[RFC PATCH v1 02/18] mm: add FGP_ATOMIC flag to __filemap_get_folio()

From: Stefan Roesch <shr@fb.com>
To: <io-uring@vger.kernel.org>, <kernel-team@fb.com>,
	<linux-mm@kvack.org>, <linux-xfs@vger.kernel.org>,
	<linux-fsdevel@vger.kernel.org>
Cc: <shr@fb.com>, <david@fromorbit.com>
Subject: [RFC PATCH v1 02/18] mm: add FGP_ATOMIC flag to __filemap_get_folio()
Date: Tue, 26 Apr 2022 10:43:19 -0700	[thread overview]
Message-ID: <20220426174335.4004987-3-shr@fb.com> (raw)
In-Reply-To: <20220426174335.4004987-1-shr@fb.com>

Define FGP_ATOMIC flag and add support for the new flag in the function
__filemap_get_folio().

Signed-off-by: Stefan Roesch <shr@fb.com>
---
 include/linux/pagemap.h | 1 +
 mm/filemap.c            | 3 +++
 2 files changed, 4 insertions(+)

diff --git a/include/linux/pagemap.h b/include/linux/pagemap.h
index 993994cd943a..b8d839e10780 100644
--- a/include/linux/pagemap.h
+++ b/include/linux/pagemap.h
@@ -509,6 +509,7 @@ pgoff_t page_cache_prev_miss(struct address_space *mapping,
 #define FGP_HEAD		0x00000080
 #define FGP_ENTRY		0x00000100
 #define FGP_STABLE		0x00000200
+#define FGP_ATOMIC		0x00000400
 
 struct folio *__filemap_get_folio(struct address_space *mapping, pgoff_t index,
 		int fgp_flags, gfp_t gfp);
diff --git a/mm/filemap.c b/mm/filemap.c
index 9a1eef6c5d35..dd3c5682276e 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -1929,6 +1929,7 @@ static void *mapping_get_entry(struct address_space *mapping, pgoff_t index)
  * * %FGP_NOFS - __GFP_FS will get cleared in gfp.
  * * %FGP_NOWAIT - Don't get blocked by page lock.
  * * %FGP_STABLE - Wait for the folio to be stable (finished writeback)
+ * * %FGP_ATOMIC - Use atomic allocations
  *
  * If %FGP_LOCK or %FGP_CREAT are specified then the function may sleep even
  * if the %GFP flags specified for %FGP_CREAT are atomic.
@@ -1988,6 +1989,8 @@ 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_ATOMIC)
+			gfp |= GFP_ATOMIC;
 
 		folio = filemap_alloc_folio(gfp, 0);
 		if (!folio)
-- 
2.30.2

