[PATCH 09/26] mm: Make readahead store folio count in readahead_control

David Howells
2026-03-26T10:47:32Z

Make readahead store folio count in readahead_control so that the
filesystem can know in advance how many folios it needs to keep track of.

Signed-off-by: David Howells <dhowells@redhat.com>
cc: Paulo Alcantara <pc@manguebit.org>
cc: Matthew Wilcox <willy@infradead.org>
cc: netfs@lists.linux.dev
cc: linux-mm@kvack.org
cc: linux-fsdevel@vger.kernel.org
---
include/linux/pagemap.h | 1 +
mm/readahead.c | 4 ++++
2 files changed, 5 insertions(+)

diff --git a/include/linux/pagemap.h b/include/linux/pagemap.h
index ec442af3f886..3c3e34e5fe8a 100644
--- a/include/linux/pagemap.h
+++ b/include/linux/pagemap.h
@@ -1361,6 +1361,7 @@ struct readahead_control {
struct file_ra_state *ra;
/* private: use the readahead_* accessors instead */
pgoff_t _index;
+ unsigned int _nr_folios;
unsigned int _nr_pages;
unsigned int _batch_count;
bool dropbehind;
diff --git a/mm/readahead.c b/mm/readahead.c
index 7b05082c89ea..53134c9d9fe9 100644
--- a/mm/readahead.c
+++ b/mm/readahead.c
@@ -292,6 +292,7 @@ void page_cache_ra_unbounded(struct readahead_control *ractl,
if (i == mark)
folio_set_readahead(folio);
ractl->_workingset |= folio_test_workingset(folio);
+ ractl->_nr_folios++;
ractl->_nr_pages += min_nrpages;
i += min_nrpages;
}
@@ -459,6 +460,7 @@ static inline int ra_alloc_folio(struct readahead_control *ractl, pgoff_t index,
return err;
}

+ ractl->_nr_folios++;
ractl->_nr_pages += 1UL << order;
ractl->_workingset |= folio_test_workingset(folio);
return 0;
@@ -802,6 +804,7 @@ void readahead_expand(struct readahead_control *ractl,
ractl->_workingset = true;
psi_memstall_enter(&ractl->_pflags);
}
+ ractl->_nr_folios++;
ractl->_nr_pages += min_nrpages;
ractl->_index = folio->index;
}
@@ -831,6 +834,7 @@ void readahead_expand(struct readahead_control *ractl,
ractl->_workingset = true;
psi_memstall_enter(&ractl->_pflags);
}
+ ractl->_nr_folios++;
ractl->_nr_pages += min_nrpages;
if (ra) {
ra->size += min_nrpages;