linux-ext4 - Re: [ext4 io hang] buffered write io hang in balance_dirty

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Date:   Tue, 2 May 2023 08:57:32 +0800
From:   Ming Lei <ming.lei@...hat.com>
To:     Christoph Hellwig <hch@....de>
Cc:     Theodore Ts'o <tytso@....edu>, Baokun Li <libaokun1@...wei.com>,
        Matthew Wilcox <willy@...radead.org>,
        linux-ext4@...r.kernel.org,
        Andreas Dilger <adilger.kernel@...ger.ca>,
        linux-block@...r.kernel.org,
        Andrew Morton <akpm@...ux-foundation.org>,
        linux-fsdevel@...r.kernel.org, linux-mm@...ck.org,
        Dave Chinner <dchinner@...hat.com>,
        Eric Sandeen <sandeen@...hat.com>,
        Zhang Yi <yi.zhang@...hat.com>,
        yangerkun <yangerkun@...wei.com>, ming.lei@...hat.com
Subject: Re: [ext4 io hang] buffered write io hang in balance_dirty_pages

On Mon, May 01, 2023 at 06:47:44AM +0200, Christoph Hellwig wrote:
> On Sat, Apr 29, 2023 at 01:10:49PM +0800, Ming Lei wrote:
> > Not sure if it is needed for non s_bdev
> 
> So you don't want to work this at all for btrfs?  Or the XFS log device,
> or ..

Basically FS can provide one generic API of shutdown_filesystem() which
shutdown FS generically, meantime calls each fs's ->shutdown() for
dealing with fs specific shutdown.

If there isn't superblock attached for one bdev, can you explain a bit what
filesystem code can do? Same with block layer bdev.

The current bio->bi_status together disk_live()(maybe bdev_live() is
needed) should be enough for FS code to handle non s_bdev.

> 
> > , because FS is over stackable device
> > directly. Stackable device has its own logic for handling underlying disks dead
> > or deleted, then decide if its own disk needs to be deleted, such as, it is
> > fine for raid1 to work from user viewpoint if one underlying disk is deleted.
> 
> We still need to propagate the even that device has been removed upwards.
> Right now some file systems (especially XFS) are good at just propagating
> it from an I/O error.  And explicity call would be much better.

It depends on the above question about how FS code handle non s_bdev
deletion/dead.


Thanks,
Ming