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Date:   Mon, 24 Feb 2020 14:01:18 -0800
From:   Jaegeuk Kim <jaegeuk@kernel.org>
To:     Chao Yu <yuchao0@huawei.com>
Cc:     linux-f2fs-devel@lists.sourceforge.net,
        linux-kernel@vger.kernel.org, chao@kernel.org
Subject: Re: [PATCH v2] f2fs: introduce DEFAULT_IO_TIMEOUT
Message-ID: <20200224220118.GD77839@google.com>
References: <20200217094544.106429-1-yuchao0@huawei.com>
 <722787da-92b0-6b98-17a1-79372c9baf7e@huawei.com>
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On 02/20, Chao Yu wrote:
> Hi Jaegeuk,
> 
> Could you help to adapt this change for f2fs_wait_on_all_pages() manually
> in your tree?
> 
> -		io_schedule_timeout(HZ/50);
> +		io_schedule_timeout(DEFAULT_IO_TIMEOUT);

Done.

> 
> Thanks,
> 
> On 2020/2/17 17:45, Chao Yu wrote:
> > As Geert Uytterhoeven reported:
> > 
> > for parameter HZ/50 in congestion_wait(BLK_RW_ASYNC, HZ/50);
> > 
> > On some platforms, HZ can be less than 50, then unexpected 0 timeout
> > jiffies will be set in congestion_wait().
> > 
> > This patch introduces a macro DEFAULT_IO_TIMEOUT to wrap a determinate
> > value with msecs_to_jiffies(20) to instead HZ/50 to avoid such issue.
> > 
> > Quoted from Geert Uytterhoeven:
> > 
> > "A timeout of HZ means 1 second.
> > HZ/50 means 20 ms, but has the risk of being zero, if HZ < 50.
> > 
> > If you want to use a timeout of 20 ms, you best use msecs_to_jiffies(20),
> > as that takes care of the special cases, and never returns 0."
> > 
> > Signed-off-by: Chao Yu <yuchao0@huawei.com>
> > ---
> > v2:
> > - use msecs_to_jiffies(20) instead.
> >  fs/f2fs/compress.c |  3 ++-
> >  fs/f2fs/data.c     |  4 ++--
> >  fs/f2fs/f2fs.h     |  3 +++
> >  fs/f2fs/gc.c       |  3 ++-
> >  fs/f2fs/inode.c    |  2 +-
> >  fs/f2fs/node.c     |  2 +-
> >  fs/f2fs/recovery.c |  5 +++--
> >  fs/f2fs/segment.c  | 10 ++++++----
> >  fs/f2fs/super.c    |  6 ++++--
> >  9 files changed, 24 insertions(+), 14 deletions(-)
> > 
> > diff --git a/fs/f2fs/compress.c b/fs/f2fs/compress.c
> > index 0282149aa4c8..b9ea531ffbb6 100644
> > --- a/fs/f2fs/compress.c
> > +++ b/fs/f2fs/compress.c
> > @@ -985,7 +985,8 @@ static int f2fs_write_raw_pages(struct compress_ctx *cc,
> >  			} else if (ret == -EAGAIN) {
> >  				ret = 0;
> >  				cond_resched();
> > -				congestion_wait(BLK_RW_ASYNC, HZ/50);
> > +				congestion_wait(BLK_RW_ASYNC,
> > +						DEFAULT_IO_TIMEOUT);
> >  				lock_page(cc->rpages[i]);
> >  				clear_page_dirty_for_io(cc->rpages[i]);
> >  				goto retry_write;
> > diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c
> > index 019c91f7b301..a877cc50a4c3 100644
> > --- a/fs/f2fs/data.c
> > +++ b/fs/f2fs/data.c
> > @@ -2332,7 +2332,7 @@ int f2fs_encrypt_one_page(struct f2fs_io_info *fio)
> >  		/* flush pending IOs and wait for a while in the ENOMEM case */
> >  		if (PTR_ERR(fio->encrypted_page) == -ENOMEM) {
> >  			f2fs_flush_merged_writes(fio->sbi);
