hulk inclusion category: bugfix bugzilla: https://gitee.com/openeuler/kernel/issues/I8EXN6 CVE: NA -------------------------------- If there are too many folios that are recently evicted in a file, then they will probably continue to be evicted. In such situation, there is no positive effect to read-ahead this file since it is only a waste of IO. The mmap_miss is increased in do_sync_mmap_readahead() and decreased in both do_async_mmap_readahead() and filemap_map_pages(). In order to skip read-ahead in above scenario, the mmap_miss have to increased exceed MMAP_LOTSAMISS. This can be done by stop decreased mmap_miss when folio has workingset flag. The async path is not to care because in above scenario, it's hard to run into the async path. Signed-off-by: Liu Shixin <liushixin2@huawei.com> Reviewed-by: Jan Kara <jack@suse.cz> --- mm/filemap.c | 9 ++++++++- 1 file changed, 8 insertions(+), 1 deletion(-) diff --git a/mm/filemap.c b/mm/filemap.c index 2eeb9978f39e..1cfcb82223fa 100644 --- a/mm/filemap.c +++ b/mm/filemap.c @@ -3168,7 +3168,14 @@ void filemap_map_pages(struct vm_fault *vmf, if (xas.xa_index >= max_idx) goto unlock; - if (mmap_miss > 0) + /* + * If there are too many folios that are recently evicted + * in a file, they will probably continue to be evicted. + * In such situation, read-ahead is only a waste of IO. + * Don't decrease mmap_miss in this scenario to make sure + * we can stop read-ahead. + */ + if (mmap_miss > 0 && !PageWorkingset(page)) mmap_miss--; vmf->address += (xas.xa_index - last_pgoff) << PAGE_SHIFT; -- 2.25.1