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>

diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c
index 5d3de00..3b87dc8 100644 (file)
--- 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);