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btrfs: send: avoid copying file data 

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.

Reviewed-by: Filipe Manana <fdmanana@suse.com>
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Omar Sandoval <osandov@fb.com>
Signed-off-by: David Sterba <dsterba@suse.com>
This commit is contained in:
Omar Sandoval 2020-08-21 00:39:52 -07:00 committed by David Sterba
parent a9b2e0de92
commit 8c7d9fe06f
2 changed files with 39 additions and 27 deletions
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65
fs/btrfs/send.c
View File

@ -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 @@ out:
return ret;
}
static int fill_read_buf(struct send_ctx *sctx, u64 offset, u32 len)
static inline u64 max_send_read_size(const struct send_ctx *sctx)
{
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);
put_unaligned_le16(BTRFS_SEND_A_DATA, &hdr->tlv_type);
put_unaligned_le16(len, &hdr->tlv_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 @@ out:
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 @@ out:
kvfree(sctx->clone_roots);
kvfree(sctx->send_buf);
kvfree(sctx->read_buf);
name_cache_free(sctx);

1
fs/btrfs/send.h
View File

@ -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,