [ 1702.985524] Chain exists of: &delayed_node->mutex --> &found->groups_sem --> &fs_info->dev_replace.lock [ 1702.986799] Possible interrupt unsafe locking scenario: [ 1702.987681] CPU0 CPU1 [ 1702.988137] ---- ---- [ 1702.988598] lock(&fs_info->dev_replace.lock); [ 1702.989069] local_irq_disable(); [ 1702.989534] lock(&delayed_node->mutex); [ 1702.990038] lock(&found->groups_sem); [ 1702.990494] <Interrupt> [ 1702.990938] lock(&delayed_node->mutex); [ 1702.991407] *** DEADLOCK *** It is because the btrfs_kobj_{add/rm}_device() will call memory allocation with GFP_KERNEL, which may flush fs page cache to free space, waiting for it self to do the commit, causing the deadlock. To solve the problem, move btrfs_kobj_{add/rm}_device() out of the dev_replace lock range, also involing split the btrfs_rm_dev_replace_srcdev() function into remove and free parts. Now only btrfs_rm_dev_replace_remove_srcdev() is called in dev_replace lock range, and kobj_{add/rm} and btrfs_rm_dev_replace_free_srcdev() are called out of the lock range. Signed-off-by: Qu Wenruo <quwenruo@cn.fujitsu.com> Signed-off-by: Chris Mason <clm@fb.com>
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@ -577,15 +577,11 @@ static int btrfs_dev_replace_finishing(struct btrfs_fs_info *fs_info,
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list_add(&tgt_device->dev_alloc_list, &fs_info->fs_devices->alloc_list);
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fs_info->fs_devices->rw_devices++;
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/* replace the sysfs entry */
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btrfs_kobj_rm_device(fs_info, src_device);
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btrfs_kobj_add_device(fs_info, tgt_device);
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btrfs_dev_replace_unlock(dev_replace);
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btrfs_rm_dev_replace_blocked(fs_info);
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btrfs_rm_dev_replace_srcdev(fs_info, src_device);
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btrfs_rm_dev_replace_remove_srcdev(fs_info, src_device);
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btrfs_rm_dev_replace_unblocked(fs_info);
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@ -600,6 +596,11 @@ static int btrfs_dev_replace_finishing(struct btrfs_fs_info *fs_info,
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mutex_unlock(&root->fs_info->fs_devices->device_list_mutex);
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mutex_unlock(&uuid_mutex);
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/* replace the sysfs entry */
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btrfs_kobj_rm_device(fs_info, src_device);
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btrfs_kobj_add_device(fs_info, tgt_device);
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btrfs_rm_dev_replace_free_srcdev(fs_info, src_device);
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/* write back the superblocks */
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trans = btrfs_start_transaction(root, 0);
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if (!IS_ERR(trans))
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@ -1800,8 +1800,8 @@ error_undo:
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goto error_brelse;
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}
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void btrfs_rm_dev_replace_srcdev(struct btrfs_fs_info *fs_info,
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struct btrfs_device *srcdev)
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void btrfs_rm_dev_replace_remove_srcdev(struct btrfs_fs_info *fs_info,
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struct btrfs_device *srcdev)
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{
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struct btrfs_fs_devices *fs_devices;
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@ -1829,6 +1829,12 @@ void btrfs_rm_dev_replace_srcdev(struct btrfs_fs_info *fs_info,
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if (srcdev->bdev)
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fs_devices->open_devices--;
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}
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void btrfs_rm_dev_replace_free_srcdev(struct btrfs_fs_info *fs_info,
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struct btrfs_device *srcdev)
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{
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struct btrfs_fs_devices *fs_devices = srcdev->fs_devices;
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call_rcu(&srcdev->rcu, free_device);
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@ -448,8 +448,10 @@ void btrfs_init_devices_late(struct btrfs_fs_info *fs_info);
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int btrfs_init_dev_stats(struct btrfs_fs_info *fs_info);
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int btrfs_run_dev_stats(struct btrfs_trans_handle *trans,
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struct btrfs_fs_info *fs_info);
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void btrfs_rm_dev_replace_srcdev(struct btrfs_fs_info *fs_info,
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struct btrfs_device *srcdev);
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void btrfs_rm_dev_replace_remove_srcdev(struct btrfs_fs_info *fs_info,
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struct btrfs_device *srcdev);
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void btrfs_rm_dev_replace_free_srcdev(struct btrfs_fs_info *fs_info,
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struct btrfs_device *srcdev);
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void btrfs_destroy_dev_replace_tgtdev(struct btrfs_fs_info *fs_info,
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struct btrfs_device *tgtdev);
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void btrfs_init_dev_replace_tgtdev_for_resume(struct btrfs_fs_info *fs_info,
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