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From: Gao Xiang <hsiangkao@linux.alibaba.com>
To: Matthew Wilcox <willy@infradead.org>
Cc: "Andreas Grünbacher" <andreas.gruenbacher@gmail.com>,
	"Christoph Hellwig" <hch@infradead.org>,
	linux-erofs@lists.ozlabs.org,
	"Linux FS-devel Mailing List" <linux-fsdevel@vger.kernel.org>,
	LKML <linux-kernel@vger.kernel.org>,
	"Darrick J. Wong" <djwong@kernel.org>,
	"Chao Yu" <chao@kernel.org>, "Liu Bo" <bo.liu@linux.alibaba.com>,
	"Joseph Qi" <joseph.qi@linux.alibaba.com>,
	"Liu Jiang" <gerry@linux.alibaba.com>
Subject: Re: [PATCH 1/2] iomap: support tail packing inline read
Date: Sat, 17 Jul 2021 23:15:58 +0800	[thread overview]
Message-ID: <YPL0LqHzEbUY4zY/@B-P7TQMD6M-0146.local> (raw)
In-Reply-To: <YPLw0uc1jVKI8uKo@casper.infradead.org>

Hi Matthew,

On Sat, Jul 17, 2021 at 04:01:38PM +0100, Matthew Wilcox wrote:
> On Sat, Jul 17, 2021 at 09:38:18PM +0800, Gao Xiang wrote:
> > Sorry about some late. I've revised a version based on Christoph's
> > version and Matthew's thought above. I've preliminary checked with
> > EROFS, if it does make sense, please kindly help check on the gfs2
> > side as well..
> 
> I don't understand how this bit works:

This part inherited from the Christoph version without change.
The following thoughts are just my own understanding...

> 
> >  	struct page *page = ctx->cur_page;
> > -	struct iomap_page *iop;
> > +	struct iomap_page *iop = NULL;
> >  	bool same_page = false, is_contig = false;
> >  	loff_t orig_pos = pos;
> >  	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;
> > -	}
> > +	if (iomap->type == IOMAP_INLINE && !pos)
> > +		WARN_ON_ONCE(to_iomap_page(page) != NULL);
> > +	else
> > +		iop = iomap_page_create(inode, page);
> 
> Imagine you have a file with bytes 0-2047 in an extent which is !INLINE
> and bytes 2048-2051 in the INLINE extent.  When you read the page, first
> you create an iop for the !INLINE extent.  Then this function is called

Yes, it first created an iop for the !INLINE extent.

> again for the INLINE extent and you'll hit the WARN_ON_ONCE.  No?

If it is called again with another INLINE extent, pos will be non-0?
so (!pos) == false. Am I missing something?

Thanks,
Gao Xiang

> 

WARNING: multiple messages have this Message-ID
From: Gao Xiang <hsiangkao@linux.alibaba.com>
To: Matthew Wilcox <willy@infradead.org>
Cc: "Darrick J. Wong" <djwong@kernel.org>,
	"Andreas Grünbacher" <andreas.gruenbacher@gmail.com>,
	LKML <linux-kernel@vger.kernel.org>,
	"Christoph Hellwig" <hch@infradead.org>,
	"Joseph Qi" <joseph.qi@linux.alibaba.com>,
	"Liu Bo" <bo.liu@linux.alibaba.com>,
	"Linux FS-devel Mailing List" <linux-fsdevel@vger.kernel.org>,
	"Liu Jiang" <gerry@linux.alibaba.com>,
	linux-erofs@lists.ozlabs.org
Subject: Re: [PATCH 1/2] iomap: support tail packing inline read
Date: Sat, 17 Jul 2021 23:15:58 +0800	[thread overview]
Message-ID: <YPL0LqHzEbUY4zY/@B-P7TQMD6M-0146.local> (raw)
In-Reply-To: <YPLw0uc1jVKI8uKo@casper.infradead.org>

Hi Matthew,

On Sat, Jul 17, 2021 at 04:01:38PM +0100, Matthew Wilcox wrote:
> On Sat, Jul 17, 2021 at 09:38:18PM +0800, Gao Xiang wrote:
> > Sorry about some late. I've revised a version based on Christoph's
> > version and Matthew's thought above. I've preliminary checked with
> > EROFS, if it does make sense, please kindly help check on the gfs2
> > side as well..
> 
> I don't understand how this bit works:

This part inherited from the Christoph version without change.
The following thoughts are just my own understanding...

