path: root/fs/btrfs/relocation.c
diff options
authorChris Mason <>2009-10-02 19:11:56 -0400
committerChris Mason <>2009-10-05 09:44:45 -0400
commit61d92c328c16419fc96dc50dd16f8b8c695409ec (patch)
treee9cd82eb56ff5f38f64d9f35229d15496e5d53de /fs/btrfs/relocation.c
parentfbf190874407f23d2891b53ffdf7d3c6be8d47ff (diff)
Btrfs: fix deadlock on async thread startup
The btrfs async worker threads are used for a wide variety of things, including processing bio end_io functions. This means that when the endio threads aren't running, the rest of the FS isn't able to do the final processing required to clear PageWriteback. The endio threads also try to exit as they become idle and start more as the work piles up. The problem is that starting more threads means kthreadd may need to allocate ram, and that allocation may wait until the global number of writeback pages on the system is below a certain limit. The result of that throttling is that end IO threads wait on kthreadd, who is waiting on IO to end, which will never happen. This commit fixes the deadlock by handing off thread startup to a dedicated thread. It also fixes a bug where the on-demand thread creation was creating far too many threads because it didn't take into account threads being started by other procs. Signed-off-by: Chris Mason <>
Diffstat (limited to 'fs/btrfs/relocation.c')
1 files changed, 2 insertions, 2 deletions
diff --git a/fs/btrfs/relocation.c b/fs/btrfs/relocation.c
index 361ad323faac..cfcc93c93a7b 100644
--- a/fs/btrfs/relocation.c
+++ b/fs/btrfs/relocation.c
@@ -3518,7 +3518,7 @@ int btrfs_relocate_block_group(struct btrfs_root *extent_root, u64 group_start)
btrfs_init_workers(&rc->workers, "relocate",
- fs_info->thread_pool_size);
+ fs_info->thread_pool_size, NULL);
rc->extent_root = extent_root;
btrfs_prepare_block_group_relocation(extent_root, rc->block_group);
@@ -3701,7 +3701,7 @@ int btrfs_recover_relocation(struct btrfs_root *root)
btrfs_init_workers(&rc->workers, "relocate",
- root->fs_info->thread_pool_size);
+ root->fs_info->thread_pool_size, NULL);
rc->extent_root = root->fs_info->extent_root;