[PATCH v1 04/14] mm: Add support for async buffered writes

[Stefan Roesch <shr@fb.com>]

This adds support for async buffered writes in the mm layer. When the
AOP_FLAGS_BUF_WASYNC flag is set, if the page is not already loaded,
the page gets created without blocking on the allocation.

Signed-off-by: Stefan Roesch <shr@fb.com>
---
 mm/filemap.c      | 5 +++++
 mm/folio-compat.c | 4 ++++
 2 files changed, 9 insertions(+)

diff --git a/mm/filemap.c b/mm/filemap.c
index 0ff4278c3961..19065ad95a4c 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -42,6 +42,7 @@
 #include <linux/ramfs.h>
 #include <linux/page_idle.h>
 #include <linux/migrate.h>
+#include <linux/sched/mm.h>
 #include <asm/pgalloc.h>
 #include <asm/tlbflush.h>
 #include "internal.h"
@@ -1986,6 +1987,10 @@ struct folio *__filemap_get_folio(struct address_space *mapping, pgoff_t index,
 			gfp |= __GFP_WRITE;
 		if (fgp_flags & FGP_NOFS)
 			gfp &= ~__GFP_FS;
+		if (fgp_flags & FGP_NOWAIT) {
+			gfp |= GFP_ATOMIC;
+			gfp &= ~__GFP_DIRECT_RECLAIM;
+		}
 
 		folio = filemap_alloc_folio(gfp, 0);
 		if (!folio)
diff --git a/mm/folio-compat.c b/mm/folio-compat.c
index 749555a232a8..a1d05509b29f 100644
--- a/mm/folio-compat.c
+++ b/mm/folio-compat.c
@@ -136,6 +136,10 @@ struct page *grab_cache_page_write_begin(struct address_space *mapping,
 
 	if (flags & AOP_FLAG_NOFS)
 		fgp_flags |= FGP_NOFS;
+
+	if (flags & AOP_FLAGS_NOWAIT)
+		fgp_flags |= FGP_NOWAIT;
+
 	return pagecache_get_page(mapping, index, fgp_flags,
 			mapping_gfp_mask(mapping));
 }
-- 
2.30.2