From: Michal Hocko <mhocko@xxxxxxxx>
vmalloc historically hasn't supported GFP_NO{FS,IO} requests because
page table allocations do not support externally provided gfp mask
and performed GFP_KERNEL like allocations.
Since few years we have scope (memalloc_no{fs,io}_{save,restore}) APIs
to enforce NOFS and NOIO constrains implicitly to all allocators within
the scope. There was a hope that those scopes would be defined on a
higher level when the reclaim recursion boundary starts/stops (e.g. when
a lock required during the memory reclaim is required etc.). It seems
that not all NOFS/NOIO users have adopted this approach and instead
they have taken a workaround approach to wrap a single [k]vmalloc
allocation by a scope API.
These workarounds do not serve the purpose of a better reclaim recursion
documentation and reduction of explicit GFP_NO{FS,IO} usege so let's
just provide them with the semantic they are asking for without a need
for workarounds.
Add support for GFP_NOFS and GFP_NOIO to vmalloc directly. All internal
allocations already comply with the given gfp_mask. The only current
exception is vmap_pages_range which maps kernel page tables. Infer the
proper scope API based on the given gfp mask.
Signed-off-by: Michal Hocko <mhocko@xxxxxxxx>
---
mm/vmalloc.c | 22 ++++++++++++++++++++--
1 file changed, 20 insertions(+), 2 deletions(-)
diff --git a/mm/vmalloc.c b/mm/vmalloc.c
index d77830ff604c..7455c89598d3 100644
--- a/mm/vmalloc.c
+++ b/mm/vmalloc.c
@@ -2889,6 +2889,8 @@ static void *__vmalloc_area_node(struct vm_struct *area, gfp_t gfp_mask,
unsigned long array_size;
unsigned int nr_small_pages = size >> PAGE_SHIFT;
unsigned int page_order;
+ unsigned int flags;
+ int ret;
array_size = (unsigned long)nr_small_pages * sizeof(struct page *);
gfp_mask |= __GFP_NOWARN;
@@ -2930,8 +2932,24 @@ static void *__vmalloc_area_node(struct vm_struct *area, gfp_t gfp_mask,
goto fail;
}
- if (vmap_pages_range(addr, addr + size, prot, area->pages,
- page_shift) < 0) {
+ /*
+ * page tables allocations ignore external gfp mask, enforce it
+ * by the scope API
+ */
+ if ((gfp_mask & (__GFP_FS | __GFP_IO)) == __GFP_IO)
+ flags = memalloc_nofs_save();
+ else if (!(gfp_mask & (__GFP_FS | __GFP_IO)))
+ flags = memalloc_noio_save();
+
+ ret = vmap_pages_range(addr, addr + size, prot, area->pages,
+ page_shift);
+
+ if ((gfp_mask & (__GFP_FS | __GFP_IO)) == __GFP_IO)
+ memalloc_nofs_restore(flags);
+ else if (!(gfp_mask & (__GFP_FS | __GFP_IO)))
+ memalloc_noio_restore(flags);
+
+ if (ret < 0) {
warn_alloc(gfp_mask, NULL,
"vmalloc error: size %lu, failed to map pages",
area->nr_pages * PAGE_SIZE);
--
2.30.2
