diff mbox series

[v2,3/5] btrfs: remove unused function btrfs_sysfs_feature_update()

Message ID 20181119093817.9291-4-jthumshirn@suse.de (mailing list archive)
State New, archived
Headers show
Series btrfs: fix compiler warning with make W=1 | expand

Commit Message

Johannes Thumshirn Nov. 19, 2018, 9:38 a.m. UTC 
btrfs_sysfs_feature_update() was introduced with commit 444e75169872 (btrfs:
sysfs: introduce helper for syncing bits with sysfs files) to provide a helper
which was used in 14e46e04958d (btrfs: synchronize incompat feature bits with
sysfs files).

But commit e410e34fad91 (Revert "btrfs: synchronize incompat feature bits with
sysfs files") reverted 14e46e04958d so btrfs_sysfs_feature_update() ended up
as an unused function.

Signed-off-by: Johannes Thumshirn <jthumshirn@suse.de>
Reviewed-by: Omar Sandoval <osandov@fb.com>
Reviewed-by: Nikolay Borisov <nborisov@suse.com>
Reviewed-by: Qu Wenruo <wqu@suse.com>
---
 fs/btrfs/sysfs.c | 33 ---------------------------------
 fs/btrfs/sysfs.h |  2 --
 2 files changed, 35 deletions(-)

Comments

David Sterba Nov. 19, 2018, 2:21 p.m. UTC | #1 
On Mon, Nov 19, 2018 at 10:38:15AM +0100, Johannes Thumshirn wrote:
> btrfs_sysfs_feature_update() was introduced with commit 444e75169872 (btrfs:
> sysfs: introduce helper for syncing bits with sysfs files) to provide a helper
> which was used in 14e46e04958d (btrfs: synchronize incompat feature bits with
> sysfs files).
> 
> But commit e410e34fad91 (Revert "btrfs: synchronize incompat feature bits with
> sysfs files") reverted 14e46e04958d so btrfs_sysfs_feature_update() ended up
> as an unused function.

    This ends up doing sysfs operations from deep in balance (where we
    should be GFP_NOFS) and under heavy balance load, we're making races
    against sysfs internals.

    Revert it for now while we figure things out.

With the memalloc_nofs_save/memalloc_nofs_restore we can get address the
GFP_NOFS problem, but I don't remember what was the other part about sysfs
internals.

The sysfs bits for features should be match the internal state so this
is a (low priority) bug, I'd prefer fixing it instead of removing the
code.
diff mbox series

Patch

diff --git a/fs/btrfs/sysfs.c b/fs/btrfs/sysfs.c
index 3717c864ba23..a22a7c5f75eb 100644
--- a/fs/btrfs/sysfs.c
+++ b/fs/btrfs/sysfs.c
@@ -858,39 +858,6 @@  int btrfs_sysfs_add_mounted(struct btrfs_fs_info *fs_info)
 	return error;
 }
 
-
-/*
- * Change per-fs features in /sys/fs/btrfs/UUID/features to match current
- * values in superblock. Call after any changes to incompat/compat_ro flags
- */
-void btrfs_sysfs_feature_update(struct btrfs_fs_info *fs_info,
-		u64 bit, enum btrfs_feature_set set)
-{
-	struct btrfs_fs_devices *fs_devs;
-	struct kobject *fsid_kobj;
-	u64 features;
-	int ret;
-
-	if (!fs_info)
-		return;
-
-	features = get_features(fs_info, set);
-	ASSERT(bit & supported_feature_masks[set]);
-
-	fs_devs = fs_info->fs_devices;
-	fsid_kobj = &fs_devs->fsid_kobj;
-
-	if (!fsid_kobj->state_initialized)
-		return;
-
-	/*
-	 * FIXME: this is too heavy to update just one value, ideally we'd like
-	 * to use sysfs_update_group but some refactoring is needed first.
-	 */
-	sysfs_remove_group(fsid_kobj, &btrfs_feature_attr_group);
-	ret = sysfs_create_group(fsid_kobj, &btrfs_feature_attr_group);
-}
-
 static int btrfs_init_debugfs(void)
 {
 #ifdef CONFIG_DEBUG_FS
diff --git a/fs/btrfs/sysfs.h b/fs/btrfs/sysfs.h
index c6ee600aff89..93feedde8485 100644
--- a/fs/btrfs/sysfs.h
+++ b/fs/btrfs/sysfs.h
@@ -88,7 +88,5 @@  int btrfs_sysfs_add_fsid(struct btrfs_fs_devices *fs_devs,
 				struct kobject *parent);
 int btrfs_sysfs_add_device(struct btrfs_fs_devices *fs_devs);
 void btrfs_sysfs_remove_fsid(struct btrfs_fs_devices *fs_devs);
-void btrfs_sysfs_feature_update(struct btrfs_fs_info *fs_info,
-		u64 bit, enum btrfs_feature_set set);
 
 #endif