From: Liam R. Howlett Date: Tue, 24 Jun 2025 15:48:22 +0000 (-0400) Subject: maple_tree: fix status setup on restore to active X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=12f1d7931283106306a8822c5279013b8a0f1242;p=thirdparty%2Flinux.git maple_tree: fix status setup on restore to active During the initial call with a maple state, an error status may be set before a valid node is populated into the maple state node. Subsequent calls with the maple state may restore the state into an active state with no node set. This was masked by the mas_walk() always resetting the status to ma_start and result in an extra walk in this rare scenario. Don't restore the state to active unless there is a value in the structs node. This also allows mas_walk() to be fixed to use the active state without exposing an issue. User visible results are marginal performance improvements when an active state can be restored and used instead of rewalking the tree. Stable is not Cc'ed because the existing code is stable and the performance gains are not worth the risk. Link: https://lore.kernel.org/all/20250611011253.19515-1-richard.weiyang@gmail.com/ Link: https://lore.kernel.org/all/20250407231354.11771-1-richard.weiyang@gmail.com/ Link: https://lore.kernel.org/all/202506191556.6bfc7b93-lkp@intel.com/ Link: https://lkml.kernel.org/r/20250624154823.52221-1-Liam.Howlett@oracle.com Fixes: a8091f039c1e ("maple_tree: add MAS_UNDERFLOW and MAS_OVERFLOW states") Signed-off-by: Liam R. Howlett Reported-by: Wei Yang Reported-by: kernel test robot Closes: https://lore.kernel.org/oe-lkp/202506191556.6bfc7b93-lkp@intel.com Reviewed-by: Wei Yang Signed-off-by: Andrew Morton --- diff --git a/lib/maple_tree.c b/lib/maple_tree.c index 34b84b14985ea..7601c7c2bc096 100644 --- a/lib/maple_tree.c +++ b/lib/maple_tree.c @@ -4927,7 +4927,7 @@ void *mas_walk(struct ma_state *mas) { void *entry; - if (!mas_is_active(mas) || !mas_is_start(mas)) + if (!mas_is_active(mas) && !mas_is_start(mas)) mas->status = ma_start; retry: entry = mas_state_walk(mas); @@ -5655,6 +5655,17 @@ int mas_expected_entries(struct ma_state *mas, unsigned long nr_entries) } EXPORT_SYMBOL_GPL(mas_expected_entries); +static void mas_may_activate(struct ma_state *mas) +{ + if (!mas->node) { + mas->status = ma_start; + } else if (mas->index > mas->max || mas->index < mas->min) { + mas->status = ma_start; + } else { + mas->status = ma_active; + } +} + static bool mas_next_setup(struct ma_state *mas, unsigned long max, void **entry) { @@ -5678,11 +5689,11 @@ static bool mas_next_setup(struct ma_state *mas, unsigned long max, break; case ma_overflow: /* Overflowed before, but the max changed */ - mas->status = ma_active; + mas_may_activate(mas); break; case ma_underflow: /* The user expects the mas to be one before where it is */ - mas->status = ma_active; + mas_may_activate(mas); *entry = mas_walk(mas); if (*entry) return true; @@ -5803,11 +5814,11 @@ static bool mas_prev_setup(struct ma_state *mas, unsigned long min, void **entry break; case ma_underflow: /* underflowed before but the min changed */ - mas->status = ma_active; + mas_may_activate(mas); break; case ma_overflow: /* User expects mas to be one after where it is */ - mas->status = ma_active; + mas_may_activate(mas); *entry = mas_walk(mas); if (*entry) return true; @@ -5972,7 +5983,7 @@ static __always_inline bool mas_find_setup(struct ma_state *mas, unsigned long m return true; } - mas->status = ma_active; + mas_may_activate(mas); *entry = mas_walk(mas); if (*entry) return true; @@ -5981,7 +5992,7 @@ static __always_inline bool mas_find_setup(struct ma_state *mas, unsigned long m if (unlikely(mas->last >= max)) return true; - mas->status = ma_active; + mas_may_activate(mas); *entry = mas_walk(mas); if (*entry) return true;