1 files changed, 60 insertions, 1 deletions

diff --git a/mm/shmem.c b/mm/shmem.c
index f368d0a..9b90d89 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -1602,7 +1602,9 @@ static long shmem_fallocate(struct file *file, int mode, loff_t offset,
 							 loff_t len)
 {
 	struct inode *inode = file->f_path.dentry->d_inode;
-	int error = -EOPNOTSUPP;
+	struct shmem_sb_info *sbinfo = SHMEM_SB(inode->i_sb);
+	pgoff_t start, index, end;
+	int error;
 
 	mutex_lock(&inode->i_mutex);
 
@@ -1617,8 +1619,65 @@ static long shmem_fallocate(struct file *file, int mode, loff_t offset,
 		shmem_truncate_range(inode, offset, offset + len - 1);
 		/* No need to unmap again: hole-punching leaves COWed pages */
 		error = 0;
+		goto out;
 	}
 
+	/* We need to check rlimit even when FALLOC_FL_KEEP_SIZE */
+	error = inode_newsize_ok(inode, offset + len);
+	if (error)
+		goto out;
+
+	start = offset >> PAGE_CACHE_SHIFT;
+	end = (offset + len + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
+	/* Try to avoid a swapstorm if len is impossible to satisfy */
+	if (sbinfo->max_blocks && end - start > sbinfo->max_blocks) {
+		error = -ENOSPC;
+		goto out;
+	}
+
+	for (index = start; index < end; index++) {
+		struct page *page;
+
+		/*
+		 * Good, the fallocate(2) manpage permits EINTR: we may have
+		 * been interrupted because we are using up too much memory.
+		 */
+		if (signal_pending(current))
+			error = -EINTR;
+		else
+			error = shmem_getpage(inode, index, &page, SGP_WRITE,
+									NULL);
+		if (error) {
+			/*
+			 * We really ought to free what we allocated so far,
+			 * but it would be wrong to free pages allocated
+			 * earlier, or already now in use: i_mutex does not
+			 * exclude all cases.  We do not know what to free.
+			 */
+			goto ctime;
+		}
+
+		if (!PageUptodate(page)) {
+			clear_highpage(page);
+			flush_dcache_page(page);
+			SetPageUptodate(page);
+		}
+		/*
+		 * set_page_dirty so that memory pressure will swap rather
+		 * than free the pages we are allocating (and SGP_CACHE pages
+		 * might still be clean: we now need to mark those dirty too).
+		 */
+		set_page_dirty(page);
+		unlock_page(page);
+		page_cache_release(page);
+		cond_resched();
+	}
+
+	if (!(mode & FALLOC_FL_KEEP_SIZE) && offset + len > inode->i_size)
+		i_size_write(inode, offset + len);
+ctime:
+	inode->i_ctime = CURRENT_TIME;
+out:
 	mutex_unlock(&inode->i_mutex);
 	return error;
 }