ext4: inline ext4_writepage() into mpage_da_submit_io()

As a prepratory step to switching to bio_submit, inline
ext4_writepage() into mpage_da_submit() and then simplify things a
bit.  This makes it clearer what mpage_da_submit needs to do.

Also, move the ClearPageChecked(page) call into
__ext4_journalled_writepage(), as a minor bit of cleanup refactoring.

This also allows us to pull i_size_read() and
ext4_should_journal_data() out of the loop, which should be a very
minor CPU savings.

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>

1 files changed, 59 insertions, 11 deletions

diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index a08ec795995f..97a0c35219ae 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -60,7 +60,12 @@ static inline int ext4_begin_ordered_truncate(struct inode *inode,
 }
 
 static void ext4_invalidatepage(struct page *page, unsigned long offset);
-static int ext4_writepage(struct page *page, struct writeback_control *wbc);
+static int noalloc_get_block_write(struct inode *inode, sector_t iblock,
+                                   struct buffer_head *bh_result, int create);
+static int ext4_set_bh_endio(struct buffer_head *bh, struct inode *inode);
+static void ext4_end_io_buffer_write(struct buffer_head *bh, int uptodate);
+static int __ext4_journalled_writepage(struct page *page, unsigned int len);
+static int ext4_bh_delay_or_unwritten(handle_t *handle, struct buffer_head *bh);
 
 /*
  * Test whether an inode is a fast symlink.
@@ -2000,12 +2005,15 @@ static void ext4_da_page_release_reservation(struct page *page,
  */
 static int mpage_da_submit_io(struct mpage_da_data *mpd)
 {
-        long pages_skipped;
         struct pagevec pvec;
         unsigned long index, end;
         int ret = 0, err, nr_pages, i;
         struct inode *inode = mpd->inode;
         struct address_space *mapping = inode->i_mapping;
+        loff_t size = i_size_read(inode);
+        unsigned int len;
+        struct buffer_head *page_bufs = NULL;
+        int journal_data = ext4_should_journal_data(inode);
 
         BUG_ON(mpd->next_page <= mpd->first_page);
         /*
@@ -2023,28 +2031,69 @@ static int mpage_da_submit_io(struct mpage_da_data *mpd)
                 if (nr_pages == 0)
                         break;
                 for (i = 0; i < nr_pages; i++) {
+                        int commit_write = 0;
                         struct page *page = pvec.pages[i];
 
                         index = page->index;
                         if (index > end)
                                 break;
+
+                        if (index == size >> PAGE_CACHE_SHIFT)
+                                len = size & ~PAGE_CACHE_MASK;
+                        else
+                                len = PAGE_CACHE_SIZE;
                         index++;
 
                         BUG_ON(!PageLocked(page));
                         BUG_ON(PageWriteback(page));
 
-                        pages_skipped = mpd->wbc->pages_skipped;
-                        err = ext4_writepage(page, mpd->wbc);
-                        if (!err && (pages_skipped == mpd->wbc->pages_skipped))
+                        /*
+                         * If the page does not have buffers (for
+                         * whatever reason), try to create them using
+                         * block_prepare_write.  If this fails,
+                         * redirty the page and move on.
+                         */
+                        if (!page_has_buffers(page)) {
+                                if (block_prepare_write(page, 0, len,
+                                                noalloc_get_block_write)) {
+                                redirty_page:
+                                        redirty_page_for_writepage(mpd->wbc,
+                                                                   page);
+                                        unlock_page(page);
+                                        continue;
+                                }
+                                commit_write = 1;
+                        }
+                        page_bufs = page_buffers(page);
+                        if (walk_page_buffers(NULL, page_bufs, 0, len, NULL,
+                                              ext4_bh_delay_or_unwritten)) {
                                 /*
-                                 * have successfully written the page
-                                 * without skipping the same
+                                 * We couldn't do block allocation for
+                                 * some reason.
                                  */
+                                goto redirty_page;
+                        }
+
+                        if (commit_write)
+                                /* mark the buffer_heads as dirty & uptodate */
+                                block_commit_write(page, 0, len);
+
+                        if (journal_data && PageChecked(page))
+                                err = __ext4_journalled_writepage(page, len);
+                        else if (buffer_uninit(page_bufs)) {
+                                ext4_set_bh_endio(page_bufs, inode);
+                                err = block_write_full_page_endio(page,
+                                        noalloc_get_block_write,
+                                        mpd->wbc, ext4_end_io_buffer_write);
+                        } else
+                                err = block_write_full_page(page,
+                                            noalloc_get_block_write, mpd->wbc);
+
+                        if (!err)
                                 mpd->pages_written++;
                         /*
                          * In error case, we have to continue because
                          * remaining pages are still locked
-                         * XXX: unlock and re-dirty them?
                          */
                         if (ret == 0)
                                 ret = err;
@@ -2627,6 +2676,7 @@ static int __ext4_journalled_writepage(struct page *page,
         int ret = 0;
         int err;
 
+        ClearPageChecked(page);
         page_bufs = page_buffers(page);
         BUG_ON(!page_bufs);
         walk_page_buffers(handle, page_bufs, 0, len, NULL, bget_one);
@@ -2749,14 +2799,12 @@ static int ext4_writepage(struct page *page,
                 /* now mark the buffer_heads as dirty and uptodate */
                 block_commit_write(page, 0, len);
 
-        if (PageChecked(page) && ext4_should_journal_data(inode)) {
+        if (PageChecked(page) && ext4_should_journal_data(inode))
                 /*
                  * It's mmapped pagecache.  Add buffers and journal it.  There
                  * doesn't seem much point in redirtying the page here.
                  */
-                ClearPageChecked(page);
                 return __ext4_journalled_writepage(page, len);
-        }
 
         if (buffer_uninit(page_bufs)) {
                 ext4_set_bh_endio(page_bufs, inode);