On Fri, Jan 15, 2016 at 1:37 AM, Qu Wenruo <quwenruo@xxxxxxxxxxxxxx> wrote:
>
>
> Filipe Manana wrote on 2016/01/14 09:56 +0000:
>>
>> On Thu, Jan 14, 2016 at 5:57 AM, Qu Wenruo <quwenruo@xxxxxxxxxxxxxx>
>> wrote:
>>>
>>> From: Wang Xiaoguang <wangxg.fnst@xxxxxxxxxxxxxx>
>>>
>>> We use btrfs extended attribute "btrfs.dedup" to record per-file online
>>> dedup status, so add a dedup property handler.
>>>
>>> Signed-off-by: Wang Xiaoguang <wangxg.fnst@xxxxxxxxxxxxxx>
>>> ---
>>> fs/btrfs/props.c | 40 ++++++++++++++++++++++++++++++++++++++++
>>> 1 file changed, 40 insertions(+)
>>>
>>> diff --git a/fs/btrfs/props.c b/fs/btrfs/props.c
>>> index f9e6023..ae8b76d 100644
>>> --- a/fs/btrfs/props.c
>>> +++ b/fs/btrfs/props.c
>>> @@ -41,6 +41,10 @@ static int prop_compression_apply(struct inode *inode,
>>> size_t len);
>>> static const char *prop_compression_extract(struct inode *inode);
>>>
>>> +static int prop_dedup_validate(const char *value, size_t len);
>>> +static int prop_dedup_apply(struct inode *inode, const char *value,
>>> size_t len);
>>> +static const char *prop_dedup_extract(struct inode *inode);
>>> +
>>> static struct prop_handler prop_handlers[] = {
>>> {
>>> .xattr_name = XATTR_BTRFS_PREFIX "compression",
>>> @@ -49,6 +53,13 @@ static struct prop_handler prop_handlers[] = {
>>> .extract = prop_compression_extract,
>>> .inheritable = 1
>>> },
>>> + {
>>> + .xattr_name = XATTR_BTRFS_PREFIX "dedup",
>>> + .validate = prop_dedup_validate,
>>> + .apply = prop_dedup_apply,
>>> + .extract = prop_dedup_extract,
>>> + .inheritable = 1
>>> + },
>>> };
>>>
>>> void __init btrfs_props_init(void)
>>> @@ -425,4 +436,33 @@ static const char *prop_compression_extract(struct
>>> inode *inode)
>>> return NULL;
>>> }
>>>
>>> +static int prop_dedup_validate(const char *value, size_t len)
>>> +{
>>> + if (!strncmp("disable", value, len))
>>> + return 0;
>>> +
>>> + return -EINVAL;
>>> +}
>>> +
>>> +static int prop_dedup_apply(struct inode *inode, const char *value,
>>> size_t len)
>>> +{
>>> + if (len == 0) {
>>> + BTRFS_I(inode)->flags &= ~BTRFS_INODE_NODEDUP;
>>> + return 0;
>>> + }
>>> +
>>> + if (!strncmp("disable", value, len)) {
>>> + BTRFS_I(inode)->flags |= BTRFS_INODE_NODEDUP;
>>> + return 0;
>>> + }
>>> +
>>> + return -EINVAL;
>>> +}
>>> +
>>> +static const char *prop_dedup_extract(struct inode *inode)
>>> +{
>>> + if (BTRFS_I(inode)->flags | BTRFS_INODE_NODEDUP)
>>> + return "disable";
>>
>>
>> | -> &
>>
>> How about writing test cases (for xfstests)? Not only for the property
>> but for the whole dedup feature, it would avoid such simple
>> mistakes...
>
>
> Yes, it's already in our schedule and we have some internal simple test
> case.
>
> But the problem is,
> Some behavior/format is not completely determined yet
> Especially for on-disk format (ondisk backend only), and ioctl interface.
How does someone guesses that? You could add an RFC tag to the patches...
>
> So I'm a little concerned about submit them too early before we made final
> decision on the ioctl interface.
What's the problem? You can submit such tests only to the btrfs list
for now and tag them as RFC and mention that.
>
>> Take a look at the good example of xfs development. For example when
>> all the recent patches for their reflink implementation was posted
>> (and before getting merged), a comprehensive set of test cases for
>> xfstests was also posted...
>
>
> Yes, test driven development is very nice, but there is also problem,
> especially for btrfs, like btrfs/047 which needs btrfs send --stream-version
> support.
Yes, this one was a special case in that around 2 years ago it seemed
the functionality was going to be merged, but it ended up not being
merged due to reasons not known to me (no reasons pointed in the
mailing list nor in private).
Better have unused tests instead of features without tests (and many
btrfs specific features had no tests or almost nothing not that long
ago).
>
> But unfortunately, there is not --stream-version support in upsteam
> btrfs-progs and the test case never get executed on upsteam btrfs-progs.
>
> Personally speaking, xfs development can only happen in that way because
> xfstest maintainer is also the maintainer of xfs.
> As Dave knows every aspect of xfs and can determine which feature will be
> merged.
He can also accept patches to remove tests or change them...
Shouldn't be an excuse to not share tests along with patches for new
features, as noted above.
> But that's not true for btrfs, so he can merge wrong patch and cause
> inconsistent with what btrfs really supports between test cases.
>
> Thanks,
> Qu
>
>
>>
>>>
>>> + return NULL;
>>> +}
>>> --
>>> 2.7.0
>>>
>>>
>>>
>>> --
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>>
>>
>>
>>
>
>
--
Filipe David Manana,
"Reasonable men adapt themselves to the world.
Unreasonable men adapt the world to themselves.
That's why all progress depends on unreasonable men."
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