diff options
| author | Miao Xie <miaox@cn.fujitsu.com> | 2014-02-20 14:08:51 +0400 |
|---|---|---|
| committer | Josef Bacik <jbacik@fb.com> | 2014-03-10 23:16:39 +0400 |
| commit | 5c902ba6223f6a6575054226931fafc51314a25f (patch) | |
| tree | dc43b931ac9d6ad7006093db05a8517fadba9320 /fs | |
| parent | 7813b3db0a9ec77ff1f4b3ee3fb4925848395d59 (diff) | |
| download | linux-5c902ba6223f6a6575054226931fafc51314a25f.tar.xz | |
Btrfs: use ACCESS_ONCE to prevent the optimize accesses to ->last_trans_log_full_commit
->last_trans_log_full_commit may be changed by the other tasks without lock,
so we need prevent the compiler from the optimize access just like
tmp = fs_info->last_trans_log_full_commit
if (tmp == ...)
...
<do something>
if (tmp == ...)
...
In fact, we need get the new value of ->last_trans_log_full_commit during
the second access. Fix it by ACCESS_ONCE().
Signed-off-by: Miao Xie <miaox@cn.fujitsu.com>
Signed-off-by: Josef Bacik <jbacik@fb.com>
Diffstat (limited to 'fs')
| -rw-r--r-- | fs/btrfs/tree-log.c | 17 |
1 files changed, 10 insertions, 7 deletions
diff --git a/fs/btrfs/tree-log.c b/fs/btrfs/tree-log.c index 7c449c699bed..5a4e10b9ac3e 100644 --- a/fs/btrfs/tree-log.c +++ b/fs/btrfs/tree-log.c @@ -2375,14 +2375,14 @@ static int wait_log_commit(struct btrfs_trans_handle *trans, &wait, TASK_UNINTERRUPTIBLE); mutex_unlock(&root->log_mutex); - if (root->fs_info->last_trans_log_full_commit != + if (ACCESS_ONCE(root->fs_info->last_trans_log_full_commit) != trans->transid && root->log_transid < transid + 2 && atomic_read(&root->log_commit[index])) schedule(); finish_wait(&root->log_commit_wait[index], &wait); mutex_lock(&root->log_mutex); - } while (root->fs_info->last_trans_log_full_commit != + } while (ACCESS_ONCE(root->fs_info->last_trans_log_full_commit) != trans->transid && root->log_transid < transid + 2 && atomic_read(&root->log_commit[index])); return 0; @@ -2392,12 +2392,12 @@ static void wait_for_writer(struct btrfs_trans_handle *trans, struct btrfs_root *root) { DEFINE_WAIT(wait); - while (root->fs_info->last_trans_log_full_commit != + while (ACCESS_ONCE(root->fs_info->last_trans_log_full_commit) != trans->transid && atomic_read(&root->log_writers)) { prepare_to_wait(&root->log_writer_wait, &wait, TASK_UNINTERRUPTIBLE); mutex_unlock(&root->log_mutex); - if (root->fs_info->last_trans_log_full_commit != + if (ACCESS_ONCE(root->fs_info->last_trans_log_full_commit) != trans->transid && atomic_read(&root->log_writers)) schedule(); mutex_lock(&root->log_mutex); @@ -2456,7 +2456,8 @@ int btrfs_sync_log(struct btrfs_trans_handle *trans, } /* bail out if we need to do a full commit */ - if (root->fs_info->last_trans_log_full_commit == trans->transid) { + if (ACCESS_ONCE(root->fs_info->last_trans_log_full_commit) == + trans->transid) { ret = -EAGAIN; btrfs_free_logged_extents(log, log_transid); mutex_unlock(&root->log_mutex); @@ -2515,7 +2516,8 @@ int btrfs_sync_log(struct btrfs_trans_handle *trans, mutex_unlock(&log_root_tree->log_mutex); goto out; } - root->fs_info->last_trans_log_full_commit = trans->transid; + ACCESS_ONCE(root->fs_info->last_trans_log_full_commit) = + trans->transid; btrfs_wait_marked_extents(log, &log->dirty_log_pages, mark); btrfs_free_logged_extents(log, log_transid); mutex_unlock(&log_root_tree->log_mutex); @@ -2547,7 +2549,8 @@ int btrfs_sync_log(struct btrfs_trans_handle *trans, * now that we've moved on to the tree of log tree roots, * check the full commit flag again */ - if (root->fs_info->last_trans_log_full_commit == trans->transid) { + if (ACCESS_ONCE(root->fs_info->last_trans_log_full_commit) == + trans->transid) { blk_finish_plug(&plug); btrfs_wait_marked_extents(log, &log->dirty_log_pages, mark); btrfs_free_logged_extents(log, log_transid); |