From: Dave Chinner <david@fromorbit.com>
To: Goldwyn Rodrigues <rgoldwyn@suse.de>
Cc: linux-fsdevel@vger.kernel.org, linux-btrfs@vger.kernel.org,
hch@lst.de, darrick.wong@oracle.com, ruansy.fnst@cn.fujitsu.com,
Goldwyn Rodrigues <rgoldwyn@suse.com>
Subject: Re: [PATCH 02/13] iomap: Read page from srcmap for IOMAP_COW
Date: Mon, 5 Aug 2019 09:52:59 +1000 [thread overview]
Message-ID: <20190804235259.GD7689@dread.disaster.area> (raw)
In-Reply-To: <20190802220048.16142-3-rgoldwyn@suse.de>
On Fri, Aug 02, 2019 at 05:00:37PM -0500, Goldwyn Rodrigues wrote:
> From: Goldwyn Rodrigues <rgoldwyn@suse.com>
>
> In case of a IOMAP_COW, read a page from the srcmap before
> performing a write on the page.
>
> Signed-off-by: Goldwyn Rodrigues <rgoldwyn@suse.com>
> ---
> fs/iomap/buffered-io.c | 14 ++++++++------
> 1 file changed, 8 insertions(+), 6 deletions(-)
>
> diff --git a/fs/iomap/buffered-io.c b/fs/iomap/buffered-io.c
> index f27756c0b31c..a96cc26eec92 100644
> --- a/fs/iomap/buffered-io.c
> +++ b/fs/iomap/buffered-io.c
> @@ -581,7 +581,7 @@ __iomap_write_begin(struct inode *inode, loff_t pos, unsigned len,
>
> static int
> iomap_write_begin(struct inode *inode, loff_t pos, unsigned len, unsigned flags,
> - struct page **pagep, struct iomap *iomap)
> + struct page **pagep, struct iomap *iomap, struct iomap *srcmap)
> {
> const struct iomap_page_ops *page_ops = iomap->page_ops;
> pgoff_t index = pos >> PAGE_SHIFT;
> @@ -607,6 +607,8 @@ iomap_write_begin(struct inode *inode, loff_t pos, unsigned len, unsigned flags,
>
> if (iomap->type == IOMAP_INLINE)
> iomap_read_inline_data(inode, page, iomap);
> + else if (iomap->type == IOMAP_COW)
> + status = __iomap_write_begin(inode, pos, len, page, srcmap);
> else if (iomap->flags & IOMAP_F_BUFFER_HEAD)
> status = __block_write_begin_int(page, pos, len, NULL, iomap);
> else
This looks busted w.r.t. IOMAP_F_BUFFER_HEAD. i.e. What's to stop
someone returning iomap->type == IOMAP_COW, iomap->flags &
IOMAP_F_BUFFER_HEAD?
In which case we can't call __iomap_write_begin(), right?
I'm with Darrick on CONFIG_IOMAP_DEBUG here - we need to start
locking down invalid behaviour and invalid combinations with asserts
that tell developers they've broken something.
Cheers,
Dave.
--
Dave Chinner
david@fromorbit.com
next prev parent reply other threads:[~2019-08-04 23:54 UTC|newest]
Thread overview: 45+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-08-02 22:00 [PATCH v2 0/13] Btrfs iomap Goldwyn Rodrigues
2019-08-02 22:00 ` [PATCH 01/13] iomap: Use a IOMAP_COW/srcmap for a read-modify-write I/O Goldwyn Rodrigues
2019-08-03 0:39 ` Darrick J. Wong
2019-08-05 0:06 ` Dave Chinner
2019-08-02 22:00 ` [PATCH 02/13] iomap: Read page from srcmap for IOMAP_COW Goldwyn Rodrigues
2019-08-03 0:23 ` Darrick J. Wong
2019-08-04 23:52 ` Dave Chinner [this message]
2019-08-02 22:00 ` [PATCH 03/13] btrfs: Eliminate PagePrivate for btrfs data pages Goldwyn Rodrigues
2019-08-02 22:00 ` [PATCH 04/13] btrfs: Add a simple buffered iomap write Goldwyn Rodrigues
2019-08-05 0:11 ` Dave Chinner
2019-08-22 15:05 ` Goldwyn Rodrigues
2019-08-02 22:00 ` [PATCH 05/13] btrfs: Add CoW in iomap based writes Goldwyn Rodrigues
2019-08-05 0:13 ` Dave Chinner
2019-08-22 15:01 ` Goldwyn Rodrigues
2019-08-02 22:00 ` [PATCH 06/13] btrfs: remove buffered write code made unnecessary Goldwyn Rodrigues
2019-08-02 22:00 ` [PATCH 07/13] btrfs: basic direct read operation Goldwyn Rodrigues
2019-08-12 12:32 ` RITESH HARJANI
2019-08-22 15:00 ` Goldwyn Rodrigues
2019-08-02 22:00 ` [PATCH 08/13] btrfs: Carve out btrfs_get_extent_map_write() out of btrfs_get_blocks_write() Goldwyn Rodrigues
2019-08-02 22:00 ` [PATCH 09/13] btrfs: Rename __endio_write_update_ordered() to btrfs_update_ordered_extent() Goldwyn Rodrigues
2019-08-02 22:00 ` [PATCH 10/13] iomap: use a function pointer for dio submits Goldwyn Rodrigues
2019-08-03 0:21 ` Darrick J. Wong
2019-08-05 16:08 ` Goldwyn Rodrigues
2019-08-04 23:43 ` Dave Chinner
2019-08-05 16:08 ` Goldwyn Rodrigues
2019-08-05 21:54 ` Dave Chinner
2019-08-08 4:26 ` Gao Xiang
2019-08-08 4:52 ` Gao Xiang
2019-08-08 5:49 ` Eric Biggers
2019-08-08 6:28 ` Gao Xiang
2019-08-08 8:16 ` Dave Chinner
2019-08-08 8:57 ` Gao Xiang
2019-08-08 9:29 ` Gao Xiang
2019-08-08 11:21 ` Gao Xiang
2019-08-08 13:11 ` Gao Xiang
2019-08-09 20:45 ` Matthew Wilcox
2019-08-09 23:45 ` Gao Xiang
2019-08-10 0:31 ` Eric Biggers
2019-08-10 0:50 ` Eric Biggers
2019-08-10 1:34 ` Gao Xiang
2019-08-10 1:13 ` Gao Xiang
2019-08-10 0:17 ` Eric Biggers
2019-08-02 22:00 ` [PATCH 11/13] btrfs: Use iomap_dio_rw for performing direct I/O writes Goldwyn Rodrigues
2019-08-02 22:00 ` [PATCH 12/13] btrfs: Remove btrfs_dio_data and __btrfs_direct_write Goldwyn Rodrigues
2019-08-02 22:00 ` [PATCH 13/13] btrfs: update inode size during bio completion Goldwyn Rodrigues
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