[PATCH v4 06/11] filemap: cap PTE range to be created to i_size in folio_map_range()

[Pankaj Raghav (Samsung)]

From: Pankaj Raghav <p.raghav@xxxxxxxxxxx>

Usually the page cache does not extend beyond the size of the inode,
therefore, no PTEs are created for folios that extend beyond the size.

But with LBS support, we might extend page cache beyond the size of the
inode as we need to guarantee folios of minimum order. Cap the PTE range
to be created for the page cache by i_size.

A fstest has been created to trigger this edge case[1].

[1]https://lore.kernel.org/fstests/20240415081054.1782715-1-mcgrof@xxxxxxxxxx/

Signed-off-by: Pankaj Raghav <p.raghav@xxxxxxxxxxx>
Co-Developed-by: Luis Chamberlain <mcgrof@xxxxxxxxxx>
Signed-off-by: Luis Chamberlain <mcgrof@xxxxxxxxxx>
---
 mm/filemap.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/mm/filemap.c b/mm/filemap.c
index f0c0cfbbd134..259531dd297b 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -3600,12 +3600,15 @@ vm_fault_t filemap_map_pages(struct vm_fault *vmf,
 	}
 	do {
 		unsigned long end;
+		unsigned long i_size;
 
 		addr += (xas.xa_index - last_pgoff) << PAGE_SHIFT;
 		vmf->pte += xas.xa_index - last_pgoff;
 		last_pgoff = xas.xa_index;
 		end = folio_next_index(folio) - 1;
-		nr_pages = min(end, end_pgoff) - xas.xa_index + 1;
+		i_size = DIV_ROUND_UP(i_size_read(mapping->host),
+				      PAGE_SIZE) - 1;
+		nr_pages = min3(end, end_pgoff, i_size) - xas.xa_index + 1;
 
 		if (!folio_test_large(folio))
 			ret |= filemap_map_order0_folio(vmf,
-- 
2.34.1