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From: Gao Xiang <hsiangkao@linux.alibaba.com>
To: Matthew Wilcox <willy@infradead.org>
Cc: linux-erofs@lists.ozlabs.org, linux-fsdevel@vger.kernel.org,
	LKML <linux-kernel@vger.kernel.org>,
	Christoph Hellwig <hch@lst.de>,
	"Darrick J . Wong" <djwong@kernel.org>,
	Andreas Gruenbacher <andreas.gruenbacher@gmail.com>
Subject: Re: [PATCH v3] iomap: support tail packing inline read
Date: Mon, 19 Jul 2021 23:29:20 +0800	[thread overview]
Message-ID: <YPWaUNeV1K13vpGF@B-P7TQMD6M-0146.local> (raw)
In-Reply-To: <YPWUBhxhoaEp8Frn@casper.infradead.org>

On Mon, Jul 19, 2021 at 04:02:30PM +0100, Matthew Wilcox wrote:
> On Mon, Jul 19, 2021 at 10:47:47PM +0800, Gao Xiang wrote:
> > @@ -246,18 +245,19 @@ iomap_readpage_actor(struct inode *inode, loff_t pos, loff_t length, void *data,
> >  	unsigned poff, plen;
> >  	sector_t sector;
> >  
> > -	if (iomap->type == IOMAP_INLINE) {
> > -		WARN_ON_ONCE(pos);
> > -		iomap_read_inline_data(inode, page, iomap);
> > -		return PAGE_SIZE;
> > -	}
> > -
> > -	/* zero post-eof blocks as the page may be mapped */
> >  	iop = iomap_page_create(inode, page);
> > +	/* needs to skip some leading uptodated blocks */
> >  	iomap_adjust_read_range(inode, iop, &pos, length, &poff, &plen);
> >  	if (plen == 0)
> >  		goto done;
> >  
> > +	if (iomap->type == IOMAP_INLINE) {
> > +		iomap_read_inline_data(inode, page, iomap, pos);
> > +		plen = PAGE_SIZE - poff;
> > +		goto done;
> > +	}
> 
> This is going to break Andreas' case that he just patched to work.
> GFS2 needs for there to _not_ be an iop for inline data.  That's
> why I said we need to sort out when to create an iop before moving
> the IOMAP_INLINE case below the creation of the iop.

I have no idea how it breaks Andreas' case from the previous commit
message: "
iomap: Don't create iomap_page objects for inline files
In iomap_readpage_actor, don't create iop objects for inline inodes.
Otherwise, iomap_read_inline_data will set PageUptodate without setting
iop->uptodate, and iomap_page_release will eventually complain.

To prevent this kind of bug from occurring in the future, make sure the
page doesn't have private data attached in iomap_read_inline_data.
"

After this patch, iomap_read_inline_data() will set iop->uptodate with
iomap_set_range_uptodate() rather than set PageUptodate() directly, 
so iomap_page_release won't complain.

Am I missing something?

Thanks,
Gao Xiang

> 
> If we're not going to do that first, then I recommend leaving the
> IOMAP_INLINE case where it is and changing it to ...
> 
> 	if (iomap->type == IOMAP_INLINE)
> 		return iomap_read_inline_data(inode, page, iomap, pos);
> 
> ... and have iomap_read_inline_data() return the number of bytes that
> it copied + zeroed (ie PAGE_SIZE - poff).

WARNING: multiple messages have this Message-ID (diff)
From: Gao Xiang <hsiangkao@linux.alibaba.com>
To: Matthew Wilcox <willy@infradead.org>
Cc: "Darrick J . Wong" <djwong@kernel.org>,
	Andreas Gruenbacher <andreas.gruenbacher@gmail.com>,
	LKML <linux-kernel@vger.kernel.org>,
	linux-fsdevel@vger.kernel.org, linux-erofs@lists.ozlabs.org,
	Christoph Hellwig <hch@lst.de>
Subject: Re: [PATCH v3] iomap: support tail packing inline read
Date: Mon, 19 Jul 2021 23:29:20 +0800	[thread overview]
Message-ID: <YPWaUNeV1K13vpGF@B-P7TQMD6M-0146.local> (raw)
In-Reply-To: <YPWUBhxhoaEp8Frn@casper.infradead.org>

