If we split a bio marked with REQ_NOWAIT, then we can trigger spurious
EAGAIN if constituent parts of that split bio end up failing request
allocations. Parts will complete just fine, but just a single failure
in one of the chained bios will yield an EAGAIN final result for the
parent bio.
Return EAGAIN early if we end up needing to split such a bio, which
allows for saner recovery handling.
Cc: stable(a)vger.kernel.org # 5.15+
Link: https://github.com/axboe/liburing/issues/766
Reported-by: Michael Kelley <mikelley(a)microsoft.com>
Signed-off-by: Jens Axboe <axboe(a)kernel.dk>
---
block/blk-merge.c | 10 ++++++++++
1 file changed, 10 insertions(+)
diff --git a/block/blk-merge.c b/block/blk-merge.c
index 071c5f8cf0cf..b7c193d67185 100644
--- a/block/blk-merge.c
+++ b/block/blk-merge.c
@@ -309,6 +309,16 @@ static struct bio *bio_split_rw(struct bio *bio, const struct queue_limits *lim,
*segs = nsegs;
return NULL;
split:
+ /*
+ * We can't sanely support splitting for a REQ_NOWAIT bio. End it
+ * with EAGAIN if splitting is required and return an error pointer.
+ */
+ if (bio->bi_opf & REQ_NOWAIT) {
+ bio->bi_status = BLK_STS_AGAIN;
+ bio_endio(bio);
+ return ERR_PTR(-EAGAIN);
+ }
+
*segs = nsegs;
/*
--
2.39.0
The patch titled
Subject: mm: multi-gen LRU: fix crash during cgroup migration
has been added to the -mm mm-hotfixes-unstable branch. Its filename is
mm-multi-gen-lru-fix-crash-during-cgroup-migration.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patche…
This patch will later appear in the mm-hotfixes-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
Before you just go and hit "reply", please:
a) Consider who else should be cc'ed
b) Prefer to cc a suitable mailing list as well
c) Ideally: find the original patch on the mailing list and do a
reply-to-all to that, adding suitable additional cc's
*** Remember to use Documentation/process/submit-checklist.rst when testing your code ***
The -mm tree is included into linux-next via the mm-everything
branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
and is updated there every 2-3 working days
------------------------------------------------------
From: Yu Zhao <yuzhao(a)google.com>
Subject: mm: multi-gen LRU: fix crash during cgroup migration
Date: Sun, 15 Jan 2023 20:44:05 -0700
lru_gen_migrate_mm() assumes lru_gen_add_mm() runs prior to itself. This
isn't true for the following scenario:
CPU 1 CPU 2
clone()
cgroup_can_fork()
cgroup_procs_write()
cgroup_post_fork()
task_lock()
lru_gen_migrate_mm()
task_unlock()
task_lock()
lru_gen_add_mm()
task_unlock()
And when the above happens, kernel crashes because of linked list
corruption (mm_struct->lru_gen.list).
Link: https://lore.kernel.org/r/20230115134651.30028-1-msizanoen@qtmlabs.xyz/
Link: https://lkml.kernel.org/r/20230116034405.2960276-1-yuzhao@google.com
Fixes: bd74fdaea146 ("mm: multi-gen LRU: support page table walks")
Signed-off-by: Yu Zhao <yuzhao(a)google.com>
Reported-by: msizanoen <msizanoen(a)qtmlabs.xyz>
Tested-by: msizanoen <msizanoen(a)qtmlabs.xyz>
Cc: <stable(a)vger.kernel.org> [6.1+]
Signed-off-by: Andrew Morton <akpm(a)linux-foundation.org>
---
--- a/mm/vmscan.c~mm-multi-gen-lru-fix-crash-during-cgroup-migration
+++ a/mm/vmscan.c
@@ -3323,13 +3323,16 @@ void lru_gen_migrate_mm(struct mm_struct
if (mem_cgroup_disabled())
return;
+ /* migration can happen before addition */
+ if (!mm->lru_gen.memcg)
+ return;
+
rcu_read_lock();
memcg = mem_cgroup_from_task(task);
rcu_read_unlock();
if (memcg == mm->lru_gen.memcg)
return;
- VM_WARN_ON_ONCE(!mm->lru_gen.memcg);
VM_WARN_ON_ONCE(list_empty(&mm->lru_gen.list));
lru_gen_del_mm(mm);
_
Patches currently in -mm which might be from yuzhao(a)google.com are
mm-multi-gen-lru-fix-crash-during-cgroup-migration.patch
mm-multi-gen-lru-rename-lru_gen_struct-to-lru_gen_folio.patch
mm-multi-gen-lru-rename-lrugen-lists-to-lrugen-folios.patch
mm-multi-gen-lru-remove-eviction-fairness-safeguard.patch
mm-multi-gen-lru-remove-aging-fairness-safeguard.patch
mm-multi-gen-lru-shuffle-should_run_aging.patch
mm-multi-gen-lru-per-node-lru_gen_folio-lists.patch
mm-multi-gen-lru-clarify-scan_control-flags.patch
mm-multi-gen-lru-simplify-arch_has_hw_pte_young-check.patch
mm-add-vma_has_recency.patch
mm-support-posix_fadv_noreuse.patch