linux-kernel - Re: [PATCH] FAT: use blkdev_issue_flush() instead of congestion

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Message-ID: <87ee79yiik.fsf@mail.parknet.co.jp>
Date:   Sun, 21 Nov 2021 18:17:55 +0900
From:   OGAWA Hirofumi <hirofumi@...l.parknet.co.jp>
To:     "NeilBrown" <neilb@...e.de>
Cc:     linux-kernel@...r.kernel.org, linux-block@...r.kernel.org
Subject: Re: [PATCH] FAT: use blkdev_issue_flush() instead of congestion_wait()

"NeilBrown" <neilb@...e.de> writes:

> congestion_wait() in this context is just a sleep - block devices do not
> in general support congestion signalling any more.
>
> The goal here is to wait for any recently written data to get to
> storage.  This can be achieved using blkdev_issue_flush().

Purpose of flush option should be for making umount faster, not data
integrity. (but current flush implement is strange at several places, IMO)

So, I don't think the issue_flush is not proper for it (flush is very
slow on some usb thumb), and rather I think it is better off to just
remove the congestion_wait().

Thanks.

> Signed-off-by: NeilBrown <neilb@...e.de>
> ---
>  fs/fat/file.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/fs/fat/file.c b/fs/fat/file.c
> index 13855ba49cd9..c50a52f40e37 100644
> --- a/fs/fat/file.c
> +++ b/fs/fat/file.c
> @@ -175,9 +175,9 @@ long fat_generic_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
>  static int fat_file_release(struct inode *inode, struct file *filp)
>  {
>  	if ((filp->f_mode & FMODE_WRITE) &&
> -	     MSDOS_SB(inode->i_sb)->options.flush) {
> +	    MSDOS_SB(inode->i_sb)->options.flush) {
>  		fat_flush_inodes(inode->i_sb, inode, NULL);
> -		congestion_wait(BLK_RW_ASYNC, HZ/10);
> +		blkdev_issue_flush(inode->i_sb->s_bdev);
>  	}
>  	return 0;
>  }

-- 
OGAWA Hirofumi <hirofumi@...l.parknet.co.jp>