| Message ID | 1501176997-24059-2-git-send-email-nborisov@suse.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On Thu, Jul 27, 2017 at 6:36 PM, Nikolay Borisov <nborisov@suse.com> wrote: > Currently btrfs_alloc_dev_extent essentially open codes btrfs_insert_item. So > let's remove the superfluous code, leaving only the important bits, namely > initialising the device extent and just calling btrfs_insert_item. So first add > definition for the stack-based set/get function. And then use them. > Additionally, remove the code which sets the uuid of the block header, since > this is something which is already handled by the core btree code. Quite honestly, I don't see the value of this change at all. It doesn't make things simpler nor more readable nor nothing. We have many, really many places using btrfs_insert_empty_item() instead of calling btrfs_insert_item(), are you planning on sending a patch to do the replacement for each of them? What's the point? Plus you are introducing now a memory leak. See below. > > Signed-off-by: Nikolay Borisov <nborisov@suse.com> > --- > fs/btrfs/ctree.h | 8 ++++++++ > fs/btrfs/volumes.c | 34 ++++++++++++---------------------- > 2 files changed, 20 insertions(+), 22 deletions(-) > > diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h > index cd9497bcdb1e..567fbf186257 100644 > --- a/fs/btrfs/ctree.h > +++ b/fs/btrfs/ctree.h > @@ -1740,6 +1740,14 @@ BTRFS_SETGET_FUNCS(dev_extent_chunk_objectid, struct btrfs_dev_extent, > BTRFS_SETGET_FUNCS(dev_extent_chunk_offset, struct btrfs_dev_extent, > chunk_offset, 64); > BTRFS_SETGET_FUNCS(dev_extent_length, struct btrfs_dev_extent, length, 64); > +BTRFS_SETGET_STACK_FUNCS(stack_dev_extent_chunk_tree, struct btrfs_dev_extent, > + chunk_tree, 64); > +BTRFS_SETGET_STACK_FUNCS(stack_dev_extent_chunk_objectid, > + struct btrfs_dev_extent, chunk_objectid, 64); > +BTRFS_SETGET_STACK_FUNCS(stack_dev_extent_chunk_offset, struct btrfs_dev_extent, > + chunk_offset, 64); > +BTRFS_SETGET_STACK_FUNCS(stack_dev_extent_length, struct btrfs_dev_extent, > + length, 64); > > static inline unsigned long btrfs_dev_extent_chunk_tree_uuid(struct btrfs_dev_extent *dev) > { > diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c > index 5a1913956f20..94e98261dbd0 100644 > --- a/fs/btrfs/volumes.c > +++ b/fs/btrfs/volumes.c > @@ -1581,42 +1581,32 @@ static int btrfs_alloc_dev_extent(struct btrfs_trans_handle *trans, > u64 chunk_offset, u64 start, u64 num_bytes) > { > int ret; > - struct btrfs_path *path; > - struct btrfs_fs_info *fs_info = device->fs_info; > - struct btrfs_root *root = fs_info->dev_root; > + struct btrfs_root *root = device->fs_info->dev_root; > struct btrfs_dev_extent *extent; > - struct extent_buffer *leaf; > struct btrfs_key key; > > WARN_ON(!device->in_fs_metadata); > WARN_ON(device->is_tgtdev_for_dev_replace); > - path = btrfs_alloc_path(); > - if (!path) > + > + extent = kzalloc(sizeof(*extent), GFP_NOFS); > + if (!extent) > return -ENOMEM; > > key.objectid = device->devid; > key.offset = start; > key.type = BTRFS_DEV_EXTENT_KEY; > - ret = btrfs_insert_empty_item(trans, root, path, &key, > - sizeof(*extent)); > - if (ret) > - goto out; > > - leaf = path->nodes[0]; > - extent = btrfs_item_ptr(leaf, path->slots[0], > - struct