From 70249194f9e5f8b17340bff3c5c2e0a5b5c8dd6b Mon Sep 17 00:00:00 2001 From: Ming Lei Date: Tue, 11 May 2021 23:22:35 +0800 Subject: [PATCH] BACKPORT: blk-mq: clear stale request in tags->rq[] before freeing one request pool refcount_inc_not_zero() in bt_tags_iter() still may read one freed request. Fix the issue by the following approach: 1) hold a per-tags spinlock when reading ->rqs[tag] and calling refcount_inc_not_zero in bt_tags_iter() 2) clearing stale request referred via ->rqs[tag] before freeing request pool, the per-tags spinlock is held for clearing stale ->rq[tag] So after we cleared stale requests, bt_tags_iter() won't observe freed request any more, also the clearing will wait for pending request reference. The idea of clearing ->rqs[] is borrowed from John Garry's previous patch and one recent David's patch. Tested-by: John Garry Reviewed-by: David Jeffery Reviewed-by: Bart Van Assche Signed-off-by: Ming Lei . Bug: 197804811 Change-Id: If49478d7b05d3f5b0a26966ddf9ae764cf2fb6b0 [Upstream: cherry picked from commit bd63141d585bef14f4caf111f6d0e27fe2300ec6] [Todd: refactored to avoid breaking KMI ] Signed-off-by: Pradeep P V K Signed-off-by: Todd Kjos Git-commit: bb96e7f45dc6ac1d6ec12190f1f286e3014fb068 Git-repo: https://android.googlesource.com/kernel/common/ Signed-off-by: Pradeep P V K (cherry picked from commit 02c9fbde9babc5d669f414f59afd28ea67403d99) Change-Id: I58693eddf77156f574a80542f719bd132906f0cc Signed-off-by: Surapusetty Naresh Babu --- block/blk-mq-tag.c | 9 +++++++-- block/blk-mq-tag.h | 7 ++++++- block/blk-mq.c | 46 +++++++++++++++++++++++++++++++++++++++++----- 3 files changed, 54 insertions(+), 8 deletions(-) diff --git a/block/blk-mq-tag.c b/block/blk-mq-tag.c index 315bbbd24eea..bdc45460b42c 100644 --- a/block/blk-mq-tag.c +++ b/block/blk-mq-tag.c @@ -221,10 +221,14 @@ struct bt_iter_data { static struct request *blk_mq_find_and_get_req(struct blk_mq_tags *tags, unsigned int bitnr) { - struct request *rq = tags->rqs[bitnr]; + struct request *rq; + unsigned long flags; + spin_lock_irqsave(&tags->lock, flags); + rq = tags->rqs[bitnr]; if (!rq || !refcount_inc_not_zero(&rq->ref)) - return NULL; + rq = NULL; + spin_unlock_irqrestore(&tags->lock, flags); return rq; } @@ -407,6 +411,7 @@ struct blk_mq_tags *blk_mq_init_tags(unsigned int total_tags, tags->nr_tags = total_tags; tags->nr_reserved_tags = reserved_tags; + spin_lock_init(&tags->lock); return blk_mq_init_bitmap_tags(tags, node, alloc_policy); } diff --git a/block/blk-mq-tag.h b/block/blk-mq-tag.h index 61deab0b5a5a..9df895ec83b5 100644 --- a/block/blk-mq-tag.h +++ b/block/blk-mq-tag.h @@ -19,8 +19,13 @@ struct blk_mq_tags { struct request **rqs; struct request **static_rqs; struct list_head page_list; -}; + /* + * used to clear request reference in rqs[] before freeing one + * request pool + */ + spinlock_t lock; +}; extern struct blk_mq_tags *blk_mq_init_tags(unsigned int nr_tags, unsigned int reserved_tags, int node, int alloc_policy); extern void blk_mq_free_tags(struct blk_mq_tags *tags); diff --git a/block/blk-mq.c b/block/blk-mq.c index c933569a8f6a..2abff347e0f7 100644 --- a/block/blk-mq.c +++ b/block/blk-mq.c @@ -1836,6 +1836,45 @@ void blk_mq_try_issue_list_directly(struct blk_mq_hw_ctx *hctx, } } +static size_t order_to_size(unsigned int order) +{ + return (size_t)PAGE_SIZE << order; +} + +/* called before freeing request pool in @tags */ +static void blk_mq_clear_rq_mapping(struct blk_mq_tag_set *set, + struct blk_mq_tags *tags, unsigned int hctx_idx) +{ + struct blk_mq_tags *drv_tags = set->tags[hctx_idx]; + struct page *page; + unsigned long flags; + + list_for_each_entry(page, &tags->page_list, lru) { + unsigned long start = (unsigned long)page_address(page); + unsigned long end = start + order_to_size(page->private); + int i; + + for (i = 0; i < set->queue_depth; i++) { + struct request *rq = drv_tags->rqs[i]; + unsigned long rq_addr = (unsigned long)rq; + + if (rq_addr >= start && rq_addr < end) { + WARN_ON_ONCE(refcount_read(&rq->ref) != 0); + cmpxchg(&drv_tags->rqs[i], rq, NULL); + } + } + } + + /* + * Wait until all pending iteration is done. + * + * Request reference is cleared and it is guaranteed to be observed + * after the ->lock is released. + */ + spin_lock_irqsave(&drv_tags->lock, flags); + spin_unlock_irqrestore(&drv_tags->lock, flags); +} + static blk_qc_t blk_mq_make_request(struct request_queue *q, struct bio *bio) { const int is_sync = op_is_sync(bio->bi_opf); @@ -1968,6 +2007,8 @@ void blk_mq_free_rqs(struct blk_mq_tag_set *set, struct blk_mq_tags *tags, } } + blk_mq_clear_rq_mapping(set, tags, hctx_idx); + while (!list_empty(&tags->page_list)) { page = list_first_entry(&tags->page_list, struct page, lru); list_del_init(&page->lru); @@ -2027,11 +2068,6 @@ struct blk_mq_tags *blk_mq_alloc_rq_map(struct blk_mq_tag_set *set, return tags; } -static size_t order_to_size(unsigned int order) -{ - return (size_t)PAGE_SIZE << order; -} - static int blk_mq_init_request(struct blk_mq_tag_set *set, struct request *rq, unsigned int hctx_idx, int node) {