linux-ext4 - Re: [PATCH 02/11] xfs: add NOWAIT semantics for readdir

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Date:   Tue, 29 Aug 2023 14:05:10 +0100
From:   Matthew Wilcox <willy@...radead.org>
To:     Hao Xu <hao.xu@...ux.dev>
Cc:     io-uring@...r.kernel.org, Jens Axboe <axboe@...nel.dk>,
        Dominique Martinet <asmadeus@...ewreck.org>,
        Pavel Begunkov <asml.silence@...il.com>,
        Christian Brauner <brauner@...nel.org>,
        Alexander Viro <viro@...iv.linux.org.uk>,
        Stefan Roesch <shr@...com>, Clay Harris <bugs@...ycon.org>,
        Dave Chinner <david@...morbit.com>,
        "Darrick J . Wong" <djwong@...nel.org>,
        linux-fsdevel@...r.kernel.org, linux-xfs@...r.kernel.org,
        linux-ext4@...r.kernel.org, linux-cachefs@...hat.com,
        ecryptfs@...r.kernel.org, linux-nfs@...r.kernel.org,
        linux-unionfs@...r.kernel.org, bpf@...r.kernel.org,
        netdev@...r.kernel.org, linux-s390@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-block@...r.kernel.org,
        linux-btrfs@...r.kernel.org, codalist@...a.cs.cmu.edu,
        linux-f2fs-devel@...ts.sourceforge.net, cluster-devel@...hat.com,
        linux-mm@...ck.org, linux-nilfs@...r.kernel.org,
        devel@...ts.orangefs.org, linux-cifs@...r.kernel.org,
        samba-technical@...ts.samba.org, linux-mtd@...ts.infradead.org,
        Wanpeng Li <wanpengli@...cent.com>
Subject: Re: [PATCH 02/11] xfs: add NOWAIT semantics for readdir

On Tue, Aug 29, 2023 at 03:41:43PM +0800, Hao Xu wrote:
> On 8/28/23 04:44, Matthew Wilcox wrote:
> > > @@ -391,10 +401,17 @@ xfs_dir2_leaf_getdents(
> > >   				bp = NULL;
> > >   			}
> > > -			if (*lock_mode == 0)
> > > -				*lock_mode = xfs_ilock_data_map_shared(dp);
> > > +			if (*lock_mode == 0) {
> > > +				*lock_mode =
> > > +					xfs_ilock_data_map_shared_generic(dp,
> > > +					ctx->flags & DIR_CONTEXT_F_NOWAIT);
> > > +				if (!*lock_mode) {
> > > +					error = -EAGAIN;
> > > +					break;
> > > +				}
> > > +			}
> > 
> > 'generic' doesn't seem like a great suffix to mean 'takes nowait flag'.
> > And this is far too far indented.
> > 
> > 			xfs_dir2_lock(dp, ctx, lock_mode);
> > 
> > with:
> > 
> > STATIC void xfs_dir2_lock(struct xfs_inode *dp, struct dir_context *ctx,
> > 		unsigned int lock_mode)
> > {
> > 	if (*lock_mode)
> > 		return;
> > 	if (ctx->flags & DIR_CONTEXT_F_NOWAIT)
> > 		return xfs_ilock_data_map_shared_nowait(dp);
> > 	return xfs_ilock_data_map_shared(dp);
> > }
> > 
> > ... which I think you can use elsewhere in this patch (reformat it to
> > XFS coding style, of course).  And then you don't need
> > xfs_ilock_data_map_shared_generic().
> 
> How about rename xfs_ilock_data_map_shared() to xfs_ilock_data_map_block()
> and rename xfs_ilock_data_map_shared_generic() to
> xfs_ilock_data_map_shared()?
> 
> STATIC void xfs_ilock_data_map_shared(struct xfs_inode *dp, struct
> dir_context *ctx, unsigned int lock_mode)
> {
>  	if (*lock_mode)
>  		return;
>  	if (ctx->flags & DIR_CONTEXT_F_NOWAIT)
>  		return xfs_ilock_data_map_shared_nowait(dp);
>  	return xfs_ilock_data_map_shared_block(dp);
> }

xfs_ilock_data_map_shared() is used for a lot of things which are not
directories.  I think a new function name is appropriate, and that
function name should include the word 'dir' in it somewhere.