From eee77673af65ca33f2332abc2d4173ac25bedefd Mon Sep 17 00:00:00 2001 From: Jens Axboe Date: Wed, 12 Dec 2018 06:46:55 -0700 Subject: [PATCH] scsi: sd: use mempool for discard special page commit 61cce6f6eeced5ddd9cac55e807fe28b4f18c1ba upstream. When boxes are run near (or to) OOM, we have a problem with the discard page allocation in sd. If we fail allocating the special page, we return busy, and it'll get retried. But since ordering is honored for dispatch requests, we can keep retrying this same IO and failing. Behind that IO could be requests that want to free memory, but they never get the chance. This means you get repeated spews of traces like this: [1201401.625972] Call Trace: [1201401.631748] dump_stack+0x4d/0x65 [1201401.639445] warn_alloc+0xec/0x190 [1201401.647335] __alloc_pages_slowpath+0xe84/0xf30 [1201401.657722] ? get_page_from_freelist+0x11b/0xb10 [1201401.668475] ? __alloc_pages_slowpath+0x2e/0xf30 [1201401.679054] __alloc_pages_nodemask+0x1f9/0x210 [1201401.689424] alloc_pages_current+0x8c/0x110 [1201401.699025] sd_setup_write_same16_cmnd+0x51/0x150 [1201401.709987] sd_init_command+0x49c/0xb70 [1201401.719029] scsi_setup_cmnd+0x9c/0x160 [1201401.727877] scsi_queue_rq+0x4d9/0x610 [1201401.736535] blk_mq_dispatch_rq_list+0x19a/0x360 [1201401.747113] blk_mq_sched_dispatch_requests+0xff/0x190 [1201401.758844] __blk_mq_run_hw_queue+0x95/0xa0 [1201401.768653] blk_mq_run_work_fn+0x2c/0x30 [1201401.777886] process_one_work+0x14b/0x400 [1201401.787119] worker_thread+0x4b/0x470 [1201401.795586] kthread+0x110/0x150 [1201401.803089] ? rescuer_thread+0x320/0x320 [1201401.812322] ? kthread_park+0x90/0x90 [1201401.820787] ? do_syscall_64+0x53/0x150 [1201401.829635] ret_from_fork+0x29/0x40 Ensure that the discard page allocation has a mempool backing, so we know we can make progress. Signed-off-by: Jens Axboe Reviewed-by: Christoph Hellwig Signed-off-by: Martin K. Petersen [bwh: Backported to 3.16: Only sd_setup_discard_cmnd() does page-allocation] Signed-off-by: Ben Hutchings --- drivers/scsi/sd.c | 17 +++++++++++++++-- 1 file changed, 15 insertions(+), 2 deletions(-) diff --git a/drivers/scsi/sd.c b/drivers/scsi/sd.c index f88e3748cb18..184ffbc92eba 100644 --- a/drivers/scsi/sd.c +++ b/drivers/scsi/sd.c @@ -129,6 +129,7 @@ static DEFINE_MUTEX(sd_ref_mutex); static struct kmem_cache *sd_cdb_cache; static mempool_t *sd_cdb_pool; +static mempool_t *sd_page_pool; static const char *sd_cache_types[] = { "write through", "none", "write back", @@ -704,9 +705,10 @@ static int sd_setup_discard_cmnd(struct scsi_device *sdp, struct request *rq) memset(rq->cmd, 0, rq->cmd_len); - page = alloc_page(GFP_ATOMIC | __GFP_ZERO); + page = mempool_alloc(sd_page_pool, GFP_ATOMIC); if (!page) return BLKPREP_DEFER; + clear_highpage(page); switch (sdkp->provisioning_mode) { case SD_LBP_UNMAP: @@ -758,7 +760,7 @@ static int sd_setup_discard_cmnd(struct scsi_device *sdp, struct request *rq) out: if (ret != BLKPREP_OK) - __free_page(page); + mempool_free(page, sd_page_pool); return ret; } @@ -3260,6 +3262,13 @@ static int __init init_sd(void) goto err_out_cache; } + sd_page_pool = mempool_create_page_pool(SD_MEMPOOL_SIZE, 0); + if (!sd_page_pool) { + printk(KERN_ERR "sd: can't init discard page pool\n"); + err = -ENOMEM; + goto err_out_ppool; + } + err = scsi_register_driver(&sd_template.gendrv); if (err) goto err_out_driver; @@ -3267,6 +3276,9 @@ static int __init init_sd(void) return 0; err_out_driver: + mempool_destroy(sd_page_pool); + +err_out_ppool: mempool_destroy(sd_cdb_pool); err_out_cache: @@ -3293,6 +3305,7 @@ static void __exit exit_sd(void) scsi_unregister_driver(&sd_template.gendrv); mempool_destroy(sd_cdb_pool); + mempool_destroy(sd_page_pool); kmem_cache_destroy(sd_cdb_cache); class_unregister(&sd_disk_class);