diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index 56032c518b26..86c6fcd8139d 100644
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -9016,13 +9016,11 @@ vm_fault_t btrfs_page_mkwrite(struct vm_fault *vmf)
 	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)
 		goto out_unlock;
-	}
+	zero_start = ret2;
 	wait_on_page_writeback(page);
 
 	lock_extent_bits(io_tree, page_start, page_end, &cached_state);
@@ -9043,6 +9041,7 @@ 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);
@@ -9075,12 +9074,6 @@ vm_fault_t btrfs_page_mkwrite(struct vm_fault *vmf)
 	}
 	ret2 = 0;
 
-	/* 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);
diff --git a/fs/buffer.c b/fs/buffer.c
index d8c7242426bb..53aabde57ca7 100644
--- a/fs/buffer.c
+++ b/fs/buffer.c
@@ -2499,23 +2499,13 @@ int block_page_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf,
 	struct page *page = vmf->page;
 	struct inode *inode = file_inode(vma->vm_file);
 	unsigned long end;
-	loff_t size;
 	int ret;
 
 	lock_page(page);
-	size = i_size_read(inode);
-	if ((page->mapping != inode->i_mapping) ||
-	    (page_offset(page) > size)) {
-		/* We overload EFAULT to mean page got truncated */
-		ret = -EFAULT;
+	ret = page_mkwrite_check_truncate(page, inode);
+	if (ret < 0)
 		goto out_unlock;
-	}
-
-	/* page is wholly or partially inside EOF */
-	if (((page->index + 1) << PAGE_SHIFT) > size)
-		end = size & ~PAGE_MASK;
-	else
-		end = PAGE_SIZE;
+	end = ret;
 
 	ret = __block_write_begin(page, 0, end, get_block);
 	if (!ret)
diff --git a/fs/ceph/addr.c b/fs/ceph/addr.c
index 7ab616601141..ef958aa4adb4 100644
--- a/fs/ceph/addr.c
+++ b/fs/ceph/addr.c
@@ -1575,7 +1575,7 @@ static vm_fault_t ceph_page_mkwrite(struct vm_fault *vmf)
 	do {
 		lock_page(page);
 
-		if ((off > size) || (page->mapping != inode->i_mapping)) {
+		if (page_mkwrite_check_truncate(page, inode) < 0) {
 			unlock_page(page);
 			ret = VM_FAULT_NOPAGE;
 			break;
diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index 28f28de0c1b6..51ab1d2cac80 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -5871,7 +5871,6 @@ 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;
@@ -5907,18 +5906,13 @@ 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
diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c
index 85af112e868d..0e77b2e6f873 100644
--- a/fs/f2fs/file.c
+++ b/fs/f2fs/file.c
@@ -51,7 +51,7 @@ static vm_fault_t f2fs_vm_page_mkwrite(struct vm_fault *vmf)
 	struct inode *inode = file_inode(vmf->vma->vm_file);
 	struct f2fs_sb_info *sbi = F2FS_I_SB(inode);
 	struct dnode_of_data dn = { .node_changed = false };
-	int err;
+	int offset, err;
 
 	if (unlikely(f2fs_cp_error(sbi))) {
 		err = -EIO;
@@ -70,13 +70,14 @@ static vm_fault_t f2fs_vm_page_mkwrite(struct vm_fault *vmf)
 	file_update_time(vmf->vma->vm_file);
 	down_read(&F2FS_I(inode)->i_mmap_sem);
 	lock_page(page);
-	if (unlikely(page->mapping != inode->i_mapping ||
-			page_offset(page) > i_size_read(inode) ||
-			!PageUptodate(page))) {
+	err = -EFAULT;
+	if (likely(PageUptodate(page)))
+		err = page_mkwrite_check_truncate(page, inode);
+	if (unlikely(err < 0)) {
 		unlock_page(page);
-		err = -EFAULT;
 		goto out_sem;
 	}
+	offset = err;
 
