Wang Shilong
2013-Oct-25 11:12 UTC
[PATCH] Btrfs: remove scrub_super_lock holding in btrfs_sync_log()
Originally, we introduced scrub_super_lock to synchronize
tree log code with scrubbing super.
However we can replace scrub_super_lock with device_list_mutex,
because writing super will hold this mutex, this will reduce an extra
lock holding when writing supers in sync log code.
Signed-off-by: Wang Shilong <wangsl.fnst@cn.fujitsu.com>
---
The idea comes from miao''s suggestion with my previous patch.(though it
addressed a not existed problem)
---
fs/btrfs/ctree.h | 3 ---
fs/btrfs/disk-io.c | 1 -
fs/btrfs/scrub.c | 18 +++++-------------
fs/btrfs/tree-log.c | 2 --
fs/btrfs/volumes.h | 4 +++-
5 files changed, 8 insertions(+), 20 deletions(-)
diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
index 0a008d8..941019d 100644
--- a/fs/btrfs/ctree.h
+++ b/fs/btrfs/ctree.h
@@ -1588,7 +1588,6 @@ struct btrfs_fs_info {
atomic_t scrubs_paused;
atomic_t scrub_cancel_req;
wait_queue_head_t scrub_pause_wait;
- struct rw_semaphore scrub_super_lock;
int scrub_workers_refcnt;
struct btrfs_workers scrub_workers;
struct btrfs_workers scrub_wr_completion_workers;
@@ -3952,9 +3951,7 @@ int btrfs_scrub_dev(struct btrfs_fs_info *fs_info, u64
devid, u64 start,
u64 end, struct btrfs_scrub_progress *progress,
int readonly, int is_dev_replace);
void btrfs_scrub_pause(struct btrfs_root *root);
-void btrfs_scrub_pause_super(struct btrfs_root *root);
void btrfs_scrub_continue(struct btrfs_root *root);
-void btrfs_scrub_continue_super(struct btrfs_root *root);
int btrfs_scrub_cancel(struct btrfs_fs_info *info);
int btrfs_scrub_cancel_dev(struct btrfs_fs_info *info,
struct btrfs_device *dev);
diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
index 62c4aba..a3ad3a2 100644
--- a/fs/btrfs/disk-io.c
+++ b/fs/btrfs/disk-io.c
@@ -2250,7 +2250,6 @@ int open_ctree(struct super_block *sb,
atomic_set(&fs_info->scrubs_paused, 0);
atomic_set(&fs_info->scrub_cancel_req, 0);
init_waitqueue_head(&fs_info->scrub_pause_wait);
- init_rwsem(&fs_info->scrub_super_lock);
fs_info->scrub_workers_refcnt = 0;
#ifdef CONFIG_BTRFS_FS_CHECK_INTEGRITY
fs_info->check_integrity_print_mask = 0;
diff --git a/fs/btrfs/scrub.c b/fs/btrfs/scrub.c
index f21e2df..12009b4 100644
--- a/fs/btrfs/scrub.c
+++ b/fs/btrfs/scrub.c
@@ -2932,13 +2932,15 @@ int btrfs_scrub_dev(struct btrfs_fs_info *fs_info, u64
devid, u64 start,
atomic_inc(&fs_info->scrubs_running);
mutex_unlock(&fs_info->scrub_lock);
- mutex_unlock(&fs_info->fs_devices->device_list_mutex);
if (!is_dev_replace) {
- down_read(&fs_info->scrub_super_lock);
+ /*
+ * by holding device list mutex, we can
+ * kick off writing super in log tree sync.
+ */
ret = scrub_supers(sctx, dev);
- up_read(&fs_info->scrub_super_lock);
}
+ mutex_unlock(&fs_info->fs_devices->device_list_mutex);
if (!ret)
ret = scrub_enumerate_chunks(sctx, dev, start, end,
@@ -2988,16 +2990,6 @@ void btrfs_scrub_continue(struct btrfs_root *root)
wake_up(&fs_info->scrub_pause_wait);
}
-void btrfs_scrub_pause_super(struct btrfs_root *root)
-{
- down_write(&root->fs_info->scrub_super_lock);
-}
-
-void btrfs_scrub_continue_super(struct btrfs_root *root)
-{
- up_write(&root->fs_info->scrub_super_lock);
-}
-
int btrfs_scrub_cancel(struct btrfs_fs_info *fs_info)
{
mutex_lock(&fs_info->scrub_lock);
diff --git a/fs/btrfs/tree-log.c b/fs/btrfs/tree-log.c
index 2ff031a..ef80ce0 100644
--- a/fs/btrfs/tree-log.c
+++ b/fs/btrfs/tree-log.c
@@ -2586,9 +2586,7 @@ int btrfs_sync_log(struct btrfs_trans_handle *trans,
* the running transaction open, so a full commit can''t hop
* in and cause problems either.
*/
- btrfs_scrub_pause_super(root);
ret = write_ctree_super(trans, root->fs_info->tree_root, 1);
- btrfs_scrub_continue_super(root);
if (ret) {
btrfs_abort_transaction(trans, root, ret);
goto out_wake_log_root;
diff --git a/fs/btrfs/volumes.h b/fs/btrfs/volumes.h
index b72f540..49e0ff0 100644
--- a/fs/btrfs/volumes.h
+++ b/fs/btrfs/volumes.h
@@ -132,7 +132,9 @@ struct btrfs_fs_devices {
/* all of the devices in the FS, protected by a mutex
* so we can safely walk it to write out the supers without
- * worrying about add/remove by the multi-device code
+ * worrying about add/remove by the multi-device code.
+ * Scrubbing super can kick off supers writing by holding
+ * this mutex lock.
*/
struct mutex device_list_mutex;
struct list_head devices;
--
1.8.3.1
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