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Date:   Wed, 17 Jul 2019 21:00:05 -0700
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 v2] f2fs: fix to read source block before
 invalidating it
Message-ID: <20190718040005.GA81995@jaegeuk-macbookpro.roam.corp.google.com>
References: <20190718013718.70335-1-jaegeuk@kernel.org>
 <20190718031214.GA78336@jaegeuk-macbookpro.roam.corp.google.com>
 <19a25101-da74-de98-6ca4-a9fd9fa09ef2@huawei.com>
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On 07/18, Chao Yu wrote:
> On 2019/7/18 11:12, Jaegeuk Kim wrote:
> > f2fs_allocate_data_block() invalidates old block address and enable new block
> > address. Then, if we try to read old block by f2fs_submit_page_bio(), it will
> > give WARN due to reading invalid blocks.
> > 
> > Let's make the order sanely back.
> 
> Hmm.. to avoid WARM, we may suffer one more memcpy, I suspect this can reduce
> online resize or foreground gc ioctl performance...

I worried about performance tho, more concern came to me that there may exist a
chance that other thread can allocate and write something in old block address.

> 
> Can we just relief to use DATA_GENERIC_ENHANCE_READ for this case...?

We need to keep consistency for this api.

Thanks,

> 
> > 
> > Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
> 
> Except performance, I'm okay with this change.
> 
> Reviewed-by: Chao Yu <yuchao0@huawei.com>
> 
> Thanks,
> 
> > ---
> > v2:
> > I was fixing the comments. :)
> > 
> >  fs/f2fs/gc.c | 70 +++++++++++++++++++++++++---------------------------
> >  1 file changed, 34 insertions(+), 36 deletions(-)
> > 
> > diff --git a/fs/f2fs/gc.c b/fs/f2fs/gc.c
> > index 6691f526fa40..8974672db78f 100644
> > --- a/fs/f2fs/gc.c
> > +++ b/fs/f2fs/gc.c
> > @@ -796,6 +796,29 @@ static int move_data_block(struct inode *inode, block_t bidx,
> >  	if (lfs_mode)
> >  		down_write(&fio.sbi->io_order_lock);
> >  
> > +	mpage = f2fs_grab_cache_page(META_MAPPING(fio.sbi),
> > +					fio.old_blkaddr, false);
> > +	if (!mpage)
> > +		goto up_out;
> > +
> > +	fio.encrypted_page = mpage;
> > +
> > +	/* read source block in mpage */
> > +	if (!PageUptodate(mpage)) {
> > +		err = f2fs_submit_page_bio(&fio);
> > +		if (err) {
> > +			f2fs_put_page(mpage, 1);
> > +			goto up_out;
> > +		}
> > +		lock_page(mpage);
> > +		if (unlikely(mpage->mapping != META_MAPPING(fio.sbi) ||
> > +						!PageUptodate(mpage))) {
> > +			err = -EIO;
> > +			f2fs_put_page(mpage, 1);
> > +			goto up_out;
> > +		}
> > +	}
> > +
> >  	f2fs_allocate_data_block(fio.sbi, NULL, fio.old_blkaddr, &newaddr,
> >  					&sum, CURSEG_COLD_DATA, NULL, false);
> >  
> > @@ -803,44 +826,18 @@ static int move_data_block(struct inode *inode, block_t bidx,
> >  				newaddr, FGP_LOCK | FGP_CREAT, GFP_NOFS);
> >  	if (!fio.encrypted_page) {
> >  		err = -ENOMEM;
> > -		goto recover_block;
> > -	}
> > -
> > -	mpage = f2fs_pagecache_get_page(META_MAPPING(fio.sbi),
> > -					fio.old_blkaddr, FGP_LOCK, GFP_NOFS);
> > -	if (mpage) {
> > -		bool updated = false;
> > -
> > -		if (PageUptodate(mpage)) {
> > -			memcpy(page_address(fio.encrypted_page),
> > -					page_address(mpage), PAGE_SIZE);
> > -			updated = true;
> > -		}
> >  		f2fs_put_page(mpage, 1);
> > -		invalidate_mapping_pages(META_MAPPING(fio.sbi),
> > -					fio.old_blkaddr, fio.old_blkaddr);
> > -		if (updated)
> > -			goto write_page;
> > -	}
> > -
> > -	err = f2fs_submit_page_bio(&fio);
> > -	if (err)
> > -		goto put_page_out;
> > -
> > -	/* write page */
> > -	lock_page(fio.encrypted_page);
> > -
> > -	if (unlikely(fio.encrypted_page->mapping != META_MAPPING(fio.sbi))) {
> > -		err = -EIO;
> > -		goto put_page_out;
> > -	}
> > -	if (unlikely(!PageUptodate(fio.encrypted_page))) {
> > -		err = -EIO;
> > -		goto put_page_out;
> > +		goto recover_block;
> >  	}
> >  
> > -write_page:
> > +	/* write target block */
> >  	f2fs_wait_on_page_writeback(fio.encrypted_page, DATA, true, true);
> > +	memcpy(page_address(fio.encrypted_page),
> > +				page_address(mpage), PAGE_SIZE);
> > +	f2fs_put_page(mpage, 1);
> > +	invalidate_mapping_pages(META_MAPPING(fio.sbi),
> > +				fio.old_blkaddr, fio.old_blkaddr);
> > +
> >  	set_page_dirty(fio.encrypted_page);
> >  	if (clear_page_dirty_for_io(fio.encrypted_page))
> >  		dec_page_count(fio.sbi, F2FS_DIRTY_META);
> > @@ -871,11 +868,12 @@ static int move_data_block(struct inode *inode, block_t bidx,
> >  put_page_out:
> >  	f2fs_put_page(fio.encrypted_page, 1);
> >  recover_block:
> > -	if (lfs_mode)
> > -		up_write(&fio.sbi->io_order_lock);
> >  	if (err)
> >  		f2fs_do_replace_block(fio.sbi, &sum, newaddr, fio.old_blkaddr,
> >  								true, true);
> > +up_out:
> > +	if (lfs_mode)
> > +		up_write(&fio.sbi->io_order_lock);
> >  put_out:
> >  	f2fs_put_dnode(&dn);
> >  out:
> > 
> 
> 
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