writeback: Remove wb->list_lock from writeback_single_inode()

writeback_single_inode() doesn't need wb->list_lock for anything on entry now.
So remove the requirement. This makes locking of writeback_single_inode()
temporarily awkward (entering with i_lock, returning with i_lock and
wb->list_lock) but it will be sanitized in the next patch.

Also inode_wait_for_writeback() doesn't need wb->list_lock for anything. It was
just taking it to make usage convenient for callers but with
writeback_single_inode() changing it's not very convenient anymore. So remove
the lock from that function.

Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Fengguang Wu <fengguang.wu@intel.com>

1 files changed, 7 insertions, 10 deletions

diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c
index 5d3de002cb8e..3b87dc80fd30 100644
--- a/fs/fs-writeback.c
+++ b/fs/fs-writeback.c
@@ -328,8 +328,7 @@ static int write_inode(struct inode *inode, struct writeback_control *wbc)
 /*
  * Wait for writeback on an inode to complete.
  */
-static void inode_wait_for_writeback(struct inode *inode,
-                                     struct bdi_writeback *wb)
+static void inode_wait_for_writeback(struct inode *inode)
 {
         DEFINE_WAIT_BIT(wq, &inode->i_state, __I_SYNC);
         wait_queue_head_t *wqh;
@@ -337,9 +336,7 @@ static void inode_wait_for_writeback(struct inode *inode,
         wqh = bit_waitqueue(&inode->i_state, __I_SYNC);
         while (inode->i_state & I_SYNC) {
                 spin_unlock(&inode->i_lock);
-                spin_unlock(&wb->list_lock);
                 __wait_on_bit(wqh, &wq, inode_wait, TASK_UNINTERRUPTIBLE);
-                spin_lock(&wb->list_lock);
                 spin_lock(&inode->i_lock);
         }
 }
@@ -418,7 +415,6 @@ writeback_single_inode(struct inode *inode, struct bdi_writeback *wb,
         unsigned dirty;
         int ret;
 
-        assert_spin_locked(&wb->list_lock);
         assert_spin_locked(&inode->i_lock);
 
         if (!atomic_read(&inode->i_count))
@@ -432,7 +428,7 @@ writeback_single_inode(struct inode *inode, struct bdi_writeback *wb,
                 /*
                  * It's a data-integrity sync.  We must wait.
                  */
-                inode_wait_for_writeback(inode, wb);
+                inode_wait_for_writeback(inode);
         }
 
         BUG_ON(inode->i_state & I_SYNC);
@@ -440,7 +436,6 @@ writeback_single_inode(struct inode *inode, struct bdi_writeback *wb,
         /* Set I_SYNC, reset I_DIRTY_PAGES */
         inode->i_state |= I_SYNC;
         spin_unlock(&inode->i_lock);
-        spin_unlock(&wb->list_lock);
 
         ret = do_writepages(mapping, wbc);
 
@@ -587,6 +582,8 @@ static long writeback_sb_inodes(struct super_block *sb,
                         trace_writeback_sb_inodes_requeue(inode);
                         continue;
                 }
+                spin_unlock(&wb->list_lock);
+
                 __iget(inode);
                 write_chunk = writeback_chunk_size(wb->bdi, work);
                 wbc.nr_to_write = write_chunk;
@@ -803,8 +800,10 @@ static long wb_writeback(struct bdi_writeback *wb,
                         trace_writeback_wait(wb->bdi, work);
                         inode = wb_inode(wb->b_more_io.prev);
                         spin_lock(&inode->i_lock);
-                        inode_wait_for_writeback(inode, wb);
+                        spin_unlock(&wb->list_lock);
+                        inode_wait_for_writeback(inode);
                         spin_unlock(&inode->i_lock);
+                        spin_lock(&wb->list_lock);
                 }
         }
         spin_unlock(&wb->list_lock);
@@ -1350,7 +1349,6 @@ int write_inode_now(struct inode *inode, int sync)
                 wbc.nr_to_write = 0;
 
         might_sleep();
-        spin_lock(&wb->list_lock);
         spin_lock(&inode->i_lock);
         ret = writeback_single_inode(inode, wb, &wbc);
         spin_unlock(&inode->i_lock);
@@ -1375,7 +1373,6 @@ int sync_inode(struct inode *inode, struct writeback_control *wbc)
         struct bdi_writeback *wb = &inode_to_bdi(inode)->wb;
         int ret;
 
-        spin_lock(&wb->list_lock);
         spin_lock(&inode->i_lock);
         ret = writeback_single_inode(inode, wb, wbc);
         spin_unlock(&inode->i_lock);