ext4: move mpage_put_bnr_to_bhs()'s functionality to mpage_da_submit_io()

This massively simplifies the ext4_da_writepages() code path by
completely removing mpage_put_bnr_bhs(), which is almost 100 lines of
code iterating over a set of pages using pagevec_lookup(), and folds
that functionality into mpage_da_submit_io()'s existing
pagevec_lookup() loop.

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

1 files changed, 38 insertions, 101 deletions

diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index 5da6cfcecd83..c65d647378f9 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -2003,7 +2003,8 @@ static void ext4_da_page_release_reservation(struct page *page,
  *
  * As pages are already locked by write_cache_pages(), we can't use it
  */
-static int mpage_da_submit_io(struct mpage_da_data *mpd)
+static int mpage_da_submit_io(struct mpage_da_data *mpd,
+                              struct ext4_map_blocks *map)
 {
         struct pagevec pvec;
         unsigned long index, end;
@@ -2014,6 +2015,7 @@ static int mpage_da_submit_io(struct mpage_da_data *mpd)
         unsigned int len, block_start;
         struct buffer_head *bh, *page_bufs = NULL;
         int journal_data = ext4_should_journal_data(inode);
+        sector_t pblock = 0, cur_logical = 0;
 
         BUG_ON(mpd->next_page <= mpd->first_page);
         /*
@@ -2031,7 +2033,7 @@ 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;
+                        int commit_write = 0, redirty_page = 0;
                         struct page *page = pvec.pages[i];
 
                         index = page->index;
@@ -2042,6 +2044,12 @@ static int mpage_da_submit_io(struct mpage_da_data *mpd)
                                 len = size & ~PAGE_CACHE_MASK;
                         else
                                 len = PAGE_CACHE_SIZE;
+                        if (map) {
+                                cur_logical = index << (PAGE_CACHE_SHIFT -
+                                                        inode->i_blkbits);
+                                pblock = map->m_pblk + (cur_logical -
+                                                        map->m_lblk);
+                        }
                         index++;
 
                         BUG_ON(!PageLocked(page));
@@ -2068,13 +2076,34 @@ static int mpage_da_submit_io(struct mpage_da_data *mpd)
                         bh = page_bufs = page_buffers(page);
                         block_start = 0;
                         do {
-                                /* redirty page if block allocation undone */
-                                if (!bh || buffer_delay(bh) ||
-                                    buffer_unwritten(bh))
+                                if (!bh)
                                         goto redirty_page;
+                                if (map && (cur_logical >= map->m_lblk) &&
+                                    (cur_logical <= (map->m_lblk +
+                                                     (map->m_len - 1)))) {
+                                        if (buffer_delay(bh)) {
+                                                clear_buffer_delay(bh);
+                                                bh->b_blocknr = pblock;
+                                        }
+                                        if (buffer_unwritten(bh) ||
+                                            buffer_mapped(bh))
+                                                BUG_ON(bh->b_blocknr != pblock);
+                                        if (map->m_flags & EXT4_MAP_UNINIT)
+                                                set_buffer_uninit(bh);
+                                        clear_buffer_unwritten(bh);
+                                }
+
+                                /* redirty page if block allocation undone */
+                                if (buffer_delay(bh) || buffer_unwritten(bh))
+                                        redirty_page = 1;
                                 bh = bh->b_this_page;
                                 block_start += bh->b_size;
-                        } while ((bh != page_bufs) && (block_start < len));
+                                cur_logical++;
+                                pblock++;
+                        } while (bh != page_bufs);
+
+                        if (redirty_page)
+                                goto redirty_page;
 
                         if (commit_write)
                                 /* mark the buffer_heads as dirty & uptodate */
@@ -2105,91 +2134,6 @@ static int mpage_da_submit_io(struct mpage_da_data *mpd)
         return ret;
 }
 
