From 1bf57fb3df9615b50219c50b381cc52e303f682c Mon Sep 17 00:00:00 2001 From: Wei Yang Date: Wed, 11 Sep 2019 13:28:39 +0000 Subject: migration/qemu-file: fix potential buf waste for extra buf_index adjustment 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 Reviewed-by: Dr. David Alan Gilbert Message-Id: <20190911132839.23336-3-richard.weiyang@gmail.com> Signed-off-by: Dr. David Alan Gilbert --- 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 66627088d4..26fb25ddc1 100644 --- a/migration/qemu-file.c +++ b/migration/qemu-file.c @@ -381,8 +381,16 @@ 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 + @@ -400,6 +408,19 @@ 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); + } } } @@ -429,11 +450,7 @@ 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; } @@ -450,11 +467,7 @@ 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) @@ -760,11 +773,7 @@ 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); } -- cgit v1.2.3-55-g7522