[PATCH v1 1/1] aoe: avoid potential deadlock at set_capacity
From: Maksim Kiselev
Date: Wed Jan 24 2024 - 02:25:06 EST
Move set_capacity() outside of the section procected by (&d->lock).
To avoid possible interrupt unsafe locking scenario:
CPU0 CPU1
---- ----
[1] lock(&bdev->bd_size_lock);
local_irq_disable();
[2] lock(&d->lock);
[3] lock(&bdev->bd_size_lock);
<Interrupt>
[4] lock(&d->lock);
*** DEADLOCK ***
Where [1](&bdev->bd_size_lock) hold by zram_add()->set_capacity().
[2]lock(&d->lock) hold by aoeblk_gdalloc(). And aoeblk_gdalloc()
is trying to acquire [3](&bdev->bd_size_lock) at set_capacity() call.
In this situation an attempt to acquire [4]lock(&d->lock) from
aoecmd_cfg_rsp() will lead to deadlock.
So the simplest solution is breaking lock dependency
[2](&d->lock) -> [3](&bdev->bd_size_lock) by moving set_capacity()
outside.
Signed-off-by: Maksim Kiselev <bigunclemax@xxxxxxxxx>
---
drivers/block/aoe/aoeblk.c | 5 ++++-
1 file changed, 4 insertions(+), 1 deletion(-)
diff --git a/drivers/block/aoe/aoeblk.c b/drivers/block/aoe/aoeblk.c
index d2dbf8aaccb5..b1b47d88f5db 100644
--- a/drivers/block/aoe/aoeblk.c
+++ b/drivers/block/aoe/aoeblk.c
@@ -333,6 +333,7 @@ aoeblk_gdalloc(void *vp)
struct gendisk *gd;
mempool_t *mp;
struct blk_mq_tag_set *set;
+ sector_t ssize;
ulong flags;
int late = 0;
int err;
@@ -396,7 +397,7 @@ aoeblk_gdalloc(void *vp)
gd->minors = AOE_PARTITIONS;
gd->fops = &aoe_bdops;
gd->private_data = d;
- set_capacity(gd, d->ssize);
+ ssize = d->ssize;
snprintf(gd->disk_name, sizeof gd->disk_name, "etherd/e%ld.%d",
d->aoemajor, d->aoeminor);
@@ -405,6 +406,8 @@ aoeblk_gdalloc(void *vp)
spin_unlock_irqrestore(&d->lock, flags);
+ set_capacity(gd, ssize);
+
err = device_add_disk(NULL, gd, aoe_attr_groups);
if (err)
goto out_disk_cleanup;
--
2.40.1