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authorQu Wenruo <quwenruo@cn.fujitsu.com>2014-10-30 16:52:31 +0800
committerChris Mason <clm@fb.com>2014-11-25 05:55:38 -0800
commit084b6e7c7607bbeb28544da659c3f5981a4689b0 (patch)
tree1a80b5597373cf5d64e6cecac1de16615af588f2 /fs/btrfs/dev-replace.c
parentad27c0dab76a7abc8809ec41ae59cf67de5ea906 (diff)
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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>
Diffstat (limited to 'fs/btrfs/dev-replace.c')
-rw-r--r--fs/btrfs/dev-replace.c11
1 files changed, 6 insertions, 5 deletions
diff --git a/fs/btrfs/dev-replace.c b/fs/btrfs/dev-replace.c
index 971c061eb1ce..3fbd0628620b 100644
--- a/fs/btrfs/dev-replace.c
+++ b/fs/btrfs/dev-replace.c
@@ -577,15 +577,11 @@ static int btrfs_dev_replace_finishing(struct btrfs_fs_info *fs_info,
list_add(&tgt_device->dev_alloc_list, &fs_info->fs_devices->alloc_list);
fs_info->fs_devices->rw_devices++;
- /* replace the sysfs entry */
- btrfs_kobj_rm_device(fs_info, src_device);
- btrfs_kobj_add_device(fs_info, tgt_device);
-
btrfs_dev_replace_unlock(dev_replace);
btrfs_rm_dev_replace_blocked(fs_info);
- btrfs_rm_dev_replace_srcdev(fs_info, src_device);
+ btrfs_rm_dev_replace_remove_srcdev(fs_info, src_device);
btrfs_rm_dev_replace_unblocked(fs_info);
@@ -600,6 +596,11 @@ static int btrfs_dev_replace_finishing(struct btrfs_fs_info *fs_info,
mutex_unlock(&root->fs_info->fs_devices->device_list_mutex);
mutex_unlock(&uuid_mutex);
+ /* replace the sysfs entry */
+ btrfs_kobj_rm_device(fs_info, src_device);
+ btrfs_kobj_add_device(fs_info, tgt_device);
+ btrfs_rm_dev_replace_free_srcdev(fs_info, src_device);
+
/* write back the superblocks */
trans = btrfs_start_transaction(root, 0);
if (!IS_ERR(trans))