[PATCH 1/7] filemap: Export filemap_invalidate_pages() to modules

["Matthew Wilcox (Oracle)" <willy@infradead.org>]

This is a better API for filesystems to use than
invalidate_inode_pages2() / invalidate_inode_pages2_range().
However, the 'nowait' argument is unnecessary for them.  It's also
wrongly implemented as it will call invalidate_inode_pages2_range()
even after filemap_range_has_page() returns false.

Move the filemap_range_has_page() call into the two existing callers
and add kernel-doc.

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
---
 block/ioctl.c           | 14 ++++++++++----
 include/linux/pagemap.h |  2 +-
 mm/filemap.c            | 42 +++++++++++++++++++++++++++--------------
 3 files changed, 39 insertions(+), 19 deletions(-)

diff --git a/block/ioctl.c b/block/ioctl.c
index 3d4ea1537457..db5238b817b4 100644
--- a/block/ioctl.c
+++ b/block/ioctl.c
@@ -908,10 +908,16 @@ static int blkdev_cmd_discard(struct io_uring_cmd *cmd,
 	if (err)
 		return err;
 
-	err = filemap_invalidate_pages(bdev->bd_mapping, start,
-					start + len - 1, nowait);
-	if (err)
-		return err;
+	if (nowait) {
+		if (filemap_range_has_page(bdev->bd_mapping, start,
+					start + len - 1))
+			return -EAGAIN;
+	} else {
+		err = filemap_invalidate_pages(bdev->bd_mapping, start,
+					start + len - 1);
+		if (err)
+			return err;
+	}
 
 	while (true) {
 		bio = blk_alloc_discard_bio(bdev, &sector, &nr_sects, gfp);
diff --git a/include/linux/pagemap.h b/include/linux/pagemap.h
index 2c3718d592d6..ed99c8ab196a 100644
--- a/include/linux/pagemap.h
+++ b/include/linux/pagemap.h
@@ -33,7 +33,7 @@ int invalidate_inode_pages2_range(struct address_space *mapping,
 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);
+		loff_t pos, loff_t end);
 
 int write_inode_now(struct inode *, int sync);
 int filemap_fdatawrite(struct address_space *);
diff --git a/mm/filemap.c b/mm/filemap.c
index d721986d5f46..fedb521d773f 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -2911,20 +2911,27 @@ int kiocb_write_and_wait(struct kiocb *iocb, size_t count)
 }
 EXPORT_SYMBOL_GPL(kiocb_write_and_wait);
 
+/**
+ * filemap_invalidate_pages - Invalidate pages from the page cache
+ * @mapping: Address space to invalidate
+ * @pos: First byte to invalidate
+ * @end: Last byte (inclusive) to invalidate
+ *
+ * Invalidates the folios containing @pos and @end from the page cache
+ * (as well as all folios between them), so may remove more pages from
+ * the page cache than you ask for.
+ *
+ * Context: May sleep.  Caller may wish to hold mapping_invalidate_lock to
+ * prevent new pages being instantiated in this range.
+ * Return: 0 on success or negative errno.
+ */
 int filemap_invalidate_pages(struct address_space *mapping,
-			     loff_t pos, loff_t end, bool nowait)
+		loff_t pos, loff_t end)
 {
-	int ret;
+	int ret = filemap_write_and_wait_range(mapping, pos, end);
 
-	if (nowait) {
-		/* we could block if there are any pages in the range */
-		if (filemap_range_has_page(mapping, pos, end))
-			return -EAGAIN;
-	} else {
-		ret = filemap_write_and_wait_range(mapping, pos, end);
-		if (ret)
-			return ret;
-	}
+	if (ret)
+		return ret;
 
 	/*
 	 * After a write we want buffered reads to be sure to go to disk to get
@@ -2935,14 +2942,21 @@ int filemap_invalidate_pages(struct address_space *mapping,
 	return invalidate_inode_pages2_range(mapping, pos >> PAGE_SHIFT,
 					     end >> PAGE_SHIFT);
 }
+EXPORT_SYMBOL_GPL(filemap_invalidate_pages);
 
 int kiocb_invalidate_pages(struct kiocb *iocb, size_t count)
 {
 	struct address_space *mapping = iocb->ki_filp->f_mapping;
+	loff_t end = iocb->ki_pos + count - 1;
+
+	if (iocb->ki_flags & IOCB_NOWAIT) {
+		/* we could block if there are any pages in the range */
+		if (filemap_range_has_page(mapping, iocb->ki_pos, end))
+			return -EAGAIN;
+		return 0;
+	}
 
-	return filemap_invalidate_pages(mapping, iocb->ki_pos,
-					iocb->ki_pos + count - 1,
-					iocb->ki_flags & IOCB_NOWAIT);
+	return filemap_invalidate_pages(mapping, iocb->ki_pos, end);
 }
 EXPORT_SYMBOL_GPL(kiocb_invalidate_pages);
 
-- 
2.47.3