[PATCH RFC 22/37] mm: shmem: Allocate metadata storage for in-memory filesystems

[Alexandru Elisei]

Set __GFP_TAGGED when a new page is faulted in, so the page allocator
reserves the corresponding metadata storage.

Signed-off-by: Alexandru Elisei <alexandru.elisei@xxxxxxx>
---
 mm/shmem.c | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/mm/shmem.c b/mm/shmem.c
index 2f2e0e618072..0b772ec34caa 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -81,6 +81,8 @@ static struct vfsmount *shm_mnt;
 
 #include <linux/uaccess.h>
 
+#include <asm/memory_metadata.h>
+
 #include "internal.h"
 
 #define BLOCKS_PER_PAGE  (PAGE_SIZE/512)
@@ -1530,7 +1532,7 @@ static struct folio *shmem_swapin(swp_entry_t swap, gfp_t gfp,
  */
 static gfp_t limit_gfp_mask(gfp_t huge_gfp, gfp_t limit_gfp)
 {
-	gfp_t allowflags = __GFP_IO | __GFP_FS | __GFP_RECLAIM;
+	gfp_t allowflags = __GFP_IO | __GFP_FS | __GFP_RECLAIM | __GFP_TAGGED;
 	gfp_t denyflags = __GFP_NOWARN | __GFP_NORETRY;
 	gfp_t zoneflags = limit_gfp & GFP_ZONEMASK;
 	gfp_t result = huge_gfp & ~(allowflags | GFP_ZONEMASK);
@@ -1941,6 +1943,8 @@ static int shmem_get_folio_gfp(struct inode *inode, pgoff_t index,
 		goto alloc_nohuge;
 
 	huge_gfp = vma_thp_gfp_mask(vma);
+	if (vma_has_metadata(vma))
+		huge_gfp |= __GFP_TAGGED;
 	huge_gfp = limit_gfp_mask(huge_gfp, gfp);
 	folio = shmem_alloc_and_acct_folio(huge_gfp, inode, index, true);
 	if (IS_ERR(folio)) {
@@ -2101,6 +2105,10 @@ static vm_fault_t shmem_fault(struct vm_fault *vmf)
 	int err;
 	vm_fault_t ret = VM_FAULT_LOCKED;
 
+	/* Fixup gfp flags for metadata enabled VMAs. */
+	if (vma_has_metadata(vma))
+		gfp |= __GFP_TAGGED;
+
 	/*
 	 * Trinity finds that probing a hole which tmpfs is punching can
 	 * prevent the hole-punch from ever completing: which in turn
-- 
2.41.0