linux-kernel - Re: [PATCH 1/2] ceph: conversion to new fscache API

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Message-ID: <1219681.1638784646@warthog.procyon.org.uk>
Date:   Mon, 06 Dec 2021 09:57:26 +0000
From:   David Howells <dhowells@...hat.com>
To:     Jeff Layton <jlayton@...nel.org>
Cc:     dhowells@...hat.com, ceph-devel@...r.kernel.org,
        idryomov@...il.com, linux-fsdevel@...r.kernel.org,
        linux-cachefs@...hat.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/2] ceph: conversion to new fscache API

Jeff Layton <jlayton@...nel.org> wrote:

>  		if (!(gfp & __GFP_DIRECT_RECLAIM) || !(gfp & __GFP_FS))

There's a function for the first part of this:

		if (!gfpflags_allow_blocking(gfp) || !(gfp & __GFP_FS))

> +	fsc->fscache = fscache_acquire_volume(name, NULL, 0);
>  
>  	if (fsc->fscache) {
>  		ent->fscache = fsc->fscache;
>  		list_add_tail(&ent->list, &ceph_fscache_list);

It shouldn't really be necessary to have ceph_fscache_list since
fscache_acquire_volume() will do it's own duplicate check.  I wonder if I
should make fscache_acquire_volume() return -EEXIST or -EBUSY rather than NULL
in such a case and not print an error, but rather leave that to the filesystem
to display.

That would allow you to get rid of the ceph_fscache_entry struct also, I
think.

> +#define FSCACHE_USE_NEW_IO_API

That doesn't exist anymore.

> +		/*
> +		 * If we're truncating up, then we should be able to just update
> +		 * the existing cookie.
> +		 */
> +		if (size > isize)
> +			ceph_fscache_update(inode);

Might look better to say "expanding" rather than "truncating up".

David