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ext4: Make ext4_bio_writepage() handle unprepared buffers

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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>
This commit is contained in:
Jan Kara 2013-01-28 20:53:28 -05:00 committed by Theodore Ts'o
parent b6a8e62f8b
commit 8a850c3fb8
1 changed files with 9 additions and 8 deletions
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17
fs/ext4/page-io.c
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@ -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) {
/*