[PATCH 4/7] ext4: Switch to page_mkwrite_check_truncate in ext4_page_mkwrite

[Andreas Gruenbacher <agruenba@redhat.com>]

Use the "page has been truncated" logic in page_mkwrite_check_truncate
instead of reimplementing it here.  Other than with the existing code,
fail with -EFAULT / VM_FAULT_NOPAGE when page_offset(page) == size here
as well, as should be expected.

Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>
Acked-by: Theodore Ts'o <tytso@mit.edu>
---
 fs/ext4/inode.c | 15 ++++-----------
 1 file changed, 4 insertions(+), 11 deletions(-)

diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index 1305b810c44a..4e00a6014fb3 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -5902,13 +5902,11 @@ vm_fault_t ext4_page_mkwrite(struct vm_fault *vmf)
 {
 	struct vm_area_struct *vma = vmf->vma;
 	struct page *page = vmf->page;
-	loff_t size;
 	unsigned long len;
 	int err;
 	vm_fault_t ret;
 	struct file *file = vma->vm_file;
 	struct inode *inode = file_inode(file);
-	struct address_space *mapping = inode->i_mapping;
 	handle_t *handle;
 	get_block_t *get_block;
 	int retries = 0;
@@ -5938,18 +5936,13 @@ vm_fault_t ext4_page_mkwrite(struct vm_fault *vmf)
 	}
 
 	lock_page(page);
-	size = i_size_read(inode);
-	/* Page got truncated from under us? */
-	if (page->mapping != mapping || page_offset(page) > size) {
+	err = page_mkwrite_check_truncate(page, inode);
+	if (err < 0) {
 		unlock_page(page);
-		ret = VM_FAULT_NOPAGE;
-		goto out;
+		goto out_ret;
 	}
+	len = err;
 
-	if (page->index == size >> PAGE_SHIFT)
-		len = size & ~PAGE_MASK;
-	else
-		len = PAGE_SIZE;
 	/*
 	 * Return if we have all the buffers mapped. This avoids the need to do
 	 * journal_start/journal_stop which can block and take a long time
-- 
2.24.1