writeback: Separate inode requeueing after writeback

Move inode requeueing after inode has been written out into a separate
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, 55 insertions, 47 deletions

diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c
index 3804a10f2be7..5d3de002cb8e 100644
--- a/fs/fs-writeback.c
+++ b/fs/fs-writeback.c
@@ -345,6 +345,60 @@ static void inode_wait_for_writeback(struct inode *inode,
 }
 
 /*
+ * Find proper writeback list for the inode depending on its current state and
+ * possibly also change of its state while we were doing writeback.  Here we
+ * handle things such as livelock prevention or fairness of writeback among
+ * inodes. This function can be called only by flusher thread - noone else
+ * processes all inodes in writeback lists and requeueing inodes behind flusher
+ * thread's back can have unexpected consequences.
+ */
+static void requeue_inode(struct inode *inode, struct bdi_writeback *wb,
+                          struct writeback_control *wbc)
+{
+        if (inode->i_state & I_FREEING)
+                return;
+
+        /*
+         * Sync livelock prevention. Each inode is tagged and synced in one
+         * shot. If still dirty, it will be redirty_tail()'ed below.  Update
+         * the dirty time to prevent enqueue and sync it again.
+         */
+        if ((inode->i_state & I_DIRTY) &&
+            (wbc->sync_mode == WB_SYNC_ALL || wbc->tagged_writepages))
+                inode->dirtied_when = jiffies;
+
+        if (mapping_tagged(inode->i_mapping, PAGECACHE_TAG_DIRTY)) {
+                /*
+                 * We didn't write back all the pages.  nfs_writepages()
+                 * sometimes bales out without doing anything.
+                 */
+                if (wbc->nr_to_write <= 0) {
+                        /* Slice used up. Queue for next turn. */
+                        requeue_io(inode, wb);
+                } else {
+                        /*
+                         * Writeback blocked by something other than
+                         * congestion. Delay the inode for some time to
+                         * avoid spinning on the CPU (100% iowait)
+                         * retrying writeback of the dirty page/inode
+                         * that cannot be performed immediately.
+                         */
+                        redirty_tail(inode, wb);
+                }
+        } else if (inode->i_state & I_DIRTY) {
+                /*
+                 * Filesystems can dirty the inode during writeback operations,
+                 * such as delayed allocation during submission or metadata
+                 * updates after data IO completion.
+                 */
+                redirty_tail(inode, wb);
+        } else {
+                /* The inode is clean. Remove from writeback lists. */
+                list_del_init(&inode->i_wb_list);
+        }
+}
+
+/*
  * Write out an inode's dirty pages.  Called under wb->list_lock and
  * inode->i_lock.  Either the caller has an active reference on the inode or
  * the inode has I_WILL_FREE set.
@@ -422,53 +476,7 @@ writeback_single_inode(struct inode *inode, struct bdi_writeback *wb,
 
         spin_lock(&wb->list_lock);
         spin_lock(&inode->i_lock);
-        if (!(inode->i_state & I_FREEING)) {
-                /*
-                 * Sync livelock prevention. Each inode is tagged and synced in
-                 * one shot. If still dirty, it will be redirty_tail()'ed below.
-                 * Update the dirty time to prevent enqueue and sync it again.
-                 */
-                if ((inode->i_state & I_DIRTY) &&
-                    (wbc->sync_mode == WB_SYNC_ALL || wbc->tagged_writepages))
-                        inode->dirtied_when = jiffies;
-
-                if (mapping_tagged(mapping, PAGECACHE_TAG_DIRTY)) {
-                        /*
-                         * We didn't write back all the pages.  nfs_writepages()
-                         * sometimes bales out without doing anything.
-                         */
-                        if (wbc->nr_to_write <= 0) {
-                                /*
-                                 * slice used up: queue for next turn
-                                 */
-                                requeue_io(inode, wb);
-                        } else {
-                                /*
-                                 * Writeback blocked by something other than
-                                 * congestion. Delay the inode for some time to
-                                 * avoid spinning on the CPU (100% iowait)
-                                 * retrying writeback of the dirty page/inode
-                                 * that cannot be performed immediately.
-                                 */
-                                redirty_tail(inode, wb);
-                        }
-                } else if (inode->i_state & I_DIRTY) {
-                        /*
-                         * Filesystems can dirty the inode during writeback
-                         * operations, such as delayed allocation during
-                         * submission or metadata updates after data IO
-                         * completion.
-                         */
-                        redirty_tail(inode, wb);
-                } else {
-                        /*
-                         * The inode is clean.  At this point we either have
-                         * a reference to the inode or it's on it's way out.
-                         * No need to add it back to the LRU.
-                         */
-                        list_del_init(&inode->i_wb_list);
-                }
-        }
+        requeue_inode(inode, wb, wbc);
         inode_sync_complete(inode);
         trace_writeback_single_inode(inode, wbc, nr_to_write);
         return ret;