From: "Darrick J. Wong" Subject: Re: [PATCH] mm: Make snapshotting pages for stable writes a per-bio operation Date: Mon, 18 Mar 2013 16:01:36 -0700 Message-ID: <20130318230136.GO5313@blackbox.djwong.org> References: <5139DB90.5090302@gmail.com> <20130312153221.0d26fe5599d4885e51bb0c7c@linux-foundation.org> <20130313011020.GA5313@blackbox.djwong.org> <20130313085021.GA29730@quack.suse.cz> <20130313194429.GE5313@blackbox.djwong.org> <20130313210216.GA7754@quack.suse.cz> <20130314224243.GI5313@blackbox.djwong.org> <20130315100105.GA4889@quack.suse.cz> <20130315232816.GN5313@blackbox.djwong.org> <20130318174134.GB7852@quack.suse.cz> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Andrew Morton , Shuge , linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-ext4@vger.kernel.org, Kevin , "Theodore Ts'o" , Jens Axboe , Catalin Marinas , Will Deacon , linux-arm-kernel@lists.infradead.org To: Jan Kara Return-path: Content-Disposition: inline In-Reply-To: <20130318174134.GB7852@quack.suse.cz> Sender: owner-linux-mm@kvack.org List-Id: linux-ext4.vger.kernel.org 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@oracle.com: Fold in a couple of small cleanups from akpm] > > Signed-off-by: Andrew Morton > > --- > > 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 > SUSE Labs, CR -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org