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From: Jaegeuk Kim <jaegeuk@kernel.org>
To: heyunlei <heyunlei@huawei.com>
Cc: linux-f2fs-devel@lists.sourceforge.net
Subject: Re: [PATCH] f2fs: add a modify discard command function
Date: Wed, 1 Mar 2017 11:48:44 -0800	[thread overview]
Message-ID: <20170301194844.GD18600@jaegeuk.local> (raw)
In-Reply-To: <6b67a9d1-645f-9dea-6fda-9324f7ac0cac@huawei.com>

On 02/28, heyunlei wrote:
> Hi Jaegeuk,
> 
> On 2017/2/28 7:08, Jaegeuk Kim wrote:
> > On 02/27, Yunlei He wrote:
> > > This patch add a function to modify discard command if one segment
> > > reuse before discard. Split this segment from multi-segments discard
> > > range, and discard the left bigger range.
> > 
> > Now MAX_DISCARD_BLOCKS() is set to section size, so there will be no
> > multi-sections discard range. Am I missing some cases?
> 
> I think MAX_DISCARD_BLOCKS() just limit small discard and fstrim, f2fs
> 
> can still send multi-segments discard range if prefree segments is continuous.

Got it.
Comments below.

> > > Signed-off-by: Yunlei He <heyunlei@huawei.com>
> > > ---
> > >  fs/f2fs/segment.c | 18 +++++++++++++++++-
> > >  1 file changed, 17 insertions(+), 1 deletion(-)
> > > 
> > > diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c
> > > index 9006d8e..5af736b 100644
> > > --- a/fs/f2fs/segment.c
> > > +++ b/fs/f2fs/segment.c
> > > @@ -672,6 +672,22 @@ static void __remove_discard_cmd(struct f2fs_sb_info *sbi, struct discard_cmd *d
> > >  	kmem_cache_free(discard_cmd_slab, dc);
> > >  }
> > > 
> > > +static void __modify_discard_cmd(struct f2fs_sb_info *sbi, struct discard_cmd *dc, block_t blkaddr)

How about modifying the name "modify" to "punch"?

> > > +{
> > > +	block_t end_block = START_BLOCK(sbi, GET_SEGNO(sbi, blkaddr) + 1);
> > > +
> > > +	if (dc->lstart + dc->len <= end_block) {
> > > +		 __remove_discard_cmd(sbi, dc);
> > > +		return;
> > > +	}
> > > +
> > > +	if (dc->lstart - blkaddr < dc->lstart + dc->len - end_block) {

The blkaddr is larger than or equal to dc->lstart all the time, resulting in
overflow?

Thanks,

> > > +		dc->lstart = end_block;
> > > +		dc->len -= (end_block - dc->lstart);
> > > +	} else
> > > +		dc->len = blkaddr - dc->lstart;
> > > +}
> > > +
> > >  /* This should be covered by global mutex, &sit_i->sentry_lock */
> > >  void f2fs_wait_discard_bio(struct f2fs_sb_info *sbi, block_t blkaddr)
> > >  {
> > > @@ -699,7 +715,7 @@ void f2fs_wait_discard_bio(struct f2fs_sb_info *sbi, block_t blkaddr)
> > >  			if (dc->state == D_SUBMIT)
> > >  				wait_for_completion_io(&dc->wait);
> > >  			else
> > > -				__remove_discard_cmd(sbi, dc);
> > > +				__modify_discard_cmd(sbi, dc, blkaddr);
> > >  		}
> > >  	}
> > >  	blk_finish_plug(&plug);
> > > --
> > > 2.10.1
> > 
> > .
> > 

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  reply	other threads:[~2017-03-01 19:48 UTC|newest]

Thread overview: 5+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-02-27  7:19 [PATCH] f2fs: add a modify discard command function Yunlei He
2017-02-27 23:08 ` Jaegeuk Kim
2017-02-28  1:51   ` heyunlei
2017-03-01 19:48     ` Jaegeuk Kim [this message]
2017-03-02  2:07       ` heyunlei

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