btrfs: add quota override flag to enable quota override for CAP_SYS_RESOURCE

This patch introduces the quota override flag to btrfs_fs_info, and a
change to quota limit checking code to temporarily allow for quota to be
overridden for processes with CAP_SYS_RESOURCE.

It's useful for administrative programs, such as log rotation, that may
need to temporarily use more disk space in order to free up a greater
amount of overall disk space without yielding more disk space to the
rest of userland.

Eventually, we may want to add the idea of an operator-specific quota,
operator reserved space, or something else to allow for administrative
override, but this is perhaps the simplest solution.

Signed-off-by: Sargun Dhillon <sargun@sargun.me>
Reviewed-by: David Sterba <dsterba@suse.com>
[ minor changelog edits ]
Signed-off-by: David Sterba <dsterba@suse.com>
This commit is contained in:
Sargun Dhillon 2017-05-11 21:17:33 +00:00 committed by David Sterba
parent a5ed45f822
commit f29efe2921
2 changed files with 7 additions and 0 deletions

View File

@ -716,6 +716,8 @@ struct btrfs_delayed_root;
#define BTRFS_FS_BTREE_ERR 11
#define BTRFS_FS_LOG1_ERR 12
#define BTRFS_FS_LOG2_ERR 13
#define BTRFS_FS_QUOTA_OVERRIDE 14
/*
* Indicate that a whole-filesystem exclusive operation is running
* (device replace, resize, device add/delete, balance)

View File

@ -2338,6 +2338,11 @@ static int qgroup_reserve(struct btrfs_root *root, u64 num_bytes, bool enforce)
if (num_bytes == 0)
return 0;
if (test_bit(BTRFS_FS_QUOTA_OVERRIDE, &fs_info->flags) &&
capable(CAP_SYS_RESOURCE))
enforce = false;
retry:
spin_lock(&fs_info->qgroup_lock);
quota_root = fs_info->quota_root;