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Re: [PATCH v3 11/17] migration/qemu-file: Fix qemu_ftell() for non-writa
From: |
Daniel P . Berrangé |
Subject: |
Re: [PATCH v3 11/17] migration/qemu-file: Fix qemu_ftell() for non-writable file |
Date: |
Thu, 16 Jun 2022 12:20:24 +0100 |
User-agent: |
Mutt/2.2.1 (2022-02-19) |
On Thu, Jun 16, 2022 at 01:28:05PM +0300, nikita.lapshin@openvz.org wrote:
> From: Nikita Lapshin <nikita.lapshin@openvz.org>
>
> qemu_ftell() will return wrong value for non-writable QEMUFile.
> This happens due to call qemu_fflush() inside qemu_ftell(), this
> function won't flush if file is readable.
Well the return value isn't necessarily wrong today - it really
depends what semantics each callers desires.
Can you say what particular caller needs these semantics changed
and the impact on them from current behaviour ?
> Signed-off-by: Nikita Lapshin <nikita.lapshin@openvz.org>
> ---
> migration/qemu-file.c | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/migration/qemu-file.c b/migration/qemu-file.c
> index 1479cddad9..53ccef80ac 100644
> --- a/migration/qemu-file.c
> +++ b/migration/qemu-file.c
> @@ -663,7 +663,8 @@ int64_t qemu_ftell_fast(QEMUFile *f)
> int64_t qemu_ftell(QEMUFile *f)
> {
> qemu_fflush(f);
> - return f->pos;
> + /* Consider that qemu_fflush() won't work if file is non-writable */
> + return f->pos + f->buf_index;
> }
IIUC, this is more or less trying to make 'qemu_ftell' be
equivalent to 'qemu_ftell_fast' semantics in the non-writable
case. But that makes me wonder if whichever calls has problems,
shouldn't be just changed to use qemu_ftell_fast instead ?
With regards,
Daniel
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- [PATCH v3 00/17] migration/snapshot: External snapshot utility, nikita . lapshin, 2022/06/16
- [PATCH v3 01/17] migration: Implemented new parameter stream_content, nikita . lapshin, 2022/06/16
- [PATCH v3 02/17] migration: should_skip() implemented, nikita . lapshin, 2022/06/16
- [PATCH v3 03/17] migration: Add vmstate part of migration stream, nikita . lapshin, 2022/06/16
- [PATCH v3 05/17] migration: Add block part of migration stream, nikita . lapshin, 2022/06/16
- [PATCH v3 06/17] migration: Add RAM part of migration stream, nikita . lapshin, 2022/06/16
- [PATCH v3 07/17] migration: analyze-migration script changed, nikita . lapshin, 2022/06/16
- [PATCH v3 08/17] migration: Test for RAM and vmstate parts, nikita . lapshin, 2022/06/16
- [PATCH v3 11/17] migration/qemu-file: Fix qemu_ftell() for non-writable file, nikita . lapshin, 2022/06/16
- Re: [PATCH v3 11/17] migration/qemu-file: Fix qemu_ftell() for non-writable file,
Daniel P . Berrangé <=
- [PATCH v3 13/17] migration/snapshot: Block layer support in qemu-snapshot, nikita . lapshin, 2022/06/16
- [PATCH v3 14/17] migration/snpashot: Implement API for RAMBlock, nikita . lapshin, 2022/06/16
- [PATCH v3 04/17] migration: Add dirty-bitmaps part of migration stream, nikita . lapshin, 2022/06/16
- [PATCH v3 09/17] migration/snapshot: Introduce qemu-snapshot tool, nikita . lapshin, 2022/06/16
- [PATCH v3 10/17] migration/snapshot: Build changes for qemu-snapshot-tool, nikita . lapshin, 2022/06/16
- [PATCH v3 12/17] migration/snapshot: Move RAM_SAVE_FLAG_xxx defines to migration/ram.h, nikita . lapshin, 2022/06/16
- [PATCH v3 16/17] migration/snapshot: Precopy load implemented, nikita . lapshin, 2022/06/16
- [PATCH v3 15/17] migration/snapshot: Save part implement, nikita . lapshin, 2022/06/16
- [PATCH v3 17/17] migration/snapshot: Postcopy load implemented, nikita . lapshin, 2022/06/16