All of lore.kernel.org
 help / color / mirror / Atom feed
From: Christoph Hellwig <hch@lst.de>
To: David Howells <dhowells@redhat.com>
Cc: Trond Myklebust <trondmy@hammerspace.com>,
	Anna Schumaker <anna.schumaker@netapp.com>,
	Steve French <sfrench@samba.org>,
	Dominique Martinet <asmadeus@codewreck.org>,
	Jeff Layton <jlayton@redhat.com>, Christoph Hellwig <hch@lst.de>,
	linux-cachefs@redhat.com, linux-afs@lists.infradead.org,
	linux-nfs@vger.kernel.org, linux-cifs@vger.kernel.org,
	ceph-devel@vger.kernel.org, v9fs-developer@lists.sourceforge.net,
	linux-fsdevel@vger.kernel.org,
	David Wysochanski <dwysocha@redhat.com>,
	"Matthew Wilcox (Oracle)" <willy@infradead.org>,
	Alexander Viro <viro@zeniv.linux.org.uk>,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH 14/33] fscache, cachefiles: Add alternate API to use kiocb for read/write to cache
Date: Tue, 16 Feb 2021 11:49:14 +0100	[thread overview]
Message-ID: <20210216104914.GA28196@lst.de> (raw)
In-Reply-To: <161340402057.1303470.8038373593844486698.stgit@warthog.procyon.org.uk>

On Mon, Feb 15, 2021 at 03:47:00PM +0000, David Howells wrote:
> Add an alternate API by which the cache can be accessed through a kiocb,
> doing async DIO, rather than using the current API that tells the cache
> where all the pages are.
> 
> The new API is intended to be used in conjunction with the netfs helper
> library.  A filesystem must pick one or the other and not mix them.
> 
> Filesystems wanting to use the new API must #define FSCACHE_USE_NEW_IO_API
> before #including the header

What exactly does this ifdef buys us?  It seems like the old and new
APIs don't even conflict.  And if we really need an ifdef I'd rather
use that for the old code to make grepping for that easier.

> +extern void cachefiles_put_object(struct fscache_object *_object,
> +				  enum fscache_obj_ref_trace why);

No need for the extern here on all the other function prototypes.

> +	if (ki->term_func) {
> +		if (ret < 0)
> +			ki->term_func(ki->term_func_priv, ret);
> +		else
> +			ki->term_func(ki->term_func_priv, ki->skipped + ret);

Why not simplify:

		if (ret > 0)
			ret += ki->skipped;
		ki->term_func(ki->term_func_priv, ret);

> +	/* If the caller asked us to seek for data before doing the read, then
> +	 * we should do that now.  If we find a gap, we fill it with zeros.
> +	 */

FYI, this is not the normal kernel comment style..

> +	ret = rw_verify_area(READ, file, &ki->iocb.ki_pos, len - skipped);
> +	if (ret < 0)
> +		goto presubmission_error_free;
> +
> +	get_file(ki->iocb.ki_filp);
> +
> +	old_nofs = memalloc_nofs_save();
> +	ret = call_read_iter(file, &ki->iocb, iter);
> +	memalloc_nofs_restore(old_nofs);

As mentioned before I think all this magic belongs in to a helper
in the VFS.

> +static const struct netfs_cache_ops cachefiles_netfs_cache_ops = {
> +	.end_operation		= cachefiles_end_operation,
> +	.read			= cachefiles_read,
> +	.write			= cachefiles_write,
> +	.expand_readahead	= NULL,
> +	.prepare_read		= cachefiles_prepare_read,
> +};

No need to set any member in a static allocated structure to zero.

Also at least in linux-next ->read and ->write seem to never actually
be called.

> +{
> +	struct cachefiles_object *object;
> +	struct cachefiles_cache *cache;
> +	struct path path;
> +	struct file *file;
> +
> +	_enter("");
> +
> +	object = container_of(op->op.object,
> +			      struct cachefiles_object, fscache);
> +	cache = container_of(object->fscache.cache,
> +			     struct cachefiles_cache, cache);
> +
> +	path.mnt = cache->mnt;
> +	path.dentry = object->backer;
> +	file = open_with_fake_path(&path, O_RDWR | O_LARGEFILE | O_DIRECT,
> +				   d_inode(object->backer), cache->cache_cred);

I think this should be plain old dentry_open?

