Patch "ALSA: memalloc: Allocate more contiguous pages for fallback case" has been added to the 6.1-stable tree

[Sasha Levin <sashal@xxxxxxxxxx>]

This is a note to let you know that I've just added the patch titled

    ALSA: memalloc: Allocate more contiguous pages for fallback case

to the 6.1-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     alsa-memalloc-allocate-more-contiguous-pages-for-fal.patch
and it can be found in the queue-6.1 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit 0759867f08a28e01838fe1e94f7d174df0943e8b
Author: Takashi Iwai <tiwai@xxxxxxx>
Date:   Mon Nov 14 15:16:58 2022 +0100

    ALSA: memalloc: Allocate more contiguous pages for fallback case
    
    [ Upstream commit cc26516374065a34e10c9a8bf3e940e42cd96e2a ]
    
    Currently the fallback SG allocation tries to allocate each single
    page, and this tends to result in the reverse order of memory
    addresses when large space is available at boot, as the kernel takes a
    free page from the top to the bottom in the zone.  The end result
    looks as if non-contiguous (although it actually is).  What's worse is
    that it leads to an overflow of BDL entries for HD-audio.
    
    For avoiding such a problem, this patch modifies the allocation code
    slightly; now it tries to allocate the larger contiguous chunks as
    much as possible, then reduces to the smaller chunks only if the
    allocation failed -- a similar strategy as the existing
    snd_dma_alloc_pages_fallback() function.
    
    Along with the trick, drop the unused address array from
    snd_dma_sg_fallback object.  It was needed in the past when
    dma_alloc_coherent() was used, but with the standard page allocator,
    it became superfluous and never referred.
    
    Fixes: a8d302a0b770 ("ALSA: memalloc: Revive x86-specific WC page allocations again")
    Reviewed-by: Kai Vehmanen <kai.vehmanen@xxxxxxxxxxxxxxx>
    Link: https://lore.kernel.org/r/20221114141658.29620-1-tiwai@xxxxxxx
    Signed-off-by: Takashi Iwai <tiwai@xxxxxxx>
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/sound/core/memalloc.c b/sound/core/memalloc.c
index ba095558b6d1..7268304009ad 100644
--- a/sound/core/memalloc.c
+++ b/sound/core/memalloc.c
@@ -720,7 +720,6 @@ static const struct snd_malloc_ops snd_dma_sg_wc_ops = {
 struct snd_dma_sg_fallback {
 	size_t count;
 	struct page **pages;
-	dma_addr_t *addrs;
 };
 
 static void __snd_dma_sg_fallback_free(struct snd_dma_buffer *dmab,
@@ -732,38 +731,49 @@ static void __snd_dma_sg_fallback_free(struct snd_dma_buffer *dmab,
 	for (i = 0; i < sgbuf->count && sgbuf->pages[i]; i++)
 		do_free_pages(page_address(sgbuf->pages[i]), PAGE_SIZE, wc);
 	kvfree(sgbuf->pages);
-	kvfree(sgbuf->addrs);
 	kfree(sgbuf);
 }
 
 static void *snd_dma_sg_fallback_alloc(struct snd_dma_buffer *dmab, size_t size)
 {
 	struct snd_dma_sg_fallback *sgbuf;
-	struct page **pages;
-	size_t i, count;
+	struct page **pagep, *curp;
+	size_t chunk, npages;
+	dma_addr_t addr;
 	void *p;
 	bool wc = dmab->dev.type == SNDRV_DMA_TYPE_DEV_WC_SG_FALLBACK;
 
 	sgbuf = kzalloc(sizeof(*sgbuf), GFP_KERNEL);
 	if (!sgbuf)
 		return NULL;
-	count = PAGE_ALIGN(size) >> PAGE_SHIFT;
-	pages = kvcalloc(count, sizeof(*pages), GFP_KERNEL);
-	if (!pages)
-		goto error;
-	sgbuf->pages = pages;
-	sgbuf->addrs = kvcalloc(count, sizeof(*sgbuf->addrs), GFP_KERNEL);
-	if (!sgbuf->addrs)
+	size = PAGE_ALIGN(size);
+	sgbuf->count = size >> PAGE_SHIFT;
+	sgbuf->pages = kvcalloc(sgbuf->count, sizeof(*sgbuf->pages), GFP_KERNEL);
+	if (!sgbuf->pages)
 		goto error;
 
-	for (i = 0; i < count; sgbuf->count++, i++) {
-		p = do_alloc_pages(dmab->dev.dev, PAGE_SIZE, &sgbuf->addrs[i], wc);
-		if (!p)
-			goto error;
-		sgbuf->pages[i] = virt_to_page(p);
+	pagep = sgbuf->pages;
+	chunk = size;
+	while (size > 0) {
+		chunk = min(size, chunk);
+		p = do_alloc_pages(dmab->dev.dev, chunk, &addr, wc);
+		if (!p) {
+			if (chunk <= PAGE_SIZE)
+				goto error;
+			chunk >>= 1;
+			chunk = PAGE_SIZE << get_order(chunk);
+			continue;
+		}
+
+		size -= chunk;
+		/* fill pages */
+		npages = chunk >> PAGE_SHIFT;
+		curp = virt_to_page(p);
+		while (npages--)
+			*pagep++ = curp++;
 	}
 
-	p = vmap(pages, count, VM_MAP, PAGE_KERNEL);
+	p = vmap(sgbuf->pages, sgbuf->count, VM_MAP, PAGE_KERNEL);
 	if (!p)
 		goto error;
 	dmab->private_data = sgbuf;