On Tue, 31 Oct 2023, Mikulas Patocka wrote:
>
>
> On Tue, 31 Oct 2023, Marek Marczykowski-Górecki wrote:
>
> > On Tue, Oct 31, 2023 at 03:01:36PM +0100, Jan Kara wrote:
> > > On Tue 31-10-23 04:48:44, Marek Marczykowski-Górecki wrote:
> > > > Then tried:
> > > > - PAGE_ALLOC_COSTLY_ORDER=4, order=4 - cannot reproduce,
> > > > - PAGE_ALLOC_COSTLY_ORDER=4, order=5 - cannot reproduce,
> > > > - PAGE_ALLOC_COSTLY_ORDER=4, order=6 - freeze rather quickly
> > > >
> > > > I've retried the PAGE_ALLOC_COSTLY_ORDER=4,order=5 case several times
> > > > and I can't reproduce the issue there. I'm confused...
> > >
> > > And this kind of confirms that allocations > PAGE_ALLOC_COSTLY_ORDER
> > > causing hangs is most likely just a coincidence. Rather something either
> > > in
> > > the block layer or in the storage driver has problems with handling bios
> > > with sufficiently high order pages attached. This is going to be a bit
> > > painful to debug I'm afraid. How long does it take for you trigger the
> > > hang? I'm asking to get rough estimate how heavy tracing we can afford so
> > > that we don't overwhelm the system...
> >
> > Sometimes it freezes just after logging in, but in worst case it takes
> > me about 10min of more or less `tar xz` + `dd`.
>
> Hi
>
> I would like to ask you to try this patch. Revert the changes to "order"
> and "PAGE_ALLOC_COSTLY_ORDER" back to normal and apply this patch on a
> clean upstream kernel.
>
> Does it deadlock?
>
> There is a bug in dm-crypt that it doesn't account large pages in
> cc->n_allocated_pages, this patch fixes the bug.
>
> Mikulas
If the previous patch didn't fix it, try this patch (on a clean upstream
kernel).
This patch allocates large pages, but it breaks them up into single-page
entries when adding them to the bio.
If this patch deadlocks, it is a sign that allocating large pages causes
the problem.
If this patch doesn't deadlock, it is a sign that processing a bio with
large pages is the problem.
Mikulas
---
drivers/md/dm-crypt.c | 26 ++++++++++++++++++++++----
1 file changed, 22 insertions(+), 4 deletions(-)
Index: linux-stable/drivers/md/dm-crypt.c
===================================================================
--- linux-stable.orig/drivers/md/dm-crypt.c 2023-10-31 17:16:03.000000000
+0100
+++ linux-stable/drivers/md/dm-crypt.c 2023-10-31 17:21:14.000000000 +0100
@@ -1700,11 +1700,16 @@ retry:
order = min(order, remaining_order);
while (order > 0) {
+ if
(unlikely(percpu_counter_read_positive(&cc->n_allocated_pages) + (1 << order) >
dm_crypt_pages_per_client))
+ goto decrease_order;
pages = alloc_pages(gfp_mask
| __GFP_NOMEMALLOC | __GFP_NORETRY |
__GFP_NOWARN | __GFP_COMP,
order);
- if (likely(pages != NULL))
+ if (likely(pages != NULL)) {
+ percpu_counter_add(&cc->n_allocated_pages, 1 <<
order);
goto have_pages;
+ }
+decrease_order:
order--;
}
@@ -1719,8 +1724,13 @@ retry:
have_pages:
size_to_add = min((unsigned)PAGE_SIZE << order, remaining_size);
- __bio_add_page(clone, pages, size_to_add, 0);
remaining_size -= size_to_add;
+ while (size_to_add) {
+ unsigned this_step = min(size_to_add,
(unsigned)PAGE_SIZE);
+ __bio_add_page(clone, pages, this_step, 0);
+ size_to_add -= this_step;
+ pages++;
+ }
}
/* Allocate space for integrity tags */
@@ -1739,13 +1749,21 @@ have_pages:
static void crypt_free_buffer_pages(struct crypt_config *cc, struct bio *clone)
{
struct folio_iter fi;
+ unsigned skip = 0;
if (clone->bi_vcnt > 0) { /* bio_for_each_folio_all crashes with an
empty bio */
bio_for_each_folio_all(fi, clone) {
- if (folio_test_large(fi.folio))
+ if (skip) {
+ skip--;
+ continue;
+ }
+ if (folio_test_large(fi.folio)) {
+ skip = (1 << folio_order(fi.folio)) - 1;
+ percpu_counter_sub(&cc->n_allocated_pages, 1 <<
folio_order(fi.folio));
folio_put(fi.folio);
- else
+ } else {
mempool_free(&fi.folio->page, &cc->page_pool);
+ }
}
}
}
