linux-ext4 - Re: [RFC 0/5] Ext4: Add support for blocksize < pagesize for dioread

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Message-ID: <20191104160823.GI28764@mit.edu>
Date:   Mon, 4 Nov 2019 11:08:23 -0500
From:   "Theodore Y. Ts'o" <tytso@....edu>
To:     Matthew Bobrowski <mbobrowski@...browski.org>
Cc:     Ritesh Harjani <riteshh@...ux.ibm.com>, jack@...e.cz,
        linux-ext4@...r.kernel.org, linux-fsdevel@...r.kernel.org
Subject: Re: [RFC 0/5] Ext4: Add support for blocksize < pagesize for
 dioread_nolock

On Mon, Nov 04, 2019 at 09:49:14PM +1100, Matthew Bobrowski wrote:
> > It sure may be giving a merge conflict (due to io_end structure).
> > But this dioread_nolock series was not dependent over iomap series.
> 
> Uh ha. Well, there's been a chunk of code injected into
> ext4_end_io_dio() here and by me removing it, I'm not entirely sure
> what the downstream effects will be for this specific change...

Yeah, that was probably my failure to do the merge correctly; I'm
hoping that Ritesh will be able to fix that up.  If not we can throw
an "experimental" config to enable dioread_nolock on subpage
blocksizes, just to warn people that under some extreme workloads,
they might end up corrupting their allocation bitmap, which then might
lead to data loss.  I suspect it would actually work fine for most
users; but out of paranoia, if we can't figure out the generic/270
failure before the merge window, we can just make dioread_nolock_1k
experimental for now.

  	      	     	       		- Ted