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btrfs-progs: receive: dynamically allocate sctx->read_buf

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In send stream v2, write commands can now be an arbitrary size. For that
reason, we can no longer allocate a fixed array in sctx for read_cmd.
Instead, read_cmd dynamically allocates sctx->read_buf. To avoid
needless reallocations, we reuse read_buf between read_cmd calls by also
keeping track of the size of the allocated buffer in sctx->read_buf_sz.

We do the first allocation of the old default size at the start of
processing the stream, and we only reallocate if we encounter a command
that needs a larger buffer.

Signed-off-by: Boris Burkov <boris@bur.io>
Signed-off-by: David Sterba <dsterba@suse.com>
This commit is contained in:
Boris Burkov 2022-03-17 10:25:45 -07:00 committed by David Sterba
parent cf269aa47b
commit a82996e1b6
2 changed files with 44 additions and 20 deletions
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58
common/send-stream.c
View File

@ -35,11 +35,11 @@ struct btrfs_send_attribute {
};
struct btrfs_send_stream {
char read_buf[BTRFS_SEND_BUF_SIZE];
char *read_buf;
size_t read_buf_size;
int fd;
int cmd;
struct btrfs_cmd_header *cmd_hdr;
struct btrfs_send_attribute cmd_attrs[BTRFS_SEND_A_MAX + 1];
u32 version;
@ -111,11 +111,12 @@ static int read_cmd(struct btrfs_send_stream *sctx)
u32 pos;
u32 crc;
u32 crc2;
struct btrfs_cmd_header *cmd_hdr;
size_t buf_len;
memset(sctx->cmd_attrs, 0, sizeof(sctx->cmd_attrs));
ASSERT(sizeof(*sctx->cmd_hdr) <= sizeof(sctx->read_buf));
ret = read_buf(sctx, sctx->read_buf, sizeof(*sctx->cmd_hdr));
ret = read_buf(sctx, sctx->read_buf, sizeof(*cmd_hdr));
if (ret < 0)
goto out;
if (ret) {
@ -124,18 +125,26 @@ static int read_cmd(struct btrfs_send_stream *sctx)
goto out;
}
sctx->cmd_hdr = (struct btrfs_cmd_header *)sctx->read_buf;
cmd = le16_to_cpu(sctx->cmd_hdr->cmd);
cmd_len = le32_to_cpu(sctx->cmd_hdr->len);
cmd_hdr = (struct btrfs_cmd_header *)sctx->read_buf;
cmd_len = le32_to_cpu(cmd_hdr->len);
cmd = le16_to_cpu(cmd_hdr->cmd);
buf_len = sizeof(*cmd_hdr) + cmd_len;
if (sctx->read_buf_size < buf_len) {
void *new_read_buf;
if (cmd_len + sizeof(*sctx->cmd_hdr) >= sizeof(sctx->read_buf)) {
ret = -EINVAL;
error("command length %u too big for buffer %zu",
cmd_len, sizeof(sctx->read_buf));
goto out;
new_read_buf = realloc(sctx->read_buf, buf_len);
if (!new_read_buf) {
ret = -ENOMEM;
errno = -ret;
error("failed to reallocate read buffer for cmd: %m");
goto out;
}
sctx->read_buf = new_read_buf;
sctx->read_buf_size = buf_len;
/* We need to reset cmd_hdr after realloc of sctx->read_buf */
cmd_hdr = (struct btrfs_cmd_header *)sctx->read_buf;
}
data = sctx->read_buf + sizeof(*sctx->cmd_hdr);
data = sctx->read_buf + sizeof(*cmd_hdr);
ret = read_buf(sctx, data, cmd_len);
if (ret < 0)
goto out;
@ -145,11 +154,12 @@ static int read_cmd(struct btrfs_send_stream *sctx)
goto out;
}
crc = le32_to_cpu(sctx->cmd_hdr->crc);
sctx->cmd_hdr->crc = 0;
crc = le32_to_cpu(cmd_hdr->crc);
/* In send, CRC is computed with header crc = 0, replicate that */
cmd_hdr->crc = 0;
crc2 = crc32c(0, (unsigned char*)sctx->read_buf,
sizeof(*sctx->cmd_hdr) + cmd_len);
sizeof(*cmd_hdr) + cmd_len);
if (crc != crc2) {
ret = -EINVAL;
@ -537,19 +547,29 @@ int btrfs_read_and_process_send_stream(int fd,
goto out;
}
sctx.read_buf = malloc(BTRFS_SEND_BUF_SIZE_V1);
if (!sctx.read_buf) {
ret = -ENOMEM;
errno = -ret;
error("unable to allocate send stream read buffer: %m");
goto out;
}
sctx.read_buf_size = BTRFS_SEND_BUF_SIZE_V1;
while (1) {
ret = read_and_process_cmd(&sctx);
if (ret < 0) {
last_err = ret;
errors++;
if (max_errors > 0 && errors >= max_errors)
goto out;
break;
} else if (ret > 0) {
if (!honor_end_cmd)
ret = 0;
goto out;
break;
}
}
free(sctx.read_buf);
out:
if (last_err && !ret)

6
kernel-shared/send.h
View File

@ -25,7 +25,11 @@
#define BTRFS_SEND_STREAM_MAGIC "btrfs-stream"
#define BTRFS_SEND_STREAM_VERSION 1
#define BTRFS_SEND_BUF_SIZE (64 * 1024)
/*
* In send stream v1, no command is larger than 64KiB. In send stream v2, no limit
* should be assumed.
*/
#define BTRFS_SEND_BUF_SIZE_V1 (64 * 1024)
#define BTRFS_SEND_READ_SIZE (1024 * 48)
enum btrfs_tlv_type {