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Commit 17bc6c30 authored by Aneesh Kumar K.V's avatar Aneesh Kumar K.V Committed by Theodore Ts'o
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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: default avatarAneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Signed-off-by: default avatar"Theodore Ts'o" <tytso@mit.edu>
CC: linux-fsdevel@vger.kernel.org
parent 74baaaae

include/linux/writeback.h

+9 −0
Original line number Diff line number Diff line
@@ -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;

};



/*

mm/page-writeback.c

+7 −3
Original line number Diff line number Diff line
@@ -876,6 +876,7 @@ int write_cache_pages(struct address_space *mapping, 
	pgoff_t end;		/* Inclusive */

	int scanned = 0;

	int range_whole = 0;

	long nr_to_write = wbc->nr_to_write;



	if (wbc->nonblocking && bdi_write_congested(bdi)) {

		wbc->encountered_congestion = 1;
@@ -939,7 +940,7 @@ retry: 
				unlock_page(page);

				ret = 0;

			}

			if (ret || (--(wbc->nr_to_write) <= 0))

			if (ret || (--nr_to_write <= 0))

				done = 1;

			if (wbc->nonblocking && bdi_write_congested(bdi)) {

				wbc->encountered_congestion = 1;
@@ -958,8 +959,11 @@ retry: 
		index = 0;

		goto retry;

	}

	if (wbc->range_cyclic || (range_whole && wbc->nr_to_write > 0))

	if (!wbc->no_nrwrite_index_update) {

		if (wbc->range_cyclic || (range_whole && nr_to_write > 0))

			mapping->writeback_index = index;

		wbc->nr_to_write = nr_to_write;

	}



	return ret;

}