jeff.liu wrote:
> Sunil Mushran wrote:
>> On 06/10/2010 04:47 PM, Paul Eggert wrote:
>>> On 06/09/2010 11:56 PM, jeff.liu wrote:
>>>
>>>> Yeah, I just realized that the behaviour I observed is caused by the
>>>> delay allocation mechanism of
>>>> the particular FS.
>>>>
>>> If the file system is using delayed allocation, then can
>>> the fiemap ioctl tell us that a file contains a hole (because nothing
>>> has been
>>> allocated there), but read() would tell us that the file contains
>>> nonzero data at the same location
>>> (because it's sitting in a buffer somewhere)? If so, we'd need to do
>>> something like invoke
>>> fdatasync() on the file before issuing the fiemap ioctl, to force
>>> allocation; or perhaps
>>> there's another ioctl that will do the allocation without having to
>>> actually do a sync.
>>>
>> I guess we'll have to use FIEMAP_FLAG_SYNC.
> Hi Sunil,
>
> Thanks for the comments.
> So we can ensure the source file synced before mapping in this way.
>
> Hi Jim and Paul,
>
> How about the tiny patch below?
I agree that this is needed, thanks.
-Eric
> From d6d619a169ff68a9a310a69d8089b9fbf83b5f91 Mon Sep 17 00:00:00 2001
> From: Jie Liu <jeff.liu@xxxxxxxxxx>
> Date: Fri, 11 Jun 2010 16:29:02 +0800
> Subject: [PATCH 1/1] copy.c: add FIEMAP_FLAG_SYNC to fiemap ioctl
>
> * src/copy.c (fiemap_copy): Force kernel to sync the source
> file before mapping.
>
> Signed-off-by: Jie Liu <jeff.liu@xxxxxxxxxx>
> ---
> src/copy.c | 1 +
> 1 files changed, 1 insertions(+), 0 deletions(-)
>
> diff --git a/src/copy.c b/src/copy.c
> index f149be4..f48c74d 100644
> --- a/src/copy.c
> +++ b/src/copy.c
> @@ -191,6 +191,7 @@ fiemap_copy (int src_fd, int dest_fd, size_t buf_size,
> do
> {
> fiemap->fm_length = FIEMAP_MAX_OFFSET;
> + fiemap->fm_flags = FIEMAP_FLAG_SYNC;
> fiemap->fm_extent_count = count;
>
> /* When ioctl(2) fails, fall back to the normal copy only if it
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