If the page is pinned, there's no point in trying to reclaim it. Furthermore if the page is from the page cache we don't want to reclaim fs-private data from the page because the pinning process may be writing to the page at any time and reclaiming fs private info on a dirty page can upset the filesystem (see link below). Link: https://lore.kernel.org/linux-mm/20180103100430.GE4911@xxxxxxxxxxxxxx Signed-off-by: Jan Kara <jack@xxxxxxx> --- mm/vmscan.c | 10 ++++++++++ 1 file changed, 10 insertions(+) This was the non-controversial part of my series [1] dealing with pinned pages in filesystems. It is already a win as it avoids crashes in the filesystem and we can drop workarounds for this in ext4. Can we merge it please? [1] https://lore.kernel.org/all/20230209121046.25360-1-jack@xxxxxxx/ diff --git a/mm/vmscan.c b/mm/vmscan.c index bf3eedf0209c..401a379ea99a 100644 --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -1901,6 +1901,16 @@ static unsigned int shrink_folio_list(struct list_head *folio_list, } } + /* + * Folio is unmapped now so it cannot be newly pinned anymore. + * No point in trying to reclaim folio if it is pinned. + * Furthermore we don't want to reclaim underlying fs metadata + * if the folio is pinned and thus potentially modified by the + * pinning process as that may upset the filesystem. + */ + if (folio_maybe_dma_pinned(folio)) + goto activate_locked; + mapping = folio_mapping(folio); if (folio_test_dirty(folio)) { /* -- 2.35.3
