iomap: factor out a iomap_writepage_map_block helper

Split the loop body that calls into the file system to map a block and
add it to the ioend into a separate helper to prefer for refactoring of
the surrounding code.

Note that this was the only place in iomap_writepage_map that could
return an error, so include the call to ->discard_folio into the new
helper as that will help to avoid code duplication in the future.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20231207072710.176093-12-hch@lst.de
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Christian Brauner <brauner@kernel.org>

diff --git a/fs/iomap/buffered-io.c b/fs/iomap/buffered-io.c
index 71f0aaf..b065df8 100644 (file)
--- a/fs/iomap/buffered-io.c
+++ b/fs/iomap/buffered-io.c
@@ -1712,6 +1712,45 @@ new_ioend:
        wbc_account_cgroup_owner(wbc, &folio->page, len);
 }
 
+static int iomap_writepage_map_blocks(struct iomap_writepage_ctx *wpc,
+               struct writeback_control *wbc, struct folio *folio,
+               struct inode *inode, u64 pos, unsigned *count,
+               struct list_head *submit_list)
+{
+       int error;
+
+       error = wpc->ops->map_blocks(wpc, inode, pos);
+       if (error)
+               goto fail;
+       trace_iomap_writepage_map(inode, &wpc->iomap);
+
+       switch (wpc->iomap.type) {
+       case IOMAP_INLINE:
+               WARN_ON_ONCE(1);
+               error = -EIO;
+               break;
+       case IOMAP_HOLE:
+               break;
+       default:
+               iomap_add_to_ioend(wpc, wbc, folio, inode, pos, submit_list);
+               (*count)++;
+       }
+
+fail:
+       /*
+        * We cannot cancel the ioend directly here on error.  We may have
+        * already set other pages under writeback and hence we have to run I/O
+        * completion to mark the error state of the pages under writeback
+        * appropriately.
+        *
+        * Just let the file system know what portion of the folio failed to
+        * map.
+        */
+       if (error && wpc->ops->discard_folio)
+               wpc->ops->discard_folio(folio, pos);
+       return error;
+}
+
 /*
  * Check interaction of the folio with the file end.
  *
@@ -1796,7 +1835,8 @@ static int iomap_writepage_map(struct iomap_writepage_ctx *wpc,
        unsigned nblocks = i_blocks_per_folio(inode, folio);
        u64 pos = folio_pos(folio);
        u64 end_pos = pos + folio_size(folio);
-       int error = 0, count = 0, i;
+       unsigned count = 0;
+       int error = 0, i;
        LIST_HEAD(submit_list);
 
        trace_iomap_writepage(inode, pos, folio_size(folio));
@@ -1822,19 +1862,10 @@ static int iomap_writepage_map(struct iomap_writepage_ctx *wpc,
        for (i = 0; i < nblocks && pos < end_pos; i++, pos += len) {
                if (ifs && !ifs_block_is_dirty(folio, ifs, i))
                        continue;
-
-               error = wpc->ops->map_blocks(wpc, inode, pos);
+               error = iomap_writepage_map_blocks(wpc, wbc, folio, inode, pos,
+                               &count, &submit_list);
                if (error)
                        break;
-               trace_iomap_writepage_map(inode, &wpc->iomap);
-               if (WARN_ON_ONCE(wpc->iomap.type == IOMAP_INLINE)) {
-                       error = -EIO;
-                       break;
-               }
-               if (wpc->iomap.type == IOMAP_HOLE)
-                       continue;
-               iomap_add_to_ioend(wpc, wbc, folio, inode, pos, &submit_list);
-               count++;
        }
        if (count)
                wpc->nr_folios++;
@@ -1844,21 +1875,6 @@ static int iomap_writepage_map(struct iomap_writepage_ctx *wpc,
        WARN_ON_ONCE(folio_test_writeback(folio));
        WARN_ON_ONCE(folio_test_dirty(folio));
 
-       /*
-        * We cannot cancel the ioend directly here on error.  We may have
-        * already set other pages under writeback and hence we have to run I/O
-        * completion to mark the error state of the pages under writeback
-        * appropriately.
-        */
-       if (unlikely(error)) {
-               /*
-                * Let the filesystem know what portion of the current page
-                * failed to map.
-                */
-               if (wpc->ops->discard_folio)
-                       wpc->ops->discard_folio(folio, pos);
-       }
-
        /*
         * We can have dirty bits set past end of file in page_mkwrite path
         * while mapping the last partial folio. Hence it's better to clear