> 
> >  	struct page *page = ctx->cur_page;
> > -	struct iomap_page *iop;
> > +	struct iomap_page *iop = NULL;
> >  	bool same_page = false, is_contig = false;
> >  	loff_t orig_pos = pos;
> >  	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;
> > -	}
> > +	if (iomap->type == IOMAP_INLINE && !pos)
> > +		WARN_ON_ONCE(to_iomap_page(page) != NULL);
> > +	else
> > +		iop = iomap_page_create(inode, page);
> 
> Imagine you have a file with bytes 0-2047 in an extent which is !INLINE
> and bytes 2048-2051 in the INLINE extent.  When you read the page, first
> you create an iop for the !INLINE extent.  Then this function is called

Yes, it first created an iop for the !INLINE extent.

> again for the INLINE extent and you'll hit the WARN_ON_ONCE.  No?

If it is called again with another INLINE extent, pos will be non-0?
so (!pos) == false. Am I missing something?

Thanks,
Gao Xiang

> 

  reply	other threads:[~2021-07-17 15:16 UTC|newest]

Thread overview: 39+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-07-16  5:07 [PATCH 0/2] erofs: iomap support for tailpacking cases Gao Xiang
2021-07-16  5:07 ` Gao Xiang
2021-07-16  5:07 ` [PATCH 1/2] iomap: support tail packing inline read Gao Xiang
2021-07-16  5:07   ` Gao Xiang
2021-07-16  9:19   ` Christoph Hellwig
2021-07-16  9:19     ` Christoph Hellwig
2021-07-16  9:46     ` Gao Xiang
2021-07-16  9:46       ` Gao Xiang
2021-07-16 13:47     ` Matthew Wilcox
2021-07-16 13:47       ` Matthew Wilcox
2021-07-16 14:38       ` Matthew Wilcox
2021-07-16 14:38         ` Matthew Wilcox
2021-07-16 13:02   ` Matthew Wilcox
2021-07-16 13:02     ` Matthew Wilcox
2021-07-16 13:56     ` Gao Xiang
2021-07-16 13:56       ` Gao Xiang
2021-07-16 14:44       ` Matthew Wilcox
2021-07-16 15:03         ` Gao Xiang
2021-07-16 15:03           ` Gao Xiang
2021-07-16 15:53           ` Andreas Grünbacher
2021-07-16 15:53             ` Andreas Grünbacher
2021-07-17 13:38             ` Gao Xiang
2021-07-17 13:38               ` Gao Xiang
2021-07-17 15:01               ` Matthew Wilcox
2021-07-17 15:15                 ` Gao Xiang [this message]
2021-07-17 15:15                   ` Gao Xiang
2021-07-17 18:40                   ` Matthew Wilcox
2021-07-19 11:19                     ` Christoph Hellwig
2021-07-19 11:19                       ` Christoph Hellwig
2021-07-19 13:45                       ` Gao Xiang
2021-07-19 13:45                         ` Gao Xiang
2021-07-19 11:15               ` Christoph Hellwig
2021-07-19 13:31                 ` Gao Xiang
2021-07-19 13:31                   ` Gao Xiang
2021-07-16  5:07 ` [PATCH 2/2] erofs: convert all uncompressed cases to iomap Gao Xiang
2021-07-16  5:07   ` Gao Xiang
2021-07-18  5:30   ` kernel test robot
2021-07-18  5:30   ` [RFC PATCH] erofs: erofs_iomap_end() can be static kernel test robot
2021-07-18 16:53     ` Gao Xiang

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