From: Matthew Wilcox (Oracle) <willy@infradead.org>
Date: Sat, 12 Aug 2023 00:20:33 +0000 (+0100)
Subject: mm: allow fault_dirty_shared_page() to be called under the VMA lock
X-Git-Tag: kvm-x86-next-2023.09.07~124^2~95
X-Git-Url: https://www.infradead.org/git/?a=commitdiff_plain;h=0790e1e2b1b71ba357e89e779451efe79dff28e6;p=users%2Fdwmw2%2Flinux.git

mm: allow fault_dirty_shared_page() to be called under the VMA lock

By making maybe_unlock_mmap_for_io() handle the VMA lock correctly, we
make fault_dirty_shared_page() safe to be called without the mmap lock
held.

Link: https://lkml.kernel.org/r/20230812002033.1002367-1-willy@infradead.org
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Reported-by: David Hildenbrand <david@redhat.com>
Tested-by: Suren Baghdasaryan <surenb@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

diff --git a/mm/internal.h b/mm/internal.h
index a037b1b37f6d7..c6ed10f0a5ad4 100644
--- a/mm/internal.h
+++ b/mm/internal.h
@@ -706,7 +706,7 @@ static inline struct file *maybe_unlock_mmap_for_io(struct vm_fault *vmf,
 	if (fault_flag_allow_retry_first(flags) &&
 	    !(flags & FAULT_FLAG_RETRY_NOWAIT)) {
 		fpin = get_file(vmf->vma->vm_file);
-		mmap_read_unlock(vmf->vma->vm_mm);
+		release_fault_lock(vmf);
 	}
 	return fpin;
 }