Re: [PATCH for-8.0 v2 2/2] migration/ram.c: Fix migration with compress enabled

[Lukas Straub <lukasstraub2@web.de>]

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Ping? This should go in rc4, there is not much time left to prepare a
PULL...

Best Regards,
Lukas Straub

On Tue, 4 Apr 2023 14:36:03 +0000
Lukas Straub <lukasstraub2@web.de> wrote:

> Since ec6f3ab9, migration with compress enabled was broken, because
> the compress threads use a dummy QEMUFile which just acts as a
> buffer and that commit accidentally changed it to use the outgoing
> migration channel instead.
> 
> Fix this by using the dummy file again in the compress threads.
> 
> Fixes: ec6f3ab9f4 ("migration: Move last_sent_block into PageSearchStatus")
> Signed-off-by: Lukas Straub <lukasstraub2@web.de>
> Reviewed-by: Peter Xu <peterx@redhat.com>
> ---
> v2:
>  - Add Fixed: and Reviewed-by: tags
> 
>  migration/ram.c | 24 +++++++++++-------------
>  1 file changed, 11 insertions(+), 13 deletions(-)
> 
> diff --git a/migration/ram.c b/migration/ram.c
> index 96e8a19a58..9d1817ab7b 100644
> --- a/migration/ram.c
> +++ b/migration/ram.c
> @@ -688,12 +688,11 @@ exit:
>   * @offset: offset inside the block for the page
>   *          in the lower bits, it contains flags
>   */
> -static size_t save_page_header(PageSearchStatus *pss, RAMBlock *block,
> -                               ram_addr_t offset)
> +static size_t save_page_header(PageSearchStatus *pss, QEMUFile *f,
> +                               RAMBlock *block, ram_addr_t offset)
>  {
>      size_t size, len;
>      bool same_block = (block == pss->last_sent_block);
> -    QEMUFile *f = pss->pss_channel;
>  
>      if (same_block) {
>          offset |= RAM_SAVE_FLAG_CONTINUE;
> @@ -867,7 +866,7 @@ static int save_xbzrle_page(RAMState *rs, PageSearchStatus *pss,
>      }
>  
>      /* Send XBZRLE based compressed page */
> -    bytes_xbzrle = save_page_header(pss, block,
> +    bytes_xbzrle = save_page_header(pss, pss->pss_channel, block,
>                                      offset | RAM_SAVE_FLAG_XBZRLE);
>      qemu_put_byte(file, ENCODING_FLAG_XBZRLE);
>      qemu_put_be16(file, encoded_len);
> @@ -1302,15 +1301,14 @@ void ram_release_page(const char *rbname, uint64_t offset)
>   * @block: block that contains the page we want to send
>   * @offset: offset inside the block for the page
>   */
> -static int save_zero_page_to_file(PageSearchStatus *pss,
> +static int save_zero_page_to_file(PageSearchStatus *pss, QEMUFile *file,
>                                    RAMBlock *block, ram_addr_t offset)
>  {
>      uint8_t *p = block->host + offset;
> -    QEMUFile *file = pss->pss_channel;
>      int len = 0;
>  
>      if (buffer_is_zero(p, TARGET_PAGE_SIZE)) {
> -        len += save_page_header(pss, block, offset | RAM_SAVE_FLAG_ZERO);
> +        len += save_page_header(pss, file, block, offset | RAM_SAVE_FLAG_ZERO);
>          qemu_put_byte(file, 0);
>          len += 1;
>          ram_release_page(block->idstr, offset);
> @@ -1327,10 +1325,10 @@ static int save_zero_page_to_file(PageSearchStatus *pss,
>   * @block: block that contains the page we want to send
>   * @offset: offset inside the block for the page
>   */
> -static int save_zero_page(PageSearchStatus *pss, RAMBlock *block,
> +static int save_zero_page(PageSearchStatus *pss, QEMUFile *f, RAMBlock *block,
>                            ram_addr_t offset)
>  {
> -    int len = save_zero_page_to_file(pss, block, offset);
> +    int len = save_zero_page_to_file(pss, f, block, offset);
>  
>      if (len) {
>          stat64_add(&ram_atomic_counters.duplicate, 1);
> @@ -1394,7 +1392,7 @@ static int save_normal_page(PageSearchStatus *pss, RAMBlock *block,
>  {
>      QEMUFile *file = pss->pss_channel;
>  
> -    ram_transferred_add(save_page_header(pss, block,
> +    ram_transferred_add(save_page_header(pss, pss->pss_channel, block,
>                                           offset | RAM_SAVE_FLAG_PAGE));
>      if (async) {
>          qemu_put_buffer_async(file, buf, TARGET_PAGE_SIZE,
> @@ -1473,11 +1471,11 @@ static bool do_compress_ram_page(QEMUFile *f, z_stream *stream, RAMBlock *block,
>      uint8_t *p = block->host + offset;
>      int ret;
>  
> -    if (save_zero_page_to_file(pss, block, offset)) {
> +    if (save_zero_page_to_file(pss, f, block, offset)) {
>          return true;
>      }
>  
> -    save_page_header(pss, block, offset | RAM_SAVE_FLAG_COMPRESS_PAGE);
> +    save_page_header(pss, f, block, offset | RAM_SAVE_FLAG_COMPRESS_PAGE);
>  
>      /*
>       * copy it to a internal buffer to avoid it being modified by VM
> @@ -2355,7 +2353,7 @@ static int ram_save_target_page_legacy(RAMState *rs, PageSearchStatus *pss)
>          return 1;
>      }
>  
> -    res = save_zero_page(pss, block, offset);
> +    res = save_zero_page(pss, pss->pss_channel, block, offset);
>      if (res > 0) {
>          /* Must let xbzrle know, otherwise a previous (now 0'd) cached
>           * page would be stale



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