On 12/25/21 at 05:53am, Hyeonggon Yoo wrote:

On Thu, Dec 23, 2021 at 05:44:35PM +0800, Baoquan He wrote:

...... 

quoted

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 7c7a0b5de2ff..843bc8e5550a 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c

@@ -4204,7 +4204,8 @@ void warn_alloc(gfp_t gfp_mask, nodemask_t *nodemask, const char *fmt, ...)
 	va_list args;
 	static DEFINE_RATELIMIT_STATE(nopage_rs, 10*HZ, 1);
 
-	if ((gfp_mask & __GFP_NOWARN) || !__ratelimit(&nopage_rs))
+	if ((gfp_mask & __GFP_NOWARN) || !__ratelimit(&nopage_rs) ||
+		(gfp_mask & __GFP_DMA) && !has_managed_dma())
 		return;

Warning when there's always no page in DMA zone is unnecessary 
and it confuses user.

The patch looks good.
Reviewed-by: Hyeonggon Yoo <redacted>

And there is some driers that allocate memory with GFP_DMA
even if that flag is unnecessary. We need to do cleanup later.

Thanks for reviewing and giving out some awesome suggestions.

Baoquan Are you planning to do it soon?
I want to help that.

Yes, I had the plan and have done a little part. I talked to Christoph
about my thought. I planned to collect all kmalloc(GFP_DMA) callsite and
post a RFC mail, CC mailing list and maintainers related. Anyone
interested or know one or several callsites well can help.

Now, Christoph has handled all under drviers/scsi, and post patches to
fix them. I have gone throug those places and found out below callsites
where we can remove GFP_DMA directly when calling kmalloc() since not
necessary. And even found one place kmalloc(GFP_DMA32).

(HEAD -> master) vxge: don't use GFP_DMA
mtd: rawnand: marvell: don't use GFP_DMA
HID: intel-ish-hid: remove wrong GFP_DMA32 flag
ps3disk: don't use GFP_DMA
atm: iphase: don't use GFP_DMA

Next, I will send a RFC mail to contain those suspect callsites. We can
track them and can help if needed. Suggest to change them with:
1) using dma_alloc_xx , or dma_map_xx after kmalloc()
2) using alloc_pages(GFP_DMA) instead

When we fix, we all post patch with subject key words as
'xxxx: don't use GFP_DMA'. Christoph has posted patch with the similar
subject, we can search subject to get all related patches for later back
porting.

I will add you to CC when sending. Could be tomorrow. Any suggestion or thought?

Thanks
Baoquan