From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mo-p05-ob.rzone.de ([81.169.146.180]:22959 "EHLO mo-p05-ob.rzone.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756634Ab3EGHQI (ORCPT ); Tue, 7 May 2013 03:16:08 -0400 Message-ID: <5188AA34.1090804@jan-o-sch.net> Date: Tue, 07 May 2013 09:16:04 +0200 From: Jan Schmidt MIME-Version: 1.0 To: Wang Shilong CC: Linux Btrfs Subject: Re: [PATCH] Btrfs: fix passing wrong arg gfp_t to decide the correct allocation mode References: <51889D15.9050308@cn.fujitsu.com> In-Reply-To: <51889D15.9050308@cn.fujitsu.com> Content-Type: text/plain; charset=UTF-8 Sender: linux-btrfs-owner@vger.kernel.org List-ID: On Tue, May 07, 2013 at 08:20 (+0200), Wang Shilong wrote: > If you look the code carefully, you will see all the tree_mod_alloc() > has to use GFP_ATOMIC. However, the original code pass the wrong arg > gfp_t in some places, this dosen't cause any problems, because in the > tree_mod_alloc(), it ignores arg gfp_t and just use GFP_ATOMIC directly, > this is not good. > > However, i think we should try best not to allocate with GFP_ATOMIC, so > i keep the gfp_t there in the hope we can change allocation mode in the > future. NAK. The code as it is now is prepared to get rid of at least some GFP_ATOMIC allocations. You won't get rid of all of them, as there are a lot of spin lock situations where we need to add to the tree mod lock anyway. As a preparation we currently pass the "best" flags (least restrictive) we can instead of always passing GFP_ATOMIC. I pointed you to this comment already: 557 /* 558 * once we switch from spin locks to something different, we should 559 * honor the flags parameter here. 560 */ 561 tm = *tm_ret = kzalloc(sizeof(*tm), GFP_ATOMIC); So, if you want less atomic allocations, find something more suitable than an rwlock for fs_info->tree_mod_log_lock an you can in fact replace "GFP_ATOMIC" with "flags" in the kzalloc(). The good thing is, because everything is already prepared you don't have to think about all the callers again an pass the correct flags. -Jan > Signed-off-by: Wang Shilong > --- > fs/btrfs/ctree.c | 37 ++++++++++++++++++------------------- > 1 files changed, 18 insertions(+), 19 deletions(-) > > diff --git a/fs/btrfs/ctree.c b/fs/btrfs/ctree.c > index de6de8e..33c9061 100644 > --- a/fs/btrfs/ctree.c > +++ b/fs/btrfs/ctree.c > @@ -553,7 +553,7 @@ static inline int tree_mod_alloc(struct btrfs_fs_info *fs_info, gfp_t flags, > * once we switch from spin locks to something different, we should > * honor the flags parameter here. > */ > - tm = *tm_ret = kzalloc(sizeof(*tm), GFP_ATOMIC); > + tm = *tm_ret = kzalloc(sizeof(*tm), flags); > if (!tm) > return -ENOMEM; > > @@ -591,14 +591,14 @@ __tree_mod_log_insert_key(struct btrfs_fs_info *fs_info, > static noinline int > tree_mod_log_insert_key_mask(struct btrfs_fs_info *fs_info, > struct extent_buffer *eb, int slot, > - enum mod_log_op op, gfp_t flags) > + enum mod_log_op op) > { > int ret; > > if (tree_mod_dont_log(fs_info, eb)) > return 0; > > - ret = __tree_mod_log_insert_key(fs_info, eb, slot, op, flags); > + ret = __tree_mod_log_insert_key(fs_info, eb, slot, op, GFP_ATOMIC); > > tree_mod_log_write_unlock(fs_info); > return ret; > @@ -608,7 +608,7 @@ static noinline int > tree_mod_log_insert_key(struct btrfs_fs_info *fs_info, struct extent_buffer *eb, > int slot, enum mod_log_op op) > { > - return tree_mod_log_insert_key_mask(fs_info, eb, slot, op, GFP_NOFS); > + return tree_mod_log_insert_key_mask(fs_info, eb, slot, op); > } > > static noinline int > @@ -616,13 +616,13 @@ tree_mod_log_insert_key_locked(struct btrfs_fs_info *fs_info, > struct extent_buffer *eb, int slot, > enum mod_log_op op) > { > - return __tree_mod_log_insert_key(fs_info, eb, slot, op, GFP_NOFS); > + return __tree_mod_log_insert_key(fs_info, eb, slot, op, GFP_ATOMIC); > } > > static noinline int > tree_mod_log_insert_move(struct btrfs_fs_info *fs_info, > struct extent_buffer *eb, int dst_slot, int src_slot, > - int nr_items, gfp_t flags) > + int nr_items) > { > struct tree_mod_elem *tm; > int ret; > @@ -642,7 +642,7 @@ tree_mod_log_insert_move(struct btrfs_fs_info *fs_info, > BUG_ON(ret < 0); > } > > - ret = tree_mod_alloc(fs_info, flags, &tm); > + ret = tree_mod_alloc(fs_info, GFP_ATOMIC, &tm); > if (ret < 0) > goto out; > > @@ -679,7 +679,7 @@ __tree_mod_log_free_eb(struct btrfs_fs_info *fs_info, struct extent_buffer *eb) > static noinline int > tree_mod_log_insert_root(struct btrfs_fs_info *fs_info, > struct extent_buffer *old_root, > - struct extent_buffer *new_root, gfp_t flags, > + struct extent_buffer *new_root, > int log_removal) > { > struct tree_mod_elem *tm; > @@ -691,7 +691,7 @@ tree_mod_log_insert_root(struct btrfs_fs_info *fs_info, > if (log_removal) > __tree_mod_log_free_eb(fs_info, old_root); > > - ret = tree_mod_alloc(fs_info, flags, &tm); > + ret = tree_mod_alloc(fs_info, GFP_ATOMIC, &tm); > if (ret < 0) > goto out; > > @@ -809,19 +809,18 @@ tree_mod_log_eb_move(struct btrfs_fs_info *fs_info, struct extent_buffer *dst, > { > int ret; > ret = tree_mod_log_insert_move(fs_info, dst, dst_offset, src_offset, > - nr_items, GFP_NOFS); > + nr_items); > BUG_ON(ret < 0); > } > > static noinline void > tree_mod_log_set_node_key(struct btrfs_fs_info *fs_info, > - struct extent_buffer *eb, int slot, int atomic) > + struct extent_buffer *eb, int slot) > { > int ret; > > ret = tree_mod_log_insert_key_mask(fs_info, eb, slot, > - MOD_LOG_KEY_REPLACE, > - atomic ? GFP_ATOMIC : GFP_NOFS); > + MOD_LOG_KEY_REPLACE); > BUG_ON(ret < 0); > } > > @@ -843,7 +842,7 @@ tree_mod_log_set_root_pointer(struct btrfs_root *root, > { > int ret; > ret = tree_mod_log_insert_root(root->fs_info, root->node, > - new_root_node, GFP_NOFS, log_removal); > + new_root_node, log_removal); > BUG_ON(ret < 0); > } > > @@ -1886,7 +1885,7 @@ static noinline int balance_level(struct btrfs_trans_handle *trans, > struct btrfs_disk_key right_key; > btrfs_node_key(right, &right_key, 0); > tree_mod_log_set_node_key(root->fs_info, parent, > - pslot + 1, 0); > + pslot + 1); > btrfs_set_node_key(parent, &right_key, pslot + 1); > btrfs_mark_buffer_dirty(parent); > } > @@ -1931,7 +1930,7 @@ static noinline int balance_level(struct btrfs_trans_handle *trans, > struct btrfs_disk_key mid_key; > btrfs_node_key(mid, &mid_key, 0); > tree_mod_log_set_node_key(root->fs_info, parent, > - pslot, 0); > + pslot); > btrfs_set_node_key(parent, &mid_key, pslot); > btrfs_mark_buffer_dirty(parent); > } > @@ -2030,7 +2029,7 @@ static noinline int push_nodes_for_insert(struct btrfs_trans_handle *trans, > orig_slot += left_nr; > btrfs_node_key(mid, &disk_key, 0); > tree_mod_log_set_node_key(root->fs_info, parent, > - pslot, 0); > + pslot); > btrfs_set_node_key(parent, &disk_key, pslot); > btrfs_mark_buffer_dirty(parent); > if (btrfs_header_nritems(left) > orig_slot) { > @@ -2083,7 +2082,7 @@ static noinline int push_nodes_for_insert(struct btrfs_trans_handle *trans, > > btrfs_node_key(right, &disk_key, 0); > tree_mod_log_set_node_key(root->fs_info, parent, > - pslot + 1, 0); > + pslot + 1); > btrfs_set_node_key(parent, &disk_key, pslot + 1); > btrfs_mark_buffer_dirty(parent); > > @@ -2963,7 +2962,7 @@ static void fixup_low_keys(struct btrfs_root *root, struct btrfs_path *path, > if (!path->nodes[i]) > break; > t = path->nodes[i]; > - tree_mod_log_set_node_key(root->fs_info, t, tslot, 1); > + tree_mod_log_set_node_key(root->fs_info, t, tslot); > btrfs_set_node_key(t, key, tslot); > btrfs_mark_buffer_dirty(path->nodes[i]); > if (tslot != 0) >