writeback: don't redirty tail an inode with dirty pages

Avoid delaying writeback for an expire inode with lots of dirty pages, but
no active dirtier at the moment.  Previously we only do that for the
kupdate case.

Any filesystem that does delayed allocation or unwritten extent conversion
after IO completion will cause this - for example, XFS.

Signed-off-by: Wu Fengguang <fengguang.wu@intel.com>
Acked-by: Jan Kara <jack@suse.cz>
Cc: Dave Chinner <david@fromorbit.com>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: Dave Chinner <david@fromorbit.com>
Cc: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c
index fca43d4d7bf4f0657edcf41def8ee1281d822f29..1ce364bbb0037698ecf499132a819058de05ecdf 100644 (file)
--- a/fs/fs-writeback.c
+++ b/fs/fs-writeback.c
@@ -363,18 +363,7 @@ writeback_single_inode(struct inode *inode, struct writeback_control *wbc)
        spin_lock(&inode_lock);
        inode->i_state &= ~I_SYNC;
        if (!(inode->i_state & I_FREEING)) {
-               if ((inode->i_state & I_DIRTY_PAGES) && wbc->for_kupdate) {
-                       /*
-                        * More pages get dirtied by a fast dirtier.
-                        */
-                       goto select_queue;
-               } else if (inode->i_state & I_DIRTY) {
-                       /*
-                        * At least XFS will redirty the inode during the
-                        * writeback (delalloc) and on io completion (isize).
-                        */
-                       redirty_tail(inode);
-               } else if (mapping_tagged(mapping, PAGECACHE_TAG_DIRTY)) {
+               if (mapping_tagged(mapping, PAGECACHE_TAG_DIRTY)) {
                        /*
                         * We didn't write back all the pages.  nfs_writepages()
                         * sometimes bales out without doing anything. Redirty
@@ -396,7 +385,6 @@ writeback_single_inode(struct inode *inode, struct writeback_control *wbc)
                                 * soon as the queue becomes uncongested.
                                 */
                                inode->i_state |= I_DIRTY_PAGES;
-select_queue:
                                if (wbc->nr_to_write <= 0) {
                                        /*
                                         * slice used up: queue for next turn
@@ -419,6 +407,14 @@ select_queue:
                                inode->i_state |= I_DIRTY_PAGES;
                                redirty_tail(inode);
                        }
+               } 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);
                } else if (atomic_read(&inode->i_count)) {
                        /*
                         * The inode is clean, inuse