 	/* block allocation */
 	__do_map_lock(sbi, F2FS_GET_BLOCK_PRE_AIO, true);
@@ -101,14 +102,8 @@ static vm_fault_t f2fs_vm_page_mkwrite(struct vm_fault *vmf)
 	if (PageMappedToDisk(page))
 		goto out_sem;
 
-	/* page is wholly or partially inside EOF */
-	if (((loff_t)(page->index + 1) << PAGE_SHIFT) >
-						i_size_read(inode)) {
-		loff_t offset;
-
-		offset = i_size_read(inode) & ~PAGE_MASK;
+	if (offset != PAGE_SIZE)
 		zero_user_segment(page, offset, PAGE_SIZE);
-	}
 	set_page_dirty(page);
 	if (!PageUptodate(page))
 		SetPageUptodate(page);
diff --git a/fs/iomap/buffered-io.c b/fs/iomap/buffered-io.c
index d33c7bc5ee92..1aaf157fd6e9 100644
--- a/fs/iomap/buffered-io.c
+++ b/fs/iomap/buffered-io.c
@@ -1062,24 +1062,16 @@ vm_fault_t iomap_page_mkwrite(struct vm_fault *vmf, const struct iomap_ops *ops)
 	struct page *page = vmf->page;
 	struct inode *inode = file_inode(vmf->vma->vm_file);
 	unsigned long length;
-	loff_t offset, size;
+	loff_t offset;
 	ssize_t ret;
 
 	lock_page(page);
-	size = i_size_read(inode);
-	offset = page_offset(page);
-	if (page->mapping != inode->i_mapping || offset > size) {
-		/* We overload EFAULT to mean page got truncated */
-		ret = -EFAULT;
+	ret = page_mkwrite_check_truncate(page, inode);
+	if (ret < 0)
 		goto out_unlock;
-	}
-
-	/* page is wholly or partially inside EOF */
-	if (offset > size - PAGE_SIZE)
-		length = offset_in_page(size);
-	else
-		length = PAGE_SIZE;
+	length = ret;
 
+	offset = page_offset(page);
 	while (length > 0) {
 		ret = iomap_apply(inode, offset, length,
 				IOMAP_WRITE | IOMAP_FAULT, ops, page,
diff --git a/fs/ubifs/file.c b/fs/ubifs/file.c
index cd52585c8f4f..91f7a1f2db0d 100644
--- a/fs/ubifs/file.c
+++ b/fs/ubifs/file.c
@@ -1563,8 +1563,7 @@ static vm_fault_t ubifs_vm_page_mkwrite(struct vm_fault *vmf)
 	}
 
 	lock_page(page);
-	if (unlikely(page->mapping != inode->i_mapping ||
-		     page_offset(page) > i_size_read(inode))) {
+	if (unlikely(page_mkwrite_check_truncate(page, inode) < 0)) {
 		/* Page got truncated out from underneath us */
 		goto sigbus;
 	}
diff --git a/include/linux/pagemap.h b/include/linux/pagemap.h
index 37a4d9e32cd3..ccb14b6a16b5 100644
--- a/include/linux/pagemap.h
+++ b/include/linux/pagemap.h
@@ -636,4 +636,32 @@ static inline unsigned long dir_pages(struct inode *inode)
 			       PAGE_SHIFT;
 }
 
+/**
+ * page_mkwrite_check_truncate - check if page was truncated
+ * @page: the page to check
+ * @inode: the inode to check the page against
+ *
+ * Returns the number of bytes in the page up to EOF,
+ * or -EFAULT if the page was truncated.
+ */
+static inline int page_mkwrite_check_truncate(struct page *page,
+					      struct inode *inode)
+{
+	loff_t size = i_size_read(inode);
+	pgoff_t index = size >> PAGE_SHIFT;
+	int offset = offset_in_page(size);
+
+	if (page->mapping != inode->i_mapping)
+		return -EFAULT;
+
+	/* page is wholly inside EOF */
+	if (page->index < index)
+		return PAGE_SIZE;
+	/* page is wholly past EOF */
+	if (page->index > index || !offset)
+		return -EFAULT;
+	/* page is partially inside EOF */
+	return offset;
+}
+
 #endif /* _LINUX_PAGEMAP_H */
