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From: Matthew Wilcox <willy@infradead.org>
To: Christoph Hellwig <hch@infradead.org>
Cc: linux-fsdevel@vger.kernel.org, linux-xfs@vger.kernel.org
Subject: Re: [PATCH 16/13] iomap: Make readpage synchronous
Date: Sat, 19 Sep 2020 18:10:37 +0100	[thread overview]
Message-ID: <20200919171037.GP32101@casper.infradead.org> (raw)
In-Reply-To: <20200919063908.GH13501@infradead.org>

On Sat, Sep 19, 2020 at 07:39:08AM +0100, Christoph Hellwig wrote:
> I think just adding the completion and status to struct
> iomap_readpage_ctx would be a lot easier to follow, at the cost
> of bloating the structure a bit for the readahead case.  If we
> are realy concerned about that, the completion could be directly
> on the iomap_readpage stack and we'd pass a pointer.

We could do that.  I was intending to reuse the code for the write_begin
path so that a pathological case where a page straddles multiple extents
can be handled by sending multiple BIOs and waiting on both of them at
the same time, instead of the current way of sending a BIO, waiting for
it to complete, sending a second BIO, waiting for it to complete, ...

I haven't fully got my head around how to do that effectively yet.
The iomap buffered write path assumes that extents are larger than page
size and you're going to get multiple pages per extent, when the situation
could be reversed and we might need to stitch together multiple extents
in order to bring a page Uptodate.  I also don't yet understand why
we read the current contents of a block when we're going to completely
overwrite it with data.


  parent reply	other threads:[~2020-09-19 17:10 UTC|newest]

Thread overview: 30+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-09-17 15:10 [PATCH 00/13] Allow readpage to return a locked page Matthew Wilcox (Oracle)
2020-09-17 15:10 ` [PATCH 01/13] mm: Add AOP_UPDATED_PAGE return value Matthew Wilcox (Oracle)
2020-09-17 22:03   ` Matthew Wilcox
2020-09-17 15:10 ` [PATCH 02/13] 9p: Tell the VFS that readpage was synchronous Matthew Wilcox (Oracle)
2020-09-18  5:59   ` [V9fs-developer] " Dominique Martinet
2020-09-18 11:19     ` Matthew Wilcox
2020-09-18 12:30   ` Dominique Martinet
2020-09-17 15:10 ` [PATCH 03/13] afs: " Matthew Wilcox (Oracle)
2020-09-17 15:10 ` [PATCH 04/13] ceph: " Matthew Wilcox (Oracle)
2020-09-17 16:49   ` Jeff Layton
2020-09-17 15:10 ` [PATCH 05/13] cifs: " Matthew Wilcox (Oracle)
2020-09-17 15:10 ` [PATCH 06/13] cramfs: " Matthew Wilcox (Oracle)
2020-09-17 15:10 ` [PATCH 07/13] ecryptfs: " Matthew Wilcox (Oracle)
2020-09-17 15:10 ` [PATCH 08/13] fuse: " Matthew Wilcox (Oracle)
2020-09-17 15:10 ` [PATCH 09/13] hostfs: " Matthew Wilcox (Oracle)
2020-09-17 15:10 ` [PATCH 10/13] jffs2: " Matthew Wilcox (Oracle)
2020-09-17 15:10 ` [PATCH 11/13] ubifs: " Matthew Wilcox (Oracle)
2020-09-17 20:46   ` Richard Weinberger
2020-09-17 15:10 ` [PATCH 12/13] udf: " Matthew Wilcox (Oracle)
2020-09-24  9:00   ` Jan Kara
2020-09-17 15:10 ` [PATCH 13/13] vboxsf: " Matthew Wilcox (Oracle)
2020-09-17 22:56 ` [PATCH 14/13] iomap: Inline iomap_iop_set_range_uptodate into its one caller Matthew Wilcox (Oracle)
2020-09-17 22:56   ` [PATCH 15/13] iomap: Inline iomap_read_finish " Matthew Wilcox (Oracle)
2020-09-19  6:31     ` Christoph Hellwig
2020-09-17 22:56   ` [PATCH 16/13] iomap: Make readpage synchronous Matthew Wilcox (Oracle)
2020-09-19  6:39     ` Christoph Hellwig
2020-09-19  6:43       ` Christoph Hellwig
2020-09-19 17:03         ` Matthew Wilcox
2020-09-19 17:10       ` Matthew Wilcox [this message]
2020-09-19  6:31   ` [PATCH 14/13] iomap: Inline iomap_iop_set_range_uptodate into its one caller Christoph Hellwig

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