-/*
- * mpage_put_bnr_to_bhs - walk blocks and assign them actual numbers
- *
- * the function goes through all passed space and put actual disk
- * block numbers into buffer heads, dropping BH_Delay and BH_Unwritten
- */
-static void mpage_put_bnr_to_bhs(struct mpage_da_data *mpd,
-                                 struct ext4_map_blocks *map)
-{
-        struct inode *inode = mpd->inode;
-        struct address_space *mapping = inode->i_mapping;
-        int blocks = map->m_len;
-        sector_t pblock = map->m_pblk, cur_logical;
-        struct buffer_head *head, *bh;
-        pgoff_t index, end;
-        struct pagevec pvec;
-        int nr_pages, i;
-
-        index = map->m_lblk >> (PAGE_CACHE_SHIFT - inode->i_blkbits);
-        end = (map->m_lblk + blocks - 1) >> (PAGE_CACHE_SHIFT - inode->i_blkbits);
-        cur_logical = index << (PAGE_CACHE_SHIFT - inode->i_blkbits);
-
-        pagevec_init(&pvec, 0);
-
-        while (index <= end) {
-                /* XXX: optimize tail */
-                nr_pages = pagevec_lookup(&pvec, mapping, index, PAGEVEC_SIZE);
-                if (nr_pages == 0)
-                        break;
-                for (i = 0; i < nr_pages; i++) {
-                        struct page *page = pvec.pages[i];
-
-                        index = page->index;
-                        if (index > end)
-                                break;
-                        index++;
-
-                        BUG_ON(!PageLocked(page));
-                        BUG_ON(PageWriteback(page));
-                        BUG_ON(!page_has_buffers(page));
-
-                        bh = page_buffers(page);
-                        head = bh;
-
-                        /* skip blocks out of the range */
-                        do {
-                                if (cur_logical >= map->m_lblk)
-                                        break;
-                                cur_logical++;
-                        } while ((bh = bh->b_this_page) != head);
-
-                        do {
-                                if (cur_logical > map->m_lblk + (blocks - 1))
-                                        break;
-
-                                if (buffer_delay(bh) || buffer_unwritten(bh)) {
-
-                                        BUG_ON(bh->b_bdev != inode->i_sb->s_bdev);
-
-                                        if (buffer_delay(bh)) {
-                                                clear_buffer_delay(bh);
-                                                bh->b_blocknr = pblock;
-                                        } else {
-                                                /*
-                                                 * unwritten already should have
-                                                 * blocknr assigned. Verify that
-                                                 */
-                                                clear_buffer_unwritten(bh);
-                                                BUG_ON(bh->b_blocknr != pblock);
-                                        }
-
-                                } else if (buffer_mapped(bh))
-                                        BUG_ON(bh->b_blocknr != pblock);
-
-                                if (map->m_flags & EXT4_MAP_UNINIT)
-                                        set_buffer_uninit(bh);
-                                cur_logical++;
-                                pblock++;
-                        } while ((bh = bh->b_this_page) != head);
-                }
-                pagevec_release(&pvec);
-        }
-}
-
-
 static void ext4_da_block_invalidatepages(struct mpage_da_data *mpd,
                                         sector_t logical, long blk_cnt)
 {
@@ -2252,7 +2196,7 @@ static void ext4_print_free_blocks(struct inode *inode)
 static void mpage_da_map_and_submit(struct mpage_da_data *mpd)
 {
         int err, blks, get_blocks_flags;
-        struct ext4_map_blocks map;
+        struct ext4_map_blocks map, *mapp = NULL;
         sector_t next = mpd->b_blocknr;
         unsigned max_blocks = mpd->b_size >> mpd->inode->i_blkbits;
         loff_t disksize = EXT4_I(mpd->inode)->i_disksize;
@@ -2343,6 +2287,7 @@ static void mpage_da_map_and_submit(struct mpage_da_data *mpd)
         }
         BUG_ON(blks == 0);
 
+        mapp = &map;
         if (map.m_flags & EXT4_MAP_NEW) {
                 struct block_device *bdev = mpd->inode->i_sb->s_bdev;
                 int i;
@@ -2351,14 +2296,6 @@ static void mpage_da_map_and_submit(struct mpage_da_data *mpd)
                         unmap_underlying_metadata(bdev, map.m_pblk + i);
         }
 
-        /*
-         * If blocks are delayed marked, we need to
-         * put actual blocknr and drop delayed bit
-         */
-        if ((mpd->b_state & (1 << BH_Delay)) ||
-            (mpd->b_state & (1 << BH_Unwritten)))
-                mpage_put_bnr_to_bhs(mpd, &map);
-
         if (ext4_should_order_data(mpd->inode)) {
                 err = ext4_jbd2_file_inode(handle, mpd->inode);
                 if (err)
@@ -2382,7 +2319,7 @@ static void mpage_da_map_and_submit(struct mpage_da_data *mpd)
         }
 
 submit_io:
-        mpage_da_submit_io(mpd);
+        mpage_da_submit_io(mpd, mapp);
         mpd->io_done = 1;
 }