[PATCH] kho: move alloc tag init to kho_init_{folio,pages}()

[PATCH] kho: move alloc tag init to kho_init_{folio,pages}()

[Pratyush Yadav]

From: "Pratyush Yadav (Google)" <pratyush@kernel.org>

Commit 8f1081892d62 ("kho: simplify page initialization in
kho_restore_page()") cleaned up the page initialization logic by
moving the folio and 0-order-page paths into separate functions. It
missed moving the alloc tag initialization.

Do it now to keep the two paths cleanly separated. While at it, touch up
the comments to be a tiny bit shorter (mainly so it doesn't end up
splitting into a multiline comment). This is purely a cosmetic change
and there should be no change in behaviour.

Signed-off-by: Pratyush Yadav (Google) <pratyush@kernel.org>
---

Notes:
    The patch for e86436ad0ad2 ("kho: init alloc tags when restoring pages
    from reserved memory") was posted after the patch for
    8f1081892d62 ("kho: simplify page initialization in
    kho_restore_page()"), but landed in mainline before it because it went
    through the hotfixes path. This led to the simplification patch missing
    the code tag bits. I don't think any of this is worth explaining in the
    commit message, so I just left it at "missed moving the alloc tags..."
    
    Tested on a qemu VM with CONFIG_MEM_ALLOC_PROFILING_DEBUG enabled.

    Not adding a Fixes tag here since this isn't a bug fix, only a cosmetic
    fix.

 kernel/liveupdate/kexec_handover.c | 15 ++++++---------
 1 file changed, 6 insertions(+), 9 deletions(-)

diff --git a/kernel/liveupdate/kexec_handover.c b/kernel/liveupdate/kexec_handover.c
index 95601623b4d6..7e5d805fa1fe 100644
--- a/kernel/liveupdate/kexec_handover.c
+++ b/kernel/liveupdate/kexec_handover.c
@@ -219,8 +219,11 @@ static int __kho_preserve_order(struct kho_mem_track *track, unsigned long pfn,
 /* For physically contiguous 0-order pages. */
 static void kho_init_pages(struct page *page, unsigned long nr_pages)
 {
-	for (unsigned long i = 0; i < nr_pages; i++)
+	for (unsigned long i = 0; i < nr_pages; i++) {
 		set_page_count(page + i, 1);
+		/* Clear each page's codetag to avoid accounting mismatch. */
+		clear_page_tag_ref(page + i);
+	}
 }
 
 static void kho_init_folio(struct page *page, unsigned int order)
@@ -229,6 +232,8 @@ static void kho_init_folio(struct page *page, unsigned int order)
 
 	/* Head page gets refcount of 1. */
 	set_page_count(page, 1);
+	/* Clear head page's codetag to avoid accounting mismatch. */
+	clear_page_tag_ref(page);
 
 	/* For higher order folios, tail pages get a page count of zero. */
 	for (unsigned long i = 1; i < nr_pages; i++)
@@ -265,14 +270,6 @@ static struct page *kho_restore_page(phys_addr_t phys, bool is_folio)
 	else
 		kho_init_pages(page, nr_pages);
 
-	/* Always mark headpage's codetag as empty to avoid accounting mismatch */
-	clear_page_tag_ref(page);
-	if (!is_folio) {
-		/* Also do that for the non-compound tail pages */
-		for (unsigned int i = 1; i < nr_pages; i++)
-			clear_page_tag_ref(page + i);
-	}
-
 	adjust_managed_page_count(page, nr_pages);
 	return page;
 }

base-commit: 6c8dd4f02805de481c200636e567a871f25399a2
-- 
2.53.0.335.g19a08e0c02-goog