linux-kernel - Re: [PATCH 11/17] iomap: assign current->backing_dev_info in iomap_file_buffered

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Message-ID: <20230424061825.GO360889@frogsfrogsfrogs>
Date:   Sun, 23 Apr 2023 23:18:25 -0700
From:   "Darrick J. Wong" <djwong@...nel.org>
To:     Christoph Hellwig <hch@....de>
Cc:     Jens Axboe <axboe@...nel.dk>, Miklos Szeredi <miklos@...redi.hu>,
        Andrew Morton <akpm@...ux-foundation.org>,
        David Howells <dhowells@...hat.com>,
        Matthew Wilcox <willy@...radead.org>,
        linux-block@...r.kernel.org, linux-fsdevel@...r.kernel.org,
        ceph-devel@...r.kernel.org, linux-ext4@...r.kernel.org,
        linux-f2fs-devel@...ts.sourceforge.net, cluster-devel@...hat.com,
        linux-xfs@...r.kernel.org, linux-nfs@...r.kernel.org,
        linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 11/17] iomap: assign current->backing_dev_info in
 iomap_file_buffered_write

On Mon, Apr 24, 2023 at 07:49:20AM +0200, Christoph Hellwig wrote:
> Move the assignment to current->backing_dev_info from the callers into
> iomap_file_buffered_write.  Note that zonefs was missing this assignment
> before.
> 
> Signed-off-by: Christoph Hellwig <hch@....de>
> ---
>  fs/gfs2/file.c         | 3 ---
>  fs/iomap/buffered-io.c | 4 ++++
>  fs/xfs/xfs_file.c      | 5 -----
>  3 files changed, 4 insertions(+), 8 deletions(-)
> 
> diff --git a/fs/gfs2/file.c b/fs/gfs2/file.c
> index 8c4fad359ff538..4d88c6080b3e30 100644
> --- a/fs/gfs2/file.c
> +++ b/fs/gfs2/file.c
> @@ -25,7 +25,6 @@
>  #include <linux/dlm.h>
>  #include <linux/dlm_plock.h>
>  #include <linux/delay.h>
> -#include <linux/backing-dev.h>
>  #include <linux/fileattr.h>
>  
>  #include "gfs2.h"
> @@ -1041,11 +1040,9 @@ static ssize_t gfs2_file_buffered_write(struct kiocb *iocb,
>  			goto out_unlock;
>  	}
>  
> -	current->backing_dev_info = inode_to_bdi(inode);
>  	pagefault_disable();
>  	ret = iomap_file_buffered_write(iocb, from, &gfs2_iomap_ops);
>  	pagefault_enable();
> -	current->backing_dev_info = NULL;
>  	if (ret > 0) {
>  		iocb->ki_pos += ret;
>  		written += ret;
> diff --git a/fs/iomap/buffered-io.c b/fs/iomap/buffered-io.c
> index 2986be63d2bea6..3d5042efda202a 100644
> --- a/fs/iomap/buffered-io.c
> +++ b/fs/iomap/buffered-io.c
> @@ -3,6 +3,7 @@
>   * Copyright (C) 2010 Red Hat, Inc.
>   * Copyright (C) 2016-2019 Christoph Hellwig.
>   */
> +#include <linux/backing-dev.h>
>  #include <linux/module.h>
>  #include <linux/compiler.h>
>  #include <linux/fs.h>
> @@ -876,8 +877,11 @@ iomap_file_buffered_write(struct kiocb *iocb, struct iov_iter *i,
>  	if (iocb->ki_flags & IOCB_NOWAIT)
>  		iter.flags |= IOMAP_NOWAIT;
>  
> +	current->backing_dev_info = inode_to_bdi(iter.inode);

Dumb question from me late on a Sunday night, but does the iomap_unshare
code need to set this too?  Since it works by dirtying pagecache folios
without actually changing the contents?

--D

>  	while ((ret = iomap_iter(&iter, ops)) > 0)
>  		iter.processed = iomap_write_iter(&iter, i);
> +	current->backing_dev_info = NULL;
> +
>  	if (iter.pos == iocb->ki_pos)
>  		return ret;
>  	return iter.pos - iocb->ki_pos;
> diff --git a/fs/xfs/xfs_file.c b/fs/xfs/xfs_file.c
> index 705250f9f90a1b..f5442e689baf15 100644
> --- a/fs/xfs/xfs_file.c
> +++ b/fs/xfs/xfs_file.c
> @@ -27,7 +27,6 @@
>  
>  #include <linux/dax.h>
>  #include <linux/falloc.h>
> -#include <linux/backing-dev.h>
>  #include <linux/mman.h>
>  #include <linux/fadvise.h>
>  #include <linux/mount.h>
> @@ -717,9 +716,6 @@ xfs_file_buffered_write(
>  	if (ret)
>  		goto out;
>  
> -	/* We can write back this queue in page reclaim */
> -	current->backing_dev_info = inode_to_bdi(inode);
> -
>  	trace_xfs_file_buffered_write(iocb, from);
>  	ret = iomap_file_buffered_write(iocb, from,
>  			&xfs_buffered_write_iomap_ops);
> @@ -753,7 +749,6 @@ xfs_file_buffered_write(
>  		goto write_retry;
>  	}
>  
> -	current->backing_dev_info = NULL;
>  out:
>  	if (iolock)
>  		xfs_iunlock(ip, iolock);
> -- 
> 2.39.2
>