btrfs_dev_extent); > - btrfs_set_dev_extent_chunk_tree(leaf, extent, > - BTRFS_CHUNK_TREE_OBJECTID); > - btrfs_set_dev_extent_chunk_objectid(leaf, extent, > + btrfs_set_stack_dev_extent_chunk_tree(extent, > + BTRFS_CHUNK_TREE_OBJECTID); > + btrfs_set_stack_dev_extent_chunk_objectid(extent, > BTRFS_FIRST_CHUNK_TREE_OBJECTID); > - btrfs_set_dev_extent_chunk_offset(leaf, extent, chunk_offset); > + btrfs_set_stack_dev_extent_chunk_offset(extent, chunk_offset); > + btrfs_set_stack_dev_extent_length(extent, num_bytes); > > - write_extent_buffer_chunk_tree_uuid(leaf, fs_info->chunk_tree_uuid); > + ret = btrfs_insert_item(trans, root, &key, extent, sizeof(*extent)); > + if (ret) > + kfree(extent); Even if ret is 0 (success), you need to kfree(extent). thanks > > - btrfs_set_dev_extent_length(leaf, extent, num_bytes); > - btrfs_mark_buffer_dirty(leaf); > -out: > - btrfs_free_path(path); > return ret; > } > > -- > 2.7.4 > > -- > To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html
On 27.07.2017 20:57, Filipe Manana wrote: > On Thu, Jul 27, 2017 at 6:36 PM, Nikolay Borisov <nborisov@suse.com> wrote: >> Currently btrfs_alloc_dev_extent essentially open codes btrfs_insert_item. So >> let's remove the superfluous code, leaving only the important bits, namely >> initialising the device extent and just calling btrfs_insert_item. So first add >> definition for the stack-based set/get function. And then use them. >> Additionally, remove the code which sets the uuid of the block header, since >> this is something which is already handled by the core btree code. > > Quite honestly, I don't see the value of this change at all. > It doesn't make things simpler nor more readable nor nothing. > We have many, really many places using btrfs_insert_empty_item() > instead of calling btrfs_insert_item(), are you planning on sending a > patch to do the replacement for each of them? What's the point? I beg you to differ. Some of the code in btrfs is a mess, it's working but it's messy. There is constant violation of abstractions (as is the case in this function, heck the uuid setting of the block header function doesn't even belong here). All of this hampers reading comprehension of the code for newcomers. You are experienced in the code and likely this doesn't apply to you but since I'm someone relatively new to the code this has been my experience. And I believe any effort to actually simplify the code, make it more coherent and succinct is a win long-term. I will wait for other feedback, if people feel patches like that are just bikeshedding then I will refrain from such cleanups in the future. > > Plus you are introducing now a memory leak. See below. Will fix it. > >> >> Signed-off-by: Nikolay Borisov <nborisov@suse.com> >> --- >> fs/btrfs/ctree.h | 8 ++++++++ >> fs/btrfs/volumes.c | 34 ++++++++++++---------------------- >> 2 files changed, 20 insertions(+), 22 deletions(-) >> >> diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h >> index cd9497bcdb1e..567fbf186257 100644 >> --- a/fs/btrfs/ctree.h >> +++ b/fs/btrfs/ctree.h >> @@ -1740,6 +1740,14 @@ BTRFS_SETGET_FUNCS(dev_extent_chunk_objectid, struct btrfs_dev_extent, >> BTRFS_SETGET_FUNCS(dev_extent_chunk_offset, struct btrfs_dev_extent, >> chunk_offset, 64); >> BTRFS_SETGET_FUNCS(dev_extent_length, struct btrfs_dev_extent, length, 64); >> +BTRFS_SETGET_STACK_FUNCS(stack_dev_extent_chunk_tree, struct btrfs_dev_extent, >> + chunk_tree, 64); >> +BTRFS_SETGET_STACK_FUNCS(stack_dev_extent_chunk_objectid, >> + struct btrfs_dev_extent, chunk_objectid, 64); >> +BTRFS_SETGET_STACK_FUNCS(stack_dev_extent_chunk_offset, struct btrfs_dev_extent, >> + chunk_offset, 64); >> +BTRFS_SETGET_STACK_FUNCS(stack_dev_extent_length, struct