btrfs: Fix NO_SPACE bug caused by delayed-iput
Steps to reproduce:
while true; do
dd if=/dev/zero of=/btrfs_dir/file count=[fs_size * 75%]
rm /btrfs_dir/file
sync
done
And we'll see dd failed because btrfs return NO_SPACE.
Reason:
Normally, btrfs_commit_transaction() call btrfs_run_delayed_iputs()
in end to free fs space for next write, but sometimes it hadn't
done work on time, because btrfs-cleaner thread get delayed-iputs
from list before, but do iput() after next write.
This is log:
[ 2569.050776] comm=btrfs-cleaner func=btrfs_evict_inode() begin
[ 2569.084280] comm=sync func=btrfs_commit_transaction() call btrfs_run_delayed_iputs()
[ 2569.085418] comm=sync func=btrfs_commit_transaction() done btrfs_run_delayed_iputs()
[ 2569.087554] comm=sync func=btrfs_commit_transaction() end
[ 2569.191081] comm=dd begin
[ 2569.790112] comm=dd func=__btrfs_buffered_write() ret=-28
[ 2569.847479] comm=btrfs-cleaner func=add_pinned_bytes() 0 + 32677888 = 32677888
[ 2569.849530] comm=btrfs-cleaner func=add_pinned_bytes() 32677888 + 23834624 = 56512512
...
[ 2569.903893] comm=btrfs-cleaner func=add_pinned_bytes() 943976448 + 21762048 = 965738496
[ 2569.908270] comm=btrfs-cleaner func=btrfs_evict_inode() end
Fix:
Make btrfs_commit_transaction() wait current running btrfs-cleaner's
delayed-iputs() done in end.
Test:
Use script similar to above(more complex),
before patch:
7 failed in 100 * 20 loop.
after patch:
0 failed in 100 * 20 loop.
Signed-off-by: Zhao Lei <zhaolei@cn.fujitsu.com>
Signed-off-by: Chris Mason <clm@fb.com>
diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
index 62cd3b6..2ef9a4b 100644
--- a/fs/btrfs/disk-io.c
+++ b/fs/btrfs/disk-io.c
@@ -2487,11 +2487,12 @@
spin_lock_init(&fs_info->qgroup_op_lock);
spin_lock_init(&fs_info->buffer_lock);
spin_lock_init(&fs_info->unused_bgs_lock);
- mutex_init(&fs_info->unused_bg_unpin_mutex);
rwlock_init(&fs_info->tree_mod_log_lock);
+ mutex_init(&fs_info->unused_bg_unpin_mutex);
mutex_init(&fs_info->reloc_mutex);
mutex_init(&fs_info->delalloc_root_mutex);
seqlock_init(&fs_info->profiles_lock);
+ init_rwsem(&fs_info->delayed_iput_sem);
init_completion(&fs_info->kobj_unregister);
INIT_LIST_HEAD(&fs_info->dirty_cowonly_roots);