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[PATCH] f2fs: fix to correct freed section number during gc

Started byChao Yu <chao2.yu@samsung.com>
First post2015-09-22 15:20 +0200
Last post2015-09-25 14:50 +0200
Articles 5 — 3 participants

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  [PATCH] f2fs: fix to correct freed section number during gc Chao Yu <chao2.yu@samsung.com> - 2015-09-22 15:20 +0200
    Re: [PATCH] f2fs: fix to correct freed section number during gc Jaegeuk Kim <jaegeuk@kernel.org> - 2015-09-23 01:00 +0200
      RE: [PATCH] f2fs: fix to correct freed section number during gc Chao Yu <chao2.yu@samsung.com> - 2015-09-23 12:20 +0200
        Re: [PATCH] f2fs: fix to correct freed section number during gc Jaegeuk Kim <jaegeuk@kernel.org> - 2015-09-23 23:10 +0200
          Re: [f2fs-dev] [PATCH] f2fs: fix to correct freed section number during gc Chao Yu <yuchaochina@hotmail.com> - 2015-09-25 14:50 +0200

#1230172 — [PATCH] f2fs: fix to correct freed section number during gc

FromChao Yu <chao2.yu@samsung.com>
Date2015-09-22 15:20 +0200
Subject[PATCH] f2fs: fix to correct freed section number during gc
Message-ID<qbvEd-6p9-17@gated-at.bofh.it>
We pass 'nfree' to has_not_enough_free_secs to check whether there is
enough free section, but 'nfree' indicates the number of segment gced,
should alter the value to section number.

Signed-off-by: Chao Yu <chao2.yu@samsung.com>
---
 fs/f2fs/gc.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/fs/f2fs/gc.c b/fs/f2fs/gc.c
index e932740..7ad2a60 100644
--- a/fs/f2fs/gc.c
+++ b/fs/f2fs/gc.c
@@ -817,7 +817,8 @@ gc_more:
 	if (unlikely(f2fs_cp_error(sbi)))
 		goto stop;
 
-	if (gc_type == BG_GC && has_not_enough_free_secs(sbi, nfree)) {
+	if (gc_type == BG_GC &&
+		has_not_enough_free_secs(sbi, nfree / sbi->segs_per_sec)) {
 		gc_type = FG_GC;
 		if (__get_victim(sbi, &segno, gc_type) || prefree_segments(sbi))
 			write_checkpoint(sbi, &cpc);
@@ -839,7 +840,7 @@ gc_more:
 	if (gc_type == FG_GC)
 		sbi->cur_victim_sec = NULL_SEGNO;
 
-	if (has_not_enough_free_secs(sbi, nfree))
+	if (has_not_enough_free_secs(sbi, nfree / sbi->segs_per_sec))
 		goto gc_more;
 
 	if (gc_type == FG_GC)
-- 
2.5.2


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#1231023

FromJaegeuk Kim <jaegeuk@kernel.org>
Date2015-09-23 01:00 +0200
Message-ID<qbEHv-2tn-7@gated-at.bofh.it>
In reply to#1230172
Hi Chao,

On Tue, Sep 22, 2015 at 09:18:18PM +0800, Chao Yu wrote:
> We pass 'nfree' to has_not_enough_free_secs to check whether there is
> enough free section, but 'nfree' indicates the number of segment gced,
> should alter the value to section number.

Yeah, but I think we need to increase nfree only when an entire section is gced
completely, since sometimes nfree can be increased across sections.

Thanks,

> 
> Signed-off-by: Chao Yu <chao2.yu@samsung.com>
> ---
>  fs/f2fs/gc.c | 5 +++--
>  1 file changed, 3 insertions(+), 2 deletions(-)
> 
> diff --git a/fs/f2fs/gc.c b/fs/f2fs/gc.c
> index e932740..7ad2a60 100644
> --- a/fs/f2fs/gc.c
> +++ b/fs/f2fs/gc.c
> @@ -817,7 +817,8 @@ gc_more:
>  	if (unlikely(f2fs_cp_error(sbi)))
>  		goto stop;
>  
> -	if (gc_type == BG_GC && has_not_enough_free_secs(sbi, nfree)) {
> +	if (gc_type == BG_GC &&
> +		has_not_enough_free_secs(sbi, nfree / sbi->segs_per_sec)) {
>  		gc_type = FG_GC;
>  		if (__get_victim(sbi, &segno, gc_type) || prefree_segments(sbi))
>  			write_checkpoint(sbi, &cpc);
> @@ -839,7 +840,7 @@ gc_more:
>  	if (gc_type == FG_GC)
>  		sbi->cur_victim_sec = NULL_SEGNO;
>  
> -	if (has_not_enough_free_secs(sbi, nfree))
> +	if (has_not_enough_free_secs(sbi, nfree / sbi->segs_per_sec))
>  		goto gc_more;
>  
>  	if (gc_type == FG_GC)
> -- 
> 2.5.2
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#1231308

FromChao Yu <chao2.yu@samsung.com>
Date2015-09-23 12:20 +0200
Message-ID<qbPjA-1ad-15@gated-at.bofh.it>
In reply to#1231023
Hi Jaegeuk,

