From: Jaegeuk Kim <jaegeuk@kernel.org>
To: Chao Yu <yuchao0@huawei.com>
Cc: linux-kernel@vger.kernel.org, linux-f2fs-devel@lists.sourceforge.net
Subject: Re: [f2fs-dev] [PATCH v4] f2fs: add bio cache for IPU
Date: Mon, 2 Sep 2019 16:04:49 -0700 [thread overview]
Message-ID: <20190902230449.GD71929@jaegeuk-macbookpro.roam.corp.google.com> (raw)
In-Reply-To: <024fe351-8e25-35cd-47a7-9755498c73f4@huawei.com>
On 09/02, Chao Yu wrote:
> On 2019/9/1 15:17, Jaegeuk Kim wrote:
> > On 08/31, Chao Yu wrote:
> >> On 2019/2/19 16:15, Chao Yu wrote:
> >>> @@ -1976,10 +2035,13 @@ static int __write_data_page(struct page *page, bool *submitted,
> >>> }
> >>>
> >>> unlock_page(page);
> >>> - if (!S_ISDIR(inode->i_mode) && !IS_NOQUOTA(inode))
> >>> + if (!S_ISDIR(inode->i_mode) && !IS_NOQUOTA(inode)) {
> >>> + f2fs_submit_ipu_bio(sbi, bio, page);
> >>> f2fs_balance_fs(sbi, need_balance_fs);
> >>> + }
> >>
> >> Above bio submission was added to avoid below deadlock:
> >>
> >> - __write_data_page
> >> - f2fs_do_write_data_page
> >> - set_page_writeback ---- set writeback flag
> >> - f2fs_inplace_write_data
> >> - f2fs_balance_fs
> >> - f2fs_gc
> >> - do_garbage_collect
> >> - gc_data_segment
> >> - move_data_page
> >> - f2fs_wait_on_page_writeback
> >> - wait_on_page_writeback --- wait writeback
> >>
> >> However, it breaks the merge of IPU IOs, to solve this issue, it looks we need
> >> to add global bio cache for such IPU merge case, then later
> >> f2fs_wait_on_page_writeback can check whether writebacked page is cached or not,
> >> and do the submission if necessary.
> >>
> >> Jaegeuk, any thoughts?
> >
> > How about calling f2fs_submit_ipu_bio() when we need to do GC in the same
> > context?
>
> However it also could happen in race case:
>
> Thread A Thread B
> - __write_data_page (inode x, page y)
> - f2fs_do_write_data_page
> - set_page_writeback ---- set writeback flag in page y
> - f2fs_inplace_write_data
> - f2fs_balance_fs
> - lock gc_mutex
> - lock gc_mutex
> - f2fs_gc
> - do_garbage_collect
> - gc_data_segment
> - move_data_page
> - f2fs_wait_on_page_writeback
> - wait_on_page_writeback --- wait writeback of page y
>
> So it needs a global bio cache for merged IPU pages, how about adding a list to
> link all ipu bios in struct f2fs_bio_info?
Hmm, I can't think of better solution than adding a list. In this case, blk_plug
doesn't work well?
>
> struct f2fs_bio_info {
> ....
> struct list_head ipu_bio_list; /* track all ipu bio */
> spinlock_t ipu_bio_lock; /* protect ipu bio list */
> }
>
> >
> >>
> >> Thanks,
> > .
> >
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next prev parent reply other threads:[~2019-09-02 23:04 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-02-19 8:15 [PATCH v4] f2fs: add bio cache for IPU Chao Yu
2019-02-28 3:49 ` Chao Yu
2019-03-01 17:55 ` Jaegeuk Kim
2019-03-04 6:27 ` Chao Yu
2019-05-14 4:55 ` [f2fs-dev] " Ju Hyung Park
2019-08-31 7:23 ` Chao Yu
2019-09-01 7:17 ` Jaegeuk Kim
2019-09-02 1:16 ` Chao Yu
2019-09-02 23:04 ` Jaegeuk Kim [this message]
2019-09-02 23:34 ` Chao Yu
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