On Fri, Apr 20, 2018 at 03:52:24PM +0800, Anand Jain wrote: > > > On 04/20/2018 12:33 AM, David Sterba wrote: > > Currently fs_info::balance_running is 0 or 1 and does not use the > > semantics of atomics. The pause and cancel check for 0, that can happen > > only after __btrfs_balance exits for whatever reason. > > > > Parallel calls to balance ioctl may enter btrfs_ioctl_balance multiple > > times but will block on the balance_mutex that protects the > > fs_info::flags bit. > > > > Signed-off-by: David Sterba <dste...@suse.com> > > --- > > fs/btrfs/ctree.h | 6 +++++- > > fs/btrfs/disk-io.c | 1 - > > fs/btrfs/ioctl.c | 6 +++--- > > fs/btrfs/volumes.c | 18 ++++++++++-------- > > 4 files changed, 18 insertions(+), 13 deletions(-) > > > > diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h > > index 011cb9a8a967..fda94a264eb7 100644 > > --- a/fs/btrfs/ctree.h > > +++ b/fs/btrfs/ctree.h > > @@ -726,6 +726,11 @@ struct btrfs_delayed_root; > > * (device replace, resize, device add/delete, balance) > > */ > > #define BTRFS_FS_EXCL_OP 16 > > +/* > > + * Indicate that balance has been set up from the ioctl and is in the main > > + * phase. The fs_info::balance_ctl is initialized. > > + */ > > +#define BTRFS_FS_BALANCE_RUNNING 17 > > > Change looks good to me as such and its a good idea to drop > fs_info::balance_running; > > However instead of making BTRFS_FS_BALANCE_RUNNING part of > btrfs_fs_info::flags > pls make it part of > btrfs_balance_control::flags > > Because: > We already have BTRFS_BALANCE_RESUME there. > And at fs_info level BTRFS_FS_EXCL_OP tells someone excl is running. > And if its a balance (either in running or implicit-paused state) > then btrfs_fs_info::balance_ctl is not NULL.
This would work fine, if the btrfs_balance_control::flags were not copy of the ioctl structure. There are the filter flags stored there, in addition to BTRFS_BALANCE_RESUME. >From that point it's the balance ioctl interface and adding the internal runtime flag does not seem to fit. The status bit could be tracked separatelly in btrfs_balance_control so it does not use the whole filesystem flag namespace, as it's always used under balance mutex. As this is simple change to the patch, I'll do that. -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
