ext4: Make ext4_bio_writepage() handle unprepared buffers (8a850c3f) · Commits · 戴 / test

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:

Jan Kara <jack@suse.cz> Signed-off-by:

"Theodore Ts'o" <tytso@mit.edu>

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) {
		/*

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