On Fri, Aug 21, 2020 at 8:42 AM Omar Sandoval <osandov@xxxxxxxxxxx> wrote:
>
> From: Omar Sandoval <osandov@xxxxxx>
>
> send_write() currently copies from the page cache to sctx->read_buf, and
> then from sctx->read_buf to sctx->send_buf. Similarly, send_hole()
> zeroes sctx->read_buf and then copies from sctx->read_buf to
> sctx->send_buf. However, if we write the TLV header manually, we can
> copy to sctx->send_buf directly and get rid of sctx->read_buf.
>
> Signed-off-by: Omar Sandoval <osandov@xxxxxx>
Reviewed-by: Filipe Manana <fdmanana@xxxxxxxx>
Looks good, and it passed some long duration tests with both full and
incremental sends here (with and without compression, no-holes, etc).
Only one minor thing below, but it's really subjective and doesn't
make much of a difference.
Thanks.
> ---
> fs/btrfs/send.c | 65 +++++++++++++++++++++++++++++--------------------
> fs/btrfs/send.h | 1 -
> 2 files changed, 39 insertions(+), 27 deletions(-)
>
> diff --git a/fs/btrfs/send.c b/fs/btrfs/send.c
> index 8af5e867e4ca..e70f5ceb3261 100644
> --- a/fs/btrfs/send.c
> +++ b/fs/btrfs/send.c
> @@ -122,8 +122,6 @@ struct send_ctx {
>
> struct file_ra_state ra;
>
> - char *read_buf;
> -
> /*
> * We process inodes by their increasing order, so if before an
> * incremental send we reverse the parent/child relationship of
> @@ -4794,7 +4792,25 @@ static int process_all_new_xattrs(struct send_ctx *sctx)
> return ret;
> }
>
> -static int fill_read_buf(struct send_ctx *sctx, u64 offset, u32 len)
> +static u64 max_send_read_size(struct send_ctx *sctx)
We could make this inline, since it's so small and trivial, and
constify the argument too.
> +{
> + return sctx->send_max_size - SZ_16K;
> +}
> +
> +static int put_data_header(struct send_ctx *sctx, u32 len)
> +{
> + struct btrfs_tlv_header *hdr;
> +
> + if (sctx->send_max_size - sctx->send_size < sizeof(*hdr) + len)
> + return -EOVERFLOW;
> + hdr = (struct btrfs_tlv_header *)(sctx->send_buf + sctx->send_size);
> + hdr->tlv_type = cpu_to_le16(BTRFS_SEND_A_DATA);
> + hdr->tlv_len = cpu_to_le16(len);
> + sctx->send_size += sizeof(*hdr);
> + return 0;
> +}
> +
> +static int put_file_data(struct send_ctx *sctx, u64 offset, u32 len)
> {
> struct btrfs_root *root = sctx->send_root;
> struct btrfs_fs_info *fs_info = root->fs_info;
> @@ -4804,8 +4820,11 @@ static int fill_read_buf(struct send_ctx *sctx, u64 offset, u32 len)
> pgoff_t index = offset >> PAGE_SHIFT;
> pgoff_t last_index;
> unsigned pg_offset = offset_in_page(offset);
> - int ret = 0;
> - size_t read = 0;
> + int ret;
> +
> + ret = put_data_header(sctx, len);
> + if (ret)
> + return ret;
>
> inode = btrfs_iget(fs_info->sb, sctx->cur_ino, root);
> if (IS_ERR(inode))
> @@ -4851,14 +4870,15 @@ static int fill_read_buf(struct send_ctx *sctx, u64 offset, u32 len)
> }
>
> addr = kmap(page);
> - memcpy(sctx->read_buf + read, addr + pg_offset, cur_len);
> + memcpy(sctx->send_buf + sctx->send_size, addr + pg_offset,
> + cur_len);
> kunmap(page);
> unlock_page(page);
> put_page(page);
> index++;
> pg_offset = 0;
> len -= cur_len;
> - read += cur_len;
> + sctx->send_size += cur_len;
> }
> iput(inode);
> return ret;
> @@ -4880,10 +4900,6 @@ static int send_write(struct send_ctx *sctx, u64 offset, u32 len)
