[074/146] mm/vmalloc: add support for __GFP_NOFAIL

Commit Message

Andrew Morton Jan. 14, 2022, 10:07 p.m. UTC

From: Michal Hocko <[e-mail]>
Subject: mm/vmalloc: add support for __GFP_NOFAIL

Dave Chinner has mentioned that some of the xfs code would benefit from
kvmalloc support for __GFP_NOFAIL because they have allocations that
cannot fail and they do not fit into a single page.

The large part of the vmalloc implementation already complies with the
given gfp flags so there is no work for those to be done.  The area and
page table allocations are an exception to that.  Implement a retry loop
for those.

Add a short sleep before retrying.  1 jiffy is a completely random
timeout.  Ideally the retry would wait for an explicit event - e.g.  a
change to the vmalloc space change if the failure was caused by the space
fragmentation or depletion.  But there are multiple different reasons to
retry and this could become much more complex.  Keep the retry simple for
now and just sleep to prevent from hogging CPUs.

Link: https://lkml.kernel.org/r/[e-mail]
Signed-off-by: Michal Hocko <[e-mail]>
Acked-by: Vlastimil Babka <[e-mail]>
Cc: Christoph Hellwig <[e-mail]>
Cc: Dave Chinner <[e-mail]>
Cc: Ilya Dryomov <[e-mail]>
Cc: Jeff Layton <[e-mail]>
Cc: Neil Brown <[e-mail]>
Cc: Sebastian Andrzej Siewior <[e-mail]>
Cc: Uladzislau Rezki (Sony) <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>
---

 mm/vmalloc.c |   22 +++++++++++++++++-----
 1 file changed, 17 insertions(+), 5 deletions(-)

Patch

--- a/mm/vmalloc.c~mm-vmalloc-add-support-for-__gfp_nofail
+++ a/mm/vmalloc.c
@@ -2847,6 +2847,8 @@  vm_area_alloc_pages(gfp_t gfp, int nid,
 	 * more permissive.
 	 */
 	if (!order) {
+		gfp_t bulk_gfp = gfp & ~__GFP_NOFAIL;
+
 		while (nr_allocated < nr_pages) {
 			unsigned int nr, nr_pages_request;
 
@@ -2864,12 +2866,12 @@  vm_area_alloc_pages(gfp_t gfp, int nid,
 			 * but mempolcy want to alloc memory by interleaving.
 			 */
 			if (IS_ENABLED(CONFIG_NUMA) && nid == NUMA_NO_NODE)
-				nr = alloc_pages_bulk_array_mempolicy(gfp,
+				nr = alloc_pages_bulk_array_mempolicy(bulk_gfp,
 							nr_pages_request,
 							pages + nr_allocated);
 
 			else
-				nr = alloc_pages_bulk_array_node(gfp, nid,
+				nr = alloc_pages_bulk_array_node(bulk_gfp, nid,
 							nr_pages_request,
 							pages + nr_allocated);
 
@@ -2924,6 +2926,7 @@  static void *__vmalloc_area_node(struct
 {
 	const gfp_t nested_gfp = (gfp_mask & GFP_RECLAIM_MASK) | __GFP_ZERO;
 	const gfp_t orig_gfp_mask = gfp_mask;
+	bool nofail = gfp_mask & __GFP_NOFAIL;
 	unsigned long addr = (unsigned long)area->addr;
 	unsigned long size = get_vm_area_size(area);
 	unsigned long array_size;
@@ -2988,8 +2991,12 @@  static void *__vmalloc_area_node(struct
 	else if ((gfp_mask & (__GFP_FS | __GFP_IO)) == 0)
 		flags = memalloc_noio_save();
 
-	ret = vmap_pages_range(addr, addr + size, prot, area->pages,
+	do {
+		ret = vmap_pages_range(addr, addr + size, prot, area->pages,
 			page_shift);
+		if (nofail && (ret < 0))
+			schedule_timeout_uninterruptible(1);
+	} while (nofail && (ret < 0));
 
 	if ((gfp_mask & (__GFP_FS | __GFP_IO)) == __GFP_IO)
 		memalloc_nofs_restore(flags);
@@ -3084,9 +3091,14 @@  again:
 				  VM_UNINITIALIZED | vm_flags, start, end, node,
 				  gfp_mask, caller);
 	if (!area) {
+		bool nofail = gfp_mask & __GFP_NOFAIL;
 		warn_alloc(gfp_mask, NULL,
-			"vmalloc error: size %lu, vm_struct allocation failed",
-			real_size);
+			"vmalloc error: size %lu, vm_struct allocation failed%s",
+			real_size, (nofail) ? ". Retrying." : "");
+		if (nofail) {
+			schedule_timeout_uninterruptible(1);
+			goto again;
+		}
 		goto fail;
 	}