mm: allow !GFP_KERNEL allocations for kvmalloc

Support for GFP_NO{FS,IO} and __GFP_NOFAIL has been implemented by
previous patches so we can allow the support for kvmalloc.  This will
allow some external users to simplify or completely remove their
helpers.

GFP_NOWAIT semantic hasn't been supported so far but it hasn't been
explicitly documented so let's add a note about that.

ceph_kvmalloc is the first helper to be dropped and changed to kvmalloc.

Link: https://lkml.kernel.org/r/20211122153233.9924-5-mhocko@kernel.org
Signed-off-by: Michal Hocko <mhocko@suse.com>
Reviewed-by: Uladzislau Rezki (Sony) <urezki@gmail.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Dave Chinner <david@fromorbit.com>
Cc: Ilya Dryomov <idryomov@gmail.com>
Cc: Jeff Layton <jlayton@kernel.org>
Cc: Neil Brown <neilb@suse.de>
Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 4 insertions, 11 deletions

diff --git a/mm/util.c b/mm/util.c
index 741ba32a43ac..7e43369064c8 100644
--- a/mm/util.c
+++ b/mm/util.c
@@ -549,13 +549,10 @@ EXPORT_SYMBOL(vm_mmap);
  * Uses kmalloc to get the memory but if the allocation fails then falls back
  * to the vmalloc allocator. Use kvfree for freeing the memory.
  *
- * Reclaim modifiers - __GFP_NORETRY and __GFP_NOFAIL are not supported.
+ * GFP_NOWAIT and GFP_ATOMIC are not supported, neither is the __GFP_NORETRY modifier.
  * __GFP_RETRY_MAYFAIL is supported, and it should be used only if kmalloc is
  * preferable to the vmalloc fallback, due to visible performance drawbacks.
  *
- * Please note that any use of gfp flags outside of GFP_KERNEL is careful to not
- * fall back to vmalloc.
- *
  * Return: pointer to the allocated memory of %NULL in case of failure
  */
 void *kvmalloc_node(size_t size, gfp_t flags, int node)
@@ -564,13 +561,6 @@ void *kvmalloc_node(size_t size, gfp_t flags, int node)
 	void *ret;
 
 	/*
-	 * vmalloc uses GFP_KERNEL for some internal allocations (e.g page tables)
-	 * so the given set of flags has to be compatible.
-	 */
-	if ((flags & GFP_KERNEL) != GFP_KERNEL)
-		return kmalloc_node(size, flags, node);
-
-	/*
 	 * We want to attempt a large physically contiguous block first because
 	 * it is less likely to fragment multiple larger blocks and therefore
 	 * contribute to a long term fragmentation less than vmalloc fallback.
@@ -582,6 +572,9 @@ void *kvmalloc_node(size_t size, gfp_t flags, int node)
 
 		if (!(kmalloc_flags & __GFP_RETRY_MAYFAIL))
 			kmalloc_flags |= __GFP_NORETRY;
+
+		/* nofail semantic is implemented by the vmalloc fallback */
+		kmalloc_flags &= ~__GFP_NOFAIL;
 	}
 
 	ret = kmalloc_node(size, kmalloc_flags, node);