On 02/01, Gao Xiang wrote:
> Hi Jaegeuk and Chao,
>
> On 2018/2/1 6:28, Jaegeuk Kim wrote:
> > On 01/31, Chao Yu wrote:
> > > On 2018/1/31 14:39, Gaoxiang (OS) wrote:
> > > > Previously, we attempt to flush the whole cp pack in a single bio,
> > > > however, when suddenly powering off at this time, we could get into
> > > > an extreme scenario that cp pack 1 page and cp pack 2 page are updated
> > > > and latest, but payload or current summaries are still partially
> > > > outdated. (see reliable write in the UFS specification)
> > > >
> > > > This patch submits the whole cp pack except cp pack 2 page at first,
> > > > and then writes the cp pack 2 page with an extra independent
> > > > bio with pre-io barrier.
> > > >
> > > > Signed-off-by: Gao Xiang <gaoxiang25@xxxxxxxxxx>
> > > > Reviewed-by: Chao Yu <yuchao0@xxxxxxxxxx>
> > > > ---
> > > > Change log from v3:
> > > > - further review comments are applied from Jaegeuk and Chao
> > > > - Tested on this patch (without multiple-device): mount, boot Android with f2fs userdata and make fragment
> > > > - If any problem with this patch or I miss something, please kindly share your comments, thanks :)
> > > > Change log from v2:
> > > > - Apply the review comments from Chao
> > > > Change log from v1:
> > > > - Apply the review comments from Chao
> > > > - time data from "finish block_ops" to " finish checkpoint" (tested on ARM64 with TOSHIBA 128GB UFS):
> > > > Before patch: 0.002273 0.001973 0.002789 0.005159 0.002050
> > > > After patch: 0.002502 0.001624 0.002487 0.003049 0.002696
> > > > fs/f2fs/checkpoint.c | 67 ++++++++++++++++++++++++++++++++++++----------------
> > > > 1 file changed, 46 insertions(+), 21 deletions(-)
> > > >
> > > > diff --git a/fs/f2fs/checkpoint.c b/fs/f2fs/checkpoint.c
> > > > index 14d2fed..916dc72 100644
> > > > --- a/fs/f2fs/checkpoint.c
> > > > +++ b/fs/f2fs/checkpoint.c
> > > > @@ -1158,6 +1158,39 @@ static void update_ckpt_flags(struct f2fs_sb_info *sbi, struct cp_control *cpc)
> > > > spin_unlock_irqrestore(&sbi->cp_lock, flags);
> > > > }
> > > > +static void commit_checkpoint(struct f2fs_sb_info *sbi,
> > > > + void *src, block_t blk_addr)
> > > > +{
> > > > + struct writeback_control wbc = {
> > > > + .for_reclaim = 0,
> > > > + };
> > > > +
> > > > + /*
> > > > + * pagevec_lookup_tag and lock_page again will take
> > > > + * some extra time. Therefore, update_meta_pages and
> > > > + * sync_meta_pages are combined in this function.
> > > > + */
> > > > + struct page *page = grab_meta_page(sbi, blk_addr);
> > > > + int err;
> > > > +
> > > > + memcpy(page_address(page), src, PAGE_SIZE);
> > > > + set_page_dirty(page);
> > > > +
> > > > + f2fs_wait_on_page_writeback(page, META, true);
> > > > + f2fs_bug_on(sbi, PageWriteback(page));
> > > > + if (unlikely(!clear_page_dirty_for_io(page)))
> > > > + f2fs_bug_on(sbi, 1);
> > > > +
> > > > + /* writeout cp pack 2 page */
> > > > + err = __f2fs_write_meta_page(page, &wbc, FS_CP_META_IO);
> > > > + f2fs_bug_on(sbi, err);
> > > > +
> > > > + f2fs_put_page(page, 0);
> > > > +
> > > > + /* submit checkpoint (with barrier if NOBARRIER is not set) */
> > > > + f2fs_submit_merged_write(sbi, META_FLUSH);
> > > > +}
> > > > +
> > > > static int do_checkpoint(struct f2fs_sb_info *sbi, struct cp_control *cpc)
> > > > {
> > > > struct f2fs_checkpoint *ckpt = F2FS_CKPT(sbi);
> > > > @@ -1260,16 +1293,6 @@ static int do_checkpoint(struct f2fs_sb_info *sbi, struct cp_control *cpc)
