path: root/fs/btrfs/disk-io.c
diff options
authorJan Schmidt <>2013-04-24 16:57:33 +0000
committerJosef Bacik <>2013-05-06 15:55:17 -0400
commitfc36ed7e0b13955ba66fc56dc5067e67ac105150 (patch)
treedea2b4ebd056c6e87e5dea53c8df20e0509b88db /fs/btrfs/disk-io.c
parent6d49ba1b47b9c6822d08f90af6f1a2d8ca1cf533 (diff)
Btrfs: separate sequence numbers for delayed ref tracking and tree mod log
Sequence numbers for delayed refs have been introduced in the first version of the qgroup patch set. To solve the problem of find_all_roots on a busy file system, the tree mod log was introduced. The sequence numbers for that were simply shared between those two users. However, at one point in qgroup's quota accounting, there's a statement accessing the previous sequence number, that's still just doing (seq - 1) just as it would have to in the very first version. To satisfy that requirement, this patch makes the sequence number counter 64 bit and splits it into a major part (used for qgroup sequence number counting) and a minor part (incremented for each tree modification in the log). This enables us to go exactly one major step backwards, as required for qgroups, while still incrementing the sequence counter for tree mod log insertions to keep track of their order. Keeping them in a single variable means there's no need to change all the code dealing with comparisons of two sequence numbers. The sequence number is reset to 0 on commit (not new in this patch), which ensures we won't overflow the two 32 bit counters. Without this fix, the qgroup tracking can occasionally go wrong and WARN_ONs from the tree mod log code may happen. Signed-off-by: Jan Schmidt <> Signed-off-by: Josef Bacik <>
Diffstat (limited to 'fs/btrfs/disk-io.c')
1 files changed, 1 insertions, 1 deletions
diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
index e4488b57a7ae..92c44ed78de1 100644
--- a/fs/btrfs/disk-io.c
+++ b/fs/btrfs/disk-io.c
@@ -2157,7 +2157,7 @@ int open_ctree(struct super_block *sb,
atomic_set(&fs_info->async_submit_draining, 0);
atomic_set(&fs_info->nr_async_bios, 0);
atomic_set(&fs_info->defrag_running, 0);
- atomic_set(&fs_info->tree_mod_seq, 0);
+ atomic64_set(&fs_info->tree_mod_seq, 0);
fs_info->sb = sb;
fs_info->max_inline = 8192 * 1024;
fs_info->metadata_ratio = 0;