RE: [PATCH v2 2/4] f2fs: introduce f2fs_submit_merged_bio_cond

From: Chao Yu
Date: Mon Jan 25 2016 - 04:51:25 EST

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Hi Jaegeuk,

> -----Original Message-----
> From: Jaegeuk Kim [mailto:jaegeuk@xxxxxxxxxx]
> Sent: Sunday, January 24, 2016 4:22 AM
> To: Chao Yu
> Cc: linux-f2fs-devel@xxxxxxxxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx
> Subject: Re: [PATCH v2 2/4] f2fs: introduce f2fs_submit_merged_bio_cond
>
> Hi Chao,
>
> Could you review this patch again?

I did the review, but found nothing, and also I couldn't reproduce this
issue.

> I just got a panic from this patch.
> I have not much time to dig this, so couldn't remain more specific info.
> Let me test this later.

OK, if there is some dmesg info, please share with me. :)

Thanks,

>
> Thanks,
>
> On Mon, Jan 18, 2016 at 06:28:11PM +0800, Chao Yu wrote:
> > f2fs use single bio buffer per type data (META/NODE/DATA) for caching
> > writes locating in continuous block address as many as possible, after
> > submitting, these writes may be still cached in bio buffer, so we have
> > to flush cached writes in bio buffer by calling f2fs_submit_merged_bio.
> >
> > Unfortunately, in the scenario of high concurrency, bio buffer could be
> > flushed by someone else before we submit it as below reasons:
> > a) there is no space in bio buffer.
> > b) add a request of different type (SYNC, ASYNC).
> > c) add a discontinuous block address.
> >
> > For this condition, f2fs_submit_merged_bio will be devastating, because
> > it could break the following merging of writes in bio buffer, split one
> > big bio into two smaller one.
> >
> > This patch introduces f2fs_submit_merged_bio_cond which can do a
> > conditional submitting with bio buffer, before submitting it will judge
> > whether:
> > - page in DATA type bio buffer is matching with specified page;
> > - page in DATA type bio buffer is belong to specified inode;
> > - page in NODE type bio buffer is belong to specified inode;
> > If there is no eligible page in bio buffer, we will skip submitting step,
> > result in gaining more chance to merge consecutive block IOs in bio cache.
> >
> > Signed-off-by: Chao Yu <chao2.yu@xxxxxxxxxxx>
> > ---
> > v2:
> > - update comments.
> > - split ("f2fs: relocate is_merged_page ") from this patch.
> > ---
> > fs/f2fs/checkpoint.c | 7 ++++-
> > fs/f2fs/data.c | 74 +++++++++++++++++++++++++++++++++++++++-------------
> > fs/f2fs/f2fs.h | 3 ++-
> > fs/f2fs/node.c | 15 ++++++++---
> > fs/f2fs/segment.c | 6 ++---
> > 5 files changed, 79 insertions(+), 26 deletions(-)
> >
> > diff --git a/fs/f2fs/checkpoint.c b/fs/f2fs/checkpoint.c
> > index 3842af9..c75b148 100644
> > --- a/fs/f2fs/checkpoint.c
> > +++ b/fs/f2fs/checkpoint.c
> > @@ -235,10 +235,15 @@ static int f2fs_write_meta_page(struct page *page,
> > f2fs_wait_on_page_writeback(page, META);
> > write_meta_page(sbi, page);
> > dec_page_count(sbi, F2FS_DIRTY_META);
> > +
> > + if (wbc->for_reclaim)
> > + f2fs_submit_merged_bio_cond(sbi, NULL, page, 0, META, WRITE);
> > +
> > unlock_page(page);
> >
> > - if (wbc->for_reclaim || unlikely(f2fs_cp_error(sbi)))
> > + if (unlikely(f2fs_cp_error(sbi)))
> > f2fs_submit_merged_bio(sbi, META, WRITE);
> > +
> > return 0;
> >
> > redirty_out:
> > diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c
