Re: "nossd" option ignored

[Eric Sandeen <sandeen@redhat.com>]

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On 6/27/14, 2:27 PM, Roman Mamedov wrote:
> Hello,
> 
> With kernel 3.14.5...
> 
> $ sudo umount /mnt/net/alpha/11
> umount: /mnt/net/alpha/11: not mounted
> 
> $ sudo mount -o inode_cache,space_cache,compress=lzo,noatime,nossd,skip_balance /dev/nbd11 /mnt/net/alpha/11
> 
> $ sudo mount | grep nbd11
> /dev/nbd11 on /mnt/net/alpha/11 type btrfs (rw,noatime,compress=lzo,ssd,space_cache,inode_cache,skip_balance)
> 
> $ dmesg | tail
> ...
> [1353819.363462] BTRFS: device fsid 8cf8eff9-fd5a-4b6f-bb85-3f2df2f63c99 devid 1 transid 25041 /dev/nbd11
> [1353819.364668] BTRFS info (device nbd11): enabling inode map caching
> [1353819.364674] BTRFS info (device nbd11): disk space caching is enabled
> [1353821.784617] BTRFS: detected SSD devices, enabling SSD mode
> 
> --
> I'm certain the "nossd" option used to work (prevent the SSD mode) with this
> exact same configuration on older kernels. Any idea why it doesn't now?
> 

Looks like it was broken by this commit in v3.14:

commit 078025347c8ed43ff330e392476d8866ac1b297f
Author: Qu Wenruo <quwenruo@cn.fujitsu.com>
Date:   Mon Jan 13 13:36:07 2014 +0800

    btrfs: Cleanup the btrfs_parse_options for remount.

due to this change:
 
                case Opt_nossd:
- -                       btrfs_info(root->fs_info, "not using ssd allocation scheme");
- -                       btrfs_set_opt(info->mount_opt, NOSSD);
+                       btrfs_clear_and_info(root, NOSSD,
+                                            "not using ssd allocation scheme");
                        btrfs_clear_opt(info->mount_opt, SSD);
- -                       btrfs_clear_opt(info->mount_opt, SSD_SPREAD);
                        break;

whereas "nossd" used to set the "NOSSD" option, it now tries to *clear* "NOSSD"

There seem to be other breakages as well.

Looks like mount option regression tests are needed.

Because "clear_and_info" says nothing if there's nothing to clear, you get no
printk, either.

The ssd options are a mess; you can mount "-o nossd,ssd_spread" for example.

I'll send a patch to at least make it behave at least as well as before, but bleah.

- -Eric
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