Re: [Qemu-devel] [PATCH] [virtio-9p] Add datasync to server side TFSYNC/RFSYNC for dotl

["Venkateswararao Jujjuri (JV)" <jvrao@linux.vnet.ibm.com>]

On 10/23/2010 5:44 AM, Blue Swirl wrote:
> On Fri, Oct 22, 2010 at 7:15 PM, Venkateswararao Jujjuri (JV)
> <jvrao@linux.vnet.ibm.com> wrote:
>> SYNOPSIS
>>    size[4] Tfsync tag[2] fid[4] datasync[4]
>>
>>    size[4] Rfsync tag[2]
>>
>> DESCRIPTION
>>
>>    The Tfsync transaction transfers ("flushes") all modified in-core data of
>>    file identified by fid to the disk device (or other  permanent  storage
>>    device)  where that  file  resides.
>>
>>    If datasync flag is specified data will be fleshed but does not flush
>>    modified metadata unless  that  metadata  is  needed  in order to allow a
>>    subsequent data retrieval to be correctly handled.
>>
>> Signed-off-by: Venkateswararao Jujjuri <jvrao@linux.vnet.ibm.com>
>> ---
>>  hw/file-op-9p.h      |    2 +-
>>  hw/virtio-9p-local.c |    8 ++++++--
>>  hw/virtio-9p.c       |   11 ++++++-----
>>  3 files changed, 13 insertions(+), 8 deletions(-)
>>
>> diff --git a/hw/file-op-9p.h b/hw/file-op-9p.h
>> index 21d60b5..c7731c2 100644
>> --- a/hw/file-op-9p.h
>> +++ b/hw/file-op-9p.h
>> @@ -86,7 +86,7 @@ typedef struct FileOperations
>>     int (*fstat)(FsContext *, int, struct stat *);
>>     int (*rename)(FsContext *, const char *, const char *);
>>     int (*truncate)(FsContext *, const char *, off_t);
>> -    int (*fsync)(FsContext *, int);
>> +    int (*fsync)(FsContext *, int, int);
>>     int (*statfs)(FsContext *s, const char *path, struct statfs *stbuf);
>>     ssize_t (*lgetxattr)(FsContext *, const char *,
>>                          const char *, void *, size_t);
>> diff --git a/hw/virtio-9p-local.c b/hw/virtio-9p-local.c
>> index 0d52020..d0c79e4 100644
>> --- a/hw/virtio-9p-local.c
>> +++ b/hw/virtio-9p-local.c
>> @@ -490,9 +490,13 @@ static int local_remove(FsContext *ctx, const char *path)
>>     return remove(rpath(ctx, path));
>>  }
>>
>> -static int local_fsync(FsContext *ctx, int fd)
>> +static int local_fsync(FsContext *ctx, int fd, int datasync)
>>  {
>> -    return fsync(fd);
>> +    if (datasync) {
>> +        return fdatasync(fd);
> 
> Please use qemu_fdatasync().

This file and functions in it are intended as wrappers of syscalls
which can be used in threadlets. Per Anthony's statement about avoiding
any QEMU specific code in threadlets, l I am planning to avoid any QEMU specific
calls
in the virtio-9p-local.c library.

While these are just wrappers for now, what is the future direction of this kind
of calls like
qemu_fdatasync() qemu_malloc() etc? Will they be OK to call in threadlets
without any locks?
If so, may be we can use them in this function.

Thanks,
JV