mm/memory.c: simplify pfnmap_lockdep_assert

Use local `mapping' to reduce the pointer chasing.

akpm: extracted from a bugfix which Linus fixed with b1b46751671be ("mm:
fix follow_pfnmap API lockdep assert").

Link: https://lkml.kernel.org/r/20241004-fix-null-deref-v4-1-d0a8ec01ac85@iiitd.ac.in
Signed-off-by: Manas <manas18244@iiitd.ac.in>
Reviewed-by: Peter Xu <peterx@redhat.com>
Cc: Anup Sharma <anupnewsmail@gmail.com>
Cc: Shuah Khan <skhan@linuxfoundation.org>
Cc: Matthew Wilcox <willy@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/mm/memory.c b/mm/memory.c
index 68e57b33363b4e8e83e4f1dcc13c287159458168..2d32023d4eb87d737f7259ff77b48298bc5d385b 100644 (file)
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -6388,7 +6388,7 @@ static inline void pfnmap_lockdep_assert(struct vm_area_struct *vma)
        struct address_space *mapping = file ? file->f_mapping : NULL;
 
        if (mapping)
-               lockdep_assert(lockdep_is_held(&vma->vm_file->f_mapping->i_mmap_rwsem) ||
+               lockdep_assert(lockdep_is_held(&mapping->i_mmap_rwsem) ||
                               lockdep_is_held(&vma->vm_mm->mmap_lock));
        else
                lockdep_assert(lockdep_is_held(&vma->vm_mm->mmap_lock));