Commit 1bf57fb3 authored by Wei Yang's avatar Wei Yang Committed by Dr. David Alan Gilbert
Browse files

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: default avatarWei Yang <richardw.yang@linux.intel.com>
Reviewed-by: default avatarDr. David Alan Gilbert <dgilbert@redhat.com>

Message-Id: <20190911132839.23336-3-richard.weiyang@gmail.com>
Signed-off-by: default avatarDr. David Alan Gilbert <dgilbert@redhat.com>
parent 89fe04b4

migration/qemu-file.c

+26 −17
Original line number Diff line number Diff line
@@ -381,7 +381,15 @@ int qemu_fclose(QEMUFile *f) 
    return ret;

}



static void add_to_iovec(QEMUFile *f, const uint8_t *buf, size_t size,

/*

 * 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 */
@@ -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);

}