Date:   Mon, 27 Jan 2020 18:58:46 +0100
From:   Ilya Dryomov <idryomov@...il.com>
To:     Luis Henriques <lhenriques@...e.com>
Cc:     Jeff Layton <jlayton@...nel.org>, Sage Weil <sage@...hat.com>,
        "Yan, Zheng" <zyan@...hat.com>,
        Gregory Farnum <gfarnum@...hat.com>,
        Ceph Development <ceph-devel@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [RFC PATCH 2/3] ceph: parallelize all copy-from requests in copy_file_range

On Mon, Jan 27, 2020 at 5:43 PM Luis Henriques <lhenriques@...e.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@...e.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

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