Re: [PATCH V2] Btrfs: fix output of compression message in btrfs_parse_options()

[Tsutomu Itoh <t-itoh@jp.fujitsu.com>]

On 2016/01/14 23:20, David Sterba wrote:
> On Thu, Jan 14, 2016 at 09:09:14AM +0900, Tsutomu Itoh wrote:
>> On 2016/01/13 21:33, David Sterba wrote:
>>> On Wed, Jan 06, 2016 at 05:03:40PM +0900, Tsutomu Itoh wrote:
>>>>    			} else if (strncmp(args[0].from, "no", 2) == 0) {
>>>>    				compress_type = "no";
>>>>    				btrfs_clear_opt(info->mount_opt, COMPRESS);
>>>>    				btrfs_clear_opt(info->mount_opt, FORCE_COMPRESS);
>>>>    				compress_force = false;
>>>> +				no_compress++;
>>>>    			} else {
>>> ...
>>>> +			if ((btrfs_test_opt(root, COMPRESS) &&
>>>> +			     (info->compress_type != saved_compress_type ||
>>>> +			      compress_force != saved_compress_force)) ||
>>>> +			    (!btrfs_test_opt(root, COMPRESS) &&
>>>> +			     no_compress == 1)) {
>>>
>>> If there are more than one 'compress=no' then the message won't be
>>> printed. I don't see a reason for doing no_compress++ above.
>>
>> I want to output message as follows. Therefore, no_compress++ is necessary.
>>
>> # mount -o compress,compress,compress=no,compress=no,compress,compress=no <dev> <path>
>>
>> [  162.048033] BTRFS: device fsid a7f6e96e-653e-42d0-8469-13025396caa2 devid 1 transid 3 <dev>
>> [  185.349034] BTRFS info (device <dev>): use zlib compression
>> [  185.349041] BTRFS info (device <dev>): use no compression
>> [  185.349045] BTRFS info (device <dev>): use zlib compression
>> [  185.349048] BTRFS info (device <dev>): use no compression
>> [  185.349050] BTRFS info (device <dev>): disk space caching is enabled
>
> I don't think it's necessary ty print all the options. Only the last one
> is applied so I'd expect to see only "... use no compression".

I see.
However, the output of other options are also the same as the above-mentioned.

e.g.
# mount -o discard,nodiscard,discard <dev> <path>

[56714.781948] BTRFS: device fsid 22f3af7e-0f1c-40fe-8eb1-091df7bd1da2 devid 1 transid 3 <dev>
[56736.296779] BTRFS info (device <dev>): turning on discard
[56736.296785] BTRFS info (device <dev>): turning off discard
[56736.296789] BTRFS info (device <dev>): turning on discard
[56736.296792] BTRFS info (device <dev>): disk space caching is enabled

Thanks,
Tsutomu