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Re: [Qemu-devel] [PATCH v4 15/19] block: raw-win32 driver reopen support
From: |
Jeff Cody |
Subject: |
Re: [Qemu-devel] [PATCH v4 15/19] block: raw-win32 driver reopen support |
Date: |
Fri, 21 Sep 2012 08:17:04 -0400 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:15.0) Gecko/20120828 Thunderbird/15.0 |
On 09/21/2012 04:43 AM, Paolo Bonzini wrote:
> Il 21/09/2012 10:33, Kevin Wolf ha scritto:
>>>> + /* could not reopen the file handle, so fall back to opening
>>>> + * new file (CreateFile) */
>>>> + if (raw_s->hfile == INVALID_HANDLE_VALUE) {
>>>> + raw_s->hfile = CreateFile(state->bs->filename, access_flags,
>>>> + FILE_SHARE_READ, NULL, OPEN_EXISTING,
>>>> + overlapped, NULL);
>>>> + if (raw_s->hfile == INVALID_HANDLE_VALUE) {
>>>> + /* this could happen because the access_flags requested are
>>>> + * incompatible with the existing share mode of s->hfile,
>>>> + * so our only option now is to close s->hfile, and try again.
>>>> + * This could end badly */
>>>> + CloseHandle(s->hfile);
>> How common is this case?
>>
>> We do have another option, namely not reopen at all and return an error.
>> Of course, this only makes sense if it doesn't mean that we almost never
>> succeed.
>
> Probably pretty common since we specify FILE_SHARE_READ for the sharing
> mode, meaning that "subsequent open operations on a file or device are
> only able to request read access".
>
Yes, I think this is by far the most common case.
> I would change it to FILE_SHARE_READ|FILE_SHARE_WRITE and remove this code.
>
> Paolo
>
I contemplated doing that, but I wasn't sure if there was any particular
reason it was originally done with FILE_SHARE_READ only in the first
place (security, etc..). I was hesitant to override that behaviour as
the new default under w32. Do we know if this is acceptable / safe?
- [Qemu-devel] [PATCH v4 09/19] block: raw-posix image file reopen, (continued)
- [Qemu-devel] [PATCH v4 09/19] block: raw-posix image file reopen, Jeff Cody, 2012/09/20
- [Qemu-devel] [PATCH v4 08/19] block: purge s->aligned_buf and s->aligned_buf_size from raw-posix.c, Jeff Cody, 2012/09/20
- [Qemu-devel] [PATCH v4 12/19] block: qcow2 image file reopen, Jeff Cody, 2012/09/20
- [Qemu-devel] [PATCH v4 19/19] block: remove keep_read_only flag from BlockDriverState struct, Jeff Cody, 2012/09/20
- [Qemu-devel] [PATCH v4 10/19] block: raw image file reopen, Jeff Cody, 2012/09/20
- [Qemu-devel] [PATCH v4 17/19] block: vpc image file reopen, Jeff Cody, 2012/09/20
- [Qemu-devel] [PATCH v4 18/19] block: convert bdrv_commit() to use bdrv_reopen(), Jeff Cody, 2012/09/20
- [Qemu-devel] [PATCH v4 15/19] block: raw-win32 driver reopen support, Jeff Cody, 2012/09/20
[Qemu-devel] [PATCH v4 16/19] block: vdi image file reopen, Jeff Cody, 2012/09/20
[Qemu-devel] [PATCH v4 11/19] block: qed image file reopen, Jeff Cody, 2012/09/20
[Qemu-devel] [PATCH v4 13/19] block: qcow image file reopen, Jeff Cody, 2012/09/20
[Qemu-devel] [PATCH v4 14/19] block: vmdk image file reopen, Jeff Cody, 2012/09/20
Re: [Qemu-devel] [PATCH v4 00/19] block: bdrv_reopen() patches, Kevin Wolf, 2012/09/21