diff options
author | Tejun Heo <tj@kernel.org> | 2012-04-19 16:29:22 -0700 |
---|---|---|
committer | Jens Axboe <axboe@kernel.dk> | 2012-04-20 10:06:40 +0200 |
commit | aaf7c680682f1999ef2e574f743c45d1674a8b8a (patch) | |
tree | 82d597ddfa7456553262435174948d9fb03fffef /block/blk-core.c | |
parent | 29e2b09ab5fa790514d47838f3c05497130908b3 (diff) |
block: fix elvpriv allocation failure handling
Request allocation is mempool backed to guarantee forward progress
under memory pressure; unfortunately, this property got broken while
adding elvpriv data. Failures during elvpriv allocation, including
ioc and icq creation failures, currently make get_request() fail as
whole. There's no forward progress guarantee for these allocations -
they may fail indefinitely under memory pressure stalling IO and
deadlocking the system.
This patch updates get_request() such that elvpriv allocation failure
doesn't make the whole function fail. If elvpriv allocation fails,
the allocation is degraded into !ELVPRIV. This will force the request
to ELEVATOR_INSERT_BACK disturbing scheduling but elvpriv alloc
failures should be rare (nothing is per-request) and anything is
better than deadlocking.
Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Diffstat (limited to 'block/blk-core.c')
-rw-r--r-- | block/blk-core.c | 53 |
1 files changed, 36 insertions, 17 deletions
diff --git a/block/blk-core.c b/block/blk-core.c index f6f68b0c830..6cf13df43c8 100644 --- a/block/blk-core.c +++ b/block/blk-core.c @@ -29,6 +29,7 @@ #include <linux/fault-inject.h> #include <linux/list_sort.h> #include <linux/delay.h> +#include <linux/ratelimit.h> #define CREATE_TRACE_POINTS #include <trace/events/block.h> @@ -930,17 +931,6 @@ retry: rw_flags |= REQ_IO_STAT; spin_unlock_irq(q->queue_lock); - /* create icq if missing */ - if ((rw_flags & REQ_ELVPRIV) && unlikely(et->icq_cache && !icq)) { - create_io_context(gfp_mask, q->node); - ioc = rq_ioc(bio); - if (!ioc) - goto fail_alloc; - icq = ioc_create_icq(ioc, q, gfp_mask); - if (!icq) - goto fail_alloc; - } - /* allocate and init request */ rq = mempool_alloc(q->rq.rq_pool, gfp_mask); if (!rq) @@ -949,17 +939,28 @@ retry: blk_rq_init(q, rq); rq->cmd_flags = rw_flags | REQ_ALLOCED; + /* init elvpriv */ if (rw_flags & REQ_ELVPRIV) { - rq->elv.icq = icq; - if (unlikely(elv_set_request(q, rq, bio, gfp_mask))) { - mempool_free(rq, q->rq.rq_pool); - goto fail_alloc; + if (unlikely(et->icq_cache && !icq)) { + create_io_context(gfp_mask, q->node); + ioc = rq_ioc(bio); + if (!ioc) + goto fail_elvpriv; + + icq = ioc_create_icq(ioc, q, gfp_mask); + if (!icq) + goto fail_elvpriv; } - /* @rq->elv.icq holds on to io_context until @rq is freed */ + + rq->elv.icq = icq; + if (unlikely(elv_set_request(q, rq, bio, gfp_mask))) + goto fail_elvpriv; + + /* @rq->elv.icq holds io_context until @rq is freed */ if (icq) get_io_context(icq->ioc); } - +out: /* * ioc may be NULL here, and ioc_batching will be false. That's * OK, if the queue is under the request limit then requests need @@ -972,6 +973,24 @@ retry: trace_block_getrq(q, bio, rw_flags & 1); return rq; +fail_elvpriv: + /* + * elvpriv init failed. ioc, icq and elvpriv aren't mempool backed + * and may fail indefinitely under memory pressure and thus + * shouldn't stall IO. Treat this request as !elvpriv. This will + * disturb iosched and blkcg but weird is bettern than dead. + */ + printk_ratelimited(KERN_WARNING "%s: request aux data allocation failed, iosched may be disturbed\n", + dev_name(q->backing_dev_info.dev)); + + rq->cmd_flags &= ~REQ_ELVPRIV; + rq->elv.icq = NULL; + + spin_lock_irq(q->queue_lock); + rl->elvpriv--; + spin_unlock_irq(q->queue_lock); + goto out; + fail_alloc: /* * Allocation failed presumably due to memory. Undo anything we |