ext4: clear the dirty bit for a page in writeback at the last minute

Move when we call clear_page_dirty_for_io() to just before we actually
write the page.  This simplifies the code somewhat, and avoids marking
pages as clean and then needing to remark them as dirty later.

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

diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index 1e718e8..ae6e2f4 100644 (file)
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -2060,7 +2060,7 @@ 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, redirty_page = 0;
+                       int commit_write = 0, skip_page = 0;
                        struct page *page = pvec.pages[i];
 
                        index = page->index;
@@ -2086,14 +2086,12 @@ static int mpage_da_submit_io(struct mpage_da_data *mpd,
                         * If the page does not have buffers (for
                         * whatever reason), try to create them using
                         * __block_write_begin.  If this fails,
-                        * redirty the page and move on.
+                        * skip the page and move on.
                         */
                        if (!page_has_buffers(page)) {
                                if (__block_write_begin(page, 0, len,
                                                noalloc_get_block_write)) {
-                               redirty_page:
-                                       redirty_page_for_writepage(mpd->wbc,
-                                                                  page);
+                               skip_page:
                                        unlock_page(page);
                                        continue;
                                }
@@ -2104,7 +2102,7 @@ static int mpage_da_submit_io(struct mpage_da_data *mpd,
                        block_start = 0;
                        do {
                                if (!bh)
-                                       goto redirty_page;
+                                       goto skip_page;
                                if (map && (cur_logical >= map->m_lblk) &&
                                    (cur_logical <= (map->m_lblk +
                                                     (map->m_len - 1)))) {
@@ -2120,22 +2118,23 @@ static int mpage_da_submit_io(struct mpage_da_data *mpd,
                                        clear_buffer_unwritten(bh);
                                }
 
-                               /* redirty page if block allocation undone */
+                               /* skip page if block allocation undone */
                                if (buffer_delay(bh) || buffer_unwritten(bh))
-                                       redirty_page = 1;
+                                       skip_page = 1;
                                bh = bh->b_this_page;
                                block_start += bh->b_size;
                                cur_logical++;
                                pblock++;
                        } while (bh != page_bufs);
 
-                       if (redirty_page)
-                               goto redirty_page;
+                       if (skip_page)
+                               goto skip_page;
 
                        if (commit_write)
                                /* mark the buffer_heads as dirty & uptodate */
                                block_commit_write(page, 0, len);
 
+                       clear_page_dirty_for_io(page);
                        /*
                         * Delalloc doesn't support data journalling,
                         * but eventually maybe we'll lift this
@@ -2277,9 +2276,8 @@ static void mpage_da_map_and_submit(struct mpage_da_data *mpd)
                err = blks;
                /*
                 * If get block returns EAGAIN or ENOSPC and there
-                * appears to be free blocks we will call
-                * ext4_writepage() for all of the pages which will
-                * just redirty the pages.
+                * appears to be free blocks we will just let
+                * mpage_da_submit_io() unlock all of the pages.
                 */
                if (err == -EAGAIN)
                        goto submit_io;
@@ -2777,7 +2775,6 @@ static int write_cache_pages_da(struct address_space *mapping,
                            (PageWriteback(page) &&
                             (wbc->sync_mode == WB_SYNC_NONE)) ||
                            unlikely(page->mapping != mapping)) {
-                       continue_unlock:
                                unlock_page(page);
                                continue;
                        }
@@ -2786,8 +2783,6 @@ static int write_cache_pages_da(struct address_space *mapping,
                                wait_on_page_writeback(page);
 
                        BUG_ON(PageWriteback(page));
-                       if (!clear_page_dirty_for_io(page))
-                               goto continue_unlock;
 
                        /*
                         * Can we merge this page to current extent?
@@ -2803,7 +2798,6 @@ static int write_cache_pages_da(struct address_space *mapping,
                                        /*
                                         * skip rest of the page in the page_vec
                                         */
-                                       redirty_page_for_writepage(wbc, page);
                                        unlock_page(page);
                                        goto ret_extent_tail;
                                }