[PATCH 7/7] btrfs: Switch to page_mkwrite_check_truncate in btrfs_page_mkwrite

[Andreas Gruenbacher <agruenba@redhat.com>]

Use the "page has been truncated" logic in page_mkwrite_check_truncate
instead of reimplementing it here.

Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>
Acked-by: David Sterba <dsterba@suse.com>
---
 fs/btrfs/inode.c | 16 +++++-----------
 1 file changed, 5 insertions(+), 11 deletions(-)

diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index 5b3ec93ff911..532cc4aa9222 100644
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -8441,16 +8441,15 @@ vm_fault_t btrfs_page_mkwrite(struct vm_fault *vmf)
 		goto out_noreserve;
 	}
 
-	ret = VM_FAULT_NOPAGE; /* make the VM retry the fault */
 again:
 	lock_page(page);
-	size = i_size_read(inode);
 
-	if ((page->mapping != inode->i_mapping) ||
-	    (page_start >= size)) {
-		/* page got truncated out from underneath us */
+	ret2 = page_mkwrite_check_truncate(page, inode);
+	if (ret2 < 0) {
+		ret = block_page_mkwrite_return(ret2);
 		goto out_unlock;
 	}
+	zero_start = ret2;
 	wait_on_page_writeback(page);
 
 	lock_extent_bits(io_tree, page_start, page_end, &cached_state);
@@ -8471,6 +8470,7 @@ vm_fault_t btrfs_page_mkwrite(struct vm_fault *vmf)
 		goto again;
 	}
 
+	size = i_size_read(inode);
 	if (page->index == ((size - 1) >> PAGE_SHIFT)) {
 		reserved_space = round_up(size - page_start,
 					  fs_info->sectorsize);
@@ -8502,12 +8502,6 @@ vm_fault_t btrfs_page_mkwrite(struct vm_fault *vmf)
 		goto out_unlock;
 	}
 
-	/* page is wholly or partially inside EOF */
-	if (page_start + PAGE_SIZE > size)
-		zero_start = offset_in_page(size);
-	else
-		zero_start = PAGE_SIZE;
-
 	if (zero_start != PAGE_SIZE) {
 		kaddr = kmap(page);
 		memset(kaddr + zero_start, 0, PAGE_SIZE - zero_start);
-- 
2.24.1