Re: [PATCH V10 13/19] iomap & xfs: only account for new added page

Ming Lei
2018-11-19T08:35:49Z

On Thu, Nov 15, 2018 at 05:46:58PM -0800, Omar Sandoval wrote:
> On Thu, Nov 15, 2018 at 04:53:00PM +0800, Ming Lei wrote:
> > After multi-page is enabled, one new page may be merged to a segment
> > even though it is a new added page.
> >
> > This patch deals with this issue by post-check in case of merge, and
> > only a freshly new added page need to be dealt with for iomap & xfs.
> >
> > Cc: Dave Chinner <dchinner@redhat.com>
> > Cc: Kent Overstreet <kent.overstreet@gmail.com>
> > Cc: Mike Snitzer <snitzer@redhat.com>
> > Cc: dm-devel@redhat.com
> > Cc: Alexander Viro <viro@zeniv.linux.org.uk>
> > Cc: linux-fsdevel@vger.kernel.org
> > Cc: Shaohua Li <shli@kernel.org>
> > Cc: linux-raid@vger.kernel.org
> > Cc: linux-erofs@lists.ozlabs.org
> > Cc: David Sterba <dsterba@suse.com>
> > Cc: linux-btrfs@vger.kernel.org
> > Cc: Darrick J. Wong <darrick.wong@oracle.com>
> > Cc: linux-xfs@vger.kernel.org
> > Cc: Gao Xiang <gaoxiang25@huawei.com>
> > Cc: Christoph Hellwig <hch@lst.de>
> > Cc: Theodore Ts'o <tytso@mit.edu>
> > Cc: linux-ext4@vger.kernel.org
> > Cc: Coly Li <colyli@suse.de>
> > Cc: linux-bcache@vger.kernel.org
> > Cc: Boaz Harrosh <ooo@electrozaur.com>
> > Cc: Bob Peterson <rpeterso@redhat.com>
> > Cc: cluster-devel@redhat.com
> > Signed-off-by: Ming Lei <ming.lei@redhat.com>
> > ---
> > fs/iomap.c | 22 ++++++++++++++--------
> > fs/xfs/xfs_aops.c | 10 ++++++++--
> > include/linux/bio.h | 11 +++++++++++
> > 3 files changed, 33 insertions(+), 10 deletions(-)
> >
> > diff --git a/fs/iomap.c b/fs/iomap.c
> > index df0212560b36..a1b97a5c726a 100644
> > --- a/fs/iomap.c
> > +++ b/fs/iomap.c
> > @@ -288,6 +288,7 @@ iomap_readpage_actor(struct inode *inode, loff_t pos, loff_t length, void *data,
> > loff_t orig_pos = pos;
> > unsigned poff, plen;
> > sector_t sector;
> > + bool need_account = false;
> >
> > if (iomap->type == IOMAP_INLINE) {
> > WARN_ON_ONCE(pos);
> > @@ -313,18 +314,15 @@ iomap_readpage_actor(struct inode *inode, loff_t pos, loff_t length, void *data,
> > */
> > sector = iomap_sector(iomap, pos);
> > if (ctx->bio && bio_end_sector(ctx->bio) == sector) {
> > - if (__bio_try_merge_page(ctx->bio, page, plen, poff))
> > + if (__bio_try_merge_page(ctx->bio, page, plen, poff)) {
> > + need_account = iop && bio_is_last_segment(ctx->bio,
> > + page, plen, poff);
>
> It's redundant to make this iop && ... since you already check
> iop && need_account below. Maybe rename it to added_page? Also, this
> indentation is wack.

We may avoid to call bio_is_last_segment() in case of !iop, and will
fix the indentation.

Looks added_page is one better name.

>
> > goto done;
> > + }
> > is_contig = true;
> > }
> >
> > - /*
> > - * If we start a new segment we need to increase the read count, and we
> > - * need to do so before submitting any previous full bio to make sure
> > - * that we don't prematurely unlock the page.
> > - */
> > - if (iop)
> > - atomic_inc(&iop->read_count);
> > + need_account = true;
> >
> > if (!ctx->bio || !is_contig || bio_full(ctx->bio)) {
> > gfp_t gfp = mapping_gfp_constraint(page->mapping, GFP_KERNEL);
> > @@ -347,6 +345,14 @@ iomap_readpage_actor(struct inode *inode, loff_t pos, loff_t length, void *data,
> > __bio_add_page(ctx->bio, page, plen, poff);
> > done:
> > /*
> > + * If we add a new page we need to increase the read count, and we
> > + * need to do so before submitting any previous full bio to make sure
> > + * that we don't prematurely unlock the page.
> > + */
> > + if (iop && need_account)
> > + atomic_inc(&iop->read_count);
> > +
> > + /*
> > * Move the caller beyond our range so that it keeps making progress.
> > * For that we have to include any leading non-uptodate ranges, but
> > * we can skip trailing ones as they will be handled in the next
> > diff --git a/fs/xfs/xfs_aops.c b/fs/xfs/xfs_aops.c
> > index 1f1829e506e8..d8e9cc9f751a 100644
> > --- a/fs/xfs/xfs_aops.c
> > +++ b/fs/xfs/xfs_aops.c
> > @@ -603,6 +603,7 @@ xfs_add_to_ioend(
> > unsigned len = i_blocksize(inode);
> > unsigned poff = offset & (PAGE_SIZE - 1);
> > sector_t sector;
> > + bool need_account;
> >
> > sector = xfs_fsb_to_db(ip, wpc->imap.br_startblock) +
> > ((offset - XFS_FSB_TO_B(mp, wpc->imap.br_startoff)) >> 9);
> > @@ -617,13 +618,18 @@ xfs_add_to_ioend(
> > }
> >
> > if (!__bio_try_merge_page(wpc->ioend->io_bio, page, len, poff)) {
> > - if (iop)
> > - atomic_inc(&iop->write_count);
> > + need_account = true;
> > if (bio_full(wpc->ioend->io_bio))
> > xfs_chain_bio(wpc->ioend, wbc, bdev, sector);
> > __bio_add_page(wpc->ioend->io_bio, page, len, poff);
> > + } else {
> > + need_account = iop && bio_is_last_segment(wpc->ioend->io_bio,
> > + page, len, poff);
>
> Same here, no need for iop &&, rename it added_page, indentation is off.
>
> > }
> >
> > + if (iop && need_account)
> > + atomic_inc(&iop->write_count);
> > +
> > wpc->ioend->io_size += len;
> > }
> >
> > diff --git a/include/linux/bio.h b/include/linux/bio.h
> > index 1a2430a8b89d..5040e9a2eb09 100644
> > --- a/include/linux/bio.h
> > +++ b/include/linux/bio.h
> > @@ -341,6 +341,17 @@ static inline struct bio_vec *bio_last_bvec_all(struct bio *bio)
> > return &bio->bi_io_vec[bio->bi_vcnt - 1];
> > }
> >
> > +/* iomap needs this helper to deal with sub-pagesize bvec */
> > +static inline bool bio_is_last_segment(struct bio *bio, struct page *page,
> > + unsigned int len, unsigned int off)
>
> Indentation.

OK.

Thanks,
Ming