[PATCH 6.1 15/30] mm: make the page fault mmap locking killable

Greg Kroah-Hartman
2023-06-29T18:44:53Z

From: Linus Torvalds <torvalds@linux-foundation.org>

commit eda0047296a16d65a7f2bc60a408f70d178b2014 upstream.

This is done as a separate patch from introducing the new
lock_mm_and_find_vma() helper, because while it's an obvious change,
it's not what x86 used to do in this area.

We already abort the page fault on fatal signals anyway, so why should
we wait for the mmap lock only to then abort later? With the new helper
function that returns without the lock held on failure anyway, this is
particularly easy and straightforward.

Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Samuel Mendoza-Jonas <samjonas@amazon.com>
Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
mm/memory.c | 6 ++----
1 file changed, 2 insertions(+), 4 deletions(-)

--- a/mm/memory.c
+++ b/mm/memory.c
@@ -5275,8 +5275,7 @@ static inline bool get_mmap_lock_careful
return false;
}

- mmap_read_lock(mm);
- return true;
+ return !mmap_read_lock_killable(mm);
}

static inline bool mmap_upgrade_trylock(struct mm_struct *mm)
@@ -5300,8 +5299,7 @@ static inline bool upgrade_mmap_lock_car
if (!search_exception_tables(ip))
return false;
}
- mmap_write_lock(mm);
- return true;
+ return !mmap_write_lock_killable(mm);
}

/*