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authorMiao Xie <miaox@cn.fujitsu.com>2014-02-20 18:08:51 +0800
committerJosef Bacik <jbacik@fb.com>2014-03-10 15:16:39 -0400
commit5c902ba6223f6a6575054226931fafc51314a25f (patch)
treedc43b931ac9d6ad7006093db05a8517fadba9320 /fs/btrfs/tree-log.c
parent7813b3db0a9ec77ff1f4b3ee3fb4925848395d59 (diff)
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/btrfs/tree-log.c')
-rw-r--r--fs/btrfs/tree-log.c17
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);