On Wed, Apr 04, 2012 at 09:46:17PM +0200, Arnd Hannemann wrote:
> Btrfs allows to turn on compression on a mounted and used filesystem
> by issuing mount -o remount,compress=lzo.
> This patch allows to turn compression off again
> while the filesystem is mounted.
I agree it makes sense to allow for turning off the compression via
remount. Currently the mount flag FORCE_COMPRESS implies COMPRESS and
your code may lead to FORCE_COMPRESS without COMPRESS. To fix that
clear the force option as well.
For completeness, there should be also possibility of
-o remount,compress-force=no
doing exactly the same, just a different syntax. Proposed fix below.
> --- a/fs/btrfs/super.c
> +++ b/fs/btrfs/super.c
> @@ -394,15 +394,20 @@ int btrfs_parse_options(struct btrfs_root *root, char
> *options)
> strcmp(args[0].from, "zlib") == 0) {
> compress_type = "zlib";
> info->compress_type = BTRFS_COMPRESS_ZLIB;
> + btrfs_set_opt(info->mount_opt, COMPRESS);
> } else if (strcmp(args[0].from, "lzo") == 0) {
> compress_type = "lzo";
> info->compress_type = BTRFS_COMPRESS_LZO;
> + btrfs_set_opt(info->mount_opt, COMPRESS);
> + } else if (strncmp(args[0].from, "no", 2) == 0) {
> + compress_type = "no";
> + info->compress_type = BTRFS_COMPRESS_NONE;
> + btrfs_clear_opt(info->mount_opt, COMPRESS);
btrfs_clear_opt(info->mount_opt,
FORCE_COMPRESS);
compress_force = false;
> } else {
> ret = -EINVAL;
> goto out;
> }
>
> - btrfs_set_opt(info->mount_opt, COMPRESS);
> if (compress_force) {
> btrfs_set_opt(info->mount_opt, FORCE_COMPRESS);
> pr_info("btrfs: force %s compression\n",
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