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Commit 8a850c3f authored by Jan Kara's avatar Jan Kara Committed by Theodore Ts'o
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ext4: Make ext4_bio_writepage() handle unprepared buffers 



So far ext4_bio_writepage() unconditionally cleared dirty bit on all
buffers underlying the page. That implicitely assumes we can write all
buffers. So far that is true because callers call into
ext4_bio_writepage() make sure all buffers in the page are mapped but:

a) it's a data corruption bug waiting to happen
b) in data=ordered mode when blocksize < pagesize we do need to write
   pages that may have only some of dirty buffers mapped.

So change ext4_bio_writepage() to skip buffers that cannot be written without
clearing their dirty bit.

Signed-off-by: default avatarJan Kara <jack@suse.cz>
Signed-off-by: default avatar"Theodore Ts'o" <tytso@mit.edu>
parent b6a8e62f

fs/ext4/page-io.c

+9 −8
Original line number Diff line number Diff line
@@ -350,14 +350,6 @@ static int io_submit_add_bh(struct ext4_io_submit *io, 
		unmap_underlying_metadata(bh->b_bdev, bh->b_blocknr);

	}



	if (!buffer_mapped(bh) || buffer_delay(bh)) {

		if (!buffer_mapped(bh))

			clear_buffer_dirty(bh);

		if (io->io_bio)

			ext4_io_submit(io);

		return 0;

	}



	if (io->io_bio && bh->b_blocknr != io->io_next_block) {

submit_and_retry:

		ext4_io_submit(io);
@@ -436,6 +428,15 @@ int ext4_bio_write_page(struct ext4_io_submit *io, 
			set_buffer_uptodate(bh);

			continue;

		}

		if (!buffer_dirty(bh) || buffer_delay(bh) ||

		    !buffer_mapped(bh) || buffer_unwritten(bh)) {

			/* A hole? We can safely clear the dirty bit */

			if (!buffer_mapped(bh))

				clear_buffer_dirty(bh);

			if (io->io_bio)

				ext4_io_submit(io);

			continue;

		}

		ret = io_submit_add_bh(io, io_page, inode, wbc, bh);

		if (ret) {

			/*