On 24/06/2024 19:56, Yosry Ahmed wrote:
[..]
- p->zeromap = bitmap_zalloc(maxpages, GFP_KERNEL);
+ p->zeromap = kvzalloc(DIV_ROUND_UP(maxpages, 8), GFP_KERNEL);
No, 8 is not right for 32-bit kernels. I think you want
p->zeromap = kvzalloc(BITS_TO_LONGS(maxpages), GFP_KERNEL);
but please check it carefully, I'm easily confused by such conversions.
Hugh
Ah yes, didnt take into account 32-bit kernel. I think its supposed to be
p->zeromap = kvzalloc(BITS_TO_LONGS(maxpages) * sizeof(unsigned long),
GFP_KERNEL);
You can do something similar to bitmap_zalloc() and use:
kvmalloc_array(BITS_TO_LONGS(nbits), sizeof(unsigned long), GFP_KERNEL
| __GFP_ZERO)
I don't see a kvzalloc_array() variant to use directly, but it should
be trivial to add it. I can see other users of kvmalloc_array() that
pass in __GFP_ZERO (e.g. fs/ntfs3/bitmap.c).
, or you could take it a step further and add bitmap_kvzalloc(),
assuming the maintainers are open to that.
Thanks! bitmap_kvzalloc makes most sense to me. It doesnt make sense
that bitmap should only be limited to MAX_PAGE_ORDER size. I can add
this patch below at the start of the series and use it in the patch for
zeropage swap optimization.
bitmap: add support for virtually contiguous bitmap
The current bitmap_zalloc API limits the allocation to MAX_PAGE_ORDER,
which prevents larger order bitmap allocations. Introduce
bitmap_kvzalloc that will allow larger allocations of bitmap.
kvmalloc_array still attempts to allocate physically contiguous memory,
but upon failure, falls back to non-contiguous (vmalloc) allocation.
Suggested-by: Yosry Ahmed <yosryahmed@xxxxxxxxxx>
Signed-off-by: Usama Arif <usamaarif642@xxxxxxxxx>
diff --git a/include/linux/bitmap.h b/include/linux/bitmap.h
index 8c4768c44a01..881c2ff2e834 100644
--- a/include/linux/bitmap.h
+++ b/include/linux/bitmap.h
@@ -131,9 +131,11 @@ struct device;
*/
unsigned long *bitmap_alloc(unsigned int nbits, gfp_t flags);
unsigned long *bitmap_zalloc(unsigned int nbits, gfp_t flags);
+unsigned long *bitmap_kvzalloc(unsigned int nbits, gfp_t flags);
unsigned long *bitmap_alloc_node(unsigned int nbits, gfp_t flags, int
node);
unsigned long *bitmap_zalloc_node(unsigned int nbits, gfp_t flags, int
node);
void bitmap_free(const unsigned long *bitmap);
+void bitmap_kvfree(const unsigned long *bitmap);
DEFINE_FREE(bitmap, unsigned long *, if (_T) bitmap_free(_T))
diff --git a/lib/bitmap.c b/lib/bitmap.c
index b97692854966..eabbfb85fb45 100644
--- a/lib/bitmap.c
+++ b/lib/bitmap.c
@@ -727,6 +727,13 @@ unsigned long *bitmap_zalloc(unsigned int nbits,
gfp_t flags)
}
EXPORT_SYMBOL(bitmap_zalloc);
+unsigned long *bitmap_kvzalloc(unsigned int nbits, gfp_t flags)
+{
+ return kvmalloc_array(BITS_TO_LONGS(nbits), sizeof(unsigned long),
+ flags | __GFP_ZERO);
+}
+EXPORT_SYMBOL(bitmap_zalloc);
+
unsigned long *bitmap_alloc_node(unsigned int nbits, gfp_t flags, int
node)
{
return kmalloc_array_node(BITS_TO_LONGS(nbits), sizeof(unsigned
long),
@@ -746,6 +753,12 @@ void bitmap_free(const unsigned long *bitmap)
}
EXPORT_SYMBOL(bitmap_free);
+void bitmap_kvfree(const unsigned long *bitmap)
+{
+ kvfree(bitmap);
+}
+EXPORT_SYMBOL(bitmap_kvfree);
+
static void devm_bitmap_free(void *data)
{
unsigned long *bitmap = data;
The main reason I want to avoid doing the multiplication inline is
because kvmalloc_array() has a check_mul_overflow() check, and I
assume it must have been added for a reason.
