diff mbox series

[v2,35/46] mm/filemap: Add folio_mkwrite_check_truncate()

Message ID 20210622121551.3398730-36-willy@infradead.org (mailing list archive)
State New, archived
Headers show
Series Folio-enabling the page cache | expand

Commit Message

Matthew Wilcox June 22, 2021, 12:15 p.m. UTC 
This is the folio equivalent of page_mkwrite_check_truncate().

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
---
 include/linux/pagemap.h | 28 ++++++++++++++++++++++++++++
 1 file changed, 28 insertions(+)

Comments

Christoph Hellwig June 23, 2021, 9:47 a.m. UTC | #1 
On Tue, Jun 22, 2021 at 01:15:40PM +0100, Matthew Wilcox (Oracle) wrote:
> This is the folio equivalent of page_mkwrite_check_truncate().
> 
> Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>

Any reason that page_mkwrite_check_truncate isn't turned into a wrapper?
Matthew Wilcox June 23, 2021, 1:19 p.m. UTC | #2 
On Wed, Jun 23, 2021 at 11:47:58AM +0200, Christoph Hellwig wrote:
> On Tue, Jun 22, 2021 at 01:15:40PM +0100, Matthew Wilcox (Oracle) wrote:
> > This is the folio equivalent of page_mkwrite_check_truncate().
> > 
> > Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
> 
> Any reason that page_mkwrite_check_truncate isn't turned into a wrapper?

It'd introduce an extra call to page_folio() for no actual benefit
diff mbox series

Patch

diff --git a/include/linux/pagemap.h b/include/linux/pagemap.h
index c30db827b65d..14f0c5260234 100644
--- a/include/linux/pagemap.h
+++ b/include/linux/pagemap.h
@@ -1120,6 +1120,34 @@  static inline unsigned long dir_pages(struct inode *inode)
 			       PAGE_SHIFT;
 }
 
+/**
+ * folio_mkwrite_check_truncate - check if folio was truncated
+ * @folio: the folio to check
+ * @inode: the inode to check the folio against
+ *
+ * Return: the number of bytes in the folio up to EOF,
+ * or -EFAULT if the folio was truncated.
+ */
+static inline ssize_t folio_mkwrite_check_truncate(struct folio *folio,
+					      struct inode *inode)
+{
+	loff_t size = i_size_read(inode);
+	pgoff_t index = size >> PAGE_SHIFT;
+	size_t offset = offset_in_folio(folio, size);
+
+	if (!folio->mapping)
+		return -EFAULT;
+
+	/* folio is wholly inside EOF */
+	if (folio_next_index(folio) - 1 < index)
+		return folio_size(folio);
+	/* folio is wholly past EOF */
+	if (folio->index > index || !offset)
+		return -EFAULT;
+	/* folio is partially inside EOF */
+	return offset;
+}
+
 /**
  * page_mkwrite_check_truncate - check if page was truncated
  * @page: the page to check