linux-ext4 - Re: [PATCH 1/1] iomap: Direct I/O for inline data

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Date:   Sun, 1 Jul 2018 08:29:01 +0200
From:   Christoph Hellwig <hch@....de>
To:     Andreas Gruenbacher <agruenba@...hat.com>
Cc:     Christoph Hellwig <hch@....de>,
        cluster-devel <cluster-devel@...hat.com>,
        linux-ext4 <linux-ext4@...r.kernel.org>,
        linux-fsdevel <linux-fsdevel@...r.kernel.org>
Subject: Re: [PATCH 1/1] iomap: Direct I/O for inline data

On Fri, Jun 29, 2018 at 04:40:40PM +0200, Andreas Gruenbacher wrote:
> On 29 June 2018 at 10:56, Christoph Hellwig <hch@....de> wrote:
> > This looks generally fine.  But I think it might be worth refactoring
> > iomap_dio_actor a bit first, e.g. something like this new patch
> > before yours, which would also nicely solve your alignmnet concern
> > (entirely untested for now):
> 
> This looks correct. I've rebased my patches on top of it and I ran the
> xfstest auto group on gfs2 and xfs on top.

As I've just been rebasing the iomap work I've done the work already,
does the version below work for you?

---
>From 5e8a0f157629bb8850b8d8fe049bb896730f0da7 Mon Sep 17 00:00:00 2001
From: Andreas Gruenbacher <agruenba@...hat.com>
Date: Sun, 1 Jul 2018 08:26:22 +0200
Subject: iomap: support direct I/O to inline data

Add support for reading from and writing to inline data to iomap_dio_rw.
This saves filesystems from having to implement fallback code for this
case.

The inline data is actually cached in the inode, so the I/O is only
direct in the sense that it doesn't go through the page cache.

Signed-off-by: Andreas Gruenbacher <agruenba@...hat.com>
---
 fs/iomap.c | 29 +++++++++++++++++++++++++++++
 1 file changed, 29 insertions(+)

diff --git a/fs/iomap.c b/fs/iomap.c
index 4d8ff0f5ecc9..98a1fdd5c091 100644
--- a/fs/iomap.c
+++ b/fs/iomap.c
@@ -1450,6 +1450,33 @@ iomap_dio_hole_actor(loff_t length, struct iomap_dio *dio)
 	return length;
 }
 
+static loff_t
+iomap_dio_inline_actor(struct inode *inode, loff_t pos, loff_t length,
+		struct iomap_dio *dio, struct iomap *iomap)
+{
+	struct iov_iter *iter = dio->submit.iter;
+	size_t copied;
+
+	BUG_ON(pos + length > PAGE_SIZE - offset_in_page(iomap->inline_data));
+
+	if (dio->flags & IOMAP_DIO_WRITE) {
+		loff_t size = inode->i_size;
+
+		if (pos > size)
+			memset(iomap->inline_data + size, 0, pos - size);
+		copied = copy_from_iter(iomap->inline_data + pos, length, iter);
+		if (copied) {
+			if (pos + copied > size)
+				i_size_write(inode, pos + copied);
+			mark_inode_dirty(inode);
+		}
+	} else {
+		copied = copy_to_iter(iomap->inline_data + pos, length, iter);
+	}
+	dio->size += copied;
+	return copied;
+}
+
 static loff_t
 iomap_dio_actor(struct inode *inode, loff_t pos, loff_t length,
 		void *data, struct iomap *iomap)
@@ -1467,6 +1494,8 @@ iomap_dio_actor(struct inode *inode, loff_t pos, loff_t length,
 		return iomap_dio_bio_actor(inode, pos, length, dio, iomap);
 	case IOMAP_MAPPED:
 		return iomap_dio_bio_actor(inode, pos, length, dio, iomap);
+	case IOMAP_INLINE:
+		return iomap_dio_inline_actor(inode, pos, length, dio, iomap);
 	default:
 		WARN_ON_ONCE(1);
 		return -EIO;
-- 
2.18.0