btrfs_dev_extent, >> + length, 64); >> >> static inline unsigned long btrfs_dev_extent_chunk_tree_uuid(struct btrfs_dev_extent *dev) >> { >> diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c >> index 5a1913956f20..94e98261dbd0 100644 >> --- a/fs/btrfs/volumes.c >> +++ b/fs/btrfs/volumes.c >> @@ -1581,42 +1581,32 @@ static int btrfs_alloc_dev_extent(struct btrfs_trans_handle *trans, >> u64 chunk_offset, u64 start, u64 num_bytes) >> { >> int ret; >> - struct btrfs_path *path; >> - struct btrfs_fs_info *fs_info = device->fs_info; >> - struct btrfs_root *root = fs_info->dev_root; >> + struct btrfs_root *root = device->fs_info->dev_root; >> struct btrfs_dev_extent *extent; >> - struct extent_buffer *leaf; >> struct btrfs_key key; >> >> WARN_ON(!device->in_fs_metadata); >> WARN_ON(device->is_tgtdev_for_dev_replace); >> - path = btrfs_alloc_path(); >> - if (!path) >> + >> + extent = kzalloc(sizeof(*extent), GFP_NOFS); >> + if (!extent) >> return -ENOMEM; >> >> key.objectid = device->devid; >> key.offset = start; >> key.type = BTRFS_DEV_EXTENT_KEY; >> - ret = btrfs_insert_empty_item(trans, root, path, &key, >> - sizeof(*extent)); >> - if (ret) >> - goto out; >> >> - leaf = path->nodes[0]; >> - extent = btrfs_item_ptr(leaf, path->slots[0], >> - struct btrfs_dev_extent); >> - btrfs_set_dev_extent_chunk_tree(leaf, extent, >> - BTRFS_CHUNK_TREE_OBJECTID); >> - btrfs_set_dev_extent_chunk_objectid(leaf, extent, >> + btrfs_set_stack_dev_extent_chunk_tree(extent, >> + BTRFS_CHUNK_TREE_OBJECTID); >> + btrfs_set_stack_dev_extent_chunk_objectid(extent, >> BTRFS_FIRST_CHUNK_TREE_OBJECTID); >> - btrfs_set_dev_extent_chunk_offset(leaf, extent, chunk_offset); >> + btrfs_set_stack_dev_extent_chunk_offset(extent, chunk_offset); >> + btrfs_set_stack_dev_extent_length(extent, num_bytes); >> >> - write_extent_buffer_chunk_tree_uuid(leaf, fs_info->chunk_tree_uuid); >> + ret = btrfs_insert_item(trans, root, &key, extent, sizeof(*extent)); >> + if (ret) >> + kfree(extent); > > Even if ret is 0 (success), you need to kfree(extent). > > thanks > >> >> - btrfs_set_dev_extent_length(leaf, extent, num_bytes); >> - btrfs_mark_buffer_dirty(leaf); >> -out: >> - btrfs_free_path(path); >> return ret; >> } >> >> -- >> 2.7.4 >> >> -- >> To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in >> the body of a message to majordomo@vger.kernel.org >> More majordomo info at http://vger.kernel.org/majordomo-info.html > > > -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On Fri, Jul 28, 2017 at 6:59 AM, Nikolay Borisov <nborisov@suse.com> wrote: > > > On 27.07.2017 20:57, Filipe Manana wrote: >> On Thu, Jul 27, 2017 at 6:36 PM, Nikolay Borisov <nborisov@suse.com> wrote: >>> Currently btrfs_alloc_dev_extent essentially open codes btrfs_insert_item. So >>> let's remove the superfluous code, leaving only the important bits, namely >>> initialising the device extent and just calling btrfs_insert_item. So first add >>> definition for the stack-based set/get function. And then use them. >>> Additionally, remove the code which sets the uuid of the block header, since >>> this is something which is already handled by the core btree code. >> >> Quite honestly, I don't see the value of this change at all. >> It doesn't make things simpler nor more readable nor nothing. >> We have many, really many places using btrfs_insert_empty_item() >> instead of calling btrfs_insert_item(), are you planning on sending a >> patch to do the replacement for each of