f2fs: use rw_sem instead of fs_lock(locks mutex)

The fs_locks is used to block other ops(ex, recovery) when doing checkpoint.
And each other operate routine(besides checkpoint) needs to acquire a fs_lock,
there is a terrible problem here, if these are too many concurrency threads acquiring
fs_lock, so that they will block each other and may lead to some performance problem,
but this is not the phenomenon we want to see.
Though there are some optimization patches introduced to enhance the usage of fs_lock,
but the thorough solution is using a *rw_sem* to replace the fs_lock.
Checkpoint routine takes write_sem, and other ops take read_sem, so that we can block
other ops(ex, recovery) when doing checkpoint, and other ops will not disturb each other,
this can avoid the problem described above completely.
Because of the weakness of rw_sem, the above change may introduce a potential problem
that the checkpoint thread might get starved if other threads are intensively locking
the read semaphore for I/O.(Pointed out by Xu Jin)
In order to avoid this, a wait_list is introduced, the appending read semaphore ops
will be dropped into the wait_list if checkpoint thread is waiting for write semaphore,
and will be waked up when checkpoint thread gives up write semaphore.
Thanks to Kim's previous review and test, and will be very glad to see other guys'
performance tests about this patch.

V2:
  -fix the potential starvation problem.
  -use more suitable func name suggested by Xu Jin.

Signed-off-by: Gu Zheng <guz.fnst@cn.fujitsu.com>
[Jaegeuk Kim: adjust minor coding standard]
Signed-off-by: Jaegeuk Kim <jaegeuk.kim@samsung.com>

1 files changed, 5 insertions, 6 deletions

diff --git a/fs/f2fs/inode.c b/fs/f2fs/inode.c
index 9339cd29204..c8c058024af 100644
--- a/fs/f2fs/inode.c
+++ b/fs/f2fs/inode.c
@@ -214,7 +214,7 @@ int update_inode_page(struct inode *inode)
 int f2fs_write_inode(struct inode *inode, struct writeback_control *wbc)
 {
 	struct f2fs_sb_info *sbi = F2FS_SB(inode->i_sb);
-	int ret, ilock;
+	int ret;
 
 	if (inode->i_ino == F2FS_NODE_INO(sbi) ||
 			inode->i_ino == F2FS_META_INO(sbi))
@@ -227,9 +227,9 @@ int f2fs_write_inode(struct inode *inode, struct writeback_control *wbc)
 	 * We need to lock here to prevent from producing dirty node pages
 	 * during the urgent cleaning time when runing out of free sections.
 	 */
-	ilock = mutex_lock_op(sbi);
+	f2fs_lock_op(sbi);
 	ret = update_inode_page(inode);
-	mutex_unlock_op(sbi, ilock);
+	f2fs_unlock_op(sbi);
 
 	if (wbc)
 		f2fs_balance_fs(sbi);
@@ -243,7 +243,6 @@ int f2fs_write_inode(struct inode *inode, struct writeback_control *wbc)
 void f2fs_evict_inode(struct inode *inode)
 {
 	struct f2fs_sb_info *sbi = F2FS_SB(inode->i_sb);
-	int ilock;
 
 	trace_f2fs_evict_inode(inode);
 	truncate_inode_pages(&inode->i_data, 0);
@@ -265,9 +264,9 @@ void f2fs_evict_inode(struct inode *inode)
 	if (F2FS_HAS_BLOCKS(inode))
 		f2fs_truncate(inode);
 
-	ilock = mutex_lock_op(sbi);
+	f2fs_lock_op(sbi);
 	remove_inode_page(inode);
-	mutex_unlock_op(sbi, ilock);
+	f2fs_unlock_op(sbi);
 
 	sb_end_intwrite(inode->i_sb);
 no_delete: