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Date: Fri, 29 Jun 2018 16:40:40 +0200
From: Andreas Gruenbacher <agruenba@...hat.com>
To: Christoph Hellwig <hch@....de>
Cc: 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 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.
Can you push this to your gfs2-iomap branch? I'll then repost an
updated version of "iomap: Direct I/O for inline data".
> ---
> From f8c58ffe79df63d23332376ce481cdc4753cc567 Mon Sep 17 00:00:00 2001
> From: Christoph Hellwig <hch@....de>
> Date: Fri, 29 Jun 2018 10:54:10 +0200
> Subject: iomap: refactor iomap_dio_actor
>
> Split the function up into two helpers for the bio based I/O and hole
> case, and a small helper to call the two. This separates the code a
> little better in preparation for supporting I/O to inline data.
>
> Signed-off-by: Christoph Hellwig <hch@....de>
Reviewed-by: Andreas Gruenbacher <agruenba@...hat.com>
> ---
> fs/iomap.c | 88 ++++++++++++++++++++++++++++++++----------------------
> 1 file changed, 52 insertions(+), 36 deletions(-)
>
> diff --git a/fs/iomap.c b/fs/iomap.c
> index 7d1e9f45f098..f05c83773cbf 100644
> --- a/fs/iomap.c
> +++ b/fs/iomap.c
> @@ -963,10 +963,9 @@ iomap_dio_zero(struct iomap_dio *dio, struct iomap *iomap, loff_t pos,
> }
>
> static loff_t
> -iomap_dio_actor(struct inode *inode, loff_t pos, loff_t length,
> - void *data, struct iomap *iomap)
> +iomap_dio_bio_actor(struct inode *inode, loff_t pos, loff_t length,
> + struct iomap_dio *dio, struct iomap *iomap)
> {
> - struct iomap_dio *dio = data;
> unsigned int blkbits = blksize_bits(bdev_logical_block_size(iomap->bdev));
> unsigned int fs_block_size = i_blocksize(inode), pad;
> unsigned int align = iov_iter_alignment(dio->submit.iter);
> @@ -980,41 +979,27 @@ iomap_dio_actor(struct inode *inode, loff_t pos, loff_t length,
> if ((pos | length | align) & ((1 << blkbits) - 1))
> return -EINVAL;
>
> - switch (iomap->type) {
> - case IOMAP_HOLE:
> - if (WARN_ON_ONCE(dio->flags & IOMAP_DIO_WRITE))
> - return -EIO;
> - /*FALLTHRU*/
> - case IOMAP_UNWRITTEN:
> - if (!(dio->flags & IOMAP_DIO_WRITE)) {
> - length = iov_iter_zero(length, dio->submit.iter);
> - dio->size += length;
> - return length;
> - }
> + if (iomap->type == IOMAP_UNWRITTEN) {
> dio->flags |= IOMAP_DIO_UNWRITTEN;
> need_zeroout = true;
> - break;
> - case IOMAP_MAPPED:
> - if (iomap->flags & IOMAP_F_SHARED)
> - dio->flags |= IOMAP_DIO_COW;
> - if (iomap->flags & IOMAP_F_NEW) {
> - need_zeroout = true;
> - } else {
> - /*
> - * Use a FUA write if we need datasync semantics, this
> - * is a pure data IO that doesn't require any metadata
> - * updates and the underlying device supports FUA. This
> - * allows us to avoid cache flushes on IO completion.
> - */
> - if (!(iomap->flags & (IOMAP_F_SHARED|IOMAP_F_DIRTY)) &&
> - (dio->flags & IOMAP_DIO_WRITE_FUA) &&
> - blk_queue_fua(bdev_get_queue(iomap->bdev)))
> - use_fua = true;
> - }
> - break;
> - default:
> - WARN_ON_ONCE(1);
> - return -EIO;
> + }
> +
> + if (iomap->flags & IOMAP_F_SHARED)
> + dio->flags |= IOMAP_DIO_COW;
> +
> + if (iomap->flags & IOMAP_F_NEW) {
> + need_zeroout = true;
> + } else {
> + /*
> + * Use a FUA write if we need datasync semantics, this
> + * is a pure data IO that doesn't require any metadata
> + * updates and the underlying device supports FUA. This
> + * allows us to avoid cache flushes on IO completion.
> + */
> + if (!(iomap->flags & (IOMAP_F_SHARED|IOMAP_F_DIRTY)) &&
> + (dio->flags & IOMAP_DIO_WRITE_FUA) &&
> + blk_queue_fua(bdev_get_queue(iomap->bdev)))
> + use_fua = true;
> }
>
> /*
> @@ -1093,6 +1078,37 @@ iomap_dio_actor(struct inode *inode, loff_t pos, loff_t length,
> return copied;
> }
>
> +static loff_t
> +iomap_dio_hole_actor(loff_t length, struct iomap_dio *dio)
> +{
> + length = iov_iter_zero(length, dio->submit.iter);
> + dio->size += length;
> + return length;
> +}
Just a minor nit: iomap_dio_hole_actor should come before iomap_dio_bio_actor.
> +
> +static loff_t
> +iomap_dio_actor(struct inode *inode, loff_t pos, loff_t length,
> + void *data, struct iomap *iomap)
> +{
> + struct iomap_dio *dio = data;
> +
> + switch (iomap->type) {
> + case IOMAP_HOLE:
> + if (WARN_ON_ONCE(dio->flags & IOMAP_DIO_WRITE))
> + return -EIO;
> + return iomap_dio_hole_actor(length, dio);
> + case IOMAP_UNWRITTEN:
> + if (!(dio->flags & IOMAP_DIO_WRITE))
> + return iomap_dio_hole_actor(length, dio);
> + return iomap_dio_bio_actor(inode, pos, length, dio, iomap);
> + case IOMAP_MAPPED:
> + return iomap_dio_bio_actor(inode, pos, length, dio, iomap);
> + default:
> + WARN_ON_ONCE(1);
> + return -EIO;
> + }
> +}
> +
> /*
> * iomap_dio_rw() always completes O_[D]SYNC writes regardless of whether the IO
> * is being issued as AIO or not. This allows us to optimise pure data writes
> --
> 2.17.1
>
Thanks,
Andreas
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