them? What's the point? > > I beg you to differ. Some of the code in btrfs is a mess, it's working > but it's messy. There is constant violation of abstractions (as is the > case in this function, heck the uuid setting of the block header > function doesn't even belong here). The uuid setting is a different thing (and that's fine to go away), unrelated to using insert_empty_item() vs insert_item(), which is what I was referring to in my previous reply. > All of this hampers reading > comprehension of the code for newcomers. You are experienced in the code > and likely this doesn't apply to you but since I'm someone relatively > new to the code this has been my experience. And I believe any effort to > actually simplify the code, make it more coherent and succinct is a win > long-term. Well, this hasn't prevented me, or others that have started contributing to btrfs after I did, from being able to understand the code and do useful changes (otherwise such kind of patches would have landed long time ago). This kind of change won't save anyone's time understanding the code. Plus, if I want to go a bit more nitpick, this change of using btrfs_insert_item() is from a performance/efficiency point of view, worse as it requires an additional memory allocation/free (the device extent). > > I will wait for other feedback, if people feel patches like that are > just bikeshedding then I will refrain from such cleanups in the future. > >> >> Plus you are introducing now a memory leak. See below. > > Will fix it. > >> >>> >>> Signed-off-by: Nikolay Borisov <nborisov@suse.com> >>> --- >>> fs/btrfs/ctree.h | 8 ++++++++ >>> fs/btrfs/volumes.c | 34 ++++++++++++---------------------- >>> 2 files changed, 20 insertions(+), 22 deletions(-) >>> >>> diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h >>> index cd9497bcdb1e..567fbf186257 100644 >>> --- a/fs/btrfs/ctree.h >>> +++ b/fs/btrfs/ctree.h >>> @@ -1740,6 +1740,14 @@ BTRFS_SETGET_FUNCS(dev_extent_chunk_objectid, struct btrfs_dev_extent, >>> BTRFS_SETGET_FUNCS(dev_extent_chunk_offset, struct btrfs_dev_extent, >>> chunk_offset, 64); >>> BTRFS_SETGET_FUNCS(dev_extent_length, struct btrfs_dev_extent, length, 64); >>> +BTRFS_SETGET_STACK_FUNCS(stack_dev_extent_chunk_tree, struct btrfs_dev_extent, >>> + chunk_tree, 64); >>> +BTRFS_SETGET_STACK_FUNCS(stack_dev_extent_chunk_objectid, >>> + struct btrfs_dev_extent, chunk_objectid, 64); >>> +BTRFS_SETGET_STACK_FUNCS(stack_dev_extent_chunk_offset, struct btrfs_dev_extent, >>> + chunk_offset, 64); >>> +BTRFS_SETGET_STACK_FUNCS(stack_dev_extent_length, struct btrfs_dev_extent, >>> + length, 64); >>> >>> static inline unsigned long btrfs_dev_extent_chunk_tree_uuid(struct btrfs_dev_extent *dev) >>> { >>> diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c >>> index 5a1913956f20..94e98261dbd0 100644 >>> --- a/fs/btrfs/volumes.c >>> +++ b/fs/btrfs/volumes.c >>> @@ -1581,42 +1581,32 @@ static int btrfs_alloc_dev_extent(struct btrfs_trans_handle *trans, >>> u64 chunk_offset, u64 start, u64 num_bytes) >>> { >>> int ret; >>> - struct btrfs_path *path; >>> - struct btrfs_fs_info *fs_info = device->fs_info; >>> - struct btrfs_root *root = fs_info->dev_root; >>> + struct btrfs_root *root = device->fs_info->dev_root; >>> struct btrfs_dev_extent *extent; >>> - struct extent_buffer *leaf; >>> struct btrfs_key key; >>> >>> WARN_ON(!device->in_fs_metadata); >>> WARN_ON(device->is_tgtdev_for_dev_replace); >>> - path = btrfs_alloc_path(); >>> - if (!path) >>> + >>> + extent = kzalloc(sizeof(*extent), GFP_NOFS); >>> + if (!extent) >>> return -ENOMEM; >>> >>> key.objectid = device->devid; >>> key.offset = start; >>> key.type = BTRFS_DEV_EXTENT_KEY; >>> - ret = btrfs_insert_empty_item(trans, root, path, &key, >>> - sizeof(*extent)); >>> - if (ret) >>> - goto out; >>> >>> - leaf = path->nodes[0]; >>> - extent = btrfs_item_ptr(leaf, path->slots[0], >>> - struct btrfs_dev_extent); >>> - btrfs_set_dev_extent_chunk_tree(leaf, extent, >>> - BTRFS_CHUNK_TREE_OBJECTID); >>> - btrfs_set_dev_extent_chunk_objectid(leaf, extent, >>> + btrfs_set_stack_dev_extent_chunk_tree(extent, >>> + BTRFS_CHUNK_TREE_OBJECTID); >>> + btrfs_set_stack_dev_extent_chunk_objectid(extent, >>> BTRFS_FIRST_CHUNK_TREE_OBJECTID); >>> - btrfs_set_dev_extent_chunk_offset(leaf, extent, chunk_offset); >>> + btrfs_set_stack_dev_extent_chunk_offset(extent, chunk_offset); >>> + btrfs_set_stack_dev_extent_length(extent, num_bytes); >>> >>> - write_extent_buffer_chunk_tree_uuid(leaf, fs_info->chunk_tree_uuid); >>> + ret = btrfs_insert_item(trans, root, &key, extent, sizeof(*extent)); >>> + if (ret) >>> + kfree(extent); >> >> Even if ret is 0 (success), you need to kfree(extent). >> >> thanks >> >>> >>> - btrfs_set_dev_extent_length(leaf, extent, num_bytes); >>> - btrfs_mark_buffer_dirty(leaf); >>> -out: >>> - btrfs_free_path(path); >>> return ret; >>> } >>> >>> -- >>> 2.7.4 >>> >>> -- >>> To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in >>> the body of a message to majordomo@vger.kernel.org >>> More majordomo info at http://vger.kernel.org/majordomo-info.html >> >> >>
On Fri, Jul 28, 2017 at 08:59:12AM +0300, Nikolay Borisov wrote: > > > On 27.07.2017 20:57, Filipe Manana wrote: > > On Thu, Jul 27, 2017 at 6:36 PM, Nikolay Borisov <nborisov@suse.com> wrote: > >> Currently btrfs_alloc_dev_extent essentially open codes btrfs_insert_item. So > >> let's remove the superfluous code, leaving only the important bits, namely > >> initialising the device extent and just calling btrfs_insert_item. So first add > >> definition for the stack-based set/get function. And then use them. > >> Additionally, remove the code which sets the uuid of the block header, since > >> this is something which is already handled by the core btree code. > > > > Quite honestly, I don't see the value of this change at all. > > It doesn't make things simpler nor more readable nor nothing. > > We have many, really many places using btrfs_insert_empty_item() > > instead of calling btrfs_insert_item(), are you planning on sending a > > patch to do the replacement for each of them? What's the point? > > I beg you to differ. Some of the code in btrfs is a mess, it's working > but it's messy. There is constant violation of abstractions (as is the > case in this function, heck the uuid setting of the block header > function doesn't even belong here). All of this hampers reading > comprehension of the code for newcomers. You are experienced in the code > and likely this doesn't apply to you but since I'm someone relatively > new to the code this has been my experience. And I believe any effort to > actually simplify the code, make it more coherent and succinct is a win > long-term. > > I will wait for other feedback, if people feel patches like that are > just bikeshedding then I will refrain from such cleanups in the future. What I don't like about this patch, also pointed out by Filipe, is the additional memory allocation. Just for the sake of code beauty, this