From: Rik van Riel riel@surriel.com
[ Upstream commit 5363ee9d110e139584c2d92a0b640bc210588506 ]
Filesystems can write to disk from page reclaim with __GFP_FS set. Marc found a case where scsi_realloc_sdev_budget_map() ends up in page reclaim with GFP_KERNEL, where it could try to take filesystem locks again, leading to a deadlock.
WARNING: possible circular locking dependency detected 6.13.0 #1 Not tainted ------------------------------------------------------ kswapd0/70 is trying to acquire lock: ffff8881025d5d78 (&q->q_usage_counter(io)){++++}-{0:0}, at: blk_mq_submit_bio+0x461/0x6e0
but task is already holding lock: ffffffff81ef5f40 (fs_reclaim){+.+.}-{0:0}, at: balance_pgdat+0x9f/0x760
The full lockdep splat can be found in Marc's report:
https://lkml.org/lkml/2025/1/24/1101
Avoid the potential deadlock by doing the allocation with GFP_NOIO, which prevents both filesystem and block layer recursion.
Reported-by: Marc Aurèle La France tsi@tuyoix.net Signed-off-by: Rik van Riel riel@surriel.com Link: https://lore.kernel.org/r/20250129104525.0ae8421e@fangorn Reviewed-by: Christoph Hellwig hch@lst.de Signed-off-by: Martin K. Petersen martin.petersen@oracle.com Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/scsi/scsi_scan.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/scsi/scsi_scan.c b/drivers/scsi/scsi_scan.c index 042329b74c6e6..fe08af4dcb67c 100644 --- a/drivers/scsi/scsi_scan.c +++ b/drivers/scsi/scsi_scan.c @@ -245,7 +245,7 @@ static int scsi_realloc_sdev_budget_map(struct scsi_device *sdev, } ret = sbitmap_init_node(&sdev->budget_map, scsi_device_max_queue_depth(sdev), - new_shift, GFP_KERNEL, + new_shift, GFP_NOIO, sdev->request_queue->node, false, true); if (!ret) sbitmap_resize(&sdev->budget_map, depth);