Re: [RFC PATCH 2/3] ceph: parallelize all copy-from requests in copy_file_range

Ilya Dryomov
2020-01-27T17:58:42Z

On Mon, Jan 27, 2020 at 5:43 PM Luis Henriques <lhenriques@suse.com> wrote:
>
> Right now the copy_file_range syscall serializes all the OSDs 'copy-from'
> operations, waiting for each request to complete before sending the next
> one. This patch modifies copy_file_range so that all the 'copy-from'
> operations are sent in bulk and waits for its completion at the end. This
> will allow significant speed-ups, specially when sending requests for
> different target OSDs.
>
> Signed-off-by: Luis Henriques <lhenriques@suse.com>
> ---
> fs/ceph/file.c | 38 +++++++++++++++++++++++++++++++--
> include/linux/ceph/osd_client.h | 2 ++
> net/ceph/osd_client.c | 1 +
> 3 files changed, 39 insertions(+), 2 deletions(-)
>
> diff --git a/fs/ceph/file.c b/fs/ceph/file.c
> index 1e6cdf2dfe90..5d8f0ba11719 100644
> --- a/fs/ceph/file.c
> +++ b/fs/ceph/file.c
> @@ -1931,6 +1931,28 @@ static int is_file_size_ok(struct inode *src_inode, struct inode *dst_inode,
> return 0;
> }
>
> +static int wait_copy_from_reqs(struct list_head *osd_reqs)
> +{
> + struct ceph_osd_request *req;
> + int ret = 0, err;
> +
> + while (!list_empty(osd_reqs)) {
> + req = list_first_entry(osd_reqs,
> + struct ceph_osd_request,
> + r_copy_item);
> + list_del_init(&req->r_copy_item);
> + err = ceph_osdc_wait_request(req->r_osdc, req);
> + if (err) {
> + if (!ret)
> + ret = err;
> + dout("copy request failed (err=%d)\n", err);
> + }
> + ceph_osdc_put_request(req);
> + }
> +
> + return ret;
> +}

This should probably go into libceph, as ceph_osdc_wait_requests().

> +
> static ssize_t __ceph_copy_file_range(struct file *src_file, loff_t src_off,
> struct file *dst_file, loff_t dst_off,
> size_t len, unsigned int flags)
> @@ -1943,12 +1965,14 @@ static ssize_t __ceph_copy_file_range(struct file *src_file, loff_t src_off,
> struct ceph_fs_client *src_fsc = ceph_inode_to_client(src_inode);
> struct ceph_object_locator src_oloc, dst_oloc;
> struct ceph_object_id src_oid, dst_oid;
> + struct ceph_osd_request *req;
> loff_t endoff = 0, size;
> ssize_t ret = -EIO;
> u64 src_objnum, dst_objnum, src_objoff, dst_objoff;
> u32 src_objlen, dst_objlen, object_size;
> int src_got = 0, dst_got = 0, err, dirty;
> bool do_final_copy = false;
> + LIST_HEAD(osd_reqs);
>
> if (src_inode->i_sb != dst_inode->i_sb) {
> struct ceph_fs_client *dst_fsc = ceph_inode_to_client(dst_inode);
> @@ -2097,7 +2121,7 @@ static ssize_t __ceph_copy_file_range(struct file *src_file, loff_t src_off,
> ceph_oid_printf(&dst_oid, "%llx.%08llx",
> dst_ci->i_vino.ino, dst_objnum);
> /* Do an object remote copy */
> - err = ceph_osdc_copy_from(
> + req = ceph_osdc_copy_from_nowait(
> &src_fsc->client->osdc,
> src_ci->i_vino.snap, 0,
> &src_oid, &src_oloc,
> @@ -2108,7 +2132,8 @@ static ssize_t __ceph_copy_file_range(struct file *src_file, loff_t src_off,
> CEPH_OSD_OP_FLAG_FADVISE_DONTNEED,
> dst_ci->i_truncate_seq, dst_ci->i_truncate_size,
> CEPH_OSD_COPY_FROM_FLAG_TRUNCATE_SEQ);
> - if (err) {
> + if (IS_ERR(req)) {
> + err = PTR_ERR(req);
> if (err == -EOPNOTSUPP) {
> src_fsc->have_copy_from2 = false;
> pr_notice("OSDs don't support 'copy-from2'; "
> @@ -2117,14 +2142,23 @@ static ssize_t __ceph_copy_file_range(struct file *src_file, loff_t src_off,
> dout("ceph_osdc_copy_from returned %d\n", err);
> if (!ret)
> ret = err;
> + /* wait for all queued requests */
> + wait_copy_from_reqs(&osd_reqs);
> goto out_caps;
> }
> + list_add(&req->r_copy_item, &osd_reqs);
> len -= object_size;
> src_off += object_size;
> dst_off += object_size;
> ret += object_size;
> }
>
> + err = wait_copy_from_reqs(&osd_reqs);
> + if (err) {
> + if (!ret)
> + ret = err;
> + goto out_caps;
> + }
> if (len)
> /* We still need one final local copy */
> do_final_copy = true;
> diff --git a/include/linux/ceph/osd_client.h b/include/linux/ceph/osd_client.h
> index 7916a178d137..2b4a14bc6154 100644
> --- a/include/linux/ceph/osd_client.h
> +++ b/include/linux/ceph/osd_client.h
> @@ -210,6 +210,8 @@ struct ceph_osd_request {
> u64 r_data_offset; /* ditto */
> bool r_linger; /* don't resend on failure */
>
> + struct list_head r_copy_item; /* used for copy-from operations */
> +

We have r_private_item for exactly this kind of ad-hoc lists, already
used in rbd and ceph_direct_read_write().

Thanks,

Ilya