is not the direction the cleanups should go. The function is IMHO readable and below my current threshold of cleanup need. -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h index cd9497bcdb1e..567fbf186257 100644 --- a/fs/btrfs/ctree.h +++ b/fs/btrfs/ctree.h @@ -1740,6 +1740,14 @@ BTRFS_SETGET_FUNCS(dev_extent_chunk_objectid, struct btrfs_dev_extent, BTRFS_SETGET_FUNCS(dev_extent_chunk_offset, struct btrfs_dev_extent, chunk_offset, 64); BTRFS_SETGET_FUNCS(dev_extent_length, struct btrfs_dev_extent, length, 64); +BTRFS_SETGET_STACK_FUNCS(stack_dev_extent_chunk_tree, struct btrfs_dev_extent, + chunk_tree, 64); +BTRFS_SETGET_STACK_FUNCS(stack_dev_extent_chunk_objectid, + struct btrfs_dev_extent, chunk_objectid, 64); +BTRFS_SETGET_STACK_FUNCS(stack_dev_extent_chunk_offset, struct btrfs_dev_extent, + chunk_offset, 64); +BTRFS_SETGET_STACK_FUNCS(stack_dev_extent_length, struct btrfs_dev_extent, + length, 64); static inline unsigned long btrfs_dev_extent_chunk_tree_uuid(struct btrfs_dev_extent *dev) { diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c index 5a1913956f20..94e98261dbd0 100644 --- a/fs/btrfs/volumes.c +++ b/fs/btrfs/volumes.c @@ -1581,42 +1581,32 @@ static int btrfs_alloc_dev_extent(struct btrfs_trans_handle *trans, u64 chunk_offset, u64 start, u64 num_bytes) { int ret; - struct btrfs_path *path; - struct btrfs_fs_info *fs_info = device->fs_info; - struct btrfs_root *root = fs_info->dev_root; + struct btrfs_root *root = device->fs_info->dev_root; struct btrfs_dev_extent *extent; - struct extent_buffer *leaf; struct btrfs_key key; WARN_ON(!device->in_fs_metadata); WARN_ON(device->is_tgtdev_for_dev_replace); - path = btrfs_alloc_path(); - if (!path) + + extent = kzalloc(sizeof(*extent), GFP_NOFS); + if (!extent) return -ENOMEM; key.objectid = device->devid; key.offset = start; key.type = BTRFS_DEV_EXTENT_KEY; - ret = btrfs_insert_empty_item(trans, root, path, &key, - sizeof(*extent)); - if (ret) - goto out; - leaf = path->nodes[0]; - extent = btrfs_item_ptr(leaf, path->slots[0], - struct btrfs_dev_extent); - btrfs_set_dev_extent_chunk_tree(leaf, extent, - BTRFS_CHUNK_TREE_OBJECTID); - btrfs_set_dev_extent_chunk_objectid(leaf, extent, + btrfs_set_stack_dev_extent_chunk_tree(extent, + BTRFS_CHUNK_TREE_OBJECTID); + btrfs_set_stack_dev_extent_chunk_objectid(extent, BTRFS_FIRST_CHUNK_TREE_OBJECTID); - btrfs_set_dev_extent_chunk_offset(leaf, extent, chunk_offset); + btrfs_set_stack_dev_extent_chunk_offset(extent, chunk_offset); + btrfs_set_stack_dev_extent_length(extent, num_bytes); - write_extent_buffer_chunk_tree_uuid(leaf, fs_info->chunk_tree_uuid); + ret = btrfs_insert_item(trans, root, &key, extent, sizeof(*extent)); + if (ret) + kfree(extent); - btrfs_set_dev_extent_length(leaf, extent, num_bytes); - btrfs_mark_buffer_dirty(leaf); -out: - btrfs_free_path(path); return ret; }
Currently btrfs_alloc_dev_extent essentially open codes btrfs_insert_item. So let's remove the superfluous code, leaving only the important bits, namely initialising the device extent and just calling btrfs_insert_item. So first add definition for the stack-based set/get function. And then use them. Additionally, remove the code which sets the uuid of the block header, since this is something which is already handled by the core btree code. Signed-off-by: Nikolay Borisov <nborisov@suse.com> --- fs/btrfs/ctree.h | 8 ++++++++ fs/btrfs/volumes.c | 34 ++++++++++++---------------------- 2 files changed, 20 insertions(+), 22 deletions(-)