Hello Jan, > 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.
Anyway, your original code looks messy about passing arg gfp_t..isn't it? And you pass GFP_NOFS to a function, but in fact this function is surrounded by rw locks. I make it clear to the caller what kind of gfp_t we should pass(although now we always come to GFP_ATOMIC)... > > -Jan > > >> Signed-off-by: Wang Shilong <wangsl-f...@cn.fujitsu.com> >> --- >> 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) >> > > -- 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