When allocating an area from a chunk, pcpu_block_update_hint_alloc() is called to update chunk metadata, including chunk's and global nr_empty_pop_pages. However, if the allocation is not atomic, some blocks may not be populated with pages yet, while we still account it here. The number of pages will be subtracted with pcpu_chunk_populated() when populating pages. Adding code comment to make that more understandable. Signed-off-by: Baoquan He <bhe@xxxxxxxxxx> --- mm/percpu.c | 14 +++++++++++--- 1 file changed, 11 insertions(+), 3 deletions(-) diff --git a/mm/percpu.c b/mm/percpu.c index a8121302a79c..09e407338573 100644 --- a/mm/percpu.c +++ b/mm/percpu.c @@ -831,13 +831,15 @@ static void pcpu_block_update_hint_alloc(struct pcpu_chunk *chunk, int bit_off, /* * Update s_block. - * block->first_free must be updated if the allocation takes its place. - * If the allocation breaks the contig_hint, a scan is required to - * restore this hint. */ if (s_block->contig_hint == PCPU_BITMAP_BLOCK_BITS) nr_empty_pages++; + /* + * block->first_free must be updated if the allocation takes its place. + * If the allocation breaks the contig_hint, a scan is required to + * restore this hint. + */ if (s_off == s_block->first_free) s_block->first_free = find_next_zero_bit( pcpu_index_alloc_map(chunk, s_index), @@ -912,6 +914,12 @@ static void pcpu_block_update_hint_alloc(struct pcpu_chunk *chunk, int bit_off, } } + /* + * If the allocation is not atomic, some blocks may not + * be populated with pages, while we account it here. + * The number of pages will be subtracted with + * pcpu_chunk_populated() when populating pages. + */ if (nr_empty_pages) pcpu_update_empty_pages(chunk, -nr_empty_pages); -- 2.34.1
