[PATCH 3/3] fs: Use memalloc_nofs_save in generic_perform_write

[Goldwyn Rodrigues <rgoldwyn@suse.de>]

From: Goldwyn Rodrigues <rgoldwyn@suse.com>

Perform generic_perform_write() under memalloc_nofs because any allocations
should not recurse into fs writebacks.
This covers grab and write cache pages,

Signed-off-by: Goldwyn Rodrigues <rgoldwyn@suse.com>
---
 mm/filemap.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/mm/filemap.c b/mm/filemap.c
index 3c9ead9a1e32..5fe54614c69f 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -36,6 +36,7 @@
 #include <linux/cleancache.h>
 #include <linux/shmem_fs.h>
 #include <linux/rmap.h>
+#include <linux/sched/mm.h>
 #include "internal.h"
 
 #define CREATE_TRACE_POINTS
@@ -3105,6 +3106,7 @@ ssize_t generic_perform_write(struct file *file,
 	long status = 0;
 	ssize_t written = 0;
 	unsigned int flags = 0;
+	unsigned nofs_flags = memalloc_nofs_save();
 
 	do {
 		struct page *page;
@@ -3177,6 +3179,8 @@ ssize_t generic_perform_write(struct file *file,
 		balance_dirty_pages_ratelimited(mapping);
 	} while (iov_iter_count(i));
 
+	memalloc_nofs_restore(nofs_flags);
+
 	return written ? written : status;
 }
 EXPORT_SYMBOL(generic_perform_write);
-- 
2.16.2