linux-ext4 - Re: [PATCH v2 17/54] fs: remove the inode from the LRU list on unlink/rmdir

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Message-ID: <20250827160843.GB2272053@perftesting>
Date: Wed, 27 Aug 2025 12:08:43 -0400
From: Josef Bacik <josef@...icpanda.com>
To: Christian Brauner <brauner@...nel.org>
Cc: linux-fsdevel@...r.kernel.org, linux-btrfs@...r.kernel.org,
	kernel-team@...com, linux-ext4@...r.kernel.org,
	linux-xfs@...r.kernel.org, viro@...iv.linux.org.uk,
	amir73il@...il.com
Subject: Re: [PATCH v2 17/54] fs: remove the inode from the LRU list on
 unlink/rmdir

On Wed, Aug 27, 2025 at 02:32:49PM +0200, Christian Brauner wrote:
> On Tue, Aug 26, 2025 at 11:39:17AM -0400, Josef Bacik wrote:
> > We can end up with an inode on the LRU list or the cached list, then at
> > some point in the future go to unlink that inode and then still have an
> > elevated i_count reference for that inode because it is on one of these
> > lists.
> > 
> > The more common case is the cached list. We open a file, write to it,
> > truncate some of it which triggers the inode_add_lru code in the
> > pagecache, adding it to the cached LRU.  Then we unlink this inode, and
> > it exists until writeback or reclaim kicks in and removes the inode.
> > 
> > To handle this case, delete the inode from the LRU list when it is
> > unlinked, so we have the best case scenario for immediately freeing the
> > inode.
> > 
> > Signed-off-by: Josef Bacik <josef@...icpanda.com>
> > ---
> 
> I'm not too fond of this particular change I think it's really misplaced
> and the correct place is indeed drop_nlink() and clear_nlink().
> 
> I'm pretty sure that the number of callers that hold i_lock around
> drop_nlink() and clear_nlink() is relatively small. So it might just be
> preferable to drop_nlink_locked() and clear_nlink_locked() and just
> switch the few places over to it. I think you have tooling to give you a
> preliminary glimpse what and how many callers do this...

Fair, I'll make the weird french guy figure it out.  Thanks,

Josef