Btrfs: use larger nr_to_write for larger extents

When btrfs fills a large delayed allocation extent, it is a good idea
to try and convince the write_cache_pages caller to go ahead and
write a good chunk of that extent.  The extra IO is basically free
because we know it is contiguous.

Signed-off-by: Chris Mason <chris.mason@oracle.com>

1 files changed, 9 insertions, 5 deletions

diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c
index 7e5c5a0749e2..8d7a152a90c6 100644
--- a/fs/btrfs/extent_io.c
+++ b/fs/btrfs/extent_io.c
@@ -2135,6 +2135,7 @@ static int __extent_writepage(struct page *page, struct writeback_control *wbc,
         delalloc_end = 0;
         page_started = 0;
         if (!epd->extent_locked) {
+                u64 delalloc_to_write;
                 /*
                  * make sure the wbc mapping index is at least updated
                  * to this page.
@@ -2154,6 +2155,14 @@ static int __extent_writepage(struct page *page, struct writeback_control *wbc,
                         tree->ops->fill_delalloc(inode, page, delalloc_start,
                                                  delalloc_end, &page_started,
                                                  &nr_written);
+                        delalloc_to_write = (delalloc_end -
+                                        max_t(u64, page_offset(page),
+                                              delalloc_start) + 1) >>
+                                        PAGE_CACHE_SHIFT;
+                        if (wbc->nr_to_write < delalloc_to_write) {
+                                wbc->nr_to_write = min_t(long, 8192,
+                                                 delalloc_to_write);
+                        }
                         delalloc_start = delalloc_end + 1;
                 }
 
@@ -2350,7 +2359,6 @@ static int extent_write_cache_pages(struct extent_io_tree *tree,
                              writepage_t writepage, void *data,
                              void (*flush_fn)(void *))
 {
-        struct backing_dev_info *bdi = mapping->backing_dev_info;
         int ret = 0;
         int done = 0;
         struct pagevec pvec;
@@ -2425,10 +2433,6 @@ retry:
                         }
                         if (ret || wbc->nr_to_write <= 0)
                                 done = 1;
-                        if (wbc->nonblocking && bdi_write_congested(bdi)) {
-                                wbc->encountered_congestion = 1;
-                                done = 1;
-                        }
                 }
                 pagevec_release(&pvec);
                 cond_resched();