[PATCHv1, RFC 23/33] fs: make block_page_mkwrite() aware about huge pages

["Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>]

Adjust check on whether part of the page beyond file size and apply
compound_head() and page_mapping() where appropriate.

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
---
 fs/buffer.c | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/fs/buffer.c b/fs/buffer.c
index edd0971f9f95..2e25d0e7a233 100644
--- a/fs/buffer.c
+++ b/fs/buffer.c
@@ -2502,7 +2502,7 @@ EXPORT_SYMBOL(block_commit_write);
 int block_page_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf,
 			 get_block_t get_block)
 {
-	struct page *page = vmf->page;
+	struct page *page = compound_head(vmf->page);
 	struct inode *inode = file_inode(vma->vm_file);
 	unsigned long end;
 	loff_t size;
@@ -2510,7 +2510,7 @@ int block_page_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf,
 
 	lock_page(page);
 	size = i_size_read(inode);
-	if ((page->mapping != inode->i_mapping) ||
+	if ((page_mapping(page) != inode->i_mapping) ||
 	    (page_offset(page) > size)) {
 		/* We overload EFAULT to mean page got truncated */
 		ret = -EFAULT;
@@ -2518,10 +2518,10 @@ int block_page_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf,
 	}
 
 	/* page is wholly or partially inside EOF */
-	if (((page->index + 1) << PAGE_SHIFT) > size)
-		end = size & ~PAGE_MASK;
+	if (((page->index + hpage_nr_pages(page)) << PAGE_SHIFT) > size)
+		end = size & ~hpage_mask(page);
 	else
-		end = PAGE_SIZE;
+		end = hpage_size(page);
 
 	ret = __block_write_begin(page, 0, end, get_block);
 	if (!ret)
-- 
2.8.1

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