[PATCH AUTOSEL 5.15 5/9] scsi: core: Use GFP_NOIO to avoid circular locking dependency

[PATCH AUTOSEL 5.15 5/9] scsi: core: Use GFP_NOIO to avoid circular locking dependency

[Sasha Levin]

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 9c155d5768144..f00b4624e46b5 100644
--- a/drivers/scsi/scsi_scan.c
+++ b/drivers/scsi/scsi_scan.c
@@ -229,7 +229,7 @@ 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);
-- 
2.39.5

[PATCH AUTOSEL 5.15 6/9] scsi: qla1280: Fix kernel oops when debug level > 2

[Sasha Levin]

From: Magnus Lindholm <linmag7@gmail.com>

[ Upstream commit 5233e3235dec3065ccc632729675575dbe3c6b8a ]

A null dereference or oops exception will eventually occur when qla1280.c
driver is compiled with DEBUG_QLA1280 enabled and ql_debug_level > 2.  I
think its clear from the code that the intention here is sg_dma_len(s) not
length of sg_next(s) when printing the debug info.

Signed-off-by: Magnus Lindholm <linmag7@gmail.com>
Link: https://lore.kernel.org/r/20250125095033.26188-1-linmag7@gmail.com
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 drivers/scsi/qla1280.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/scsi/qla1280.c b/drivers/scsi/qla1280.c
index d0b4e063bfe1e..eb8e9c54837e0 100644
--- a/drivers/scsi/qla1280.c
+++ b/drivers/scsi/qla1280.c
@@ -2875,7 +2875,7 @@ qla1280_64bit_start_scsi(struct scsi_qla_host *ha, struct srb * sp)
 			dprintk(3, "S/G Segment phys_addr=%x %x, len=0x%x\n",
 				cpu_to_le32(upper_32_bits(dma_handle)),
 				cpu_to_le32(lower_32_bits(dma_handle)),
-				cpu_to_le32(sg_dma_len(sg_next(s))));
+				cpu_to_le32(sg_dma_len(s)));
 			remseg--;
 		}
 		dprintk(5, "qla1280_64bit_start_scsi: Scatter/gather "
-- 
2.39.5