[PATCH 1/1] mm/readahead: add kerneldoc for read_pages

[Frederick Mayle]

Formalize one of the invariants provided by the current implementation
so that callers can depend on it, as discussed in [1].

Link: https://lore.kernel.org/all/20260501061146.6e61392d125cf1847d7cc181@xxxxxxxxxxxxxxxxxxxx/ [1]
Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Frederick Mayle <fmayle@xxxxxxxxxx>
---
 mm/readahead.c | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/mm/readahead.c b/mm/readahead.c
index 8c12b63ccd4a..23bec5497308 100644
--- a/mm/readahead.c
+++ b/mm/readahead.c
@@ -146,6 +146,17 @@ file_ra_state_init(struct file_ra_state *ra, struct address_space *mapping)
 }
 EXPORT_SYMBOL_GPL(file_ra_state_init);
 
+/**
+ * read_pages() - Start IO for a contiguous range of allocated folios in the
+ *                page cache.
+ * @rac: Readahead control.
+ *
+ * When read_pages() returns, it is guaranteed that all of the folios will have
+ * been processed or removed so that ``readahead_count(rac) == 0``. However,
+ * that does not imply that ``readahead_index(rac)`` will be updated to point
+ * to the end of the originally requested range because, for example, the
+ * filesystem may expand the range upwards.
+ */
 static void read_pages(struct readahead_control *rac)
 {
 	const struct address_space_operations *aops = rac->mapping->a_ops;

base-commit: 2d565cbaafd43b10b75da56e43e5db9852a56afd
-- 
2.54.0.563.g4f69b47b94-goog