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Re: [Qemu-devel] [PATCH] hostmem-file: add a property 'notrunc' to avoid
From: |
Igor Mammedov |
Subject: |
Re: [Qemu-devel] [PATCH] hostmem-file: add a property 'notrunc' to avoid data corruption |
Date: |
Thu, 20 Oct 2016 15:47:32 +0200 |
On Thu, 20 Oct 2016 21:33:53 +0800
Haozhong Zhang <address@hidden> wrote:
> On 10/20/16 11:21 -0200, Eduardo Habkost wrote:
> >On Thu, Oct 20, 2016 at 02:34:12PM +0200, Igor Mammedov wrote:
> >> On Thu, 20 Oct 2016 14:13:01 +0800
> >> Haozhong Zhang <address@hidden> wrote:
> >>
> >> > If a file is used as the backend of memory-backend-file and its size is
> >> > not identical to the property 'size', the file will be truncated. For a
> >> > file used as the backend of vNVDIMM, its data is expected to be
> >> > persistent and the truncation may corrupt the existing data.
> >> I wonder if it's possible just skip 'size' property in your case instead
> >> 'notrunc' property. That way if size is not present one'd get actual size
> >> using get_file_size() and set 'size' to it?
> >> And if 'size' is provided and 'size' != file_size then error out.
> >
> >I think it is valid to start with a zero-size file and then let
> >QEMU extend it.
>
> For vNVDIMM, extending from zero-size file can be valid when a file is
> first used. However, it's not valid for the second and following use
> of the same file.
I'd avoid 0 sized backend files and enforce non 0 size value
with exact match to actual file size. i.e. let mgmt side take care of
proper backend file allocation.
>
> >But I agree we should: 1) make 'size' optional as
> >you suggested; 2) never truncate the file to a smaller size.
> >
>
> I will add another patch for this. Is there any way in QEMU to decide
> whether a memory-backend-file object is used for vNVDIMM when the
> object is being created? Or 'size' can be optional for all kinds of
> usages?
>
> Thanks,
> Haozhong
- Re: [Qemu-devel] [PATCH] hostmem-file: add a property 'notrunc' to avoid data corruption, (continued)
- Re: [Qemu-devel] [PATCH] hostmem-file: add a property 'notrunc' to avoid data corruption, Eduardo Habkost, 2016/10/20
- Re: [Qemu-devel] [PATCH] hostmem-file: add a property 'notrunc' to avoid data corruption, Haozhong Zhang, 2016/10/20
- Re: [Qemu-devel] [PATCH] hostmem-file: add a property 'notrunc' to avoid data corruption, Eduardo Habkost, 2016/10/20
- Re: [Qemu-devel] [PATCH] hostmem-file: add a property 'notrunc' to avoid data corruption, Igor Mammedov, 2016/10/20
- Re: [Qemu-devel] [PATCH] hostmem-file: add a property 'notrunc' to avoid data corruption, Eduardo Habkost, 2016/10/20
- Re: [Qemu-devel] [PATCH] hostmem-file: add a property 'notrunc' to avoid data corruption, Igor Mammedov, 2016/10/20
- Re: [Qemu-devel] [PATCH] hostmem-file: add a property 'notrunc' to avoid data corruption, Eduardo Habkost, 2016/10/20
- Re: [Qemu-devel] [PATCH] hostmem-file: add a property 'notrunc' to avoid data corruption, Igor Mammedov, 2016/10/21
- Re: [Qemu-devel] [PATCH] hostmem-file: add a property 'notrunc' to avoid data corruption, Eduardo Habkost, 2016/10/21
- Re: [Qemu-devel] [PATCH] hostmem-file: add a property 'notrunc' to avoid data corruption,
Igor Mammedov <=
- Re: [Qemu-devel] [PATCH] hostmem-file: add a property 'notrunc' to avoid data corruption, Eduardo Habkost, 2016/10/20
- Re: [Qemu-devel] [PATCH] hostmem-file: add a property 'notrunc' to avoid data corruption, Igor Mammedov, 2016/10/20
- Re: [Qemu-devel] [PATCH] hostmem-file: add a property 'notrunc' to avoid data corruption, Eduardo Habkost, 2016/10/20
- Re: [Qemu-devel] [PATCH] hostmem-file: add a property 'notrunc' to avoid data corruption, Igor Mammedov, 2016/10/20
Re: [Qemu-devel] [PATCH] hostmem-file: add a property 'notrunc' to avoid data corruption, Daniel P. Berrange, 2016/10/20
Re: [Qemu-devel] [PATCH] hostmem-file: add a property 'notrunc' to avoid data corruption, Kevin Wolf, 2016/10/20