> > -			congestion_wait(BLK_RW_ASYNC, HZ/50);
> > +			congestion_wait(BLK_RW_ASYNC, DEFAULT_IO_TIMEOUT);
> >  			gfp_flags |= __GFP_NOFAIL;
> >  			goto retry_encrypt;
> >  		}
> > @@ -2923,7 +2923,7 @@ static int f2fs_write_cache_pages(struct address_space *mapping,
> >  					if (wbc->sync_mode == WB_SYNC_ALL) {
> >  						cond_resched();
> >  						congestion_wait(BLK_RW_ASYNC,
> > -								HZ/50);
> > +							DEFAULT_IO_TIMEOUT);
> >  						goto retry_write;
> >  					}
> >  					goto next;
> > diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
> > index 816a5adb83a4..72c91a6dd549 100644
> > --- a/fs/f2fs/f2fs.h
> > +++ b/fs/f2fs/f2fs.h
> > @@ -558,6 +558,9 @@ enum {
> >  
> >  #define DEFAULT_RETRY_IO_COUNT	8	/* maximum retry read IO count */
> >  
> > +/* congestion wait timeout value, default: 20ms */
> > +#define	DEFAULT_IO_TIMEOUT	(msecs_to_jiffies(20))
> > +
> >  /* maximum retry quota flush count */
> >  #define DEFAULT_RETRY_QUOTA_FLUSH_COUNT		8
> >  
> > diff --git a/fs/f2fs/gc.c b/fs/f2fs/gc.c
> > index 897de003e423..3db11d5a50d5 100644
> > --- a/fs/f2fs/gc.c
> > +++ b/fs/f2fs/gc.c
> > @@ -974,7 +974,8 @@ static int move_data_page(struct inode *inode, block_t bidx, int gc_type,
> >  		if (err) {
> >  			clear_cold_data(page);
> >  			if (err == -ENOMEM) {
> > -				congestion_wait(BLK_RW_ASYNC, HZ/50);
> > +				congestion_wait(BLK_RW_ASYNC,
> > +						DEFAULT_IO_TIMEOUT);
> >  				goto retry;
> >  			}
> >  			if (is_dirty)
> > diff --git a/fs/f2fs/inode.c b/fs/f2fs/inode.c
> > index 78c3f1d70f1d..156cc5ef3044 100644
> > --- a/fs/f2fs/inode.c
> > +++ b/fs/f2fs/inode.c
> > @@ -518,7 +518,7 @@ struct inode *f2fs_iget_retry(struct super_block *sb, unsigned long ino)
> >  	inode = f2fs_iget(sb, ino);
> >  	if (IS_ERR(inode)) {
> >  		if (PTR_ERR(inode) == -ENOMEM) {
> > -			congestion_wait(BLK_RW_ASYNC, HZ/50);
> > +			congestion_wait(BLK_RW_ASYNC, DEFAULT_IO_TIMEOUT);
> >  			goto retry;
> >  		}
> >  	}
> > diff --git a/fs/f2fs/node.c b/fs/f2fs/node.c
> > index 9824f055a5bc..d5edbe2ce4a1 100644
> > --- a/fs/f2fs/node.c
> > +++ b/fs/f2fs/node.c
> > @@ -2602,7 +2602,7 @@ int f2fs_recover_inode_page(struct f2fs_sb_info *sbi, struct page *page)
> >  retry:
> >  	ipage = f2fs_grab_cache_page(NODE_MAPPING(sbi), ino, false);
> >  	if (!ipage) {
> > -		congestion_wait(BLK_RW_ASYNC, HZ/50);
> > +		congestion_wait(BLK_RW_ASYNC, DEFAULT_IO_TIMEOUT);
> >  		goto retry;
> >  	}
> >  
> > diff --git a/fs/f2fs/recovery.c b/fs/f2fs/recovery.c
> > index 348e8d463b3e..dd804c07eeb0 100644
> > --- a/fs/f2fs/recovery.c
> > +++ b/fs/f2fs/recovery.c
> > @@ -534,7 +534,7 @@ static int do_recover_data(struct f2fs_sb_info *sbi, struct inode *inode,
> >  	err = f2fs_get_dnode_of_data(&dn, start, ALLOC_NODE);
> >  	if (err) {
> >  		if (err == -ENOMEM) {
> > -			congestion_wait(BLK_RW_ASYNC, HZ/50);
> > +			congestion_wait(BLK_RW_ASYNC, DEFAULT_IO_TIMEOUT);
> >  			goto retry_dn;
