> * Jaeseon Sim <jason.sim@xxxxxxxxxxx> [230907 00:41]: > > > On Thu, Sep 07, 2023 at 12:02:02PM +0800, Peng Zhang wrote: > > > > > > > > > > > > 在 2023/9/7 11:49, Matthew Wilcox 写道: > > > > > On Thu, Sep 07, 2023 at 12:39:14PM +0900, 심재선 wrote: > > > > > > Use GFP_KERNEL on mas_node_count instead of GFP_NOWAIT | __GFP_NOWARN > > > > > > in order to allow memory reclaim. > > > > There are many paths that call maple tree's mas_node_count(). Some paths > > > > cannot reclaim memory. > > > > > > Right ... but we should be handling the ENOMEM inside the maple tree and > > > allocating some nodes with GFP_KERNEL instead of failing fork(). > > > > > > > > What testing did you do of this patch? In particular, did you try it > > > > > with lockdep enabled? > > I did power on/off test with this patch. > > I did not try it with lockdep enabled. > > To accomplish the same result, but with a much smaller scope that will > work with lockdep, I would suggest changing mas_expected_entries() to > use mas_node_count_gfp() (which already exists) and pass in GFP_KERNEL. > > Since fork is the only current user of mas_expected_entries(), this > won't break other users and we can deal with changing it for others if > it is needed. > > If we do go this route, please add a note in the documentation about > using GFP_KERNEL. > > Willy, does that work for you? > > Thanks, > Liam Dear Liam, Can I ask you the reason why mas_node_count is using GFP_NOWAIT | __GFP_NOWARN? I wonder if other callers for mas_node_count might have similar issue. >From your opinion, I'll post v2 patch as follows diff --git a/lib/maple_tree.c b/lib/maple_tree.c index ee1ff0c59fd7..b0229271c24e 100644 --- a/lib/maple_tree.c +++ b/lib/maple_tree.c @@ -5574,7 +5574,7 @@ int mas_expected_entries(struct ma_state *mas, unsigned long nr_entries) /* Internal nodes */ nr_nodes += DIV_ROUND_UP(nr_nodes, nonleaf_cap); /* Add working room for split (2 nodes) + new parents */ - mas_node_count(mas, nr_nodes + 3); + mas_node_count_gfp(mas, nr_nodes + 3, GFP_KERNEL); /* Detect if allocations run out */ mas->mas_flags |= MA_STATE_PREALLOC; -- 2.17.1 Thanks Jaeseon
