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charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 24.06.25 12:35, Pavel Begunkov wrote: > There is no guaranteed alignment for user pointers, however the > calculation of an offset of the first page into a folio after > coalescing uses some weird bit mask logic, get rid of it. > > Cc: stable@vger.kernel.org > Reported-by: David Hildenbrand > Fixes: a8edbb424b139 ("io_uring/rsrc: enable multi-hugepage buffer coalescing") > Signed-off-by: Pavel Begunkov > --- > io_uring/rsrc.c | 8 +++++++- > io_uring/rsrc.h | 1 + > 2 files changed, 8 insertions(+), 1 deletion(-) > > diff --git a/io_uring/rsrc.c b/io_uring/rsrc.c > index e83a294c718b..5132f8df600f 100644 > --- a/io_uring/rsrc.c > +++ b/io_uring/rsrc.c > @@ -734,6 +734,8 @@ bool io_check_coalesce_buffer(struct page **page_array, int nr_pages, > > data->nr_pages_mid = folio_nr_pages(folio); > data->folio_shift = folio_shift(folio); > + data->first_page_offset = page_array[0] - compound_head(page_array[0]); > + data->first_page_offset <<= PAGE_SHIFT; Would that also cover when we have something like nr_pages = 4 pages[0] = folio_page(folio, 1); pages[1] = folio_page(folio, 2); pages[2] = folio_page(folio2, 1); pages[3] = folio_page(folio2, 2); Note that we can create all kinds of crazy partially-mapped THP layouts using VMAs. -- Cheers, David / dhildenb