Re: [PATCH v3 12/20] ceph: Make ceph_init_request() check caps on readahead

[Jeff Layton <jlayton@redhat.com>]

On Thu, 2022-03-10 at 16:17 +0000, David Howells wrote:
> Move the caps check from ceph_readahead() to ceph_init_request(),
> conditional on the origin being NETFS_READAHEAD so that in a future patch,
> ceph can point its ->readahead() vector directly at netfs_readahead().
> 
> Changes
> =======
> ver #3)
>  - Split from the patch to add a netfs inode context[1].
>  - Need to store the caps got in rreq->netfs_priv for later freeing.
> 
> Signed-off-by: David Howells <dhowells@redhat.com>
> cc: ceph-devel@vger.kernel.org
> cc: linux-cachefs@redhat.com
> Link: https://lore.kernel.org/r/8af0d47f17d89c06bbf602496dd845f2b0bf25b3.camel@kernel.org/ [1]
> ---
> 
>  fs/ceph/addr.c |   69 +++++++++++++++++++++++++++++++++-----------------------
>  1 file changed, 41 insertions(+), 28 deletions(-)
> 
> diff --git a/fs/ceph/addr.c b/fs/ceph/addr.c
> index 9189257476f8..6d056db41f50 100644
> --- a/fs/ceph/addr.c
> +++ b/fs/ceph/addr.c
> @@ -354,6 +354,45 @@ static void ceph_netfs_issue_read(struct netfs_io_subrequest *subreq)
>  	dout("%s: result %d\n", __func__, err);
>  }
>  
> +static int ceph_init_request(struct netfs_io_request *rreq, struct file *file)
> +{
> +	struct inode *inode = rreq->inode;
> +	int got = 0, want = CEPH_CAP_FILE_CACHE;
> +	int ret = 0;
> +
> +	if (file) {
> +		struct ceph_rw_context *rw_ctx;
> +		struct ceph_file_info *fi = file->private_data;
> +
> +		rw_ctx = ceph_find_rw_context(fi);
> +		if (rw_ctx)
> +			return 0;
> +	}
> +
> +	if (rreq->origin != NETFS_READAHEAD)
> +		return 0;
> +

^^^
I think you should move this check above the if (file) block above it.
We don't need to anything at all if we're not in readahead.

> +	/*
> +	 * readahead callers do not necessarily hold Fcb caps
> +	 * (e.g. fadvise, madvise).
> +	 */
> +	ret = ceph_try_get_caps(inode, CEPH_CAP_FILE_RD, want, true, &got);
> +	if (ret < 0) {
> +		dout("start_read %p, error getting cap\n", inode);
> +		return ret;
> +	}
> +
> +	if (!(got & want)) {
> +		dout("start_read %p, no cache cap\n", inode);
> +		return -EACCES;
> +	}
> +	if (ret == 0)
> +		return -EACCES;
> +
> +	rreq->netfs_priv = (void *)(uintptr_t)got;
> +	return 0;
> +}
> +
>  static void ceph_readahead_cleanup(struct address_space *mapping, void *priv)
>  {
>  	struct inode *inode = mapping->host;
> @@ -365,7 +404,7 @@ static void ceph_readahead_cleanup(struct address_space *mapping, void *priv)
>  }
>  
>  static const struct netfs_request_ops ceph_netfs_read_ops = {
> -	.is_cache_enabled	= ceph_is_cache_enabled,
> +	.init_request		= ceph_init_request,
>  	.begin_cache_operation	= ceph_begin_cache_operation,
>  	.issue_read		= ceph_netfs_issue_read,
>  	.expand_readahead	= ceph_netfs_expand_readahead,
> @@ -393,33 +432,7 @@ static int ceph_readpage(struct file *file, struct page *subpage)
>  
>  static void ceph_readahead(struct readahead_control *ractl)
>  {
> -	struct inode *inode = file_inode(ractl->file);
> -	struct ceph_file_info *fi = ractl->file->private_data;
> -	struct ceph_rw_context *rw_ctx;
> -	int got = 0;
> -	int ret = 0;
> -
> -	if (ceph_inode(inode)->i_inline_version != CEPH_INLINE_NONE)
> -		return;
> -
> -	rw_ctx = ceph_find_rw_context(fi);
> -	if (!rw_ctx) {
> -		/*
> -		 * readahead callers do not necessarily hold Fcb caps
> -		 * (e.g. fadvise, madvise).
> -		 */
> -		int want = CEPH_CAP_FILE_CACHE;
> -
> -		ret = ceph_try_get_caps(inode, CEPH_CAP_FILE_RD, want, true, &got);
> -		if (ret < 0)
> -			dout("start_read %p, error getting cap\n", inode);
> -		else if (!(got & want))
> -			dout("start_read %p, no cache cap\n", inode);
> -
> -		if (ret <= 0)
> -			return;
> -	}
> -	netfs_readahead(ractl, &ceph_netfs_read_ops, (void *)(uintptr_t)got);
> +	netfs_readahead(ractl, &ceph_netfs_read_ops, NULL);
>  }
>  
>  #ifdef CONFIG_CEPH_FSCACHE
> 
> 

-- 
Jeff Layton <jlayton@redhat.com>