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Btrfs: move kobj stuff out of dev_replace lock range

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To avoid deadlock described in commit 084b6e7c76 ("btrfs: Fix a
lockdep warning when running xfstest."), we should move kobj stuff out
of dev_replace lock range.

  "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: Liu Bo <bo.li.liu@oracle.com>
Signed-off-by: Anand Jain <anand.jain@oracle.com>
[added lockup description]
Signed-off-by: David Sterba <dsterba@suse.com>
This commit is contained in:
Liu Bo 2015-08-14 18:33:07 +08:00 committed by David Sterba
parent f190aa471a
commit 73416dab23
1 changed files with 4 additions and 4 deletions
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8
fs/btrfs/dev-replace.c
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@ -375,10 +375,6 @@ int btrfs_dev_replace_start(struct btrfs_root *root,
WARN_ON(!tgt_device);
dev_replace->tgtdev = tgt_device;
ret = btrfs_sysfs_add_device_link(tgt_device->fs_devices, tgt_device);
if (ret)
btrfs_err(root->fs_info, "kobj add dev failed %d\n", ret);
printk_in_rcu(KERN_INFO
"BTRFS: dev_replace from %s (devid %llu) to %s started\n",
src_device->missing ? "<missing disk>" :
@ -401,6 +397,10 @@ int btrfs_dev_replace_start(struct btrfs_root *root,
args->result = BTRFS_IOCTL_DEV_REPLACE_RESULT_NO_ERROR;
btrfs_dev_replace_unlock(dev_replace);
ret = btrfs_sysfs_add_device_link(tgt_device->fs_devices, tgt_device);
if (ret)
btrfs_err(root->fs_info, "kobj add dev failed %d\n", ret);
btrfs_wait_ordered_roots(root->fs_info, -1);
/* force writing the updated state information to disk */