From: Pankaj Raghav p.raghav@samsung.com
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. While doing a read, do_fault_around() can create PTEs for pages that lie beyond the EOF leading to incorrect error return when accessing a page beyond the mapped file.
Cap the PTE range to be created for the page cache up to the end of file(EOF) in filemap_map_pages() so that return error codes are consistent with POSIX[1] for LBS configurations.
generic/749 has been created to trigger this edge case. This also fixes generic/749 for tmpfs with huge=always on systems with 4k base page size.
[1](from mmap(2)) SIGBUS Attempted access to a page of the buffer that lies beyond the end of the mapped file. For an explanation of the treatment of the bytes in the page that corresponds to the end of a mapped file that is not a multiple of the page size, see NOTES.
Signed-off-by: Luis Chamberlain mcgrof@kernel.org Signed-off-by: Pankaj Raghav p.raghav@samsung.com Link: https://lore.kernel.org/r/20240822135018.1931258-6-kernel@pankajraghav.com Tested-by: David Howells dhowells@redhat.com Acked-by: Darrick J. Wong djwong@kernel.org Reviewed-by: Hannes Reinecke hare@suse.de Reviewed-by: Matthew Wilcox (Oracle) willy@infradead.org Reviewed-by: Darrick J. Wong djwong@kernel.org Reviewed-by: Daniel Gomez da.gomez@samsung.com Reviewed-by: Dave Chinner dchinner@redhat.com Signed-off-by: Christian Brauner brauner@kernel.org (cherry picked from commit 743a2753a02e805347969f6f89f38b736850d808) Signed-off-by: Kiryl Shutsemau kas@kernel.org --- mm/filemap.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-)
diff --git a/mm/filemap.c b/mm/filemap.c index ab24dbf5e747..7d4d3bea4e1e 100644 --- a/mm/filemap.c +++ b/mm/filemap.c @@ -3608,7 +3608,7 @@ vm_fault_t filemap_map_pages(struct vm_fault *vmf, struct vm_area_struct *vma = vmf->vma; struct file *file = vma->vm_file; struct address_space *mapping = file->f_mapping; - pgoff_t last_pgoff = start_pgoff; + pgoff_t file_end, last_pgoff = start_pgoff; unsigned long addr; XA_STATE(xas, &mapping->i_pages, start_pgoff); struct folio *folio; @@ -3632,6 +3632,11 @@ vm_fault_t filemap_map_pages(struct vm_fault *vmf, folio_put(folio); goto out; } + + file_end = DIV_ROUND_UP(i_size_read(mapping->host), PAGE_SIZE) - 1; + if (end_pgoff > file_end) + end_pgoff = file_end; + do { unsigned long end;