> > index b118055..19e9924 100644
> > --- a/fs/f2fs/data.c
> > +++ b/fs/f2fs/data.c
> > @@ -116,20 +116,18 @@ static void __submit_merged_bio(struct f2fs_bio_info *io)
> > io->bio = NULL;
> > }
> >
> > -bool is_merged_page(struct f2fs_sb_info *sbi, struct page *page,
> > - enum page_type type)
> > +static bool __has_merged_page(struct f2fs_bio_info *io, struct inode *inode,
> > + struct page *page, nid_t ino)
> > {
> > - enum page_type btype = PAGE_TYPE_OF_BIO(type);
> > - struct f2fs_bio_info *io = &sbi->write_io[btype];
> > struct bio_vec *bvec;
> > struct page *target;
> > int i;
> >
> > - down_read(&io->io_rwsem);
> > - if (!io->bio) {
> > - up_read(&io->io_rwsem);
> > + if (!io->bio)
> > return false;
> > - }
> > +
> > + if (!inode && !page && !ino)
> > + return true;
> >
> > bio_for_each_segment_all(bvec, io->bio, i) {
> >
> > @@ -144,18 +142,34 @@ bool is_merged_page(struct f2fs_sb_info *sbi, struct page *page,
> > target = ctx->w.control_page;
> > }
> >
> > - if (page == target) {
> > - up_read(&io->io_rwsem);
> > + if (inode && inode == target->mapping->host)
> > + return true;
> > + if (page && page == target)
> > + return true;
> > + if (ino && ino == ino_of_node(target))
> > return true;
> > - }
> > }
> >
> > - up_read(&io->io_rwsem);
> > return false;
> > }
> >
> > -void f2fs_submit_merged_bio(struct f2fs_sb_info *sbi,
> > - enum page_type type, int rw)
> > +static bool has_merged_page(struct f2fs_sb_info *sbi, struct inode *inode,
> > + struct page *page, nid_t ino,
> > + enum page_type type)
> > +{
> > + enum page_type btype = PAGE_TYPE_OF_BIO(type);
> > + struct f2fs_bio_info *io = &sbi->write_io[btype];
> > + bool ret;
> > +
> > + down_read(&io->io_rwsem);
> > + ret = __has_merged_page(io, inode, page, ino);
> > + up_read(&io->io_rwsem);
> > + return ret;
> > +}
> > +
> > +static void __f2fs_submit_merged_bio(struct f2fs_sb_info *sbi,
> > + struct inode *inode, struct page *page,
> > + nid_t ino, enum page_type type, int rw)
> > {
> > enum page_type btype = PAGE_TYPE_OF_BIO(type);
> > struct f2fs_bio_info *io;
> > @@ -164,6 +178,9 @@ void f2fs_submit_merged_bio(struct f2fs_sb_info *sbi,
> >
> > down_write(&io->io_rwsem);
> >
> > + if (!__has_merged_page(io, inode, page, ino))
> > + goto out;
> > +
> > /* change META to META_FLUSH in the checkpoint procedure */
> > if (type >= META_FLUSH) {
> > io->fio.type = META_FLUSH;
> > @@ -173,9 +190,24 @@ void f2fs_submit_merged_bio(struct f2fs_sb_info *sbi,
> > io->fio.rw = WRITE_FLUSH_FUA | REQ_META | REQ_PRIO;
> > }
> > __submit_merged_bio(io);
> > +out:
> > up_write(&io->io_rwsem);
> > }
> >
> > +void f2fs_submit_merged_bio(struct f2fs_sb_info *sbi, enum page_type type,
> > + int rw)
> > +{
> > + __f2fs_submit_merged_bio(sbi, NULL, NULL, 0, type, rw);
> > +}
> > +
> > +void f2fs_submit_merged_bio_cond(struct f2fs_sb_info *sbi,
> > + struct inode *inode, struct page *page,
> > + nid_t ino, enum page_type type, int rw)
> > +{
> > + if (has_merged_page(sbi, inode, page, ino, type))
> > + __f2fs_submit_merged_bio(sbi, inode, page, ino, type, rw);
> > +}
> > +
> > /*
> > * Fill the locked page with data located in the block address.
> > * Return unlocked page.
> > @@ -1215,12 +1247,18 @@ out:
> > inode_dec_dirty_pages(inode);
> > if (err)
> > ClearPageUptodate(page);
> > +
> > + if (wbc->for_reclaim) {
