90 	 * We should use WRITE_ONCE() here because we can have concurrent reads  in __vma_start_write()
92 	 * We don't really care about the correctness of that early check, but  in __vma_start_write()
93 	 * we should use WRITE_ONCE() for cleanliness and to keep KCSAN happy.  in __vma_start_write()
112 	 * We are the only writer, so no need to use vma_refcount_put().  in vma_mark_detached()
132  * locked result to avoid performance overhead, in which case we fall back to
135  * reused and attached to a different mm before we lock it.
151 	 * We can use READ_ONCE() for the mm_lock_seq here, and don't need  in vma_start_read()
153 	 * we don't rely on for anything - the mm_lock_seq read against which we  in vma_start_read()
181 	 * False unlocked result is impossible because we modify and check  in vma_start_read()
185 	 * We must use ACQUIRE semantics for the mm_lock_seq so that if we are  in vma_start_read()
186 	 * racing with vma_end_write_all(), we only start reading from the VMA  in vma_start_read()
208 	other_mm = vma->vm_mm; /* use a copy as vma can be freed after we drop vm_refcnt */  in vma_start_read()
240 		/* Check if the VMA got isolated after we found it */  in lock_vma_under_rcu()
251 	 * At this point, we have a stable reference to a VMA: The VMA is  in lock_vma_under_rcu()
252 	 * locked and we know it hasn't already been isolated.  in lock_vma_under_rcu()
253 	 * From here on, we can access the VMA without worrying about which  in lock_vma_under_rcu()
258 	/* Check if the vma we locked is the right one. */  in lock_vma_under_rcu()
306 	/* Start mmap_lock speculation in case we need to verify the vma later */  in lock_next_vma()
316 		 * Infinite loop should not happen because the vma we find will  in lock_next_vma()
334 	 * vma can be ahead of the last search position but we need to verify  in lock_next_vma()
335 	 * it was not shrunk after we found it and another vma has not been  in lock_next_vma()
336 	 * installed ahead of it. Otherwise we might observe a gap that should  in lock_next_vma()
383 	 * We don't have this operation yet.  in mmap_upgrade_trylock()
411  * For example, if we have a kernel bug that causes a page
412  * fault, we don't want to just use mmap_read_lock() to get
414  * to happen while we're holding the mm lock for writing.
420  * We can also actually take the mm lock for writing if we
436 	 * Well, dang. We might still be successful, but only  in lock_mm_and_find_vma()
437 	 * if we can extend a vma to do so.  in lock_mm_and_find_vma()
445 	 * We can try to upgrade the mmap lock atomically,  in lock_mm_and_find_vma()
446 	 * in which case we can continue to use the vma  in lock_mm_and_find_vma()
447 	 * we already looked up.  in lock_mm_and_find_vma()
449 	 * Otherwise we'll have to drop the mmap lock and  in lock_mm_and_find_vma()