linux-ext4 - Re: [PATCH -next 0/7] fs/buffer: split pagecache lookups into atomic or blocking

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Message-ID: <20250417-annahme-geprobt-bc84bbd12af3@brauner>
Date: Thu, 17 Apr 2025 11:57:36 +0200
From: Christian Brauner <brauner@...nel.org>
To: Luis Chamberlain <mcgrof@...nel.org>
Cc: Davidlohr Bueso <dave@...olabs.net>, 
	Linus Torvalds <torvalds@...ux-foundation.org>, jack@...e.cz, tytso@....edu, adilger.kernel@...ger.ca, 
	willy@...radead.org, hare@...e.de, djwong@...nel.org, linux-ext4@...r.kernel.org, 
	linux-fsdevel@...r.kernel.org, linux-mm@...ck.org
Subject: Re: [PATCH -next 0/7] fs/buffer: split pagecache lookups into atomic
 or blocking

On Wed, Apr 16, 2025 at 12:27:57PM -0700, Luis Chamberlain wrote:
> On Tue, Apr 15, 2025 at 04:16:28PM -0700, Davidlohr Bueso wrote:
> > Hello,
> > 
> > This is a respin of the series[0] to address the sleep in atomic scenarios for
> > noref migration with large folios, introduced in:
> > 
> >       3c20917120ce61 ("block/bdev: enable large folio support for large logical block sizes")
> > 
> > The main difference is that it removes the first patch and moves the fix (reducing
> > the i_private_lock critical region in the migration path) to the final patch, which
> > also introduces the new BH_Migrate flag. It also simplifies the locking scheme in
> > patch 1 to avoid folio trylocking in the atomic lookup cases. So essentially blocking
> > users will take the folio lock and hence wait for migration, and otherwise nonblocking
> > callers will bail the lookup if a noref migration is on-going. Blocking callers
> > will also benefit from potential performance gains by reducing contention on the
> > spinlock for bdev mappings.
> > 
> > It is noteworthy that this series is probably too big for Linus' tree, so there are
> > two options:
> > 
> >  1. Revert 3c20917120ce61, add this series + 3c20917120ce61 for next. Or,
> 
> Reverting due to a fix series is odd, I'd advocate this series as a set
> of fixes to Linus' tree because clearly folio migration was not complete

I agree.