> > + f2fs_submit_merged_bio_cond(sbi, NULL, page, 0, DATA, WRITE);
> > + remove_dirty_inode(inode);
> > + }
> > +
> > unlock_page(page);
> > f2fs_balance_fs(sbi, need_balance_fs);
> > - if (wbc->for_reclaim || unlikely(f2fs_cp_error(sbi))) {
> > +
> > + if (unlikely(f2fs_cp_error(sbi)))
> > f2fs_submit_merged_bio(sbi, DATA, WRITE);
> > - remove_dirty_inode(inode);
> > - }
> > +
> > return 0;
> >
> > redirty_out:
> > @@ -1407,7 +1445,7 @@ static int f2fs_write_data_pages(struct address_space *mapping,
> > locked = true;
> > }
> > ret = f2fs_write_cache_pages(mapping, wbc, __f2fs_writepage, mapping);
> > - f2fs_submit_merged_bio(sbi, DATA, WRITE);
> > + f2fs_submit_merged_bio_cond(sbi, inode, NULL, 0, DATA, WRITE);
> > if (locked)
> > mutex_unlock(&sbi->writepages);
> >
> > diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
> > index 79cadd3..6c413b1e 100644
> > --- a/fs/f2fs/f2fs.h
> > +++ b/fs/f2fs/f2fs.h
> > @@ -1882,8 +1882,9 @@ void destroy_checkpoint_caches(void);
> > /*
> > * data.c
> > */
> > -bool is_merged_page(struct f2fs_sb_info *, struct page *, enum page_type);
> > void f2fs_submit_merged_bio(struct f2fs_sb_info *, enum page_type, int);
> > +void f2fs_submit_merged_bio_cond(struct f2fs_sb_info *, struct inode *,
> > + struct page *, nid_t, enum page_type, int);
> > int f2fs_submit_page_bio(struct f2fs_io_info *);
> > void f2fs_submit_page_mbio(struct f2fs_io_info *);
> > void set_data_blkaddr(struct dnode_of_data *);
> > diff --git a/fs/f2fs/node.c b/fs/f2fs/node.c
> > index 342597a..851a80b 100644
> > --- a/fs/f2fs/node.c
> > +++ b/fs/f2fs/node.c
> > @@ -1258,8 +1258,13 @@ continue_unlock:
> > goto next_step;
> > }
> >
> > - if (wrote)
> > - f2fs_submit_merged_bio(sbi, NODE, WRITE);
> > + if (wrote) {
> > + if (ino)
> > + f2fs_submit_merged_bio_cond(sbi, NULL, NULL,
> > + ino, NODE, WRITE);
> > + else
> > + f2fs_submit_merged_bio(sbi, NODE, WRITE);
> > + }
> > return nwritten;
> > }
> >
> > @@ -1356,9 +1361,13 @@ static int f2fs_write_node_page(struct page *page,
> > set_node_addr(sbi, &ni, fio.blk_addr, is_fsync_dnode(page));
> > dec_page_count(sbi, F2FS_DIRTY_NODES);
> > up_read(&sbi->node_write);
> > +
> > + if (wbc->for_reclaim)
> > + f2fs_submit_merged_bio_cond(sbi, NULL, page, 0, NODE, WRITE);
> > +
> > unlock_page(page);
> >
> > - if (wbc->for_reclaim || unlikely(f2fs_cp_error(sbi)))
> > + if (unlikely(f2fs_cp_error(sbi)))
> > f2fs_submit_merged_bio(sbi, NODE, WRITE);
> >
> > return 0;
> > diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c
> > index e16235b..0246acc 100644
> > --- a/fs/f2fs/segment.c
> > +++ b/fs/f2fs/segment.c
> > @@ -253,7 +253,8 @@ int commit_inmem_pages(struct inode *inode, bool abort)
> > if (!abort) {
> > f2fs_unlock_op(sbi);
> > if (submit_bio)
> > - f2fs_submit_merged_bio(sbi, DATA, WRITE);
> > + f2fs_submit_merged_bio_cond(sbi, inode, NULL, 0,
> > + DATA, WRITE);
> > }
> > return err;
> > }
> > @@ -1421,8 +1422,7 @@ void f2fs_wait_on_page_writeback(struct page *page,
> > if (PageWriteback(page)) {
> > struct f2fs_sb_info *sbi = F2FS_P_SB(page);
> >
> > - if (is_merged_page(sbi, page, type))
> > - f2fs_submit_merged_bio(sbi, type, WRITE);
> > + f2fs_submit_merged_bio_cond(sbi, NULL, page, 0, type, WRITE);
> > wait_on_page_writeback(page);
> > }
> > }
> > --
> > 2.6.3
> >

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