ext4: simple cleanups to write_cache_pages_da()

Eliminate duplicate code, unneeded variables, etc., to make it easier
to understand the code.  No behavioral changes were made in this patch.

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

diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index fcd08ca..1e718e8 100644 (file)
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -2723,17 +2723,14 @@ static int write_cache_pages_da(struct address_space *mapping,
                                struct mpage_da_data *mpd,
                                pgoff_t *done_index)
 {
-       struct inode *inode = mpd->inode;
-       struct buffer_head *bh, *head;
-       sector_t logical;
-       int ret = 0;
-       int done = 0;
-       struct pagevec pvec;
-       unsigned nr_pages;
-       pgoff_t index;
-       pgoff_t end;            /* Inclusive */
-       long nr_to_write = wbc->nr_to_write;
-       int tag;
+       struct buffer_head      *bh, *head;
+       struct inode            *inode = mpd->inode;
+       struct pagevec          pvec;
+       unsigned int            nr_pages;
+       sector_t                logical;
+       pgoff_t                 index, end;
+       long                    nr_to_write = wbc->nr_to_write;
+       int                     i, tag, ret = 0;
 
        pagevec_init(&pvec, 0);
        index = wbc->range_start >> PAGE_CACHE_SHIFT;
@@ -2745,13 +2742,11 @@ static int write_cache_pages_da(struct address_space *mapping,
                tag = PAGECACHE_TAG_DIRTY;
 
        *done_index = index;
-       while (!done && (index <= end)) {
-               int i;
-
+       while (index <= end) {
                nr_pages = pagevec_lookup_tag(&pvec, mapping, &index, tag,
                              min(end - index, (pgoff_t)PAGEVEC_SIZE-1) + 1);
                if (nr_pages == 0)
-                       break;
+                       return 0;
 
                for (i = 0; i < nr_pages; i++) {
                        struct page *page = pvec.pages[i];
@@ -2763,47 +2758,37 @@ static int write_cache_pages_da(struct address_space *mapping,
                         * mapping. However, page->index will not change
                         * because we have a reference on the page.
                         */
-                       if (page->index > end) {
-                               done = 1;
-                               break;
-                       }
+                       if (page->index > end)
+                               goto out;
 
                        *done_index = page->index + 1;
 
                        lock_page(page);
 
                        /*
-                        * Page truncated or invalidated. We can freely skip it
-                        * then, even for data integrity operations: the page
-                        * has disappeared concurrently, so there could be no
-                        * real expectation of this data interity operation
-                        * even if there is now a new, dirty page at the same
-                        * pagecache address.
+                        * If the page is no longer dirty, or its
+                        * mapping no longer corresponds to inode we
+                        * are writing (which means it has been
+                        * truncated or invalidated), or the page is
+                        * already under writeback and we are not
+                        * doing a data integrity writeback, skip the page
                         */
-                       if (unlikely(page->mapping != mapping)) {
-continue_unlock:
+                       if (!PageDirty(page) ||
+                           (PageWriteback(page) &&
+                            (wbc->sync_mode == WB_SYNC_NONE)) ||
+                           unlikely(page->mapping != mapping)) {
+                       continue_unlock:
                                unlock_page(page);
                                continue;
                        }
 
-                       if (!PageDirty(page)) {
-                               /* someone wrote it for us */
-                               goto continue_unlock;
-                       }
-
-                       if (PageWriteback(page)) {
-                               if (wbc->sync_mode != WB_SYNC_NONE)
-                                       wait_on_page_writeback(page);
-                               else
-                                       goto continue_unlock;
-                       }
+                       if (PageWriteback(page))
+                               wait_on_page_writeback(page);
 
                        BUG_ON(PageWriteback(page));
                        if (!clear_page_dirty_for_io(page))
                                goto continue_unlock;
 
-                       /* BEGIN __mpage_da_writepage */
-
                        /*
                         * Can we merge this page to current extent?
                         */
@@ -2820,8 +2805,7 @@ continue_unlock:
                                         */
                                        redirty_page_for_writepage(wbc, page);
                                        unlock_page(page);
-                                       ret = MPAGE_DA_EXTENT_TAIL;
-                                       goto out;
+                                       goto ret_extent_tail;
                                }
 
                                /*
@@ -2838,15 +2822,15 @@ continue_unlock:
                                (PAGE_CACHE_SHIFT - inode->i_blkbits);
 
                        if (!page_has_buffers(page)) {
-                               mpage_add_bh_to_extent(mpd, logical, PAGE_CACHE_SIZE,
+                               mpage_add_bh_to_extent(mpd, logical,
+                                                      PAGE_CACHE_SIZE,
                                                       (1 << BH_Dirty) | (1 << BH_Uptodate));
-                               if (mpd->io_done) {
-                                       ret = MPAGE_DA_EXTENT_TAIL;
-                                       goto out;
-                               }
+                               if (mpd->io_done)
+                                       goto ret_extent_tail;
                        } else {
                                /*
-                                * Page with regular buffer heads, just add all dirty ones
+                                * Page with regular buffer heads,
+                                * just add all dirty ones
                                 */
                                head = page_buffers(page);
                                bh = head;
@@ -2862,18 +2846,19 @@ continue_unlock:
                                                mpage_add_bh_to_extent(mpd, logical,
                                                                       bh->b_size,
                                                                       bh->b_state);
-                                               if (mpd->io_done) {
-                                                       ret = MPAGE_DA_EXTENT_TAIL;
-                                                       goto out;
-                                               }
+                                               if (mpd->io_done)
+                                                       goto ret_extent_tail;
                                        } else if (buffer_dirty(bh) && (buffer_mapped(bh))) {
                                                /*
-                                                * mapped dirty buffer. We need to update
-                                                * the b_state because we look at
-                                                * b_state in mpage_da_map_blocks. We don't
-                                                * update b_size because if we find an
-                                                * unmapped buffer_head later we need to
-                                                * use the b_state flag of that buffer_head.
+                                                * mapped dirty buffer. We need
+                                                * to update the b_state
+                                                * because we look at b_state
+                                                * in mpage_da_map_blocks.  We
+                                                * don't update b_size because
+                                                * if we find an unmapped
+                                                * buffer_head later we need to
+                                                * use the b_state flag of that
+                                                * buffer_head.
                                                 */
                                                if (mpd->b_size == 0)
                                                        mpd->b_state = bh->b_state & BH_FLAGS;
@@ -2882,14 +2867,10 @@ continue_unlock:
                                } while ((bh = bh->b_this_page) != head);
                        }
 
-                       ret = 0;
-
-                       /* END __mpage_da_writepage */
-
                        if (nr_to_write > 0) {
                                nr_to_write--;
                                if (nr_to_write == 0 &&
-                                   wbc->sync_mode == WB_SYNC_NONE) {
+                                   wbc->sync_mode == WB_SYNC_NONE)
                                        /*
                                         * We stop writing back only if we are
                                         * not doing integrity sync. In case of
@@ -2900,15 +2881,15 @@ continue_unlock:
                                         * pages, but have not synced all of the
                                         * old dirty pages.
                                         */
-                                       done = 1;
-                                       break;
-                               }
+                                       goto out;
                        }
                }
                pagevec_release(&pvec);
                cond_resched();
        }
-       return ret;
+       return 0;
+ret_extent_tail:
+       ret = MPAGE_DA_EXTENT_TAIL;
 out:
        pagevec_release(&pvec);
        cond_resched();