From a42afc5f56f319107e987aa6adf2f65d93d527c7 Mon Sep 17 00:00:00 2001 From: Theodore Ts'o Date: Wed, 27 Oct 2010 21:30:09 -0400 Subject: [PATCH] ext4: simplify ext4_writepage() The actual code in ext4_writepage() is unnecessarily convoluted. Simplify it so it is easier to understand, but otherwise logically equivalent. Signed-off-by: "Theodore Ts'o" --- fs/ext4/inode.c | 73 +++++++++++++++++-------------------------------- 1 file changed, 25 insertions(+), 48 deletions(-) diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c index 55961ff4efc2..a08ec795995f 100644 --- a/fs/ext4/inode.c +++ b/fs/ext4/inode.c @@ -2704,7 +2704,7 @@ static void ext4_end_io_buffer_write(struct buffer_head *bh, int uptodate); static int ext4_writepage(struct page *page, struct writeback_control *wbc) { - int ret = 0; + int ret = 0, commit_write = 0; loff_t size; unsigned int len; struct buffer_head *page_bufs = NULL; @@ -2717,60 +2717,37 @@ static int ext4_writepage(struct page *page, else len = PAGE_CACHE_SIZE; - if (page_has_buffers(page)) { - page_bufs = page_buffers(page); - if (walk_page_buffers(NULL, page_bufs, 0, len, NULL, - ext4_bh_delay_or_unwritten)) { - /* - * We don't want to do block allocation - * So redirty the page and return - * We may reach here when we do a journal commit - * via journal_submit_inode_data_buffers. - * If we don't have mapping block we just ignore - * them. We can also reach here via shrink_page_list - */ + /* + * 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_buffers(page)) { + if (block_prepare_write(page, 0, len, + noalloc_get_block_write)) { + redirty_page: redirty_page_for_writepage(wbc, page); unlock_page(page); return 0; } - } else { + commit_write = 1; + } + page_bufs = page_buffers(page); + if (walk_page_buffers(NULL, page_bufs, 0, len, NULL, + ext4_bh_delay_or_unwritten)) { /* - * The test for page_has_buffers() is subtle: - * We know the page is dirty but it lost buffers. That means - * that at some moment in time after write_begin()/write_end() - * has been called all buffers have been clean and thus they - * must have been written at least once. So they are all - * mapped and we can happily proceed with mapping them - * and writing the page. - * - * Try to initialize the buffer_heads and check whether - * all are mapped and non delay. We don't want to - * do block allocation here. + * We don't want to do block allocation So redirty the + * page and return We may reach here when we do a + * journal commit via + * journal_submit_inode_data_buffers. If we don't + * have mapping block we just ignore them. We can also + * reach here via shrink_page_list */ - ret = block_prepare_write(page, 0, len, - noalloc_get_block_write); - if (!ret) { - page_bufs = page_buffers(page); - /* check whether all are mapped and non delay */ - if (walk_page_buffers(NULL, page_bufs, 0, len, NULL, - ext4_bh_delay_or_unwritten)) { - redirty_page_for_writepage(wbc, page); - unlock_page(page); - return 0; - } - } else { - /* - * We can't do block allocation here - * so just redity the page and unlock - * and return - */ - redirty_page_for_writepage(wbc, page); - unlock_page(page); - return 0; - } + goto redirty_page; + } + if (commit_write) /* now mark the buffer_heads as dirty and uptodate */ block_commit_write(page, 0, len); - } if (PageChecked(page) && ext4_should_journal_data(inode)) { /* @@ -2781,7 +2758,7 @@ static int ext4_writepage(struct page *page, return __ext4_journalled_writepage(page, len); } - if (page_bufs && buffer_uninit(page_bufs)) { + if (buffer_uninit(page_bufs)) { ext4_set_bh_endio(page_bufs, inode); ret = block_write_full_page_endio(page, noalloc_get_block_write, wbc, ext4_end_io_buffer_write); -- 2.20.1