> +extern struct fscache_retrieval *fscache_alloc_retrieval(struct fscache_cookie *,
> +							 struct address_space *,
> +							 fscache_rw_complete_t, void *);

No need for the extern.  And no need to indent the parameters totally out
sight, a single tab should be enough.  And it's always nice to spell out
the parameter names.

> +	op = fscache_alloc_retrieval(cookie, NULL, NULL, NULL);
> +	if (!op)
> +		return -ENOMEM;
> +	//atomic_set(&op->n_pages, 1);

???

> +static inline
> +int fscache_begin_read_operation(struct netfs_read_request *rreq,

Normal kernel style is to have the static and the inline on the
same line as the return type.

> +				 struct fscache_cookie *cookie)
> +{
> +	if (fscache_cookie_valid(cookie) && fscache_cookie_enabled(cookie))
> +		return __fscache_begin_read_operation(rreq, cookie);
> +	else
> +		return -ENOBUFS;
> +}

No need for an else after a return.  I personally also prefer to always
handle the error case first, ala:

        if (!fscache_cookie_valid(cookie) || !fscache_cookie_enabled(cookie))
	                return -ENOBUFS;
	return __fscache_begin_read_operation(rreq, cookie);

Also do we really need this inline fast path to start with?

  reply	other threads:[~2021-02-16 10:50 UTC|newest]

