Re: [PATCH 1/1] ceph: parallelize all copy-from requests in copy_file_range
From: Ilya Dryomov
Date: Thu Jan 30 2020 - 09:15:46 EST
On Wed, Jan 29, 2020 at 7:20 PM Luis Henriques <lhenriques@xxxxxxxx> 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 wait for its completion at the end. This
> will allow significant speed-ups, specially when sending requests to
> different target OSDs.
>
> There's also a throttling mechanism so that OSDs aren't flooded with
> requests when a client performs a big file copy. Currently the throttling
> mechanism simply waits for the requests when the number of in-flight
> requests reaches (wsize / object size) * 4.
>
> Signed-off-by: Luis Henriques <lhenriques@xxxxxxxx>
> ---
> fs/ceph/file.c | 34 ++++++++++++++++++++--
> include/linux/ceph/osd_client.h | 5 +++-
> net/ceph/osd_client.c | 50 ++++++++++++++++++++++++---------
> 3 files changed, 72 insertions(+), 17 deletions(-)
>
> diff --git a/fs/ceph/file.c b/fs/ceph/file.c
> index 1e6cdf2dfe90..77a16324dcb4 100644
> --- a/fs/ceph/file.c
> +++ b/fs/ceph/file.c
> @@ -1943,12 +1943,14 @@ 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;
> + int src_got = 0, dst_got = 0, err, dirty, ncopies;
> 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);
> @@ -2083,6 +2085,12 @@ static ssize_t __ceph_copy_file_range(struct file *src_file, loff_t src_off,
> goto out_caps;
> }
> object_size = src_ci->i_layout.object_size;
> +
> + /*
> + * Throttle the object copies: ncopies holds the number of allowed
> + * in-flight 'copy-from' requests before waiting for their completion
> + */
> + ncopies = (src_fsc->mount_options->wsize / object_size) * 4;
> while (len >= object_size) {
> ceph_calc_file_object_mapping(&src_ci->i_layout, src_off,
> object_size, &src_objnum,
> @@ -2097,7 +2105,7 @@ 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(
> &src_fsc->client->osdc,
> src_ci->i_vino.snap, 0,
> &src_oid, &src_oloc,
> @@ -2108,7 +2116,8 @@ 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) {
No point in checking for EOPNOTSUPP here, because ceph_osdc_copy_from()
won't ever return that. This loop needs more massaging and more testing
on old OSDs...
> src_fsc->have_copy_from2 = false;
> pr_notice("OSDs don't support 'copy-from2'; "
> @@ -2117,14 +2126,33 @@ 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 */
> + ceph_osdc_wait_requests(&osd_reqs);
> goto out_caps;
> }
> + list_add(&req->r_private_item, &osd_reqs);
> len -= object_size;
> src_off += object_size;
> dst_off += object_size;
> ret += object_size;
So ret is incremented here, but you have numerious tests where ret is
assigned an error only if ret is 0. Unless I'm missing something, this
interferes with returning errors from __ceph_copy_file_range().
> + if (--ncopies == 0) {
> + err = ceph_osdc_wait_requests(&osd_reqs);
> + if (err) {
> + if (!ret)
> + ret = err;
> + goto out_caps;
> + }
> + ncopies = (src_fsc->mount_options->wsize /
> + object_size) * 4;
The object size is constant within a file, so ncopies should be too.
Perhaps introduce a counter instead of recalculating ncopies here?
> + }
> }
>
> + err = ceph_osdc_wait_requests(&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 5a62dbd3f4c2..25565dbfd65a 100644
> --- a/include/linux/ceph/osd_client.h
> +++ b/include/linux/ceph/osd_client.h
> @@ -526,7 +526,8 @@ extern int ceph_osdc_writepages(struct ceph_osd_client *osdc,
> struct timespec64 *mtime,
> struct page **pages, int nr_pages);
>
> -int ceph_osdc_copy_from(struct ceph_osd_client *osdc,
> +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,
> @@ -537,6 +538,8 @@ int ceph_osdc_copy_from(struct ceph_osd_client *osdc,
> u32 truncate_seq, u64 truncate_size,
> u8 copy_from_flags);
>
> +int ceph_osdc_wait_requests(struct list_head *osd_reqs);
> +
> /* watch/notify */
> struct ceph_osd_linger_request *
> ceph_osdc_watch(struct ceph_osd_client *osdc,
> diff --git a/net/ceph/osd_client.c b/net/ceph/osd_client.c
> index b68b376d8c2f..c123e231eaf4 100644
> --- a/net/ceph/osd_client.c
> +++ b/net/ceph/osd_client.c
> @@ -5346,23 +5346,47 @@ 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)
> +int ceph_osdc_wait_requests(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_private_item);
> + list_del_init(&req->r_private_item);
> + err = ceph_osdc_wait_request(req->r_osdc, req);
> + if (err) {
> + if (!ret)
> + ret = err;
> + dout("copy request failed (err=%d)\n", err);
This dout needs updating, but I'd just remove it. The error code is
there in other messages.
> + }
> + ceph_osdc_put_request(req);
> + }
> +
> + return ret;
> +}
> +EXPORT_SYMBOL(ceph_osdc_wait_requests);
Move this function after ceph_osdc_wait_request(), so that they are
close to each other (and osd_req_op_copy_from_init() isn't separated
from ceph_osdc_copy_from() by something unrelated).
Thanks,
Ilya