vfs: Add no_nrwrite_index_update writeback control flag

If no_nrwrite_index_update is set we don't update nr_to_write and
address space writeback_index in write_cache_pages.  This change
enables a file system to skip these updates in write_cache_pages and do
them in the writepages() callback.  This patch will be followed by an
ext4 patch that make use of these new flags.

Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
CC: linux-fsdevel@vger.kernel.org

1 files changed, 9 insertions, 0 deletions

diff --git a/include/linux/writeback.h b/include/linux/writeback.h
index bd91987c065f..e585657e9831 100644
--- a/include/linux/writeback.h
+++ b/include/linux/writeback.h
@@ -63,6 +63,15 @@ struct writeback_control {
         unsigned for_writepages:1;      /* This is a writepages() call */
         unsigned range_cyclic:1;        /* range_start is cyclic */
         unsigned more_io:1;             /* more io to be dispatched */
+        /*
+         * write_cache_pages() won't update wbc->nr_to_write and
+         * mapping->writeback_index if no_nrwrite_index_update
+         * is set.  write_cache_pages() may write more than we
+         * requested and we want to make sure nr_to_write and
+         * writeback_index are updated in a consistent manner
+         * so we use a single control to update them
+         */
+        unsigned no_nrwrite_index_update:1;
 };
 
 /*