> -----Original Message-----
> From: Jaegeuk Kim [mailto:jaegeuk@kernel.org]
> Sent: Wednesday, September 23, 2015 6:54 AM
> To: Chao Yu
> Cc: linux-f2fs-devel@lists.sourceforge.net; linux-kernel@vger.kernel.org
> Subject: Re: [PATCH] f2fs: fix to correct freed section number during gc
> 
> Hi Chao,
> 
> On Tue, Sep 22, 2015 at 09:18:18PM +0800, Chao Yu wrote:
> > We pass 'nfree' to has_not_enough_free_secs to check whether there is
> > enough free section, but 'nfree' indicates the number of segment gced,
> > should alter the value to section number.
> 
> Yeah, but I think we need to increase nfree only when an entire section is gced
> completely, since sometimes nfree can be increased across sections.

Agree, I will fix that.

Still have one question, for foreground gc, why would we give up retry writing
out pages of last victim, but trying to select another victim for cleanup?
Will new introduced method cause long latency for caller than before?

Thanks,


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#1231726

FromJaegeuk Kim <jaegeuk@kernel.org>
Date2015-09-23 23:10 +0200
Message-ID<qbZsC-7t4-7@gated-at.bofh.it>
In reply to#1231308
Hi Chao,

On Wed, Sep 23, 2015 at 06:11:36PM +0800, Chao Yu wrote:
> Hi Jaegeuk,
> 
> > -----Original Message-----
> > From: Jaegeuk Kim [mailto:jaegeuk@kernel.org]
> > Sent: Wednesday, September 23, 2015 6:54 AM
> > To: Chao Yu
> > Cc: linux-f2fs-devel@lists.sourceforge.net; linux-kernel@vger.kernel.org
> > Subject: Re: [PATCH] f2fs: fix to correct freed section number during gc
> > 
> > Hi Chao,
> > 
> > On Tue, Sep 22, 2015 at 09:18:18PM +0800, Chao Yu wrote:
> > > We pass 'nfree' to has_not_enough_free_secs to check whether there is
> > > enough free section, but 'nfree' indicates the number of segment gced,
> > > should alter the value to section number.
> > 
> > Yeah, but I think we need to increase nfree only when an entire section is gced
> > completely, since sometimes nfree can be increased across sections.
> 
> Agree, I will fix that.
> 
> Still have one question, for foreground gc, why would we give up retry writing
> out pages of last victim, but trying to select another victim for cleanup?
> Will new introduced method cause long latency for caller than before?

Hmm. Very occasionally, I've seen that gc goes into an infinite loop to clean up
one victim. In order to avoid that, I added giving up and then doing gc again.
I think there is no problem in normal cases. Even in an abnormal case, I expect
that next victim would be selected again because that should have lowest moving
cost.

> 
> Thanks,
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#1232771 — Re: [f2fs-dev] [PATCH] f2fs: fix to correct freed section number during gc

FromChao Yu <yuchaochina@hotmail.com>
Date2015-09-25 14:50 +0200
SubjectRe: [f2fs-dev] [PATCH] f2fs: fix to correct freed section number during gc
Message-ID<qcABQ-1BX-15@gated-at.bofh.it>
In reply to#1231726
Hi Jaegeuk,

> On Sep 24, 2015, at 5:08 AM, Jaegeuk Kim <jaegeuk@kernel.org> wrote:
> 
> Hi Chao,
> 
> On Wed, Sep 23, 2015 at 06:11:36PM +0800, Chao Yu wrote:
>> Hi Jaegeuk,
>> 
>>> -----Original Message-----
>>> From: Jaegeuk Kim [mailto:jaegeuk@kernel.org]
>>> Sent: Wednesday, September 23, 2015 6:54 AM
>>> To: Chao Yu
>>> Cc: linux-f2fs-devel@lists.sourceforge.net; linux-kernel@vger.kernel.org
>>> Subject: Re: [PATCH] f2fs: fix to correct freed section number during gc
>>> 
>>> Hi Chao,
>>> 
>>> On Tue, Sep 22, 2015 at 09:18:18PM +0800, Chao Yu wrote:
>>>> We pass 'nfree' to has_not_enough_free_secs to check whether there is
>>>> enough free section, but 'nfree' indicates the number of segment gced,
>>>> should alter the value to section number.
>>> 
>>> Yeah, but I think we need to increase nfree only when an entire section is gced
>>> completely, since sometimes nfree can be increased across sections.
>> 
>> Agree, I will fix that.
>> 
>> Still have one question, for foreground gc, why would we give up retry writing
>> out pages of last victim, but trying to select another victim for cleanup?
>> Will new introduced method cause long latency for caller than before?
> 
> Hmm. Very occasionally, I've seen that gc goes into an infinite loop to clean up
> one victim. In order to avoid that, I added giving up and then doing gc again.
> I think there is no problem in normal cases. Even in an abnormal case, I expect
> that next victim would be selected again because that should have lowest moving
> cost.

Got it, thanks for your explanation! :)

I have sent the v2 patch, please help to review.

Thanks,

> 
>> 
>> Thanks,
> 
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