+ mm-vmalloc-clarify-why-vmap_range_noflush-might-sleep.patch added to mm-unstable branch

+ mm-vmalloc-clarify-why-vmap_range_noflush-might-sleep.patch added to mm-unstable branch

[Andrew Morton]

The patch titled
     Subject: mm/vmalloc: clarify why vmap_range_noflush() might sleep
has been added to the -mm mm-unstable branch.  Its filename is
     mm-vmalloc-clarify-why-vmap_range_noflush-might-sleep.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-vmalloc-clarify-why-vmap_range_noflush-might-sleep.patch

This patch will later appear in the mm-unstable branch at
    git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

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------------------------------------------------------
From: Brendan Jackman <jackmanb@google.com>
Subject: mm/vmalloc: clarify why vmap_range_noflush() might sleep
Date: Mon, 15 Dec 2025 10:40:25 +0000

The only reason vmap_range_noflush() can sleep is because of pagetable
allocations.

The actual allocation mechanism is arch-specific so might_alloc() doesn't
work here (what GFP flags would be used?).  Hence, just add a comment.

Also note that this might do a TLB shootdown.  This is not actually
sleeping but it requires IRQs on for x86, and might_sleep() incidentally
serves to detect violations of that too.

Link: https://lkml.kernel.org/r/20251215-b4-vmalloc-might_alloc-v3-1-92dd8e406868@google.com
Signed-off-by: Brendan Jackman <jackmanb@google.com>
Cc: Anshuman Khandual <anshuman.khandual@arm.com>
Cc: "Uladzislau Rezki (Sony)" <urezki@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 mm/vmalloc.c |    5 +++++
 1 file changed, 5 insertions(+)

--- a/mm/vmalloc.c~mm-vmalloc-clarify-why-vmap_range_noflush-might-sleep
+++ a/mm/vmalloc.c
@@ -305,6 +305,11 @@ static int vmap_range_noflush(unsigned l
 	int err;
 	pgtbl_mod_mask mask = 0;
 
+	/*
+	 * Might allocate pagetables (for most archs a more precise annotation
+	 * would be might_alloc(GFP_PGTABLE_KERNEL)). Also might shootdown TLB
+	 * (requires IRQs enabled on x86).
+	 */
 	might_sleep();
 	BUG_ON(addr >= end);
 
_

Patches currently in -mm which might be from jackmanb@google.com are

mm-vmalloc-clarify-why-vmap_range_noflush-might-sleep.patch