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From 7e5cd32fbb38103b11a8a87ca5af943d0fb2804a Mon Sep 17 00:00:00 2001
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From: Boris Burkov <borisb@fb.com>
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Date: Fri, 21 Aug 2020 00:40:00 -0700
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Subject: [PATCH] btrfs-progs: receive: support v2 send stream larger tlv_len
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An encoded extent can be up to 128K in length, which exceeds the largest
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value expressible by the current send stream format's 16 bit tlv_len
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field. Since encoded writes cannot be split into multiple writes by
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btrfs send, the send stream format must change to accommodate encoded
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writes.
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Supporting this changed format requires retooling how we store the
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commands we have processed. We currently store pointers to the struct
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btrfs_tlv_headers in the command buffer. This is not sufficient to
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represent the new BTRFS_SEND_A_DATA format. Instead, parse the attribute
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headers and store them in a new struct btrfs_send_attribute which has a
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32-bit length field. This is transparent to users of the various TLV_GET
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macros.
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Reviewed-by: Nikolay Borisov <nborisov@suse.com>
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Signed-off-by: Boris Burkov <boris@bur.io>
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---
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 common/send-stream.c | 34 +++++++++++++++++++++++++---------
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 1 file changed, 25 insertions(+), 9 deletions(-)
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diff --git a/common/send-stream.c b/common/send-stream.c
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index e9be922b..7d182238 100644
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--- a/common/send-stream.c
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+++ b/common/send-stream.c
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@@ -24,13 +24,23 @@
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 #include "crypto/crc32c.h"
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 #include "common/utils.h"
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+struct btrfs_send_attribute {
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+	u16 tlv_type;
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+	/*
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+	 * Note: in btrfs_tlv_header, this is __le16, but we need 32 bits for
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+	 * attributes with file data as of version 2 of the send stream format
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+	 */
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+	u32 tlv_len;
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+	char *data;
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+};
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+
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 struct btrfs_send_stream {
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 	char read_buf[BTRFS_SEND_BUF_SIZE];
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 	int fd;
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 	int cmd;
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 	struct btrfs_cmd_header *cmd_hdr;
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-	struct btrfs_tlv_header *cmd_attrs[BTRFS_SEND_A_MAX + 1];
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+	struct btrfs_send_attribute cmd_attrs[BTRFS_SEND_A_MAX + 1];
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 	u32 version;
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 	/*
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@@ -152,6 +162,7 @@ static int read_cmd(struct btrfs_send_stream *sctx)
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 		struct btrfs_tlv_header *tlv_hdr;
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 		u16 tlv_type;
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 		u16 tlv_len;
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+		struct btrfs_send_attribute *send_attr;
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 		tlv_hdr = (struct btrfs_tlv_header *)data;
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 		tlv_type = le16_to_cpu(tlv_hdr->tlv_type);
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@@ -164,10 +175,15 @@ static int read_cmd(struct btrfs_send_stream *sctx)
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 			goto out;
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 		}
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-		sctx->cmd_attrs[tlv_type] = tlv_hdr;
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+		send_attr = &sctx->cmd_attrs[tlv_type];
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+		send_attr->tlv_type = tlv_type;
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+		send_attr->tlv_len = tlv_len;
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+		pos += sizeof(*tlv_hdr);
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+		data += sizeof(*tlv_hdr);
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-		data += sizeof(*tlv_hdr) + tlv_len;
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-		pos += sizeof(*tlv_hdr) + tlv_len;
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+		send_attr->data = data;
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+		pos += send_attr->tlv_len;
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+		data += send_attr->tlv_len;
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 	}
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 	sctx->cmd = cmd;
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@@ -180,7 +196,7 @@ out:
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 static int tlv_get(struct btrfs_send_stream *sctx, int attr, void **data, int *len)
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 {
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 	int ret;
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-	struct btrfs_tlv_header *hdr;
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+	struct btrfs_send_attribute *send_attr;
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 	if (attr <= 0 || attr > BTRFS_SEND_A_MAX) {
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 		error("invalid attribute requested, attr = %d", attr);
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@@ -188,15 +204,15 @@ static int tlv_get(struct btrfs_send_stream *sctx, int attr, void **data, int *l
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 		goto out;
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 	}
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-	hdr = sctx->cmd_attrs[attr];
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-	if (!hdr) {
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+	send_attr = &sctx->cmd_attrs[attr];
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+	if (!send_attr->data) {
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 		error("attribute %d requested but not present", attr);
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 		ret = -ENOENT;
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 		goto out;
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 	}
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-	*len = le16_to_cpu(hdr->tlv_len);
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-	*data = hdr + 1;
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+	*len = send_attr->tlv_len;
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+	*data = send_attr->data;
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 	ret = 0;
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-- 
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2.35.1
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