On Mon, Nov 02, 2020 at 06:43:06PM +0000, Matthew Wilcox (Oracle) wrote:
> Move the complicated condition and the calculations out of
> filemap_update_page() into its own function.
The logic looks good, but the flow inside of filemap_update_page looks
odd. The patch below relative to this commit shows how I'd do it:
diff --git a/mm/filemap.c b/mm/filemap.c
index 81b569d818a3f8..304180c022d38a 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -2266,40 +2266,39 @@ static int filemap_update_page(struct kiocb *iocb,
if (!trylock_page(page)) {
if (iocb->ki_flags & (IOCB_NOWAIT | IOCB_NOIO))
goto error;
- if (iocb->ki_flags & IOCB_WAITQ) {
- if (!first)
- goto error;
- error = __lock_page_async(page, iocb->ki_waitq);
- if (error)
- goto error;
- } else {
+ if (!(iocb->ki_flags & IOCB_WAITQ)) {
put_and_wait_on_page_locked(page, TASK_KILLABLE);
return AOP_TRUNCATED_PAGE;
}
+ if (!first)
+ goto error;
+ error = __lock_page_async(page, iocb->ki_waitq);
+ if (error)
+ goto error;
}
+ error = AOP_TRUNCATED_PAGE;
if (!page->mapping)
- goto truncated;
- if (filemap_range_uptodate(iocb, mapping, iter, page)) {
- unlock_page(page);
- return 0;
- }
+ goto error_unlock_page;
- if (iocb->ki_flags & (IOCB_NOIO | IOCB_NOWAIT | IOCB_WAITQ)) {
- unlock_page(page);
+ if (!filemap_range_uptodate(iocb, mapping, iter, page)) {
error = -EAGAIN;
- } else {
+ if (iocb->ki_flags & (IOCB_NOIO | IOCB_NOWAIT | IOCB_WAITQ))
+ goto error_unlock_page;
error = filemap_read_page(iocb->ki_filp, mapping, page);
- if (!error)
- return 0;
+ if (error)
+ goto error;
+ return 0; /* filemap_read_page unlocks the page */
}
+
+ unlock_page(page);
+ return 0;
+
+error_unlock_page:
+ unlock_page(page);
error:
put_page(page);
return error;
-truncated:
- unlock_page(page);
- put_page(page);
- return AOP_TRUNCATED_PAGE;
}
static struct page *filemap_create_page(struct file *file,
