Re: [PATCH 1/2] libceph: have ceph_osdc_copy_from() return the osd request

[Jeff Layton <jlayton@kernel.org>]

On Wed, 2021-11-03 at 11:24 +0000, Luís Henriques wrote:
> This patch modifies the behaviour of ceph_osdc_copy_from() function so
> that it will create the osd request and send it but won't block waiting
> for the result.  It is now the responsibility of the callers (currently
> only ceph_do_objects_copy()) to do the wait and release the request.
> 
> Signed-off-by: Luís Henriques <lhenriques@suse.de>
> ---
>  fs/ceph/file.c                  |  9 ++++++++-
>  include/linux/ceph/osd_client.h | 21 +++++++++++----------
>  net/ceph/osd_client.c           | 27 ++++++++++++++-------------
>  3 files changed, 33 insertions(+), 24 deletions(-)
> 
> diff --git a/fs/ceph/file.c b/fs/ceph/file.c
> index 6005b430f6f7..a39703b8ef99 100644
> --- a/fs/ceph/file.c
> +++ b/fs/ceph/file.c
> @@ -2218,6 +2218,7 @@ static ssize_t ceph_do_objects_copy(struct ceph_inode_info *src_ci, u64 *src_off
>  {
>  	struct ceph_object_locator src_oloc, dst_oloc;
>  	struct ceph_object_id src_oid, dst_oid;
> +	struct ceph_osd_request *req;
>  	size_t bytes = 0;
>  	u64 src_objnum, src_objoff, dst_objnum, dst_objoff;
>  	u32 src_objlen, dst_objlen;
> @@ -2243,7 +2244,7 @@ static ssize_t ceph_do_objects_copy(struct ceph_inode_info *src_ci, u64 *src_off
>  		ceph_oid_printf(&dst_oid, "%llx.%08llx",
>  				dst_ci->i_vino.ino, dst_objnum);
>  		/* Do an object remote copy */
> -		ret = ceph_osdc_copy_from(&fsc->client->osdc,
> +		req = ceph_osdc_copy_from(&fsc->client->osdc,
>  					  src_ci->i_vino.snap, 0,
>  					  &src_oid, &src_oloc,
>  					  CEPH_OSD_OP_FLAG_FADVISE_SEQUENTIAL |
> @@ -2254,6 +2255,12 @@ static ssize_t ceph_do_objects_copy(struct ceph_inode_info *src_ci, u64 *src_off
>  					  dst_ci->i_truncate_seq,
>  					  dst_ci->i_truncate_size,
>  					  CEPH_OSD_COPY_FROM_FLAG_TRUNCATE_SEQ);
> +		if (IS_ERR(req))
> +			ret = PTR_ERR(req);
> +		else {
> +			ret = ceph_osdc_wait_request(&fsc->client->osdc, req);
> +			ceph_osdc_put_request(req);
> +		}
>  		if (ret) {
>  			if (ret == -EOPNOTSUPP) {
>  				fsc->have_copy_from2 = false;
> diff --git a/include/linux/ceph/osd_client.h b/include/linux/ceph/osd_client.h
> index 83fa08a06507..74d590cd29c9 100644
> --- a/include/linux/ceph/osd_client.h
> +++ b/include/linux/ceph/osd_client.h
> @@ -515,16 +515,17 @@ int ceph_osdc_call(struct ceph_osd_client *osdc,
>  		   struct page *req_page, size_t req_len,
>  		   struct page **resp_pages, size_t *resp_len);
>  
> -int ceph_osdc_copy_from(struct ceph_osd_client *osdc,
> -			u64 src_snapid, u64 src_version,
> -			struct ceph_object_id *src_oid,
> -			struct ceph_object_locator *src_oloc,
> -			u32 src_fadvise_flags,
> -			struct ceph_object_id *dst_oid,
> -			struct ceph_object_locator *dst_oloc,
> -			u32 dst_fadvise_flags,
> -			u32 truncate_seq, u64 truncate_size,
> -			u8 copy_from_flags);
> +struct ceph_osd_request *
> +ceph_osdc_copy_from(struct ceph_osd_client *osdc,
> +		    u64 src_snapid, u64 src_version,
> +		    struct ceph_object_id *src_oid,
> +		    struct ceph_object_locator *src_oloc,
> +		    u32 src_fadvise_flags,
> +		    struct ceph_object_id *dst_oid,
> +		    struct ceph_object_locator *dst_oloc,
> +		    u32 dst_fadvise_flags,
> +		    u32 truncate_seq, u64 truncate_size,
> +		    u8 copy_from_flags);
>  
>  /* watch/notify */
>  struct ceph_osd_linger_request *
> diff --git a/net/ceph/osd_client.c b/net/ceph/osd_client.c
> index ff8624a7c964..78384b431748 100644
> --- a/net/ceph/osd_client.c
> +++ b/net/ceph/osd_client.c
> @@ -5347,23 +5347,24 @@ static int osd_req_op_copy_from_init(struct ceph_osd_request *req,
>  	return 0;
>  }
>  
> -int ceph_osdc_copy_from(struct ceph_osd_client *osdc,
> -			u64 src_snapid, u64 src_version,
> -			struct ceph_object_id *src_oid,
> -			struct ceph_object_locator *src_oloc,
> -			u32 src_fadvise_flags,
> -			struct ceph_object_id *dst_oid,
> -			struct ceph_object_locator *dst_oloc,
> -			u32 dst_fadvise_flags,
> -			u32 truncate_seq, u64 truncate_size,
> -			u8 copy_from_flags)
> +struct ceph_osd_request *
> +ceph_osdc_copy_from(struct ceph_osd_client *osdc,
> +		    u64 src_snapid, u64 src_version,
> +		    struct ceph_object_id *src_oid,
> +		    struct ceph_object_locator *src_oloc,
> +		    u32 src_fadvise_flags,
> +		    struct ceph_object_id *dst_oid,
> +		    struct ceph_object_locator *dst_oloc,
> +		    u32 dst_fadvise_flags,
> +		    u32 truncate_seq, u64 truncate_size,
> +		    u8 copy_from_flags)
>  {
>  	struct ceph_osd_request *req;
>  	int ret;
>  
>  	req = ceph_osdc_alloc_request(osdc, NULL, 1, false, GFP_KERNEL);
>  	if (!req)
> -		return -ENOMEM;
> +		return ERR_PTR(-ENOMEM);
>  
>  	req->r_flags = CEPH_OSD_FLAG_WRITE;
>  
> @@ -5382,11 +5383,11 @@ int ceph_osdc_copy_from(struct ceph_osd_client *osdc,
>  		goto out;
>  
>  	ceph_osdc_start_request(osdc, req, false);
> -	ret = ceph_osdc_wait_request(osdc, req);
> +	return req;
>  

I don't really understand why this function is part of net/ceph. It's
odd in that it basically allocates, initializes and starts the request
and then passes back the pointer to it. That doesn't really follow the
pattern of the other OSD READ/WRITE ops, where we basically set them up
and start them more directly from the fs/ceph code.

I think it'd make more sense to just get rid of ceph_osdc_copy_from
altogether, export the osd_req_op_copy_from_init symbol and open-code
the whole thing in ceph_do_objects_copy. This isn't otherwise called
from rbd or anything else so I don't see the benefit of keeping this
function as part of libceph.

>  out:
>  	ceph_osdc_put_request(req);
> -	return ret;
> +	return ERR_PTR(ret);
>  }
>  EXPORT_SYMBOL(ceph_osdc_copy_from);
>  

-- 
Jeff Layton <jlayton@kernel.org>