Thread overview: 81+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-02-15 15:44 [PATCH 00/33] Network fs helper library & fscache kiocb API [ver #3] David Howells
2021-02-15 15:44 ` [PATCH 01/33] iov_iter: Add ITER_XARRAY David Howells
2021-02-15 15:44 ` [PATCH 02/33] mm: Add an unlock function for PG_private_2/PG_fscache David Howells
2021-02-16 10:26   ` Christoph Hellwig
2021-02-15 15:44 ` [PATCH 03/33] mm: Implement readahead_control pageset expansion David Howells
2021-02-16 10:32   ` Christoph Hellwig
2021-02-16 13:22     ` Matthew Wilcox
2021-02-17 14:36       ` Mike Marshall
2021-02-17 14:36         ` Mike Marshall
2021-02-17 15:42       ` David Howells
2021-02-17 16:59         ` Mike Marshall
2021-02-17 16:59           ` Mike Marshall
2021-02-17 22:20         ` David Howells
2021-02-16 11:48   ` David Howells
2021-02-17 16:13   ` Matthew Wilcox
2021-02-17 22:34   ` David Howells
2021-02-17 22:49     ` Matthew Wilcox
2021-02-18 17:47   ` David Howells
2021-02-15 15:45 ` [PATCH 04/33] vfs: Export rw_verify_area() for use by cachefiles David Howells
2021-02-16 10:26   ` Christoph Hellwig
2021-02-16 11:55   ` David Howells
2021-02-15 15:45 ` [PATCH 05/33] netfs: Make a netfs helper module David Howells
2021-02-15 15:45 ` [PATCH 06/33] netfs, mm: Move PG_fscache helper funcs to linux/netfs.h David Howells
2021-02-15 15:45 ` [PATCH 07/33] netfs, mm: Add unlock_page_fscache() and wait_on_page_fscache() David Howells
2021-02-15 15:45 ` [PATCH 08/33] netfs: Provide readahead and readpage netfs helpers David Howells
2021-02-15 15:45 ` [PATCH 09/33] netfs: Add tracepoints David Howells
2021-02-15 15:46 ` [PATCH 10/33] netfs: Gather stats David Howells
2021-02-15 15:46 ` [PATCH 11/33] netfs: Add write_begin helper David Howells
2021-02-15 15:46 ` [PATCH 12/33] netfs: Define an interface to talk to a cache David Howells
2021-02-15 15:46 ` [PATCH 13/33] netfs: Hold a ref on a page when PG_private_2 is set David Howells
2021-02-15 15:47 ` [PATCH 14/33] fscache, cachefiles: Add alternate API to use kiocb for read/write to cache David Howells
2021-02-16 10:49   ` Christoph Hellwig [this message]
2021-02-16 15:08   ` David Howells
2021-02-15 15:47 ` [PATCH 15/33] afs: Disable use of the fscache I/O routines David Howells
2021-02-15 15:47 ` [PATCH 16/33] afs: Pass page into dirty region helpers to provide THP size David Howells
2021-02-15 15:47 ` [PATCH 17/33] afs: Print the operation debug_id when logging an unexpected data version David Howells
2021-02-15 15:47 ` [PATCH 18/33] afs: Move key to afs_read struct David Howells
2021-02-15 15:47 ` [PATCH 19/33] afs: Don't truncate iter during data fetch David Howells
2021-02-15 15:48 ` [PATCH 20/33] afs: Log remote unmarshalling errors David Howells
2021-02-15 15:48 ` [PATCH 21/33] afs: Set up the iov_iter before calling afs_extract_data() David Howells
2021-02-15 15:48 ` [PATCH 22/33] afs: Use ITER_XARRAY for writing David Howells
2021-02-15 15:48 ` [PATCH 23/33] afs: Wait on PG_fscache before modifying/releasing a page David Howells
2021-02-15 15:49 ` [PATCH 24/33] afs: Extract writeback extension into its own function David Howells
2021-02-15 15:49 ` [PATCH 25/33] afs: Prepare for use of THPs David Howells
2021-02-15 15:49 ` [PATCH 26/33] afs: Use the fs operation ops to handle FetchData completion David Howells
2021-02-15 15:49 ` [PATCH 27/33] afs: Use new fscache read helper API David Howells
2021-02-15 15:49 ` [PATCH 28/33] ceph: disable old fscache readpage handling David Howells
2021-02-15 15:50 ` [PATCH 29/33] ceph: rework PageFsCache handling David Howells
2021-02-15 15:50 ` [PATCH 30/33] ceph: fix fscache invalidation David Howells
2021-02-15 15:50 ` [PATCH 31/33] ceph: convert readpage to fscache read helper David Howells
2021-02-15 15:50 ` [PATCH 32/33] ceph: plug write_begin into " David Howells
2021-02-15 15:51 ` [PATCH 33/33] ceph: convert ceph_readpages to ceph_readahead David Howells
2021-02-15 18:05 ` [PATCH 00/33] Network fs helper library & fscache kiocb API [ver #3] Jeff Layton
2021-02-15 18:05   ` Jeff Layton
2021-02-16  0:40   ` Steve French
2021-02-16  0:40     ` Steve French
2021-02-16  2:10     ` Matthew Wilcox
2021-02-16  5:18       ` Steve French
2021-02-16  5:18         ` Steve French
2021-02-16  5:22       ` Steve French
2021-02-16  5:22         ` Steve French
2021-02-23 20:27         ` Matthew Wilcox
2021-02-23 20:27           ` [f2fs-dev] " Matthew Wilcox
2021-02-24  4:57           ` Steve French
2021-02-24  4:57             ` [f2fs-dev] " Steve French
2021-02-24  4:57             ` Steve French
2021-02-24 13:32       ` David Howells
2021-02-24 15:51         ` Matthew Wilcox
2021-02-16 11:01     ` Jeff Layton
2021-02-16 11:01       ` Jeff Layton
2021-02-15 22:46 ` [PATCH 34/33] netfs: Use in_interrupt() not in_softirq() David Howells
2021-02-16  8:42   ` Christoph Hellwig
2021-02-16  9:06     ` Sebastian Andrzej Siewior
2021-02-16  9:29   ` David Howells
2021-02-16  9:30     ` Christoph Hellwig
2021-02-18 14:02     ` [PATCH 34/33] netfs: Pass flag rather than use in_softirq() David Howells
2021-02-18 15:06       ` Marc Dionne
2021-02-18 15:06         ` Marc Dionne
2021-02-18 15:16       ` Marc Dionne
2021-02-18 15:16         ` Marc Dionne
2021-02-19  9:01       ` Sebastian Andrzej Siewior

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20210216104914.GA28196@lst.de \
    --to=hch@lst.de \
    --cc=anna.schumaker@netapp.com \
    --cc=asmadeus@codewreck.org \
    --cc=ceph-devel@vger.kernel.org \
    --cc=dhowells@redhat.com \
    --cc=dwysocha@redhat.com \
    --cc=jlayton@redhat.com \
    --cc=linux-afs@lists.infradead.org \
    --cc=linux-cachefs@redhat.com \
    --cc=linux-cifs@vger.kernel.org \
    --cc=linux-fsdevel@vger.kernel.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=linux-nfs@vger.kernel.org \
    --cc=sfrench@samba.org \
    --cc=trondmy@hammerspace.com \
    --cc=v9fs-developer@lists.sourceforge.net \
    --cc=viro@zeniv.linux.org.uk \
    --cc=willy@infradead.org \
    --subject='Re: [PATCH 14/33] fscache, cachefiles: Add alternate API to use kiocb for read/write to cache' \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.