On Mon, Jul 19, 2021 at 04:02:30PM +0100, Matthew Wilcox wrote:
> On Mon, Jul 19, 2021 at 10:47:47PM +0800, Gao Xiang wrote:
> > @@ -246,18 +245,19 @@ iomap_readpage_actor(struct inode *inode, loff_t pos, loff_t length, void *data,
> >  	unsigned poff, plen;
> >  	sector_t sector;
> >  
> > -	if (iomap->type == IOMAP_INLINE) {
> > -		WARN_ON_ONCE(pos);
> > -		iomap_read_inline_data(inode, page, iomap);
> > -		return PAGE_SIZE;
> > -	}
> > -
> > -	/* zero post-eof blocks as the page may be mapped */
> >  	iop = iomap_page_create(inode, page);
> > +	/* needs to skip some leading uptodated blocks */
> >  	iomap_adjust_read_range(inode, iop, &pos, length, &poff, &plen);
> >  	if (plen == 0)
> >  		goto done;
> >  
> > +	if (iomap->type == IOMAP_INLINE) {
> > +		iomap_read_inline_data(inode, page, iomap, pos);
> > +		plen = PAGE_SIZE - poff;
> > +		goto done;
> > +	}
> 
> This is going to break Andreas' case that he just patched to work.
> GFS2 needs for there to _not_ be an iop for inline data.  That's
> why I said we need to sort out when to create an iop before moving
> the IOMAP_INLINE case below the creation of the iop.

I have no idea how it breaks Andreas' case from the previous commit
message: "
iomap: Don't create iomap_page objects for inline files
In iomap_readpage_actor, don't create iop objects for inline inodes.
Otherwise, iomap_read_inline_data will set PageUptodate without setting
iop->uptodate, and iomap_page_release will eventually complain.

To prevent this kind of bug from occurring in the future, make sure the
page doesn't have private data attached in iomap_read_inline_data.
"

After this patch, iomap_read_inline_data() will set iop->uptodate with
iomap_set_range_uptodate() rather than set PageUptodate() directly, 
so iomap_page_release won't complain.

Am I missing something?

Thanks,
Gao Xiang

> 
> If we're not going to do that first, then I recommend leaving the
> IOMAP_INLINE case where it is and changing it to ...
> 
> 	if (iomap->type == IOMAP_INLINE)
> 		return iomap_read_inline_data(inode, page, iomap, pos);
> 
> ... and have iomap_read_inline_data() return the number of bytes that
> it copied + zeroed (ie PAGE_SIZE - poff).

  parent reply	other threads:[~2021-07-19 15:48 UTC|newest]

Thread overview: 25+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-07-19 14:47 [PATCH v3] iomap: support tail packing inline read Gao Xiang
2021-07-19 14:47 ` Gao Xiang
2021-07-19 15:02 ` Matthew Wilcox
2021-07-19 15:02   ` Matthew Wilcox
2021-07-19 15:13   ` Christoph Hellwig
2021-07-19 15:13     ` Christoph Hellwig
2021-07-19 16:11     ` Gao Xiang
2021-07-19 16:11       ` Gao Xiang
2021-07-19 16:31       ` Matthew Wilcox
2021-07-19 16:45         ` Gao Xiang
2021-07-19 16:45           ` Gao Xiang
2021-07-19 15:29   ` Gao Xiang [this message]
2021-07-19 15:29     ` Gao Xiang
2021-07-19 15:31     ` Andreas Grünbacher
2021-07-19 15:31       ` Andreas Grünbacher
2021-07-19 15:36       ` Gao Xiang
2021-07-19 15:36         ` Gao Xiang
2021-07-20 11:23 ` Andreas Grünbacher
2021-07-20 11:23   ` Andreas Grünbacher
2021-07-20 12:10   ` Gao Xiang
2021-07-20 12:10     ` Gao Xiang
2021-07-20 11:34 ` Andreas Grünbacher
2021-07-20 11:34   ` Andreas Grünbacher
2021-07-20 12:23   ` Gao Xiang
2021-07-20 12:23     ` Gao Xiang

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