filemap: introduce filemap_invalidate_pages

kiocb_invalidate_pages() is useful for the write path, however not
everything is backed by kiocb and we want to reuse the function for bio
based discard implementation. Extract and and reuse a new helper called
filemap_invalidate_pages(), which takes a argument indicating whether it
should be non-blocking and might return -EAGAIN.
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/f81374b52c92d0dce0f01a279d1eed42b54056aa.1726072086.git.asml.silence@gmail.comSigned-off-by: Jens Axboe <axboe@kernel.dk>

include/linux/pagemap.h

@@ -32,6 +32,8 @@ int invalidate_inode_pages2_range(struct address_space *mapping,
 		pgoff_t start, pgoff_t end);
 int kiocb_invalidate_pages(struct kiocb *iocb, size_t count);
 void kiocb_invalidate_post_direct_write(struct kiocb *iocb, size_t count);
+int filemap_invalidate_pages(struct address_space *mapping,
+			     loff_t pos, loff_t end, bool nowait);
 
 int write_inode_now(struct inode *, int sync);
 int filemap_fdatawrite(struct address_space *);

mm/filemap.c

@@ -2712,14 +2712,12 @@ int kiocb_write_and_wait(struct kiocb *iocb, size_t count)
 }
 EXPORT_SYMBOL_GPL(kiocb_write_and_wait);
 
-int kiocb_invalidate_pages(struct kiocb *iocb, size_t count)
+int filemap_invalidate_pages(struct address_space *mapping,
+			     loff_t pos, loff_t end, bool nowait)
 {
-	struct address_space *mapping = iocb->ki_filp->f_mapping;
-	loff_t pos = iocb->ki_pos;
-	loff_t end = pos + count - 1;
 	int ret;
 
-	if (iocb->ki_flags & IOCB_NOWAIT) {
+	if (nowait) {
 		/* we could block if there are any pages in the range */
 		if (filemap_range_has_page(mapping, pos, end))
 			return -EAGAIN;
@@ -2738,6 +2736,15 @@ int kiocb_invalidate_pages(struct kiocb *iocb, size_t count)
 	return invalidate_inode_pages2_range(mapping, pos >> PAGE_SHIFT,
 					     end >> PAGE_SHIFT);
 }
+
+int kiocb_invalidate_pages(struct kiocb *iocb, size_t count)
+{
+	struct address_space *mapping = iocb->ki_filp->f_mapping;
+
+	return filemap_invalidate_pages(mapping, iocb->ki_pos,
+					iocb->ki_pos + count - 1,
+					iocb->ki_flags & IOCB_NOWAIT);
+}
 EXPORT_SYMBOL_GPL(kiocb_invalidate_pages);
 
 /**