Commit 4000e3d0 authored by SeongJae Park's avatar SeongJae Park Committed by Andrew Morton
Browse files

mm/madvise: remove redundant mmap_lock operations from process_madvise() 

Optimize redundant mmap lock operations from process_madvise() by directly
doing the mmap locking first, and then the remaining works for all ranges
in the loop.

[akpm@linux-foundation.org: update comment, per Lorenzo]
Link: https://lkml.kernel.org/r/20250206061517.2958-5-sj@kernel.org


Signed-off-by: default avatarSeongJae Park <sj@kernel.org>
Reviewed-by: default avatarShakeel Butt <shakeel.butt@linux.dev>
Reviewed-by: default avatarLiam R. Howlett <howlett@gmail.com>
Reviewed-by: default avatarLorenzo Stoakes <lorenzo.stoakes@oracle.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Davidlohr Bueso <dave@stgolabs.net>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
parent 457753da

mm/madvise.c

+25 −3
Original line number Diff line number Diff line
@@ -1778,16 +1778,33 @@ static ssize_t vector_madvise(struct mm_struct *mm, struct iov_iter *iter, 


	total_len = iov_iter_count(iter);



	ret = madvise_lock(mm, behavior);

	if (ret)

		return ret;



	while (iov_iter_count(iter)) {

		ret = do_madvise(mm, (unsigned long)iter_iov_addr(iter),

				 iter_iov_len(iter), behavior);

		unsigned long start = (unsigned long)iter_iov_addr(iter);

		size_t len_in = iter_iov_len(iter);

		size_t len;



		if (!is_valid_madvise(start, len_in, behavior)) {

			ret = -EINVAL;

			break;

		}



		len = PAGE_ALIGN(len_in);

		if (start + len == start)

			ret = 0;

		else

			ret = madvise_do_behavior(mm, start, len_in, len,

					behavior);

		/*

		 * An madvise operation is attempting to restart the syscall,

		 * but we cannot proceed as it would not be correct to repeat

		 * the operation in aggregate, and would be surprising to the

		 * user.

		 *

		 * As we have already dropped locks, it is safe to just loop and

		 * We drop and reacquire locks so it is safe to just loop and

		 * try again. We check for fatal signals in case we need exit

		 * early anyway.

		 */
@@ -1796,12 +1813,17 @@ static ssize_t vector_madvise(struct mm_struct *mm, struct iov_iter *iter, 
				ret = -EINTR;

				break;

			}



			/* Drop and reacquire lock to unwind race. */

			madvise_unlock(mm, behavior);

			madvise_lock(mm, behavior);

			continue;

		}

		if (ret < 0)

			break;

		iov_iter_advance(iter, iter_iov_len(iter));

	}

	madvise_unlock(mm, behavior);



	ret = (total_len - iov_iter_count(iter)) ? : ret;