On Mon, Mar 18, 2013 at 06:41:34PM +0100, Jan Kara wrote:
> On Fri 15-03-13 16:28:16, Darrick J. Wong wrote:
> > Walking a bio's page mappings has proved problematic, so create a new bio flag
> > to indicate that a bio's data needs to be snapshotted in order to guarantee
> > stable pages during writeback. Next, for the one user (ext3/jbd) of
> > snapshotting, hook all the places where writes can be initiated without
> > PG_writeback set, and set BIO_SNAP_STABLE there. We must also flag journal
> > "metadata" bios for stable writeout if data=journal, since file data is written
> > through the journal. Finally, the MS_SNAP_STABLE mount flag (only used by
> > ext3) is now superfluous, so get rid of it.
> >
> > Signed-off-by: Darrick J. Wong <darrick.wong@xxxxxxxxxx>
> >
> > [darrick.wong@xxxxxxxxxx: Fold in a couple of small cleanups from akpm]
> > Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
> > ---
> > fs/buffer.c | 9 ++++++++-
> > fs/ext3/super.c | 3 ++-
> > fs/jbd/commit.c | 28 +++++++++++++++++++++++++---
> > include/linux/blk_types.h | 3 ++-
> > include/linux/buffer_head.h | 1 +
> > include/linux/jbd.h | 1 +
> > include/uapi/linux/fs.h | 1 -
> > mm/bounce.c | 21 +--------------------
> > mm/page-writeback.c | 4 ----
> > 9 files changed, 40 insertions(+), 31 deletions(-)
> >
> > diff --git a/fs/buffer.c b/fs/buffer.c
> > index b4dcb34..71578d6 100644
> > --- a/fs/buffer.c
> > +++ b/fs/buffer.c
> > @@ -2949,7 +2949,7 @@ static void guard_bh_eod(int rw, struct bio *bio, struct buffer_head *bh)
> > }
> > }
> >
> > -int submit_bh(int rw, struct buffer_head * bh)
> > +int _submit_bh(int rw, struct buffer_head *bh, unsigned long bio_flags)
> > {
> > struct bio *bio;
> > int ret = 0;
> > @@ -2984,6 +2984,7 @@ int submit_bh(int rw, struct buffer_head * bh)
> >
> > bio->bi_end_io = end_bio_bh_io_sync;
> > bio->bi_private = bh;
> > + bio->bi_flags |= bio_flags;
> >
> > /* Take care of bh's that straddle the end of the device */
> > guard_bh_eod(rw, bio, bh);
> > @@ -2997,6 +2998,12 @@ int submit_bh(int rw, struct buffer_head * bh)
> > bio_put(bio);
> > return ret;
> > }
> > +EXPORT_SYMBOL_GPL(_submit_bh);
> > +
> > +int submit_bh(int rw, struct buffer_head *bh)
> > +{
> > + return _submit_bh(rw, bh, 0);
> > +}
> > EXPORT_SYMBOL(submit_bh);
> >
> > /**
> > diff --git a/fs/ext3/super.c b/fs/ext3/super.c
> > index 1d6e2ed..e845b6de 100644
> > --- a/fs/ext3/super.c
> > +++ b/fs/ext3/super.c
> > @@ -2063,11 +2063,12 @@ static int ext3_fill_super (struct super_block *sb, void *data, int silent)
> > ext3_mark_recovery_complete(sb, es);
> > ext3_msg(sb, KERN_INFO, "recovery complete");
> > }
> > + if (test_opt(sb, DATA_FLAGS) == EXT3_MOUNT_JOURNAL_DATA)
> > + EXT3_SB(sb)->s_journal->j_flags |= JFS_JOURNALS_DATA;
> Sadly this isn't enough. You can have inodes which journal data (there's
> an inode flag for this) in data=ordered mode. So what you have to do is to
Arrrgh, I forgot that you can do that per-inode. :(
> flag journal_heads (or buffer_heads) as containing journalled data. Or you
> can actually use PageChecked flag for this (it is going to be set on all
> write-enabled pages with journalled data). But it definitely requires also
> some playing with ->page_mkwrite() (calling ext3_journal_get_write_access()
> from there) and generally I'd rather postpone that to a separate commit. So
> just keep it simple and always set the bio flag as you did in the previous
> version. I'll write an optimization (mostly because ext4 needs it as well)
> and send it to you for testing.
Yeah, this is getting a bit complicated for a single patch.
--D
>
> Honza
> --
> Jan Kara <jack@xxxxxxx>
> SUSE Labs, CR
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