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[Qemu-devel] [PATCH V2 2/2] migration/qemu-file: fix potential buf waste
From: |
Wei Yang |
Subject: |
[Qemu-devel] [PATCH V2 2/2] migration/qemu-file: fix potential buf waste for extra buf_index adjustment |
Date: |
Wed, 11 Sep 2019 13:28:39 +0000 |
From: Wei Yang <address@hidden>
In add_to_iovec(), qemu_fflush() will be called if iovec is full. If
this happens, buf_index is reset. Currently, this is not checked and
buf_index would always been adjust with buf size.
This is not harmful, but will waste some space in file buffer.
This patch make add_to_iovec() return 1 when it has flushed the file.
Then the caller could check the return value to see whether it is
necessary to adjust the buf_index any more.
Signed-off-by: Wei Yang <address@hidden>
Reviewed-by: Dr. David Alan Gilbert <address@hidden>
---
v2:
* wrap these common steps into add_buf_to_iovec()
---
migration/qemu-file.c | 43 ++++++++++++++++++++++++++-----------------
1 file changed, 26 insertions(+), 17 deletions(-)
diff --git a/migration/qemu-file.c b/migration/qemu-file.c
index 47f16d0e54..417eeba64b 100644
--- a/migration/qemu-file.c
+++ b/migration/qemu-file.c
@@ -382,8 +382,16 @@ int qemu_fclose(QEMUFile *f)
return ret;
}
-static void add_to_iovec(QEMUFile *f, const uint8_t *buf, size_t size,
- bool may_free)
+/*
+ * Add buf to iovec. Do flush if iovec is full.
+ *
+ * Return values:
+ * 1 iovec is full and flushed
+ * 0 iovec is not flushed
+ *
+ */
+static int add_to_iovec(QEMUFile *f, const uint8_t *buf, size_t size,
+ bool may_free)
{
/* check for adjacent buffer and coalesce them */
if (f->iovcnt > 0 && buf == f->iov[f->iovcnt - 1].iov_base +
@@ -401,6 +409,19 @@ static void add_to_iovec(QEMUFile *f, const uint8_t *buf,
size_t size,
if (f->iovcnt >= MAX_IOV_SIZE) {
qemu_fflush(f);
+ return 1;
+ }
+
+ return 0;
+}
+
+static void add_buf_to_iovec(QEMUFile *f, size_t len)
+{
+ if (!add_to_iovec(f, f->buf + f->buf_index, len, false)) {
+ f->buf_index += len;
+ if (f->buf_index == IO_BUF_SIZE) {
+ qemu_fflush(f);
+ }
}
}
@@ -430,11 +451,7 @@ void qemu_put_buffer(QEMUFile *f, const uint8_t *buf,
size_t size)
}
memcpy(f->buf + f->buf_index, buf, l);
f->bytes_xfer += l;
- add_to_iovec(f, f->buf + f->buf_index, l, false);
- f->buf_index += l;
- if (f->buf_index == IO_BUF_SIZE) {
- qemu_fflush(f);
- }
+ add_buf_to_iovec(f, l);
if (qemu_file_get_error(f)) {
break;
}
@@ -451,11 +468,7 @@ void qemu_put_byte(QEMUFile *f, int v)
f->buf[f->buf_index] = v;
f->bytes_xfer++;
- add_to_iovec(f, f->buf + f->buf_index, 1, false);
- f->buf_index++;
- if (f->buf_index == IO_BUF_SIZE) {
- qemu_fflush(f);
- }
+ add_buf_to_iovec(f, 1);
}
void qemu_file_skip(QEMUFile *f, int size)
@@ -761,11 +774,7 @@ ssize_t qemu_put_compression_data(QEMUFile *f, z_stream
*stream,
}
qemu_put_be32(f, blen);
- add_to_iovec(f, f->buf + f->buf_index, blen, false);
- f->buf_index += blen;
- if (f->buf_index == IO_BUF_SIZE) {
- qemu_fflush(f);
- }
+ add_buf_to_iovec(f, blen);
return blen + sizeof(int32_t);
}
--
2.15.1