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SubjectRe: [PATCH] staging: android: ashmem: remove usage of list iterator after the loop body
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在 2022/4/1 上午5:39, Jakob Koschel 写道:
> In preparation to limit the scope of a list iterator to the list
> traversal loop, use a dedicated pointer to point to the found element
> [1].
>
> Before, the code implicitly used the head when no element was found
> when using &pos->list. Since the new variable is only set if an
> element was found, the head needs to be used explicitly if the
> variable is NULL.
>
> Link: https://lore.kernel.org/all/CAHk-=wgRr_D8CB-D9Kg-c=EHreAsk5SqXPwr9Y7k9sA6cWXJ6w@mail.gmail.com/ [1]
> Signed-off-by: Jakob Koschel <jakobkoschel@gmail.com>
> ---
> drivers/staging/android/ashmem.c | 21 ++++++++++++---------
> 1 file changed, 12 insertions(+), 9 deletions(-)
>
> diff --git a/drivers/staging/android/ashmem.c b/drivers/staging/android/ashmem.c
> index ddbde3f8430e..a1e245827cf6 100644
> --- a/drivers/staging/android/ashmem.c
> +++ b/drivers/staging/android/ashmem.c
> @@ -703,30 +703,33 @@ static int ashmem_pin(struct ashmem_area *asma, size_t pgstart, size_t pgend,
> static int ashmem_unpin(struct ashmem_area *asma, size_t pgstart, size_t pgend,
> struct ashmem_range **new_range)
> {
> - struct ashmem_range *range, *next;
> + struct ashmem_range *range = NULL, *iter, *next;
> unsigned int purged = ASHMEM_NOT_PURGED;
>
> restart:
> - list_for_each_entry_safe(range, next, &asma->unpinned_list, unpinned) {
> + list_for_each_entry_safe(iter, next, &asma->unpinned_list, unpinned) {
> /* short circuit: this is our insertion point */
> - if (range_before_page(range, pgstart))
> + if (range_before_page(iter, pgstart)) {
> + range = iter;
> break;
> + }
>
> /*
> * The user can ask us to unpin pages that are already entirely
> * or partially pinned. We handle those two cases here.
> */
> - if (page_range_subsumed_by_range(range, pgstart, pgend))
> + if (page_range_subsumed_by_range(iter, pgstart, pgend))
> return 0;
> - if (page_range_in_range(range, pgstart, pgend)) {
> - pgstart = min(range->pgstart, pgstart);
> - pgend = max(range->pgend, pgend);
> - purged |= range->purged;
> - range_del(range);
> + if (page_range_in_range(iter, pgstart, pgend)) {
> + pgstart = min(iter->pgstart, pgstart);
> + pgend = max(iter->pgend, pgend);
> + purged |= iter->purged;
> + range_del(iter);
> goto restart;
> }
> }
>
> + range = list_prepare_entry(range, &asma->unpinned_list, unpinned);
> range_alloc(asma, range, purged, pgstart, pgend, new_range);
> return 0;
> }
>
> base-commit: f82da161ea75dc4db21b2499e4b1facd36dab275

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