ext4: call mpage_da_submit_io() from mpage_da_map_blocks()
Theodore Ts'o [Thu, 28 Oct 2010 01:30:09 +0000 (21:30 -0400)]
Eventually we need to completely reorganize the ext4 writepage
callpath, but for now, we simplify things a little by calling
mpage_da_submit_io() from mpage_da_map_blocks(), since all of the
places where we call mpage_da_map_blocks() it is followed up by a call
to mpage_da_submit_io().

We're also a wee bit better with respect to error handling, but there
are still a number of issues where it's not clear what the right thing
is to do with ext4 functions deep in the writeback codepath fails.

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

fs/ext4/inode.c

index 670ab15..55961ff 100644 (file)
@@ -60,6 +60,7 @@ 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);
 
 /*
  * Test whether an inode is a fast symlink.
@@ -2033,7 +2034,7 @@ static int mpage_da_submit_io(struct mpage_da_data *mpd)
                        BUG_ON(PageWriteback(page));
 
                        pages_skipped = mpd->wbc->pages_skipped;
-                       err = mapping->a_ops->writepage(page, mpd->wbc);
+                       err = ext4_writepage(page, mpd->wbc);
                        if (!err && (pages_skipped == mpd->wbc->pages_skipped))
                                /*
                                 * have successfully written the page
@@ -2189,14 +2190,15 @@ static void ext4_print_free_blocks(struct inode *inode)
 }
 
 /*
- * mpage_da_map_blocks - go through given space
+ * mpage_da_map_and_submit - go through given space, map them
+ *       if necessary, and then submit them for I/O
  *
  * @mpd - bh describing space
  *
  * The function skips space we know is already mapped to disk blocks.
  *
  */
-static int mpage_da_map_blocks(struct mpage_da_data *mpd)
+static void mpage_da_map_and_submit(struct mpage_da_data *mpd)
 {
        int err, blks, get_blocks_flags;
        struct ext4_map_blocks map;
@@ -2206,18 +2208,14 @@ static int mpage_da_map_blocks(struct mpage_da_data *mpd)
        handle_t *handle = NULL;
 
        /*
-        * We consider only non-mapped and non-allocated blocks
+        * If the blocks are mapped already, or we couldn't accumulate
+        * any blocks, then proceed immediately to the submission stage.
         */
-       if ((mpd->b_state  & (1 << BH_Mapped)) &&
-               !(mpd->b_state & (1 << BH_Delay)) &&
-               !(mpd->b_state & (1 << BH_Unwritten)))
-               return 0;
-
-       /*
-        * If we didn't accumulate anything to write simply return
-        */
-       if (!mpd->b_size)
-               return 0;
+       if ((mpd->b_size == 0) ||
+           ((mpd->b_state  & (1 << BH_Mapped)) &&
+            !(mpd->b_state & (1 << BH_Delay)) &&
+            !(mpd->b_state & (1 << BH_Unwritten))))
+               goto submit_io;
 
        handle = ext4_journal_current_handle();
        BUG_ON(!handle);
@@ -2254,17 +2252,18 @@ static int mpage_da_map_blocks(struct mpage_da_data *mpd)
 
                err = blks;
                /*
-                * If get block returns with error we simply
-                * return. Later writepage will redirty the page and
-                * writepages will find the dirty page again
+                * 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.
                 */
                if (err == -EAGAIN)
-                       return 0;
+                       goto submit_io;
 
                if (err == -ENOSPC &&
                    ext4_count_free_blocks(sb)) {
                        mpd->retval = err;
-                       return 0;
+                       goto submit_io;
                }
 
                /*
@@ -2289,7 +2288,7 @@ static int mpage_da_map_blocks(struct mpage_da_data *mpd)
                /* invalidate all the pages */
                ext4_da_block_invalidatepages(mpd, next,
                                mpd->b_size >> mpd->inode->i_blkbits);
-               return err;
+               return;
        }
        BUG_ON(blks == 0);
 
@@ -2312,7 +2311,8 @@ static int mpage_da_map_blocks(struct mpage_da_data *mpd)
        if (ext4_should_order_data(mpd->inode)) {
                err = ext4_jbd2_file_inode(handle, mpd->inode);
                if (err)
-                       return err;
+                       /* This only happens if the journal is aborted */
+                       return;
        }
 
        /*
@@ -2323,10 +2323,16 @@ static int mpage_da_map_blocks(struct mpage_da_data *mpd)
                disksize = i_size_read(mpd->inode);
        if (disksize > EXT4_I(mpd->inode)->i_disksize) {
                ext4_update_i_disksize(mpd->inode, disksize);
-               return ext4_mark_inode_dirty(handle, mpd->inode);
+               err = ext4_mark_inode_dirty(handle, mpd->inode);
+               if (err)
+                       ext4_error(mpd->inode->i_sb,
+                                  "Failed to mark inode %lu dirty",
+                                  mpd->inode->i_ino);
        }
 
-       return 0;
+submit_io:
+       mpage_da_submit_io(mpd);
+       mpd->io_done = 1;
 }
 
 #define BH_FLAGS ((1 << BH_Uptodate) | (1 << BH_Mapped) | \
@@ -2403,9 +2409,7 @@ flush_it:
         * We couldn't merge the block to our extent, so we
         * need to flush current  extent and start new one
         */
-       if (mpage_da_map_blocks(mpd) == 0)
-               mpage_da_submit_io(mpd);
-       mpd->io_done = 1;
+       mpage_da_map_and_submit(mpd);
        return;
 }
 
@@ -2437,15 +2441,13 @@ static int __mpage_da_writepage(struct page *page,
        if (mpd->next_page != page->index) {
                /*
                 * Nope, we can't. So, we map non-allocated blocks
-                * and start IO on them using writepage()
+                * and start IO on them
                 */
                if (mpd->next_page != mpd->first_page) {
-                       if (mpage_da_map_blocks(mpd) == 0)
-                               mpage_da_submit_io(mpd);
+                       mpage_da_map_and_submit(mpd);
                        /*
                         * skip rest of the page in the page_vec
                         */
-                       mpd->io_done = 1;
                        redirty_page_for_writepage(wbc, page);
                        unlock_page(page);
                        return MPAGE_DA_EXTENT_TAIL;
@@ -3071,9 +3073,7 @@ retry:
                 * them for I/O.
                 */
                if (!mpd.io_done && mpd.next_page != mpd.first_page) {
-                       if (mpage_da_map_blocks(&mpd) == 0)
-                               mpage_da_submit_io(&mpd);
-                       mpd.io_done = 1;
+                       mpage_da_map_and_submit(&mpd);
                        ret = MPAGE_DA_EXTENT_TAIL;
                }
                trace_ext4_da_write_pages(inode, &mpd);