btrfs: wait for delayed iputs on no space

btrfs will report no_space when we run following write and delete
file loop:
 # FILE_SIZE_M=[ 75% of fs space ]
 # DEV=[ some dev ]
 # MNT=[ some dir ]
 #
 # mkfs.btrfs -f "$DEV"
 # mount -o nodatacow "$DEV" "$MNT"
 # for ((i = 0; i < 100; i++)); do dd if=/dev/zero of="$MNT"/file0 bs=1M count="$FILE_SIZE_M"; rm -f "$MNT"/file0; done
 #

Reason:
 iput() and evict() is run after write pages to block device, if
 write pages work is not finished before next write, the "rm"ed space
 is not freed, and caused above bug.

Fix:
 We can add "-o flushoncommit" mount option to avoid above bug, but
 it have performance problem. Actually, we can to wait for on-the-fly
 writes only when no-space happened, it is which this patch do.

Signed-off-by: Zhao Lei <zhaolei@cn.fujitsu.com>
Signed-off-by: Chris Mason <clm@fb.com>

diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
index 1acd63fcb252b453469e8da431407b35eef2aa38..38b76cc02f486db1e9d7f887860aba8137d61205 100644 (file)
--- a/fs/btrfs/extent-tree.c
+++ b/fs/btrfs/extent-tree.c
@@ -3918,6 +3918,9 @@ commit_trans:
                    !atomic_read(&root->fs_info->open_ioctl_trans)) {
                        need_commit--;
 
+                       if (need_commit > 0)
+                               btrfs_wait_ordered_roots(fs_info, -1);
+
                        trans = btrfs_join_transaction(root);
                        if (IS_ERR(trans))
                                return PTR_ERR(trans);