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

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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: SeongJae Park <sj@kernel.org>
Reviewed-by: Shakeel Butt <shakeel.butt@linux.dev>
Reviewed-by: Liam R. Howlett <howlett@gmail.com>
Reviewed-by: Lorenzo 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: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
SeongJae Park 2025-02-05 22:15:17 -08:00 committed by Andrew Morton
parent 457753da64
commit 4000e3d0a3
1 changed files with 25 additions and 3 deletions
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28
mm/madvise.c
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@ -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;