> > > > }
> > > > }
> > > > - /* need to wait for end_io results */
> > > > - wait_on_all_pages_writeback(sbi);
> > > > - if (unlikely(f2fs_cp_error(sbi)))
> > > > - return -EIO;
> > > > -
> > > > - /* flush all device cache */
> > > > - err = f2fs_flush_device_cache(sbi);
> > > > - if (err)
> > > > - return err;
> > > > -
> > > > /* write out checkpoint buffer at block 0 */
> > > > update_meta_page(sbi, ckpt, start_blk++);
> > > > @@ -1297,15 +1320,6 @@ static int do_checkpoint(struct f2fs_sb_info *sbi, struct cp_control *cpc)
> > > > start_blk += NR_CURSEG_NODE_TYPE;
> > > > }
> > > > - /* writeout checkpoint block */
> > > > - update_meta_page(sbi, ckpt, start_blk);
> > > > -
> > > > - /* wait for previous submitted node/meta pages writeback */
> > > > - wait_on_all_pages_writeback(sbi);
> > > > -
> > > > - if (unlikely(f2fs_cp_error(sbi)))
> > > > - return -EIO;
> > > > -
> > > > filemap_fdatawait_range(NODE_MAPPING(sbi), 0, LLONG_MAX);
> > > > filemap_fdatawait_range(META_MAPPING(sbi), 0, LLONG_MAX);
> >
> > - remove
> >
> You mean remove
> filemap_fdatawait_range(NODE_MAPPING(sbi), 0, LLONG_MAX);
> and
> filemap_fdatawait_range(META_MAPPING(sbi), 0, LLONG_MAX);
> or remove
> filemap_fdatawait_range(META_MAPPING(sbi), 0, LLONG_MAX);
Yup, both of them.
>
> Actually, I have no idea why do these two filemap_fdatawait_range stay here
> and what are these used and waited for in this place,
> however I found it was modified recently and for many times, I guess they
> have some use.
>
> > > > @@ -1313,12 +1327,23 @@ static int do_checkpoint(struct f2fs_sb_info *sbi, struct cp_control *cpc)
> > > > sbi->last_valid_block_count = sbi->total_valid_block_count;
> > > > percpu_counter_set(&sbi->alloc_valid_block_count, 0);
> > > > - /* Here, we only have one bio having CP pack */
> > > > - sync_meta_pages(sbi, META_FLUSH, LONG_MAX, FS_CP_META_IO);
> > > > + /* Here, we have one bio having CP pack except cp pack 2 page */
> > > > + sync_meta_pages(sbi, META, LONG_MAX, FS_CP_META_IO);
> > > > +
> > > > + /* flush all device cache */
> > > > + err = f2fs_flush_device_cache(sbi);
> > > > + if (err)
> > > > + return err;
> > > > /* wait for previous submitted meta pages writeback */
> > > > wait_on_all_pages_writeback(sbi);
> > >
> > > Move f2fs_flush_device_cache here? since meta area can cross the multiple
> > > devices, we should make sure all metadata were in device cache at least, and
> > > then trigger the flush.
> >
> > Agreed, and need to flush, only if we have multiple devices.
> >
>
> OK, and it seems that
> - current f2fs_flush_device_cache
> - for (i = 1; i < sbi->s_ndevs; i++) {
> it would skip if it only has only one devices?
Yup, right.
>
> > >
> > > > + if (unlikely(f2fs_cp_error(sbi)))
> > > > + return -EIO;
> > > > +
> > > > + /* barrier and flush checkpoint cp pack 2 page if it can */
> > > > + commit_checkpoint(sbi, ckpt, start_blk);
> > >
> > > Jaegeuk, are we really allow to make critical do_checkpoint which is on path of
> > > fsync()/sync() be asynchronous?
> >
> > Yeah, so we need to wait end_io on synchronous paths like f2fs_sync_fs(1).
> >
>
> How about adding a CP_SYNC (or CP_ASYNC) control flag in cp_control.reason?
> and which paths could be synchronous paths:
> sync, umount, recovery - synchronous, right?
>
> Thanks,
>
> > >
> > > Thanks,
> > >
> > > > +
> > > > release_ino_entry(sbi, false);
> > > > if (unlikely(f2fs_cp_error(sbi)))
> > > >