>
> btrfs_debug(fs_info, "send_write offset=%llu, len=%d", offset, len);
>
> - ret = fill_read_buf(sctx, offset, len);
> - if (ret < 0)
> - goto out;
> -
> ret = begin_cmd(sctx, BTRFS_SEND_C_WRITE);
> if (ret < 0)
> goto out;
> @@ -4894,7 +4910,9 @@ static int send_write(struct send_ctx *sctx, u64 offset, u32 len)
>
> TLV_PUT_PATH(sctx, BTRFS_SEND_A_PATH, p);
> TLV_PUT_U64(sctx, BTRFS_SEND_A_FILE_OFFSET, offset);
> - TLV_PUT(sctx, BTRFS_SEND_A_DATA, sctx->read_buf, len);
> + ret = put_file_data(sctx, offset, len);
> + if (ret < 0)
> + goto out;
>
> ret = send_cmd(sctx);
>
> @@ -5013,8 +5031,8 @@ static int send_update_extent(struct send_ctx *sctx,
> static int send_hole(struct send_ctx *sctx, u64 end)
> {
> struct fs_path *p = NULL;
> + u64 read_size = max_send_read_size(sctx);
> u64 offset = sctx->cur_inode_last_extent;
> - u64 len;
> int ret = 0;
>
> /*
> @@ -5041,16 +5059,19 @@ static int send_hole(struct send_ctx *sctx, u64 end)
> ret = get_cur_path(sctx, sctx->cur_ino, sctx->cur_inode_gen, p);
> if (ret < 0)
> goto tlv_put_failure;
> - memset(sctx->read_buf, 0, BTRFS_SEND_READ_SIZE);
> while (offset < end) {
> - len = min_t(u64, end - offset, BTRFS_SEND_READ_SIZE);
> + u64 len = min(end - offset, read_size);
>
> ret = begin_cmd(sctx, BTRFS_SEND_C_WRITE);
> if (ret < 0)
> break;
> TLV_PUT_PATH(sctx, BTRFS_SEND_A_PATH, p);
> TLV_PUT_U64(sctx, BTRFS_SEND_A_FILE_OFFSET, offset);
> - TLV_PUT(sctx, BTRFS_SEND_A_DATA, sctx->read_buf, len);
> + ret = put_data_header(sctx, len);
> + if (ret < 0)
> + break;
> + memset(sctx->send_buf + sctx->send_size, 0, len);
> + sctx->send_size += len;
> ret = send_cmd(sctx);
> if (ret < 0)
> break;
> @@ -5066,17 +5087,16 @@ static int send_extent_data(struct send_ctx *sctx,
> const u64 offset,
> const u64 len)
> {
> + u64 read_size = max_send_read_size(sctx);
> u64 sent = 0;
>
> if (sctx->flags & BTRFS_SEND_FLAG_NO_FILE_DATA)
> return send_update_extent(sctx, offset, len);
>
> while (sent < len) {
> - u64 size = len - sent;
> + u64 size = min(len - sent, read_size);
> int ret;
>
> - if (size > BTRFS_SEND_READ_SIZE)
> - size = BTRFS_SEND_READ_SIZE;
> ret = send_write(sctx, offset + sent, size);
> if (ret < 0)
> return ret;
> @@ -7145,12 +7165,6 @@ long btrfs_ioctl_send(struct file *mnt_file, struct btrfs_ioctl_send_args *arg)
> goto out;
> }
>
> - sctx->read_buf = kvmalloc(BTRFS_SEND_READ_SIZE, GFP_KERNEL);
> - if (!sctx->read_buf) {
> - ret = -ENOMEM;
> - goto out;
> - }
> -
> sctx->pending_dir_moves = RB_ROOT;
> sctx->waiting_dir_moves = RB_ROOT;
> sctx->orphan_dirs = RB_ROOT;
> @@ -7354,7 +7368,6 @@ long btrfs_ioctl_send(struct file *mnt_file, struct btrfs_ioctl_send_args *arg)
>
> kvfree(sctx->clone_roots);
> kvfree(sctx->send_buf);
> - kvfree(sctx->read_buf);
>
> name_cache_free(sctx);
>
> diff --git a/fs/btrfs/send.h b/fs/btrfs/send.h
> index ead397f7034f..de91488b7cd0 100644
> --- a/fs/btrfs/send.h
> +++ b/fs/btrfs/send.h
> @@ -13,7 +13,6 @@
> #define BTRFS_SEND_STREAM_VERSION 1
>
> #define BTRFS_SEND_BUF_SIZE SZ_64K
> -#define BTRFS_SEND_READ_SIZE (48 * SZ_1K)
>
> enum btrfs_tlv_type {
> BTRFS_TLV_U8,
> --
> 2.28.0
>
--
Filipe David Manana,
“Whether you think you can, or you think you can't — you're right.”