> >  		}
> >  		goto out;
> > @@ -617,7 +617,8 @@ static int do_recover_data(struct f2fs_sb_info *sbi, struct inode *inode,
> >  			err = check_index_in_prev_nodes(sbi, dest, &dn);
> >  			if (err) {
> >  				if (err == -ENOMEM) {
> > -					congestion_wait(BLK_RW_ASYNC, HZ/50);
> > +					congestion_wait(BLK_RW_ASYNC,
> > +							DEFAULT_IO_TIMEOUT);
> >  					goto retry_prev;
> >  				}
> >  				goto err;
> > diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c
> > index c3252603ff79..1628bc8327f1 100644
> > --- a/fs/f2fs/segment.c
> > +++ b/fs/f2fs/segment.c
> > @@ -245,7 +245,8 @@ static int __revoke_inmem_pages(struct inode *inode,
> >  								LOOKUP_NODE);
> >  			if (err) {
> >  				if (err == -ENOMEM) {
> > -					congestion_wait(BLK_RW_ASYNC, HZ/50);
> > +					congestion_wait(BLK_RW_ASYNC,
> > +							DEFAULT_IO_TIMEOUT);
> >  					cond_resched();
> >  					goto retry;
> >  				}
> > @@ -312,7 +313,7 @@ void f2fs_drop_inmem_pages_all(struct f2fs_sb_info *sbi, bool gc_failure)
> >  skip:
> >  		iput(inode);
> >  	}
> > -	congestion_wait(BLK_RW_ASYNC, HZ/50);
> > +	congestion_wait(BLK_RW_ASYNC, DEFAULT_IO_TIMEOUT);
> >  	cond_resched();
> >  	if (gc_failure) {
> >  		if (++looped >= count)
> > @@ -415,7 +416,8 @@ static int __f2fs_commit_inmem_pages(struct inode *inode)
> >  			err = f2fs_do_write_data_page(&fio);
> >  			if (err) {
> >  				if (err == -ENOMEM) {
> > -					congestion_wait(BLK_RW_ASYNC, HZ/50);
> > +					congestion_wait(BLK_RW_ASYNC,
> > +							DEFAULT_IO_TIMEOUT);
> >  					cond_resched();
> >  					goto retry;
> >  				}
> > @@ -2801,7 +2803,7 @@ static unsigned int __issue_discard_cmd_range(struct f2fs_sb_info *sbi,
> >  			blk_finish_plug(&plug);
> >  			mutex_unlock(&dcc->cmd_lock);
> >  			trimmed += __wait_all_discard_cmd(sbi, NULL);
> > -			congestion_wait(BLK_RW_ASYNC, HZ/50);
> > +			congestion_wait(BLK_RW_ASYNC, DEFAULT_IO_TIMEOUT);
> >  			goto next;
> >  		}
> >  skip:
> > diff --git a/fs/f2fs/super.c b/fs/f2fs/super.c
> > index 1456979222cf..dcfa5836767c 100644
> > --- a/fs/f2fs/super.c
> > +++ b/fs/f2fs/super.c
> > @@ -1884,7 +1884,8 @@ static ssize_t f2fs_quota_read(struct super_block *sb, int type, char *data,
> >  		page = read_cache_page_gfp(mapping, blkidx, GFP_NOFS);
> >  		if (IS_ERR(page)) {
> >  			if (PTR_ERR(page) == -ENOMEM) {
> > -				congestion_wait(BLK_RW_ASYNC, HZ/50);
> > +				congestion_wait(BLK_RW_ASYNC,
> > +						DEFAULT_IO_TIMEOUT);
> >  				goto repeat;
> >  			}
> >  			set_sbi_flag(F2FS_SB(sb), SBI_QUOTA_NEED_REPAIR);
> > @@ -1938,7 +1939,8 @@ static ssize_t f2fs_quota_write(struct super_block *sb, int type,
> >  							&page, NULL);
> >  		if (unlikely(err)) {
> >  			if (err == -ENOMEM) {
> > -				congestion_wait(BLK_RW_ASYNC, HZ/50);
> > +				congestion_wait(BLK_RW_ASYNC,
> > +						DEFAULT_IO_TIMEOUT);
> >  				goto retry;
> >  			}
> >  			set_sbi_flag(F2FS_SB(sb), SBI_QUOTA_NEED_REPAIR);
> >